2014 was the worst year ever for Eastern Equine Encephalitis (EEE) in Ontario (though our numbers still pale in comparison to more endemic areas in the southern US, such as Florida). A recent article published in the Animal Health Lab (AHL) Newletter (December 2014) by Dr. Alison Moore from OMAFRA sums things up well:
"Twenty-two horses and 2 emus in the province died or were euthanized due to the disease with potentially as many deaths being suspected by attending veterinarians. Two horses were confirmed infected but survived. Counties in Eastern Ontario suffered the greatest casualties. Diagnosis in 21 horses was by serum IgM ELISA testing and 3 were diagnosed by RT-PCR on brain tissue. The affected horses were diagnosed between the end of July and the end of October. Ages of affected horses ranged from 2-20+ years, with no breed or sex predilection. Most of the infected horses were unvaccinated backyard horses and only a single horse per property was clinically affected. Most horses had an acute onset of disease with death or euthanasia performed within 24-48 hours. Common clinical signs included ataxia progressing to recumbency, with fever noted in some and blindness and head pressing noted in others. In the 2 horses that survived, the clinical signs were mild (ataxia and lethargy). The 2 emus were diagnosed with hemorrhagic enteritis and EEEV confirmed in the intestine and liver by RT-PCR.
The virus causing EEE is transmitted by mosquitoes. In Ontario, the most important species is Culiseta melanura, which feeds on birds. Bridge vectors, mosquitoes that feed on both birds and mammals, then complete the cycle to humans and horses. Outbreaks occur in hardwood, flooded areas with competent avian reservoirs and mammals present. Horses and humans are dead-end hosts as they do not produce sufficient viremia to infect mosquitoes.
So why was 2014 such a devastating year? Some speculate that eastern Ontario was relatively warmer this year than other parts of the province, others say it was due to the amount of spring precipitation. Others implicate the spring migration of wading birds such as herons from Florida. Herons are a preferred host for Culiseta sp. over winter in Florida, a major reservoir state for EEEV. The spring migration of herons and similar birds is thought to disseminate the virus to the northern USA and Canada. OMAFRA and Public Health Ontario will be working together over the winter to determine any associations between ecological and meteorological factors and disease occurrence."
Given the amount of activity we saw with this virus this past summer, vaccination of horses against EEE (particularly in hard-hit areas) will be important come spring to help avoid a repeat of this year's outbreak.
More information about the occurrence of EEE and other equine neurologic diseases in Ontario is available on the OMAFRA website: Equine Neurological Disease Surveillance 2014.
The latest Worms & Germs infosheet, all about Lyme disease and ticks, is now available on the Resources - Pets page. Although it's getting colder and occasionally snowy up in Ontario, there are lots of parts of North America where ticks are active all year round. It's particularly important for any "snowbirds" who may travel south with their pets over the winter to be aware of the potential for exposure to ticks and the diseases they transmit (not just Lyme disease!), and to make sure their pets (as well as they themselves) are properly protected. (The same goes for exposure to mosquitoes, which can transmit (among other things) heartworm.)
Remember that dogs (nor any other mammal for that matter) cannot transmit Borrelia burgorferi, the bacterium that causes Lyme disease, to people; however, this is a good example of a "one health" disease that clearly affects both people and animals. Finding the disease in one species is an indication that the other is at risk as well, when there is exposure to a common source (i.e. the ticks).
Thanks to University of Guelph professor and parasitologist Dr. Andrew Perigrine for his input on the infosheet as well.
Image: A female blacklegged tick, Ixodes scapularis, engorged with a host blood meal. (Source: CDC Public Health Image Library 15993)
Since I’ve spent most of my day answering questions about Ebola, here are some of the common Q&As.
Can dogs be infected with Ebola?
Yes, but what that really means is unclear. Most of the available information comes from a study in Gabon where they tested dogs in a community during an Ebola outbreak. They found antibodies against the virus in a large percentage of dogs. That’s not really surprising, as these dogs were apparently scavenging bodies of people and animals that had died from Ebola. So, it’s not hard to see how they’d be exposed.
Having antibodies against the virus means the virus got into their body and the body mounted an immune response. That doesn’t mean the dogs got sick or that they were shedding the virus. In that study, they could not find evidence of the virus in the dogs’ bodies. That doesn’t mean it was never there at relevant levels, but they couldn’t find it at the time.
Can dogs infect people with Ebola?
That’s the big question. Dogs can get infected (see above), but IF the virus can reproduce in a dogs and IF the virus is then present in adequate levels in blood and other secretions, THEN there would be the potential for dogs to be a source of human infection. That’s a lot of IFs for which we don’t have good information.
What do I think?
I think the risk of transmission of Ebola from dogs is very low. There’s currently no evidence that dogs have an important (or any) role in transmission of the virus in natural situations. It’s not zero risk (there aren’t many "it can never happen" situations with emerging diseases), and considering the how deadly the disease is the measures that can be used to mitigate that risk (small though it may be) are important.
So, how can we reduce the risk with an exposed dog?
Basically, treat the dog the same way you would treat a person with Ebola exposure or infection. An exposed person is quarantined and monitored for signs of disease. People are not infectious until they are sick. A sick person is handled with strict infection control precautions because of the potential that the virus is present in various body secretions.
With a dog, it’s probably warranted to err on the side of caution and treat an exposed dog like an infected person. Why? Because we don’t know that dogs are not infectious until they’re sick. So, it might be best to have them isolated and handled with strict biosafety practices, rather than just watch them at home (particularly given the potential for the dog to escape the house).
Is that degree of containment practical?
Maybe. It depends on the facility, personnel and motivation. Last week, I sketched out a containment plan for our facility in case we had a suspect case. It was done knowing there’s virtually no chance it would be needed, but it was a good mental exercise to consider what to do. The more you think about it, the more complex it can get. Containment is possible for a good facility with reliable personnel and a clear containment plan. However, you can’t just drop the dog off at any kennel, shelter or veterinary clinic and say "we’ll be back for it in 21 days." You need the right facility and personnel, and access to that will be variable.
There’s prudence and then there’s "let’s kill it so we don’t have to think about it."
The Spanish response to Ebola in a nursing assistant is a demonstration of the latter. Health Officials in Spain have obtained a court order to "euthanize and incinerate" the dog owned by a nursing assistant who was infected with Ebola virus while caring for a Spanish priest who acquired the infection in Sierra Leone. The case has received a lot of attention, as the first case of Ebola from this outbreak that was acquired outside of Africa.
There’s obviously cause for concern and prudence, and the woman’s husband is logically in quarantine. However, euthanasia of the dog seems like overkill. Yes, we have to be careful. But we don’t need to overreact.
The odds of this dog being infected are very, very slim. Even if the dog was infected, there is no evidence that dogs are a source of infection. The concern about dogs has been around dogs eating carcasses of other animals that have died of Ebola virus infection, and direct contact with people with active disease. In one study in a village in Gabon during an Ebola outbreak, a large percentage of dogs had antibodies against the virus, indicating exposure (Allela et al, Emerging Infectious Diseases 2005). But, exposure doesn’t mean the dogs were ever able to transmit the virus, and eating a body full of Ebola virus is very different from living in the house with one person in the early stage of infection.
I’m not saying transmission from a dog in some form or another is impossible, or that no precautions are required for pets that have been in contact with an infected person. In some ways, it’s good to see animals considered in this scenario. However, why not take the opportunity to quarantine and test the dog to see if it was infected? That would be better for the dog, for its owner, and for the next time the situation occurs. You can’t answer all the questions with one dog, but you can start to gather information. Euthanasia is the easy knee-jerk approach that removes all risk, but there are ways to house and monitor a dog for a few weeks with no contact. Since Ebola virus is spread by direct contact with infectious body fluids, it’s containable with good facilities and appropriate precautions. To me, that would have been a better approach from many aspects.
Awareness is good.
Being proactive is wise.
Being paranoid? That’s another story.
As this unprecedented Ebola virus outbreak in West Africa continues to expand, many people in North America have journeyed from ignoring it, to considering it a disease that you only get if you’re in Africa, to thinking they need for move to some remote island and live in a bio-bubble to avoid it.
With news reports of people being quarantined in North American hospitals because they returned from West Africa with a fever, and with a confirmed case in a person who travelled from Liberia to Dallas, some people are freaking out. Among the frequent alarmist responses is a demand for a full ban on any travel from West Africa (or even Africa as a whole, from people who don’t realize the distance from Liberia to South Africa is over 5000 km, similar to the distance from New York to Alaska).
With a virus that is relatively poorly transmissible and only transmitted when people are symptomatic, reasonable travel controls and attention by healthcare workers (a big "oops" occurred in Dallas in this case) should prevent this virus for establishing any kind of foothold in North America.
People need to put things in perspective. Most likely, there will be no locally transmitted North American Ebola deaths this year. At the same time, tens of thousands of people in North America will die from seasonal flu.
...I wonder how many of the people screaming for a lock-down on Africa got a flu shot last year.
Orange County CA is currently experiencing a major outbreak of West Nile infection in people. Since January 94 cases have been confirmed, three of which were fatal, representing nearly a quarter of the 400 cases reported across the country so far this year. The number of cases of infection with a mosquito-borne virus like West Nile (or EEE, which we’ve been seeing over the last month in Ontario horses) can be affected by a lot of factors, including climate/weather, flooding or drought, bird populations and movements, mosquito populations and local mosquito species, and population density of those affected, be they people or animals.
Often we associated wet weather and flooding with increased incidence of diseases like West Nile, but this year California is experiencing a drought. How does that make sense? It’s been suggested that the dry weather is driving birds into more populated areas to look for water. More infected birds in the area provides more opportunity for mosquitoes to bite the birds and then transmit the virus to a person. The number of mosquito pools testing positive in Orange County (80%) is the highest its been since West Nile first hit California a decade ago, and 6.5 times more dead birds (260 total) have tested positive for WNV compared to 2013.
Most of the human cases in California included some signs of illness. When you consider that 80% of people infected with WNV show no signs of the disease, that means there has actually been an even larger number of people actually infected.
The impact on the local horse population has not been mentioned, but it is unlikely that horses will escape this outbreak unscathed. After a relatively slow year for WNV in 2013, I wonder how many horse owners in the area may have decided to forgo vaccinating their horses this year, and may now be regretting it. It’s easy for us to get complacent about infection control when things are going well. In the case of West Nile, people may stop taking precautions to avoid mosquitoes, to remove standing water from their property, and vaccinating their horses. It’s important to remain vigilant though, because there are so many different factors involved in the cycles of various diseases that predicting their resurgence can be extremely difficult, if not impossible. Taking some simple preventative steps, and making basic infection control practices habit can help reduce the impact of unexpected outbreaks, and help keep everyone (people and animals) healthier and safer.
An outbreak of equine herpesvirus type 1 (EHV-1) neurological disease has occurred on an Oregon farm. At last report, five horses had tested positive for the virus (though it's not clear if all of them had neurological disease) and one had died.
EHV-1 outbreaks are not exactly rare these days. There's certainly more reporting of sporadic disease and outbreaks, but it also seems like there's been a true increase in outbreaks over the past 10-15 years. During my residency, we saw EHV-1 neuro cases not uncommonly, but almost always as single cases. Now, clusters like this are more common, for no clear reason.
Anyway, this outbreak appears to be contained, and it's good that there's been no movement on or off the farm in a while. This will likely end up being a sporadic, contained cluster on a farm with no broader implications. Since EHV-1 is very common, being found in the majority of horses, there's always some risk of disease occurring. That's one of the main challenges we have in understanding and controlling this virus.
Tracking of EHV-1, and other equine (and dog and cat) diseases will soon be available on Worms & Germs MAP. Stay tuned.
There's been a lot of press about strangles (Streptococcus equi) outbreaks in Ontario lately, including a biosecurity update from the Ontario Ministry of Agriculture and Food (OMAF). In some ways, it's surprising since this is an endemic disease and strangles is pretty much always causing trouble somewhere in the province. However, a little press is never a bad thing, if it can help get people to do what they need to do (but often don't do) to control this highly contagious equine disease.
A big problem with strangles control is the unwillingness of some people to admit they have cases and/or people knowingly taking exposed horses off the farm, thereby spreading the bacterium to other farms.
Along that line, here's our latest educational poster. As with all of our materials, feel free to print, copy, post or disseminate at will. A higher resolution version can be downloaded from the Worms & Germs Resources - Horses page.
The American Heartworm Society (AHS) recently issued a release emphasizing that "Contrary to what owners may think, heartworm disease is a year-round threat" and encouraging people to use heartworm preventive medications year round.
I’m in Canada, not the US, but some US regions have a similar climate and similar issues to us. Also, some people try to directly apply US recommendations to Canada, so I’ve critiqued their reasoning below, from an Ontario context.
The AHS based the release on 3 "facts":
Fact #1: Pesky pests pay no attention to the calendar.
- Mosquitos and heartworm don’t pay attention to the calendar, but they do pay attention to the weather. The picture to the right is the view of our deck (prior to the last couple rounds of snow). I don’t think there are many mosquitoes hanging around out there. Yes, they are somewhere, since they don’t become extinct over the winter, but is mosquito exposure a reasonable concern now? No.
- Furthermore, development of Dirofilaria immitis (the heartworm parasite) in mosquitoes ceases at temperatures below 57F, a level we haven’t seen in a while (and likely won’t for a couple of more months). So, even if there are mosquitoes hanging around at the beginning and end of the "heartworm season" in temperate areas, if the parasite can’t develop, it doesn’t matter much.
Fact #2: Mosquitoes know when to come in from the cold. When weather changes prompt pets to spend more time inside, mosquitoes follow, keeping the possibility of heartworm transmission alive. This means that so-called “indoor” pets are as much at risk as their more outdoorsy counterparts.
- I’d like to see some data backing that up. I haven’t had a mosquito bite in a while.
Fact #3: Staying on schedule with heartworm prevention keeps pets safe.
- Potentially, but assuming every pet owner is forgetful and unable to figure out how to treat their animal once a month over a prescribed part of the year isn’t really a reasonable justification for a treatment regimen that uses more drug and costs more money.
- There is no evidence that 12-months-a-year treatment results in any better compliance than targeted seasonal treatment. (If I can’t remember to give it 6 months of the year, does adding 6 more months really help?)
- Around here, the vast majority of heartworm cases are in dogs that are not on heartworm prevention medications, not in dogs in which treatment failed, potentially because of compliance problems. Is it possible that some people would be more reliable with monthly treatment? Sure. It’s also possible that some people would be as bad (or worse) with year round treatment. It’s also possible that some dogs would go untreated altogether if their owners balked at the cost of year-round treatment.
The bottom line for me:
Heartworm’s a nasty disease and one that we need to prevent.
There are effective preventive medications.
Ontario isn’t Louisiana. In some areas of North America, year round treatment is absolutely needed. In others, the risk period is much shorter.
Decisions about the approach to prevention need to be based on the risk in the area, the duration of likely mosquito exposure, the outdoor temperature and the owner’s ability to comply with treatment. This is a discussion that needs to take place between pet owner and veterinarian on an individual basis.
There is no one-size-fits-all approach to heartworm prevention.
Merlin and I will each get hundreds of mosquito bites this year (surrounded by wetland as we are). He'll get his monthly heartworm prophylaxis during what I feel to be the "at-risk" time of year. That doesn't include today, when it was -21C this morning!
For the third time in the past year, Macon-Bill Animal Welfare in Georgia (USA) has a problem with canine parvovirus. The shelter is closed for two weeks in response to a puppy testing positive for this highly contagious virus that can cause serious disease in dogs (almost exclusively in unvaccinated puppies). At first glance, it may seem like an overly-aggressive response. A single parvo case isn’t too surprising in a shelter, and if appropriate routine precautions are followed, there are sound protocols to isolate parvo suspects and a good vaccination program, the risk to other animals can be contained.
In this outbreak, 14 puppies have been euthanized (though some reports differ). Again, the news reports are pretty crappy and it’s unclear whether all the puppies were sick or whether they were euthanized because they were exposed. The statement that parvovirus infection is "most times fatal for dogs" is wrong, since it’s usually treatable, but it certainly takes time, effort and money - things that may be of limited availability in a shelter. Also, if the shelter has inadequate facilities or personnel to properly treat and contain parvo, euthanasia gets considered more readily that in better equipped facilities.
The first report also says that the shelter refunded adoption fees of people who adopted puppies that subsequently died from parvo, so it does sound like there was probably a real (and possibly large) outbreak.
Closing a shelter is an extreme move but it’s sometimes required. It helps reduce the number of animals in the facility in order to make isolation of sick animals, separation of groups, management of exposed and infected animals and many other aspects of the infection control response easier. It also stops adding fuel to the fire, by halting admission of new susceptible animals that can get sick and thereby propagate the outbreak.
Some shelter outbreaks are the result of poor routine management (and some incompetence). Some are the result of inadequate response to an infectious animal. Some are an over-reaction to a limited and containable problem. Some will occur despite the best practices in the best facility. That’s the nature of infectious diseases. Any time there’s an outbreak, a shelter needs to figure out which of the above categories they fit in so that they can reduce the risk of future problems.
(For tracking of selected infectious diseases and outbreaks, stay tuned for the launch of WormsAndGermsMap. More information to come!)
It was only a matter of time, so it’s not particularly surprising, but a potentially devastating pig disease has made its way into Ontario. It’s not a concern to people or other animals, but it’s worth mentioning here anyway (both to say it’s not a public health or non-pig health concern, and since it’s a good infectious disease topic).
The disease in question is porcine epidemic diarrhea, a rather generically named disease that is caused by the similarly un-originally named porcine epidemic diarrhea (PED) virus, a type of Coronaviridae. Not surprisingly, it causes diarrhea in pigs, but the disease can be devastating. Once on a farm, a large percentage (up to 100% of pigs) can be affected, and death rates can be as high as 100% in young pigs. First identified in the UK in 1971, it’s worked its way across many regions, eventually making it to the US. Its high transmissibility (it can be spread by anything contaminated with pig manure, and it survives very well in the cold, even outside) and presence in the US has indicated a pretty substantial risk of incursion into Ontario, so finding cases in Ontario is unfortunately not surprising.
This evening, the Ontario Ministry of Agriculture and Food announced that the disease has been found on a Middlesex, Ontario farm. It’s a major concern because the disease can have a major impact on pig farms and it’s very difficult to control. Farmers have been urged to tighten up biosecurity measures for months since the virus emerged in the US in April 2013, and biosecurity measures will be even tighter now to try to prevent further spread. Presumably, a detailed investigation is underway to determine how the virus got onto the farm (and whether it might be on other Ontario farms).
This is a major concern for pig producers in Ontario but of no threat to other animal species, including people.
Last week, I mentioned the antibiotic use plenary session at the ASM-ESCMID conference on methicillin-resistant staphylococci in animals. The session was designed to discuss the use of "critically important antibiotics" in companion animals - drugs like carbapenems (imipenem, meropenem) and vancomycin, which are used for treating serious multidrug-resistant infections in people as well. After the (very lively) session, I was asked when I was going to write a follow-up post, so here it is.
The session went well and I’ll hit on some highlights.
I was on a panel with good colleagues Ulrika Gronlund-Andersson (Sweden) and Engeline van Duijkeren (Netherlands). Both are extremely well versed in the field and come from countries with different, but in general restrictive, policies pertaining to antibiotic use in animals. They also (not completely coincidentally) come from countries with less antibiotic resistance in companion animals, which means they don’t see the same degree of resistant bugs in patients that I do.
I was there as the guy from North America where we have absolutely no control over antibiotic use. It was strange being the one supporting more liberal use of antibiotics, since I’m often seen as being on the other extreme when I speak in North America. As I wrote earlier, I think (at least in my patient population) that we need to use some "big gun" drugs at times, but we also need to use them right.
It was a tough crowd. There were some nice differences in opinion, partly reflected in individuals’ backgrounds (clinical vs non-clinical, northern Europe vs other regions), but there were some great points too.
At one end, there was the opinion that banning the use of these drugs in animals altogether is acceptable. (A comment along the lines of "there are lots of dogs and cats available in animal shelters as a replacement if a pet gets a multidrug-resistant infection" was made, to varying degrees of agreement and outrage). I was at the other end of the spectrum, which really wasn’t at the other end of the whole spectrum, meaning I think we need to use these drugs at times, but we certainly don’t want unrestricted, imprudent use. We need to use them right, and very sparingly. I emphasized the point that every culture result is attached to a patient AND there’s a moral obligation to make sure that patient doesn’t suffer AND every patient is attached to an owner AND that attachment might be profound, with definite emotional and even health effects for the person associated with the animal's presence and condition.
An interesting set of comments came from a clinical colleague in southern Europe who said something along the lines of “I see vets in my country misusing these drugs so badly that I think we need to ban them. People won’t do it right so they shouldn’t do it." That’s hard to argue, and shows how we need to improve antibiotic use in veterinary practice. If it's clear they're being used poorly, we should lose access to them.
Another comment was along the lines of “I’m not concerned about OVC, where they have awareness, some restrictions and someone [me] as both a monitor and resource. But, that’s not the way most of the world works.” Again (taking the compliment and not trying to sound arrogant here), it’s hard to argue that point. However, it again comes back to figuring out how to improve antibiotic use and do things right. I think we’ve done at good job at our institution reining in use of important drugs, through education, peer pressure, surveillance and a bit of internal restriction.
There were a couple of comments like "If you only use them very sparingly, there can’t be any realistic risk, particularly compared to massive use in humans" and “Our hospital only uses them a couple of times a month,” supporting the general notion that internal restriction can be effective, and that makes sense, at least to me.
At the end, the moderator (another good colleague and expert in his own right, Luca Guardabassi from Denmark) polled the audience: Should these drugs be banned completely from animals or allowed with restrictions?
It was a pretty even split, but I think banning them came out ahead (with the disclaimer that the audience was biased towards people from countries with fewer resistance issues and more restrictions, and fewer clinical people). (A few people also came up to me after and said “I agree with you, but I was too chicken to say anything.”)
It was a great discussion, and I think it made both sides rethink their positions somewhat. I still think we need to have access to these drugs, since otherwise we’ll be saying "Sorry, your dog has a multidrug-resistant infection but I can’t use the antibiotic that would treat it, so we need to euthanize him now." At the same time, the status quo can’t continue. Misuse and overuse of critically important drugs is a problem in North America and beyond, and we have to figure out how to deal with it. Ultimately, restriction might be required, but it’s much better for the veterinary profession to deal with it internally, by improving practices on their own and internally restricting or regulating how they are used.
One question I posed to the audience was, rank these actions in terms of what you think their impact would be on antibiotic resistance in people and animals:
- 1% reduction in fluoroquinolone use in humans
- 5% reduction in amoxicillin/clavulanic acid use in humans
- 5% reduction in ceftiofur use in food animals
- 1% reduction in fluoroquinolone use in companion animals
- 5% reduction in amoxicillin/clavulanic acid use in companion animals
- 75% reduction in carbapenem use in animals
- Ban on vancomycin use in animals
More food for thought (and maybe for a future post).
Yes, Ulrika, Engeline, Luca and I are still on speaking terms. A little wine and a (4 hour) Italian dinner heal all wounds.
Australian Elmer Fudds beware… there are concerns that feral pig hunting is a risk factor for brucellosis in New South Wales. Brucellosis is a rare disease, but a report like this raises concern because it can be nasty, and it can also be hard to diagnose (or it's not considered right away).
We don’t have feral pigs in Ontario, but they are common in many areas, including parts of the US. In Australia, it’s been estimated that there are over 13 million feral pigs ranging over approximately 38% of the country. Any contact with animals carries some degree of infectious disease risk, and hunting is no exception. In fact, some risks are higher because of the close contact with the target animal and its bodily fluids after its been killed.
The brucellosis story is a bit old, and relates to a NSW Public Health Bulletin from a few years ago (Irwin et al. 2009) of four cases of this bacterial infection detected between December 2006 and September 2009. The infected individuals, all men, reported having hunted feral pigs before the onset of disease, and they all butchered the pigs without any protective gear (e.g. gloves). They didn’t have any of the common risk factors for brucellosis, such as overseas travel or consumption of unpasteurized milk from areas where the disease is endemic in dairy animals, so it was likely that the pigs were the source. Public health authorities trapped and tested 200 pigs, all of which were negative. However, 200 negative pigs from a multimillion population certainly doesn’t mean the pigs are Brucella- free, as was shown when Brucella suis was found in testicular samples of pigs from southern Queensland in a separate investigation.
All of the men reported typical symptoms including fever, sweating, abdominal pain, vomiting, back pain and "loin" pain (a term that’s not typically used since it’s not very descriptive - brucellosis often causes testicular swelling so maybe that’s what it means. Either way, it doesn’t sound pleasant).
Brucellosis is a disease that warrants some attention because it can be nasty and it can take a while to diagnose. Fortunately, it’s rare in most developed countries, although the same link between brucellosis cases and hunting feral swine has been seen in the US as well. Hunters need to be aware of a wide range of potential zoonotic diseases. Additionally, brucellosis is a concern for pet owners since sporadic human cases associated with transmission from pets have been reported, and this may be an emerging or previously overlooked problem.
It doesn’t. (Just like monkeypox doesn’t come from monkeys.)
Cowpox is a viral infection and the natural reservoirs are actually rodents. Humans, cats and cows are amongst the more common "accidental hosts" - species that get infected sporadically but are not reservoirs. Contact with an infected rodent can result in transmission of cowpox to people. The virus can also come from an animal that gets cowpox from a rodent and then passes it on to a person, as a Dutch teenager found out...
A 17-year-old girl found a kitten in the ditch and picked it up. It was sick and ultimately died (probably not from cowpox). She later developed a skin lesion on her wrist, which progressed to red lumps over her arm. Not surprisingly, cowpox didn’t jump to mind when she saw her doctor, so it took a while before a diagnosis was made, but they figured it out eventually. Since cowpox infection is usually self-limiting in individuals with a normal immune system, the girl eventually got better without any specific treatment. It took a couple months, though, and left a scar.
Presumably the girl got cowpox from the kitten, which probably got cowpox from contact with an infected rodent. This is an unusual series of events, certainly, but far from unprecedented. Cats are one of the main non-reservoir species that are implicated in cowpox transmission to people, presumably because they get infected while hunting wildlife (e.g. rodents). Cowpox is a pretty rare infection in people and usually not very severe, so it’s nothing to be paranoid about, but it’s another reason to use good hygiene practices and keep cats from going outside and hunting.
FYI Cowpox got its name because infected cows often develop lesions on their udders, and it was a common infection of dairymaids in times when cows were milked by hand. This virus also features prominently in the development of the world's first vaccine in the late 1700s, as the cowpox virus itself was used as a vaccine against the deadly smallpox virus.
We've just posted a new info sheet about Capnocytophaga. One member of this bacterial group in particular, Capnocytophaga canimorsus, makes the news periodically because it can cause devastating infection in some individuals, like the Ottawa woman who lost three limbs after one of her own dogs accidentally bit her. This kind of severe infection, which is also sometimes called dog bite septicemia, is actually quite rare, but people with certain risk factors such as diabetes, alcoholism, and particularly lack of a functional spleen are at much higher risk. The bacterium very commonly lives in the mouths of dogs and cats, and is considered a part of the normal oral microflora in these animals. People are therefore commonly exposed to Capnocytophaga, yet infection is rare, but because it can be so catastrophic it's important to know the facts, especially if you or someone you know may be at higher risk.
You can read more about Capnocytophaga on the new info sheet, which you can find along with all our other info sheets on the Worms & Germs Resources - Pets page. You can also read about Capnocytophaga in the posts in our archives.
One of our most frequent pieces of advice on W&GB when it comes to kids is to always make sure they are supervised when they are around pets. This is important for at least two major reasons, one being avoiding potential high-risk contacts when it comes to infectious disease transmission (e.g. face-to-mouth, hand-to-bum), and the other being reducing the risk of injury (and subsequent infection) from bites and scratches. Children often don't know or aren't aware of the signs that a pet is stressed or uncomfortable, essentially forcing the pet to take progressively more drastic measures to get its message across, potentially ending in a snap or a bite. The problem is a lot of the time the supervising adult also doesn't know these signs, and thus many a bite or scratch may happen even when a parent is watching carefully from only a few feet away.
Yesterday I came across an excellent post on this very topic on another blog written by Robin Bennett, a certified professional dog trainer (CPDT-KA) in Virginia. Her post was very aptly entitled "Why Supervising Dogs and Kids Doesn't Work." Click on the title to see the entire post, but here are a few of the great points she makes:
- Watch for inappropriate child behaviour. In Robin's words, "Don’t marvel that your dog has the patience of Job if he is willing to tolerate [being poked, prodded, yanked, pulled, pushed, etc]. And please don’t videotape it for YouTube! Be thankful your dog has good bite inhibition and intervene before it’s too late."
- Intervene early. If the dog loses that loose, wiggly body posture and starts to stiffen up, don't wait until the animal has to escalate its message to growling or snapping to step in.
- Support the dog's good choices. If the dog chooses to move away from a child because it is uncomfortable, support that choice and don't let the child continue to follow the animal. If the pet can't get away, it may scratch or bite to try to make the child go away instead. Don't force the dog to make that choice. (This applies equally to cats or any other pet!)
It's very important for pet owners to educate themselves about basic pet behaviour, whether they have dogs, cats or other animals, and to teach that same information to their children. Another great program that teaches kids how to behave around dogs, and unfamiliar dogs in particular, is the "Be a tree" program, details of which can be found on the Doggone Safe dog bite prevention website.
I grew up with cats, and they were all indoor/outdoor. I never really thought about it since that was just the way things were done. Yet, as much as he’d like to convince us otherwise, our current cat Finnegan is an indoor cat. There are a lot of reasons for this.
One reason for keeping Finnegan in the house is zoonotic disease prevention. I was recently giving a talk about "Pets and immunocompromised owners" at the American College of Veterinary Internal Medicine forum, and a recurring theme for reducing the risks associated with cats was keeping them inside. (Want to reduce the risk of the cat being exposed to Toxoplasma? Keep it inside. Want to reduce the risk of Salmonella exposure? Keep the cat inside...).
Another important reason is the animal's own health:
- Cat vs car rarely ends well for the cat, and untold thousands of cats meet their ends on roads every year.
- Cat vs cat isn’t as bad but can lead to cat bite abscesses and transmission of a few different pathogens such as feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV).
- When outside, cats can also be exposed to various insect borne pathogens that can be of concern. This kind of risk varies between regions, with areas such as those where there are ticks carrying Cytauxzoon felis (a parasite normally carried by bobcats) perhaps being the biggest concern.
Wildlife is another concern, in two ways. Just like with cars, cat vs larger critter such as a coyote rarely ends well for the cat. From an ecological standpoint though, greater problems occur from cats killing smaller wildlife. It’s been estimated that free-roaming domestic cats kill billions (yes, Billions) of birds and small mammals every year. I won’t go into all the details here, but there’s a good article on the Canadian Cooperative Wildlife Health Centre’s website healthywildlife.ca about the impact such avid feline predators can have on local ecology.
Some people would argue that cats are better off going outside. Looking back at the cats with which I grew up, a lot died early because they were allowed to go outside. It’s hard for me to justify the risk to the cat, wildlife and public health for some anthropomorphic “he’d really enjoy being outside” argument.
Something I often discuss when doing infection control talks is needlestick injuries. The contrast between the approach to needlestick injuries (and blood exposure in general) in veterinary and human medicine is pretty astounding. In humans, there are strong educational campaigns, careful reporting, testing and treatment protocols, and increasing use of "safety engineered sharps devices" like retractable or guarded needles. In veterinary medicine, getting stuck with a needle is often considered "part of the job" and "no big deal". A study we did of veterinary technicians a few years ago found that 74% of techs had suffered a needlestick injury in the past year (Weese & Faires, Canadian Veterinary Journal 2009). I’ve had many such injuries during my career, pretty much all before I started to focus on infection control, and I honestly didn’t put much though into them (beyond ”oh crap, that hurt!”).
There are some valid reasons for the differences between human and veterinary medicine when it comes to needlestick injury prevention, not the least of which is the risk of HIV and hepatitis B virus transmission. In some ways, getting people to pay attention to needlesticks in veterinary medicine is tough because we don’t have viruses such as these in our patients. Needlesticks can cause pain, significant trauma and rarely severe (including fatal) problems (e.g. from drug reactions or infections), but the vast majority are rather inconsequential. However, a line that I frequently use is: “We don’t have an analogue of HIV or hepatitis B… at the moment. New diseases continue to emerge and you never want to be the index case.”
Is this really a risk? Well, yes. Beyond some new disease that could emerge and be a serious problem, we also have new issues being identified from bugs that we’ve known about for a while. Recent concern has been expressed about transmission of Bartonella species. This is a strange group of bacteria that are commonly found in cats and dogs. Bartonella henselae is the cause of cat scratch disease, a well-known problem, but Bartonella are attracting a lot more attention these days because they are being implicated in a range of often vague human diseases. Bartonella can be found in the blood of healthy cats (and to a lesser degree dogs), raising questions about whether a needlestick could result in transmission of these bacteria to people.
Two case reports highlight these concerns.
The first one (Lin et al, Vector Borne and Zoonotic Diseases 2011) tells the story of a veterinarian who developed a fever of unknown origin and back pain. Ultimately, he was diagnosed with Bartonella henselae infection which they speculated may have been transmitted following a needlestick injury. The needlestick link is weak here though. As a veterinarian, there are lots of other opportunities to be exposed to Bartonella henselae. It’s not uncommonly present in the blood of healthy cats and the main route of exposure is through fleas. Fleas feed on the cat, pick up the bacterium, then shed it in their feces. Cat scratches are a common route of transmission as the contaminated flea feces may be driven into the body. The veterinarian in the report didn’t recall having been bitten or scratched recently, but recall bias is an issue since scratches are common and often forgotten if not severe. Flea exposure wasn’t queried. Also, the needle with which he was stuck was a clean needle that had not been used yet. It still could have been the source of infection if it acted like a scratch, driving infected flea dirt on his skin into the wound, but I don't think this report is very strong.
The second article (Oliveira et al, Journal of Veterinary Internal Medicine 2010) describes infection by a different Bartonella speces, B. vinsonii berkhoffii, also in a veterinarian. The person was taking an aspirate from a mass with a needle and syringe and was poked in the finger as the dog was struggling. Five days after the needlestick, the person was still healthy. A blood sample was taken from the person and Bartonella was not found. However, by day 34 after the incident, the veterinarian reported having had frequent headaches for the past week, fatigue and some intermittent numbness in one arm. Bartonella vinsonii berkhoffii was detected in the person’s blood at that time. There was also an increase in anti-Bartonella antibodies between the two blood samples, which supports an active infection. The bacterium was not found in the tumour aspirate, but as a dog-associated bacterium and one that is rarely identified in people, and with the timing of exposure and disease, it’s quite suggestive that the needlestick was the source.
These may just be two reports, but they may just be the tip of the iceberg, because disease caused by Bartonella infections is often vague and probably routinely gets missed. There’s also increasing evidence of wide-ranging types of infection that may be overlooked, so people (and particularly veterinary staff) need to be aware and pay attention to the potential risk.
Needlestick injuries shouldn’t be considered part of the job. There are risks, but a little common sense goes a long way.
Information sheets on both cat scratch disease and needlestick injuries (and how to avoid them) are available on the Worms & Germs Resources - Pets page.
The latest edition of the University of Guelph Animal Health Laboratory's newsletter contains an interesting report about 4 horses that died over the past few years from what was suspected to be contaminated intravenous fluid solutions. These cases were dead horses that were submitted for post-mortem examination from three different farms, so if anything, this could be an underestimation of the problem.
The first two horses were from the same farm. They were young Thoroughbreds that were routinely treated with intravenous electrolytes, vitamins and minerals (whether by the trainer or veterinarian is unknown). The first horse was found with its head hanging low after treatment. It later developed seizures and died. The second horse showed similar signs. The bacterium Klebsiella pneumoniae was isolated from a few different tissues of the first horse, as well as one of the "jugs" used to administer the fluids. The second horse had the same general lesions as the first, but Klebsiella wasn't isolated; however, this may have been because the body wasn't in great shape by the time it was submitted to the lab, and various other bacteria had overgrown the Klebsiella, making it difficult to isolate.
Another case was a young Standardbred that died after receiving intravenous fluids with vitamins, and a glyceryl guaiacolate jug. It had signs of bloodstream infection (septicemia) and Klebsiella oxytoca was isolated from multiple organs. Various bacteria were isolated from remnants of fluid in treatment bottles.
The final case was a five-year-old Standardbred that died after receiving a home-mixed vitamin jug. It had lesions similar to the other horses and consistent with a bloodstream infection. Klebsiella oxytoca was isolated from multiple organs.
Contamination of multidose drug vials or fluid solutions can occur if bacteria are inoculated into the bottle with a needle when a dose if withdrawn. We've shown this happens with multidose vials in a hospital situation, and of the farm it's even more likely to occur because it's a dirtier environment and, in the case of farm personnel, individuals have less experience with sterile technique. Fluid solutions can be contaminated in the same manner or when something is added to the fluids (e.g. vitamins). Contamination of reused fluid administration sets (i.e. fluid jugs/bags and the IV tubing) is quite likely, and that's why use of sterlie, single-use administration sets is recommended. Adverse events from a little bit of contamination are uncommon, but as shown here, they can happen and they can be severe. There's no information about what contributed to the contamination in these cases, but it's almost certain that poor infection control practices were at the root of the problem. Trying to save money by skimping on sterilization, reusing items without proper care, and using poor hygiene practices in general can end up costing much more.
An abstract for the upcoming CSTE (Council of State and Territorial Epidemiologists) conference in California describes a rare but concerning case of Brucella canis infection in a child. All I have to go by is the abstract (since the meeting hasn’t happened yet and I won’t be there anyway), but it provides an interesting outline.
Brucella canis is a bacterium that is (not surprisingly, given the name) associated with dogs. It’s present in dogs internationally, with higher rates of infection in strays and shelter dogs. It can cause a variety of problems in dogs, most often abortion, stillbirth and birth of weak puppies, but also things like reproductive failure and genital inflammation in males, and diskospondylitis (a kind of back problem). After a dog gets infected, the bacterium can localize to genital tissues, where it tends to hang out, resulting in intermittent shedding of B. canis in urine, vaginal discharge, fetal fluids, semen and, to a lesser extent, some other tissues. Humans can then be exposed via contact with these fluids. The main risk to humans comes from handling breeding dogs, particularly female dogs that have aborted puppies. However, people seem to be relatively resistant to B. canis infection, and there are actually only a small number of reports of human infections with this bacterium.
The risk to average pet owners is very low, but as this report shows, low doesn’t mean zero. This abstract deals with an infection in a 3-year-old child from New York city. The family had acquired a Yorkshire terrier puppy from a local store in March 2012. As is expected, there was close contact between the child and the puppy.
Near the end of April, the child was taken to an emergency room because of fever and difficulty breathing. Bacterial infection wasn’t the main suspect and he was discharged without antibiotics (presumably having improved from how he was at the time of admission). However, a blood culture was collected and it came back positive for Brucella canis. While the boy had been doing well, he was treated with 45 days of antibiotics to try to make sure the bacterium was eliminated, since it can cause chronic problems.
In a step that’s too often overlooked in zoonotic disease occurrences, there was an investigation of the source. That’s not surprising since this is a rare and concerning bacterium, and it’s pretty clear that pet contact tracing is required. The puppy was healthy but the bacterium was isolated from its blood. Because of the test result, the puppy was euthanized. (There’s no mention of whether this was at the owner’s request or based on the recommendation of public health personnel.)
The source of the puppy was a major concern, since it’s important to make sure that there aren’t other infected puppies around. The puppy came from a "commercial breeding facility" in Iowa - yet another instance of the potential for widespread national and international distribution of pathogens from large commercial pet operations. The facility was quarantined but there’s no more information in the abstract about whether other positive animals were found, whether infected puppies may have been sent elsewhere in the country, and what measures were taken to correct the problem.
A littermate of the New York puppy was sold by the same store. It also tested positive for B. canis and was treated.
This is a rare incident, but it highlights some points for me:
- Large commercial breeding facilities for dogs are unnecessary and create increased risk of disease in animals and by extension people. Yes, this could occur with a small private breeder, but the more animals, the more risk of infectious disease, and the larger the facility, the larger the potential impact should a disease issue develop.
- Proper counseling of people whose pets are diagnosed with a zoonotic pathogen is needed. I don’t know the story at all about why the first puppy was euthanized, but it might have been avoidable. What to do with animals that are healthy but shedding potentially concerning pathogens is a tough area to address. That’s particularly true for a bug like B. canis, since it can be hard to eliminate.
- Good communication is needed between the medical field, public health, veterinary medicine and the public. It’s hard to say how smoothly this investigation actually went, but it shows a good response to a rare but potentially serious problem.
- People that sell animals need to keep accurate contact information from purchasers. It’s good to see that they were able to track down the owners of the original puppy's infected littermate. Contact tracing is important with infectious diseases and it can be exceedingly difficult at times.
- There’s an inherent risk in pet ownership. We know that and have to accept it. The child was high risk because of his age. That doesn’t mean we don’t let kids have pets, but we have to understand the risk and use some basic hygiene practices to reduce that risk. Would it have had any impact on this case? Who knows, but it never hurts to improve.
We've just posted a new info sheet about cat scratch disease (CSD), which is caused by a bacterium (Bartonella henselae) commonly carried in the bloodstream of healthy cats. Signs of CSD in people can be quite non-specific, so (as always) it's important to let your physician know if you've been bitten or scratched by a cat if you're feeling ill, so that CSD is considered. Other than proper training and handling of cats to avoid bites and scratches, the next most important component of CSD prevention is flea control.
You can read more about CSD and B. henselae on the new info sheet, which you can find along with all our other info sheets on the Worms & Germs Resources - Pets page. You can also read about CSD in the posts in our archives.
I’ve received a lot of emails over the past 24 hours about the recent report of equine herpesvirus type 1 (EHV-1) neurological disease in an Ontario horse. The two main questions are whether there’s an outbreak and whether horse owners in Ontario should be concerned.
I don’t have any firsthand knowledge about this case (or any information beyond what’s been written elsewhere), but as far as I know, this is just a single sporadic case. That doesn’t mean an outbreak can’t occur, but most often, these just occur singly.
Whether there’s cause for concern is a tough question to answer. Yes, EHV-1 can be a serious problem, causing neurological disease in adult horses, abortion in pregnant mares, and severe disease in neonatal foals. Yet, at the same time, it’s an endemic disease that most often occurs as sporadic cases rather than large outbreaks (people just don’t hear about single cases as often, although they are now reported a lot more than they were a few years ago). The EHV-1 virus is very common and can be found in its dormant form in a large percentage of horses, so it’s not like some pathogens with which an unexposed population can suddenly be threatened when a single case is identified. In general I pay close attention to EHV-1 cases, but they are not a cause for panic. If a case occurs, we need to see if some broader issue is at play, and put steps in place to limit the problem, but we don’t need to cause massive disruption. In short, we want to ensure that good surveillance and infection control measures are in place, but not freak out in the process.
People have really taken a 180 degree turn in how they handle EHV-1 over the past 10 years or so. I don’t think we see EHV-1 neurological disease any more than when I was a resident. Back then, we saw sporadic cases and the odd small cluster, and people didn’t get too worked up about it in terms of the risk of transmission. Outbreaks, such as one I can remember associated with a large Ontario Standardbred yearling sale, certainly got lots of attention, but it was short-lived. Things changed (for good reason) based on some large, high-profile outbreaks in the last decade. It’s not known why such outbreaks now seem to be more common.
Anyway, if you live in Ontario and have a horse, don’t panic. Your horse is probably at no greater risk today than it was last month, assuming it wasn't in contact with the affected horse (which was diagnosed in early April). Virtually every horse is at some degree of EHV risk every day, but the odds of disease occurring are very low.
Some key prevention tips include:
- Use good general infection control practices to reduce exposure of horses to pathogens brought in by newly arrived horses.
- Observe your horses regularly and if there are any problems, isolate the horse and have a veterinarian examine it ASAP.
- When travelling to shows, races or other events, take measures to reduce direct and indirect contact between horses.
The 15 cm of snow that fell last night is as good of an indicator as any that agricultural fair season is over in this region. But, planning ahead is important (and often not done well with fair petting zoos), so it's never to early to make a plan for next season. Petting zoos can be fun and educational, but are also associated with infectious disease risk. There's always some inherent risk with any kind of animal contact, since all animals (and people) carry a multitude of infectious agents. However, understanding pathogen shedding patterns is useful to help determine the best control measures.
A recent study in Comparative Immunology, Microbiology and Infectious Diseases (Roug et al 2012) looked at shedding of selected pathogens by cattle, sheep, goats, pigs, poultry, rabbits and horses at a California county fair. Here are some of the highlights:
- E. coli O157 was found in one animal. This is the main outbreak concern when it comes to petting zoos, because very low numbers of bacteria are required to cause disease and human infections can be very severe. Surprisingly, the positive animal was a pig, not a ruminant, as would be typical.
- Salmonella was isolated from feces of 3 animals: 2 pigs and 1 chicken.
- Campylobacter jejuni, another potential cause of diarrhea in people, was found in 3 animals: 2 cattle and 1 sheep. The 2 positive cattle were adult dairy cattle and they represented 17% of all tested cattle. That's a surprisingly high rate for adult dairy cattle, in my experience.
- Other Campylobacter species were found in 2 cattle, 3 goats (30% of all goats tested) and 1 chicken.
- Antibiotic-resistant E. coli were common, particularly in pigs.
- The parasites Cryptosporidium and Giardia, and the bacterium Vibrio, were not found.
The study didn't look at other aspects of the petting zoo, such as the types of contacts that were allowed, but based on the pictures that were included with the paper, they weren't optimal. Given the results, the picture of two children in the pen with the pigs (including one child who was sitting on the ground leaning against a pig) should raise some concern.
Does this study change anything? Not really, but more information can't hurt. We know that petting zoo animals can carry pathogens, and we have to assume that every animal in a petting zoo is carrying something that could cause an infection given the "right" circumstances. That's why there's a focus on good general hygiene and infection control practices (especially hand hygiene), along with excluding animals that are at particularly high risk. As the authors say "The study findings should not be interpreted as a deterrent to visit agricultural fairs, but as a reminder that good hygiene and sanitation are critical in these settings."
Doug Powell, renowned for his food safety efforts and Barfblog, often uses the phrase "don’t eat poop" when it comes to food safety. I’ve stolen that line and I now use it a lot too when talking about zoonotic disease. However, over time, I’ve started to wonder whether the line always applies.
I was giving a talk last week and the question of "how clean is too clean?" came up. It’s not the first time, and I have a tough time answering it these days. The response relates to a few things, such as the hugely important role of our commensal bacterial population and the "hygiene hypothesis."
While some people might be turned off by the concept, we are outnumbered by bacteria in our own bodies. We have approximately 10 bacterial cells in or on us for every one of our own cells. When you compare the number of bacterial genes to our genes, the difference gets even bigger. While bacteria can cause disease, they are also critical to our health - we actually can’t live without them. They help our immune system develop and function. They help with digestion. The help us fight off other more harmful microorganisms. They produce vitamins and other compounds. They interact with us in ways that we don’t full understand, and probably in ways we’ve never even thought about. We know clearly the intestinal bacterial population plays a role in things like allergic diseases, and there’s increasing evidence of interaction between our intestinal bacteria and our brain.
A key part of our development is learning to how to live with and tolerate our bacterial microbiota. If our bodies recognized all bacteria as bad foreign invaders, we’d kill ourselves trying to kill them. Instead, we develop tolerance to certain bacterial populations. Developing tolerance is a critical aspect of healthy life, and things that interfere with development of tolerance might set the scene for future diseases, particularly allergic and inflammatory diseases. That’s where the hygiene hypothesis comes in: are we now too clean?
So, the concept that all bugs are bad is clearly wrong. Which bugs are good and how to live with the abundant microbial world in and around us is the tougher question to answer. Previous approaches to infectious diseases, based on "find bacterium… must kill…", are too simplistic and potential harmful in some situations. There’s new research indicating that the best treatment for recurrent Clostridium difficile infection may be administration of feces from a healthy donor by enema. So, clearly exposure to feces is not always bad.
Back to the original question (I was killing time on a plane as I wrote this so I had a chance to ramble on….): How clean to we want things to be, and can we be too clean? Furthermore, does reduction in our exposure to microorganisms predispose us to various diseases, such as allergic and inflammatory diseases? The answer to both of theseis presumably yes. However, what level of clean is good and what level is excessive?
In a hospital, we want clean... very clean. We have a highly susceptible population and lots of bad bugs in circulation. We want close attention paid to disinfection and thorough hand hygiene in hospitals, no doubt about it. But what about in the general population? Antibacterial soaps are not generally recommended for households because there’s no evidence they are needed and they might increase the likelihood of antibiotic resistance (since bacteria that become resistant to antibacterial agents in soaps can also be resistant to some antibiotics). We don’t need high level disinfection as a routine practice all over the house. At certain times and in certain areas, sure, it's certainly still a good idea. For example, if you’re working with raw chicken, careful attention to hygiene and surface disinfection is important because of the high likelihood of exposure to some important pathogens (e.g. Salmonella). But do we need to be spraying disinfectants around the rest of the house on a routine basis (as some TV commercials indicate)? Probably not.
Being a germaphobe can be good, but maybe it can also be bad. We need to think about the role of this complex and massive (yet still poorly defined) microbial population that lives with us. How much exposure to bacteria from different sources is actually needed for health, especially in kids? How much is harmful? There has to be a middle ground, and hopefully we’ll find it.
I’m not trying to say never wash your hands, just like I’d never say wash your hands after you touch anything, anytime. In certain locations (e.g. hospitals, food preparation areas) we need to pay extra attention to hygiene and disinfection. But what about the rest of the time? How do we find that balance? No one knows, but it’s an important question to consider.
Life with Merlin has been busy but going pretty well. There's been no pee on the floor in the past 48 hours so we're making progress. Speaking of pee (which, sadly, I seem to do a lot), we need to decide about leptospirosis vaccination for Merlin.
A good preventive medicine program is important for every pet. There's no "one size fits all" version - the program needs to be tailored for every region and pet/owner combination. We have Merlin's deworming covered. I gave him a booster vaccine the other day, which covers distemper, parvo and a couple of respiratory viruses (adenovirus type 2 and parainfluenza). Rabies vaccination will be coming soon, when he's a bit older (at least 3 months). Now that we have the "core" components covered, we need to think about the elective aspects. One of those is vaccination against leptospirosis.
When thinking about vaccination, it's a cost-benefit decision. The costs and benefits can be hard to accurately assess, but a few basic questions are key: Is there a risk of exposure? Is the disease of concern? Is there a safe and effective vaccine?
Is there a risk of exposure?
Leptospirosis, a potentially life-threatening infection caused by different types of Leptospira bacteria, has been called a "re-emerging" disease in many parts of North America since rates of infection have increased over the last 20 or so years.
Leptospirosis certainly occurs in dogs around here. We don't see a lot of cases but it's far from rare and it can be nasty.
Wildlife are the main reservoir. Infected wildlife shed the bacterium in their urine, and urine-contaminated water and wet areas are the main sources of infection. Raccoons are the biggest concern around here, and there is certainly no shortage of raccoons around my house (including in the garage sometimes). Since Merlin is a Labrador, he's bound to spend a lot of time swimming in ponds and wallowing around in wet areas on our property... prime sites to be contaminated by pee from infected wildlife. So, there's a reasonable chance that he'll be exposed.
Is the disease of concern?
There's no doubt here. While it's uncommon, it can be nasty. Life-threatening infections can occur and kidney failure is a major problem. Treatment of lepto can be difficult and expensive.
Is there a safe and effective vaccine?
Lepto vaccines have had a bad rap. Older vaccines weren't very effective (often not protecting against the strains that are of concern) and were associated with a high rate of adverse reactions. Those former concerns have persisted in some people despite the fact that there's a new generation of vaccines that are much more effective and safer. The new vaccines are better designed, better tested and cover a broader range of strains. There's quality research indicating that they work. Like any vaccine, they're not 100% effective but they are quite good overall.
Information about adverse reactions is harder to get. Adverse event reporting is sporadic at best, but the available information doesn't indicate that these vaccines cause a greater incidence of adverse reactions than any other vaccine. Any given vaccine can cause a problem in any given dog, but the overall risk is low.
So, don't tell Merlin but another set of vaccines is in his future.
Discussion is ongoing about whether sinks are needed in the exam room now that hand sanitizers are available.
- I'm not sure who's discussing this. Hand sanitizers are great and should be used as much as possible, but that doesn't mean handwashing is obsolete. Some pathogens we deal with are resistant to alcohol, such as parvovirus, Clostridium spores and ringworm. We need to wash hands when these bugs might be present. Hand sanitizers also don't help if you have chunks of pus, blood or feces on your hands. If there's no sink in the exam room, handwashing usually won't be done when it's supposed to be. If someone has to leave the room and walk to a sink, it just doesn't happen often, even if it's a short distance. A person also runs the risk of contaminating other surfaces along the way, between the exam room door and the sink.
Experts agree, however, that if you have a sink, your clients will expect you to use it to wash your hands.
- I'm not sure who these experts are, or what they're experts in. Certainly not common sense or infection control. What they're implying here is that pet owners will think veterinarians aren't doing a good job if they see a sink and the vet doesn't use it, but that if no sink is present, no one will think twice about a vet failing to practice good hand hygiene. If an owner is going to clue in to the presence of the sink and failure to wash hands (something we should be encouraging), their common sense and observation skills won't evaporate if there's no sink.
This is similar to an interview with an architect on dvm360.com where the guy says "if I have a sink I better wash my hands or the client thinks my hands aren't clean. In many cases it's better off not to have a sink..." (note: the banging you hear is me hitting my head against a wall). The same architect cited in this article, so hopefully he's actually the only one pushing this approach.
Pet owners aren't dumb.
Infection control isn't rocket science.
Handwashing is important and under-used.
We need sinks in exam rooms.
Common sense needs to be more common.
It's difficult to put sinks in existing exam rooms - some clinics just can't do this easily. That's tolerable if they are diligent in their infection control practices, use hand sanitizers as appropriate and make sure they get to a sink (without contaminating things along the way) when they need to wash their hands. Not putting sinks in a newly designed clinic is just dumb.
I've had a few (well... more than a few) calls about potential risks to animals from the large Canadian E. coli O157 beef recall. The main concern is for dogs that are fed potentially contaminated raw meat that has been recalled, but there is also potential for exposure through cross-contamination if people in the household consumed any suspect products, and through dogs getting into garbage containing meat packaging. The other issue is whether dogs and cats can become exposed, start shedding the bacterium in their feces and subsequently infect people. Contamination of a pet's food bowl leading to human exposure is also a potential concern, especially considering the fact that as few as 10 of these E. coli bacteria can cause infection in people.
Overall, these risks are quite low. The contaminated meat is primarily a human concern. The role of E. coli O157 in disease in dogs is pretty unclear, but there's no evidence it's a significant problem. Experimentally, disease can be induced in dogs fed relatively high numbers of E. coli O157, but natural disease seems to be rare (including in dogs on beef farms where exposure is probably relatively common). I think it's reasonable to suspect that this strain of E. coli can cause disease in dogs, but it doesn't happen very often. We also don't recognize hemolytic/uremic syndrome (HUS) in dogs (the severe form of E. coli O157 infection that can cause kidney disease in people).
The risk to people from recalled meat is real. The risk to people from pets is pretty remote. Studies have not identified pet contact as a risk factor for human E. coli O157 infection. Dogs have been implicated as vectors in a limited number of specific household situations, albeit with rather weak evidence and only when focused on people and animals on beef farms.
Overall, the risks to pets and from pets are pretty limited. The main concern with the recalled meat is human disease. That being said, I wouldn't recommend people feed recalled meat to animals instead of disposing of it, since there is a possible though slight risk to both humans and animals.
A Wyoming (USA) dog has died of necrotizing fasciitis (more popularly and dramatically known as "flesh-eating disease"). This isn't unheard of in dogs, but it's a pretty rare disease. The six-year-old Great Dane's infection apparently raised some concern because of the diagnosis of necrotizing fasciitis in three people in the area. However, there is no known connection between the dog and the human cases.
While not anything new, the case is noteworthy for a few reasons, not the least of which is the high mortality rate associated with this disease. A few different types of bacteria can cause "flesh-eating disease," but streptococci are most common. The news reports say the dog had Group A strep, which is quite surprising and raises a lot of questions, such as:
- Was it really Group A strep? Most of these infections in dogs are caused by a related bug, Streptococcus canis, which is a Group G strep. Group A strep is essentially unheard of in dogs and I have to wonder whether the bacterium was misidentified by the lab or the reporting is inaccurate.
- If it actually was Group A strep, what's the public health concern? Group A strep is a common bug in people (the one that causes strep throat) but invasive infections like necrotizing fasciitis are a much bigger concern, and potential dog-human transmission would have to be considered.
- If this was Group A strep, are public health authorities taking the same steps was they would in response to finding Group A strep necrotizing fasciitis in a human in the household (such as the Public Health Agency of Canada's Guidelines for the Prevention and Control of Invasive Group A Streptococcal Disease?) This would make sense to me.
- If this was really Group G strep (the most likely scenario), did the dog receive a fluoroquinolone antibiotic before the infection set in? It doesn't sound like that was the case from the article, but knowing for sure would be interesting. Most cases of Group G strep necrotizing fasciitis that we see are associated with enrofloxacin treatment of an initially mild infection, since this drug can induce increased virulence in Group G strep.
Regardless of whether it was Group A or Group G strep, it's an unfortunate situation for the dog and the family, but people shouldn't be too concerned because this is a very rare, sporadic disease in dogs and one that has not been linked to any risk to other species.
Earlier this year, a troop of Boy Scouts in the US beat off a rabid beaver that was attacking their leader (I wonder if there's a badge for that). Boy Scouts and infectious diseases are in the news again, but not with as happy a story.
In the recent incident reported on ProMED, ten Boy Scouts that attended a camp on the banks of the Semois River in Belgium developed leptospirosis - a potentially severe bacterial infection caused by Leptospira bacteria. The bacteria are shed in the urine of a variety of animal species, and people can become infected through contact with contaminated water or animals. The boys reported having played with a rat, which was likely actually a muskrat, based on the description of its size.
Three of the boys were hospitalized. Hopefully all are on the way to recovering.
This is yet another reminder that wildlife should be left alone. It's possible the boys were infected from the environment, but handling a muskrat (which was presumably sick if they were able to get that close to it) certainly increases the risk of exposure to a variety of infectious diseases.
Image of a North American muskrat (photo credit: Linda Tanner)(click image for source)
It's perhaps a good sign for public health when I don't tend to come home from a local fair and write a rant about the sorry state of the petting zoo. Around here, things seem to have improved at most events over the past few years, probably largely because of the efforts of local public health personnel. However, some establishments still fall through the cracks and regardless, even with optimal management, there's always some degree of risk with contact between animals and the public.
Welsh authorities are investigating a small (so far... and hopefully to remain that way) outbreak of E. coli O157 that has been tentatively linked to Cantref Adventure Farm. The two children became ill after visiting the farm. Two family members of one child have also tested positive for the bacterium, and it's believed that one of them was infected via contact with child (as opposed to direct contact with animals at the farm). Since both kids visited the farm in the days before they got sick, and since petting zoos are a prime source of E. coli outbreaks, it's logical to assume the farm was the source. Even though this has not yet proven, the reason to make this early assumption before a link can be definitively established is to get the word out to others that may have visited the petting zoo, in case there are more cases of illness. Authorities are telling people who visited the farm since the beginning of August to contact their physician. It's not clear whether they want to test everyone (by collecting a stool sample) or just have them checked out to make sure they are okay.
Meanwhile, the investigation at the farm is ongoing. Presumably, stool samples from animals on the premises and environmental samples have been collected to see if the same strain of E. coli is present. All direct contact between the public and animals on the farm has been stopped, and the site is being thoroughly cleaned. That's a pretty standard response overall, and hopefully if the petting zoo was the source, transmission has ceased.
Petting zoos can be fun and educational and we don't want to over-react and assume they are all inherently dangerous. There's always some degree of risk of infectious disease exposure, and the key is making sure petting zoos are run optimally to reduce, as much as possible, the risk to the public. The public also has to play a role, by following rules, supervising children and (probably most importantly) actually using hand sanitizers and handwashing stations that are provided.
.Dirofilaria immitis is the parasite that causes heartworm in dogs (and rarely cats). This mosquito-borne parasite can cause serious disease in dogs, and a lot of effort is spent trying to prevent heartworm infection. It can also cause disease in people who are bitten by a mosquito that has fed on an infected dog, but human infections are quite rare and of limited health risk. The main concern with regard to human infection is that it can create a small mass in the lungs. The mass itself isn’t usually a problem, but if it gets seen on an x-ray, it may appear very similar to a lung tumour, potentially leading to the use of more invasive diagnostic techniques (e.g. lung biopsy) to rule out cancer.
Dirofilaria immitis is not the only species of Dirofiliria. In fact, there are mulitple different Dirofilaria species with different hosts, some of which can also rarely infect people.
When it comes to dogs, D. immitis is the main concern, but dogs are also the host of Dirofilaria repens, which is most common in Mediterranean countries, eastern Europe and sub-Saharan Africa. Now, there’s a new one to add to the list, based on a paper in the Journal of Clinical Microbiology (To et al. 2012) that describes a novel Dirofilaria species in Hong Kong. Interestingly, it was found first by identifying disease in people.
Three human cases were identified in Hong Kong over a 10 month period in 2011-2012. When the researchers recovered the parasite from these individuals, they determined that, while it looked like other Dirofilaria, it was genetically different from any known species. They have tentatively named it «Candidatus Dirofilaria hongkongensis» (not very original but descriptive).
They then tested blood samples from 200 dogs and 100 cats, and found a parasite in six dogs that was identical to the new Dirofilaria from the human patients. They also tested the dogs with a commonly used commercial heartworm test that detects D. immitis and they were all negative, except for one dog that was actually infected with both the new species and D. immitis.
This is an interesting report and shows the need to be aware of potentially emerging issues. Some important questions need to be answered:
- What’s the risk to people? Obviously it can cause disease, since the three people in this report were actually sick. However, is this a very rare condition or something that may be more common? Is it something that’s been around for a long time and not diagnosed or is it really new?
- How do people get infected? They presumably get it from being bitten by an infected mosquito (as for other Dirofilaria) but how does the mosquito get infected? Are dogs the main source, one of many sources or are they inconsequetial?
- Does this new Dirofilaria cause disease in dogs? The six positive dogs were healthy, at least at the time of testing. Heartworm caused by D. immitis is a gradually progressive disease, meaning the signs become worse over time, so the fact that these dogs were clinically normal doesn’t mean there’s no risk, as they could start showing signs later on.
- What is the risk outside of Hong Kong? It’s hard to say because we know so little about this parasite, but it’s probably limited, at least at this point in time.
I’ve written about lymphocytic choriomeningitis virus (LCMV) before, as an interesting but pretty uncommon rodent-associated disease. Human infections are mainly associated with handling rodents, although other routes of transmission, such as organ transplantation from an infected donor, have also been reported. Being a disease associated with rodents and considering how rodents are produced in North America (i.e. mass production in large breeding colonies, followed by transportation to large distributors and massive mixing of animals), LCMV is bound to be a recurring problem associated with the pet rodent trade.
An issue of the CDC's ominously titled Morbidity and Mortality Weekly Report describes the risk of infection with LCMV to people who work in rodent breeding facilities. It all started with the diagnosis of meningitis in a person who worked in a rodent breeding facility in Indiana. An astute doctor suspected LCMV and the diagnosis was confirmed. The breeding facility was a pretty large one, housing approximately 155 000 (!) mice and 14 000 rats. An investigation of facility personnel ensued and approximately 25% of employees had antibodies against the virus, indicating previous infection. A large percentage of the workers reported having had signs consistent with disease (e.g flu-like illness), indicating that they were likely infected and not just exposed.
Considerable effort was put into testing the animals. Of over 1000 animals tested, 21% of mice had detectable levels of the virus in their bodies. That’s pretty impressive and concerning, both for employees and anyone receiving animals from this facility.
In response to this investigation, all mice at the facility were euthanized, and the facility was thoroughly cleaned and disinfected.
This report highlights the risk of exposure to LCMV for people who work with rodents, especially in large facilities such as this. It also highlights the risks posed to people buying rodents from these facilities, which also includes other diseases in addition to LCMV. Good general hygiene and infection control practices should greatly reduce the risk of LCMV transmission to rodent owners. In particular, efforts should be directed at new rodents, since LCMV shedding is probably greatest during the initial period after an animal enters a household or other facility. Virus shedding it often transient, and once they get out of the high-risk facility and become acclimatized to their new home, shedding rates in these rodents probably decrease over a short period of time. Overall, the risk of LCMV in someone with a pet rodent is low, but these basic preventive practices are easy to do and make a lot of sense.
Photo: Female mouse with her litter. (Photo credit: Seweryn Olkowicz) (click image for source)
When bacteria containing NDM-1 (New Delhi metallobetalactamase 1) were first identified a few years ago, I talked about it during presentations as something bad that's coming our way. NDM-1 is an enzyme that gives the bacteria that possesses it resistance to a huge range of antibiotics, to the point that few or no viable treatment options are available. Given the close relationship between animals and humans, I figured it was only a matter of time before cases were identified in animals, especially household pets. A presentation by an FDA researcher at the 2012 Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) has confirmed the finding of NDM-1 in E coli from a pet cat in the US. I can't take much credit for foresight because it was pretty predictable, but it re-affirms concerns about emerging diseases and how infectious pathogens can move between people and animals.
Not much is known about this current case, since the E coli isolate was submitted for testing as part of a large ongoing surveillance study by Dr. Dawn Boothe of Auburn University. At this point, it's unclear whether the cat had been on antibiotics earlier, whether the owner had been diagnosed with the infection, whether the owner had traveled to areas where this bug was first found (e.g. India), and other relevant pieces of information remain unknown (or at least unreported).
The cat was positive for the NMD-1 E.coli on multiple samples. The most intriguing aspect of this case is the fact that the culture samples from the cat were collected in 2008 and 2009 - at least a year before NDM-1 was first identified in the US. That's strange and concerning, and raises lots of questions about where this super-E.coli originated.
Some possible origins of the NMD-1 E.coli in this cat include:
- The owner may have traveled to an area where the bug was present, became a carrier and spread it to his/her cat upon returning home.
- The owner could have been infected when traveling, but it the infection may have been minor such that it didn't require medical care or a culture wasn't taken (so no one knew it was being caused by a super-bug), and subsequently the owner passed it on to the cat. (Remember that NDM-1 is a major concern because very few antibiotics are effective against it. However, the enzyme doesn't make the bacterium that carries it inherently more able to cause disease, so minor infections are possible.)
- On ProMed, the moderator stated that he believes stowaway rodents from India or Pakistan likely carried the bug to the US and spread it amongst other rodents, with eventual exposure of the cat through catching an infected rodent. It's possible but it's a major stretch, in my opinion.
- Perhaps the cat came from one of those endemic regions. That's pretty unlikely but there's a lot of animal movement around the world, with very little regulation, so it is possible.
We may never know how this cat got infected, but this case should be a reminder that we need to pay attention to animal populations in parallel with the human population. I keep saying it, but getting action has been difficult. People like to talk about "One Medicine," but actually getting people to practice "One Medicine" has been easier said than done.
The Guelph Humane Society has re-opened after a temporary closure to manage a potential ringworm outbreak. The shelter took an aggressive, proactive approach to the issue, including testing and treatment of all animals and thorough disinfection of the facility.
Looking back on a proactive outbreak response like this one, it's always hard to say if a bad outbreak didn't develop because it wasn't going to, or because of the early aggressive response (i.e. did it get better because of what they did or despite what they did). However, if you sit back and wait (or remain in denial), you can be sure that it's much more likely that badness will develop.
Once things have settled down, people sometimes complain that an aggressive response was unnecessary because nothing bad happened, but they're often the same people that complain that not enough was done when an major outbreak occurs. An ongoing challenge in infection control is fighting complacency, since successful infection prevention and control programs sometimes lead to people forgetting about the bad things that can happen and why such programs are in place to begin with. We should applaud facilities that "suck it up" and accept the negative PR, time and financial consequences of an appropriate response in order to protect the health and welfare of the animals for which they care and all the people (employees and public) who have contact with them.
I'm not really sure what to think about canine norovirus. Is it a rare, oddball infection or is it an important, overlooked and/or emerging problem?
- There are only a few reports of norovirus infections in dogs, but I doubt many people are looking for it.
- I've looked for it a few times during outbreaks, but not enough to convince me it's not here.
- Most outbreaks of canine gastrointestinal disease are not investigated, and norovirus testing isn't commonly available.
So, I think it's hard to say much about this bug at the moment.
However, another outbreak report involving canine norovirus (Mesquita and Nascimento, Transboundary and Emerging Diseases 2012) has been published, increasing concern that this might be an overlooked or developing issue. This latest report from Portugal describes an outbreak in a kennel that started after the introduction of some dogs imported from Russia (yet another example of the problems that can occur with dog importation, especially in the absence of good quarantine and infection control practices).
The outbreak started after two dogs from Russia were brought into a Portuguese kennel. Both had diarrhea at the time of arrival (strike 1 - introduction of new dogs, particularly sick dogs, is just asking for an outbreak) and were put into the general dog population (strike 2). Two days later, the other five dogs in the kennel developed diarrhea (not surprising). All were positive for canine norovirus (ok, that's surprising) and within one week, all the dogs appeared to have fully recovered.
There's no mention of whether testing for other causes of diarrhea was performed, but I assume that's the case. The sudden onset, rapid transmission and relatively short, self-limiting course of disease is consistent with norovirus infection.
Canine norovirus has been found in Portugal before, and the virus found in these dogs was very similar to previous Portuguese isolates. Whether that means the dogs acquired the virus in Portugal en route to the kennel or whether this virus is widely disseminated internationally isn't clear (in large part because so few people have looked for canine norovirus).
Much more remains to be learned about this virus. It should be considered in outbreaks of diarrhea in dogs, especially outbreaks involving rapid transmission between animals. A major obstacle to obtaining more information about this pathogen is the general failure to investigate outbreaks in which it may be involved. While outbreaks are often dramatic, testing is usually limited because of the cost. That's especially true when dogs aren't dying. Often, testing for rare or potentially new problems only occurs when there's a complete disaster and/or if an interested researcher or diagnostic laboratory gets wind of it and is willing (and able) to do some testing at no cost. That's not often an option. I do testing as much as I can, but I don't have any money dedicated to outbreak investigation so it depends on whether I have spare resources to put into an investigation at the time.
The risk to people from canine norovirus is not known, but is probably limited. There is some evidence of potential transmission of noroviruses from pigs or calves to people, but the risk from canine norovirus isn't clear. Common sense practices to avoid contact with diarrhea (from any animal) should be used, as much to prevent exposure to the pile of other pathogens that can be in dog poop, as to prevent potential exposure to canine norovirus.
An 8-week-old puppy in Van Buren County, Michigan has died from infection by a virus that normally infects horses. This is a rather rare occurrence of a nonetheless devastating infection. The puppy was euthanized after developing seizures and other neurological abnormalities, and Eastern equine encephalitis (EEE) virus infection was ultimately diagnosed. Testing for this and other viruses was probably undertaken because of concerns about rabies.
EEE virus is a mosquito-borne virus that circulates in the bird population and is spread by mosquitoes. Horses are the main victims of infection but disease can occur in various other mammals, including people and dogs.
Canine infections are very rare and this can be considered an "oddball" infection. There's no evidence that dogs are at any elevated degree of risk compared to previous years, but it is a reminder that while infections are rare, dogs can be susceptible to EEE. The puppy's young age probably played a role and certain groups (e.g. puppies, elderly dogs, dogs with compromised immune systems) are presumably at greater risk of illness than the normal dog population. The other obvious implication of this report is that it is clear that EEE is circulating in mosquitoes in the area. That means other susceptible species, namely horses and people, are also at risk of exposure.
EEE in people is pretty high on the badness scale. It's fortunately rare but when it strikes, it's usually fatal. The same is true for horses. There is a vaccine for horses but not for people, so the main protective mechanism for people is mosquito avoidance.
As with EEE in horses, infected dogs pose no real risk to humans. The virus is not spread by regular contact and dogs don't develop high enough viral levels in their blood to be able to infect more mosquitoes (who could then infect people). There's a potential risk of transmission through contact with infected tissues during post mortem examination (necropsies) but standard practices used to prevent transmission of other diseases (e.g. rabies) should be effective for EEE as well.
After being a relatively rare problem in most regions over the past few years, West Nile virus (WNV) case numbers have boomed lately, with large outbreaks in some US states.
Forty-nine (49) confirmed or probable human cases have been reported in Ontario, the largest number in a decade. Considering we're just heading into the typical peak WNV season, it's quite concerning as the worst may be yet to come. At this time last year, there were only 24 reported cases.
Human cases have been reported in at least four other provinces: Alberta, Manitoba, Saskatchewan and Quebec.
Two equine cases of WNV have been reported, one in Saskatchewan and one in Quebec. It's hard to have a lot of confidence in this number because of the poor surveillance and reporting for this disease in animals in Canada, given that the CFIA has largely washed their hands of dealing with it. Infection with West Nile virus has been pretty much a non-entity in most regions over the past few years, at least in terms of diagnosed cases, and it remains to be seen whether equine cases will mirror the spike in human cases this year. Typically the trends are similar each year, so the next few weeks will tell us a lot.
The US is in the midst of its largest WNV outbreak ever. At least 1118 human cases have been reported so far in at least 37 states, with at least 41 deaths. Typically less than 300 cases are reported by this time of year. Texas has experienced a huge outbreak, accounting for about half of the US cases.
There hasn't (apparently) been a surge in equine cases, with less than 100 cases of WNV reported in horses as of August 18. Whether that's because of infrequent testing, biological or geographic factors resulting in less equine exposure or vaccination of horses (remember that there is no WNV vaccine for people) isn't clear.
Concern is being raised about risks to pets, but the true risk is very limited. While WNV infections have been reported in dogs and cats, these are extremely rare and dogs and cats are failry resistant to the virus.
Often, when a new infectious disease emerges, the first year or two are the boom years, after which things settle down. That was the pattern with WNV in most areas; however, this year in on track to meet or surpass the numbers from those early years.
Why is this happening? No one knows for sure. Changing weather patterns, by chance or through the larger spectre of global warming, are probably playing a major role. Warmer temperatures let mosquitoes mature faster and allow the virus to grow quicker in the mosquitoes. Milder winters help mosquitoes survive. Any factor that fosters more mosquito numbers and growth, particularly the subset of mosquitoes that bites both birds (the reservoir of the virus) and people, can increase the risk of human and animal exposure. Changes in rainfall, wetland management, climate and human proximity to mosquito breeding sites can all play a role.
'Tis the season for ringworm, I guess.
The Guelph Humane Society has closed to visitors, and adoptions have been suspended in response to concerns about the potential for a ringworm outbreak. Implementing a proactive response, all animals are being tested for ringworm and all cats are being treated. While the scope of the problem isn't yet clear (and hopefully it's minimal), this type of response is the optimal approach because waiting to "see what happens" and waiting for culture results (which can take a long time) before deciding to take aggressive measures results is a much greater chance of things getting out of hand.
In an outbreak like this, the first week or so is critical. Introduction of an animal that's carrying ringworm is hard to prevent, as is limited transmission within a shelter (even with good routine infection control practices) from that first case. That's the non-preventable component of shelter diseases. However, it's the 2nd generation of transmission (transmission of ringworm from that initial animal or group of animals to the broader population) that leads to things getting out of control. That's the preventable fraction of infections, on which we can have the biggest impact. It's during this early phase where intervention is critical It's always better to have an overly aggressive response and simply tone it down after a few days, than to have an inadequate response that lets things spiral out of control.
More information about ringworm can be found on the Worms & Germs Resources - Pets page.
A few years ago, I looked out my kitchen window one holiday morning and saw a newborn foal running outside of a fence line. The foal had been born to my neighbours' mare, a maiden mare, and they were out of town. The mare had rejected the foal and wasn't interested in any of my attempts to get them back together. She also had little colostrum (the first, antibody-rich milk that foals need to drink early in life to survive). To make a long story short, I ended up doing a field transfusion, collecting blood from another horse on the farm to give to the foal, to provide it with those much-needed antibodies. The donor horse was healthy and I didn't know of any disease issues in the area, so I was pretty confident that there wasn't a significant risk of disease transmission, but you never know. Ideally, equine blood donors are screened for infectious diseases, particularly equine infectious anemia (EIA), since EIA is a rare but nasty disease that can be spread by blood.
When I started to read a report the other day about a transfusion-associated EIA infection in a German foal, my first thoughts were "that's bad," followed by my ever-optimistic side thinking "well, maybe it was an emergency transfusion and it was a bad but unavoidable consequence" or "maybe it the donor was properly screened but was infected with the EIA virus after it's last test" (the latter situation is an ever-present risk when you are screening donors in advance (days, weeks or months) of collecting the blood for transfusion, since test results only tell you what their status was at the time of testing).
Unfortunately, it didn't take long to see that this wasn't an unfortunate or relatively unavoidable infection. Rather, I can only interpret this as stunning negligence.
Here's the story
- On August 2, EIA was confirmed in a 3-month-old foal in North Rhine Westphalia. When the foal was two days old, it had a septic joint (and probably an overall deficiency in antibodies) and was treated with a plasma transfusion, which is a pretty standard procedure in such a case.
- EIA antibodies were then detected in the donor.
- Since 2009, 20 other horses had received plasma from this horse. Four have been confirmed as infected, and horses that live with these infected animals have been quarantined until test results are back. Positive horses are typically euthanized because they pose a lifelong risk of transmission of the virus to other horses. The four positive horses in this case have been euthanized (and presumably the foal as well).
So, this wasn't some random emergency field transfusion, or a donor that got infected after testing. It appears that this donor has been used for years with no testing, despite the fact that it's well known that EIA transmission is a risk from blood transfusions and the virus is present (albeit rare) in Germany. While there are no standards of care for equine blood transfusions (as opposed to dogs), EIA testing is a standard recommendation in anything I've seen written about equine blood donor programs (click here for one example). Sometimes you get put into situations where testing can't be done in time for logistical reasons, but I can't see how anyone would not test horses that are to be used for a formal donation program or repeated transfusions. Failure to do low cost and easy EIA screening of that donor horse has resulted in the deaths of multiple horses, with the potential for even broader secondary transmission of this virus to additional animals.
The scope of the outbreak isn't really clear from press reports, but "a couple" of other animals now have signs of the skin disease. Investigation of the timing and likely sources of exposure of new cases is crucial. They may just be animals that were infected early, before the problem was recognized (the best case scenario) but investigating these "new" cases is very important because if these animals were exposed after the outbreak was identified, then there are problems with containment.
Shelter personnel have declared that they aren't planning on euthanizing more animals, but the shelter remains closed for adoptions. Stray animals will continue to be accepted. This creates a tricky situation where new animals (e.g. fuel for the fire, if things aren't under control) come in and can actually propagate the outbreak. It also creates overcrowding issues since the shelter was probably pretty full to start with, and continuing admissions with no adoptions can't be maintained for long. The shelter is looking at renting units in which to put animals - this is a relatively common approach for creating more contained spaces, and one that can be useful if good infection control practices are in place (although I've seen too many outbreaks where the offending pathogen quickly makes its way into the new units). Clear policies, sound training, careful supervision, exquisite planning and good communication are critical for making a situation like that work.
While the shelter has gone from an unrealistically optimistic time frame to a warning about long-term efforts, as with most things in life, the middle ground is usually the most accurate. Ringworm outbreaks can't be declared over in a few days (it's possible to contain it in a short period of time, but not declare an outbreak over). A few days isn't even enough time to get culture results back to figure out exactly what's happening. Testing, isolation, cohorting, mass treatment, evaluation of training, evaluation of infection control practices, and similar measures are needed, but if done right, an outbreak can be contained in a reasonably short period of time. Given the need to repeatedly treat all animals (affected animals are being bathed every three days with a medicated solution) and the time lag for ringworm culture, it's going to take at least a few weeks, but let's hope this outbreak ultimately gets measured in weeks rather than months.
It might just be my perception, but it seems like there are a lot more reports of nasty dog bite infections in the news lately, particularly infections caused by the bacterium Capnocytophaga canimorsus. I don't know whether that's because they are becoming more common, more commonly diagnosed (since the bug is hard to identify), more commonly reported in the press or a combination of all three (or whether my perception is simply incorrect).
The latest report is from Omaha, Nebraska, where a 50-year-old man died four days after suffering a minor dog bite on the cheek. The cause of infection wasn't reported, but the article says that he was unable to fight the infection because he didn't have a spleen. For me, minor bite + fatal infection + no spleen = Capnocytophaga infection until proven otherwise, since this is a textbook description of such an infection, and Capnocytophaga can be found in the mouth of virtually every dog.
This follows the high-profile case of a cancer survivor who lost her hands and feet from Capnocytophaga infection complications and a UK inquest into the death of a man caused by infection with this bacterium, among other cases.
Here are the simple take home messages:
- Avoid bites and any interactions whereby dog saliva may come in contact with non-intact skin.
- Know if you are at high-risk for an infection caused by a bug like Capnocytophaga. This bacterium typically doesn't cause disease in healthy individuals but can produce rapidly fatal disease in certain people.
- Realize that minor bites can cause major problems (even if you are otherwise healthy).
- Use good first aid practices if you or someone you're with is bitten, including careful washing of the wound and seeking medical care if you are at increased risk of infection, or if the bite is over the hands, feet, face, joints or other sensitive areas.
The facility was closed to the public on August 4th because three cats and one dog were showing unspecified signs of ringworm.
Samples were collected for testing, but they decided to euthanize the 4 animals.
"You’re kind of under the gun to decide what you want to do,” said their operations manager. I can certainly empathize. It's not easy to deal with an outbreak. However, from my standpoint, if you feel like you're under the gun in that kind of situation, you're likely to make (or to have already made) mistakes. If you're managing the situation well, getting advice and following standard practices, you may be stressed, exhausted, humbled and concerned, but you shouldn't feel "under the gun." Maybe euthanasia was warranted here, but with a small number of infected animals, the ability to potentially isolate and treat them, and lots of information about how to manage ringworm to avoid further spread, it's important to avoid a panic response that leads to premature euthanasia decisions.
The three cats that were euthanized apparently did not have ringworm, but the shelter is "certain" (not sure how) that the dog had ringworm. Sudden onset of skin lesions in dogs and cats at the same time is certainly suggestive of ringworm, and if the dog was truly infected, it's hard to believe the cats were not (especially since cats are most often affected in ringworm outbreaks compared to dogs). So I wouldn't be too quick to rule out ringworm in the cats. Ringworm culture can take a couple of weeks, so it's not clear to me whether this interpretation is based on culture results or not.
"With the results being better than expected, the humane society will not have to move larger numbers of possibly infected animals to a different facility — the usual procedure in an outbreak." While I can't say too much from a distance, I can say that moving animals to another facility is certainly not a typical outbreak response measure. It's an effective outbreak propagation measure, since it can easily disseminate ringworm to other places, so it's good to hear that they are not planning on moving animals. It's much better to manage things well at one site than to have to manage things at multiple sites.
They state that "the situation now appears to be under control." Hopefully that's true, but it's way too early to say. You can't declare an outbreak over a few days after you declare that it started. There hasn't even been enough time for any animal or environmental ringworm culture results to come back. Closing, testing, treating all exposed animals and thorough cleaning and disinfecting of the environment can be a great start, but trying to say "we won" too early often leads to inadequate response and continuation of the outbreak.
"We’re keeping our fingers crossed and hoping that everything comes back negative so we can be open for business sometime next week" Again, I'm not involved and I'm working with sparse information, but this seems to be way too early to reopen the shelter. You need to make sure things are really under control before you get out of "outbreak mode" and before you can be "open for business" again. That's especially true with a disease like ringworm that is highly transmissible and can be spread to people. Too often, a small outbreak is identified and declared over prematurely, only to be followed by a big mess in short order. Let's hope that's not the case here.
Image: Photo of a dermatophyte-positive culture specimen, which can take two weeks or longer to grow.
If I was reincarnated as a mosquito, I'd want to live where I do now (convenient, eh?). I live in the country surrounded by areas of "protected wetland," which, in many cases, is a fancy word for swamp. I try to avoid mosquitoes, but getting bitten is a regular (daily) event. As I was getting swarmed last night, I was thinking that the mosquito-borne disease I'm really concerned about is Eastern equine encephalitis (EEE). While quite rare in Ontario, with only a handful or no cases in horses every year, it's a worry because it's almost always fatal. It also affects people, not via transmission from horses but from being bitten by mosquitoes that pick up the virus from birds. It's very rare in people, but it's highly fatal.
This is the time of year that we start seeing mosquito-borne infections in Ontario, and a Disease Alert from the province re-inforces concerns about EEE. The alert was issued in response to a case of EEE in a horse in New York state, not far from the Canadian border. The horse, from the Ogdensburg, NY area, showed signs of illness on July 23 and died the next day (a pretty typical progression for this disease). Since mosquitoes don't respect borders, cases in this neighbouring region suggest that infected mosquitoes might also be active in Ontario.
EEE isn't the only mosquito-borne virus that we worry about - West Nile virus being the other main issue around here - so mosquito control and avoidance are important. While you can never guarantee that you or your animal will not encounter a mosquito, various things can be done to reduce mosquito numbers (e.g. eliminating sites of standing water (which are mosquito breeding sites) wherever possible... swamps being a logical exception) and to reduce the risk of being bitten (e.g. avoiding high risk areas and times, long clothing, mosquito repellants). Vaccines are available for EEE and West Nile virus in horses (but not people), and the risk of these diseases should be considered when designing a horse's vaccination program.
As with most "pocket pets," guinea pigs don’t get a lot of attention in the scientific literature. As a result, we are limited in what we know about certain diseases in this species, and we tend to rely a lot on personal experience, small case studies and extrapolation from other species. It’s not that these sources of information are bad, they’re just not a replacement for larger, more controlled studies.
A recent study in the journal Mycoses (Kraemer et al. 2012) provides a rather comprehensive overview of ringworm (dermatophytosis) in these little fuzzy critters. The authors surveyed 74 owners of guinea pigs with ringworm and veterinarians. Here are some highlights from the results:
- 97% of ringworm infections were caused by Trichophyton mentagrophytes. Ringworm can be caused by a few different species of fungi, with a different organism, Microsporum canis, being most common in dogs and cats.
- 43% of the time, a new guinea pig was introduced into the household in the weeks preceding the onset of disease, and around one-third of affected guinea pigs had been in the household for less than 3 months. That’s not too surprising, since new animals are often a prime source of infectious diseases. It shows the importance of ensuring that new pets are examined carefully and are healthy before they are brought into the household. It’s certainly no guarantee that there won’t be problems, since healthy-appearing animals can be shedding various infectious agents, but it helps reduce the risk.
- Ringworm lesions were most common around the head. Hair loss was the most common sign, with scaling and crusting also common.
- Signs of ringworm were also present in other guinea pigs in the household in over one-third of cases.
- Various treatments were used and some animals weren’t specifically treated. In fact, 7/8 of the guinea pigs that did not receive specific anti-fungal therapy got better. It's known that ringworm can be self-limiting (meaning the animal will get better on its own over time). However, treatment can speed the process up and decrease the likelihood of transmission to other animals or people.
- In 24% of cases, people in the household also had signs of ringworm, on the head, neck and arms. Children were most commonly involved. That’s not too surprising since kids probably had more contact and closer contact with the animals than their parents.
While not a severe disease, ringworm is a problem because it’s highly transmissible. It can easily and quickly spread between animals, and between animals and people, and elimination of ringworm from a highly contamination household can be a major hassle. Presumably the risk of widespread environmental contamination is less with guinea pigs compared to dogs and cats because of their smaller size and tendency to be kept confined to cages most of the time.
Ringworm should be considered in any guinea pig that develops hair loss or other skin/hair problems. This is particularly true if it’s a new acquisition or if a new guinea pig has been introduced to the household recently.
If ringworm is suspected, a prompt visit to the veterinarian is in order. The guinea pig should be handled sparingly (or ideally, not at all) until the cause of the skin disease is identified. Close attention should be paid to hand hygiene, and even the use of gloves could be considered, although gloves aren’t a cure-all and people sometimes misuse gloves to such an extent that they actually increase the risk of spreading disease.
If a new guinea pig is obtained, it’s ideal to have it examined by a veterinarian before it comes into the household. I’m a realist and realize this is unlikely, but it’s ideal. In lieu of that, it’s important to get a guinea pig from a reputable source, to ensure that other guinea pigs from the same source don’t have skin disease, and to carefully examine the animal for skin lesions before it gets home. It’s also ideal to keep any new guinea pig in its own cage for a couple weeks to act as a quarantine period and allow for identification of any incubating diseases.
If owners of an infected guinea pig develop skin lesions, they should be examined by their physician, and make sure the physician knows they have been in contact with an infected animal.
Sometimes, I get a little concerned when research papers get picked up by the press. It's not necessarily because the research is weak, it's just that results sometimes get overstated or misinterpreted when they work their way outside of scientific forums.
A paper published in the latest edition of the American Journal of Veterinary Research is one of those. The paper (Tsuchiya et al. 2012) describes a study that looked at the impact of interferon-alpha (used to stimulate the immune system) and enrofloxacin (an antibiotic) on body temperature and lung fluid white blood cell counts in 32 horses that were shipped for approximately 26 hours in commercial vans. Horses either received just interferon or interferon and enrofloxacin before being shipped.
- After shipping, 3 antibiotic-treated and 9 untreated horses developed fevers. That's actually not statistically significant, by my calculations, and it's quite strange that the authors didn't do that analysis (and that the reviewers didn't pick that up).
- Two antibiotic-treated and 7 untreated horses were treated with antibiotics after arrival because of concerns about infections. Again, that's not statistically significant and it's surprising (and concerning) no one pointed that out.
- Overall, the average temperature of horses in the treatment group was significantly lower after arrival, but the clinical relevance of that is questionable since it was only a 0.4 C difference. Further, it's hard to say what a temperature immediately after arrival really means, since that's pretty early for a bacterial infection to have developed.
- There were significant differences in tracheobroncial fluid (fluid collected from the airways) between the groups, with lower white blood cell counts in the treated group. That's an interesting finding and is consistent with less inflammation. What that means in terms of disease prevention is harder to say, but it's something worth investigating further.
- There does not appear to have been any difference between the two groups in the ultimate health status of the horses.
This study provides some interesting information to help us think about how, when and why infections and inflammation develop after shipping. Results suggest that antibiotics might be useful in certain situations, but many questions remain. Any antibiotic use runs some risk of complications such as antibiotic-associated diarrhea. It also increases the risk of antibiotic resistance (and ultimately more problems trying to treat disease). We have to remember these issues when considering these results. Further, while it is typically much better to prevent disease than treat it, in situations like this, it's hard to say whether mass prophylactic treatment is actually preferable to early treatment, since horses can be observed closely after arrival and treated when early signs of disease develop. Ultimately, it's still not even clear from these data whether pre-treatment with antibiotics actually does have a positive clinical effect.
It's important to remember what this study tells us, and what it doesn't. Despite what some lay articles that have picked up the story say, it doesn't mean that antibiotics are broadly useful for keeping shipped horses healthy. The authors address this by stating "The use of enrofloxacin raises concerns regarding the emergence of antimicrobial-resistant bacteria, and it is important that antimicrobials such as enrofloxacin are not used inappropriately. The guidelines for enrofloxacin use in the Japan Racing Association’s medical office require that it is only administered as prophylaxis against transportation-associated fever when the duration of transportation is expected to be ≥ 20 hours and the horse has had clinical signs of transportation-associated fever before or is considered to be at risk for developing transportation-associated fever (eg, if the horse has undergone laryngoplasty or has a history of pneumonia)."
Regarding the big picture, however, this should make us think again about how we manage horses. Antibiotics should never be used as a crutch in place of good management. In a situation like this, where 19% of horses treated with interferon and enrofloxacin and 56% of horses treated with interferon alone get sick, something's wrong. Antibiotics may be an easy way to try to reduce the likelihood of disease in some situations, but that doesn't mean it's a good idea. Considering the number of horses that get sick (and die) every year from shipping-associated illness, maybe we need to rethink how they are transported. Is lack of antibiotics the problem, or is it how (and how long) horses are shipped? Maybe long, interrupted trips aren't a good idea, antibiotics or not.
Q-fever, a serious disease caused by the bacterium Coxiella burnetii, is an important concern at petting zoos because small ruminants (sheep and goats) are commonly present at these events and they are the major source of this pathogen. The risk is greatest around adult animal at the time of birthing, and around the new lambs and kids (baby goats), because this is when large numbers of highly infectious Coxiella can be shed. That’s one of the reasons why pregnant small ruminants shouldn’t be part of any petting zoo, but unfortunately this particular recommendation is widely disregarded.
Other than petting zoos, the general public can also have contact with small ruminants through various other routes. An outbreak of Q-fever in the Netherlands (a country with serious Q-fever problems) was reported in association with one of these atypical events, namely "lamb viewing days" on a farm (Whelan et al, Epi Infect 2012).
This farm was open to the public every year during lambing season, and attracted about 12000 visitors from the area annually. Visitors could watch lambs being born (if the timing was right) and interact with young lambs. After finding a cluster of Q-fever cases in the region, an investigation ensued, which compared people who were diagnosed with Q-fever in the region to a group of people without Q-fever. Here are some of the highlights:
- 21% of people with Q-fever reported visiting the farm compared to just 1% of controls.
- When various other factors were controlled in the analysis, having visited the farm meant someone was 43.3 times as likely to have Q-fever compared to someone who didn’t visit the farm.
- Coxiella burnetii was identified in numerous sheep, as well as from 7 of 8 air samples collected on the farm. (Coxiella is a very small, hardy organism that can resist drying, and it can therefore often be found in the dust in the air in areas that have a lot of environmental contamination, like pens where goats and sheep give birth.)
- Specific contacts (e.g. holding a lamb, witnessing a birth) were not identified as risk factors, but the small sample size of people that reported what types of contact they had may have limited the ability to detect a difference.
Visiting farms and having contact with farm animals shouldn’t necessarily be considered a high-risk behaviour. In fact, in some ways it’s a good thing. Greater contact between people and animals and a better understanding of farm animals can be very beneficial. However, we’ve known for a long time that some situations pose an increased and unnecessarily high risk. People organizing farm encounters or petting zoos need to take some basic precautions to reduce the risk to visitors. These are pretty simple and can be done without significantly affecting the visitors' experience. Visitors also need to take some responsibility themselves and follow recommendations, like practicing good hand hygiene and keeping food and drink out of animal areas (just to name a couple). Additionally, the more visitors know about risks and preventive measures, the more they can pressure facilities into doing things right. Public health personnel can work hard to try to improve petting zoos and other events, but nothing will change things quicker than an informed public withholding their money from places that put them at unnecessary risk.
When I'm giving talks about zoonotic diseaes to people in the human healthcare field, I sometimes mention tuberculosis (TB) as an example of a serious human disease with poorly defined (but theoretically important) risks of transmission between people and pets. TB is a very important disease of increasing of concern because of its resurgence in many areas and the spread of drug-resistant strains.
We don't know much about TB and pets. There are some older studies that provide conflicting information, suggesting that Mycobacterium tuberculosis, the bacterium that causes TB, can be commonly or rarely isolated from dogs owned by TB patients.
A recent study from South Africa (Parsons et al. Research in Veterinary Science 2012) provides more information. The study involved two main components:
- For the first component, they examined 100 stray dogs in Cape Town, South Africa, for evidence of TB. The dogs were being euthanized for population control purposes so the researchers were able to do necropsies (post-mortem exams) to look for the bacterium and signs of disease that may not have been outwardly apparent. They isolated the bacterium from 4% of the dogs, with only one of those having any signs of disease. That shows that TB is present in dogs in the area, albeit at a low rate. The fact that 3 of 4 TB-positive dogs had no evidence of disease is both good and bad. It's good for the dog's health that illness doesn't always occur (just like in people), but it also means that apparently healthy dogs can be carrying this concerning bacterium. The risk of transmission from healthy carriers isn't known. It's probably rather low since close and prolonged contact are required to transmit TB between people, and healthy carrier dogs are probably not shedding many TB bacteria through their respiratory tract. Greater concerns are probably present in dogs with TB infection of the lungs who are coughing and spewing TB bacteria into the air.
- The second component of the study involved testing of 24 dogs living with people with TB. They used two different tests: the TB skin test (a test that's commonly used in people but one that's been typically considered useless in dogs) and an interferon gamma release assay (IGRA)(a test more commonly used now in humans). They concluded (not surprisingly) that the skin test was pretty useless, but their data suggest the IGRA may be a good test for dogs. 50% of dogs in those households had evidence of TB exposure through IGRA, consistent with one older study that indicated transmission of TB from people to pets may be common.
What are the implications of all this?
For the average person and pet, not much. TB transmission requires close and prolonged contact with an infected individual. You don't get it walking down the street behind someone with TB.
The concern is in situations when people with TB may have contact with pets - the same concern as in situations when people with TB may have contact with other people. The potential for transmission is something to pay attention to in households where there is an infected person, or in populations where there may be high TB rates and common pet contact (e.g. some homeless populations).
Results of this study should be a reminder that when considering who's potentially been exposed to a person with TB and making plans to reduce the risk of transmission, you need to consider all individuals - human and animal - with which the person has contact. Therefore, measures taken by people to avoid transmission of TB to other people should be equally applied to reducing transmission to pets. Pet exposure should always be considered, particularly when dealing with multidrug-resistant (MDR) or extensively drug-resistant (XDR) TB, since such strains are huge concerns in people and we don't want to create canine or feline vectors of these strains. The study results also indicate that pets owned by TB patients may be at increased risk of disease from TB, not just at risk of being infected and harbouring the bug. Therefore, knowing that a pet has had close and prolonged contact with a person with TB is relevant to veterinarians when evaluating sick animals.
Plague cases tend to get a lot of press. The fact that this disease killed a large percentage of the human population in a few different pandemics (albeit centuries ago for the most part) probably plays a role in that. Despite the impression by some that it's just a historical disease, plague is alive and well in certain parts of the world, including parts of the US, and infects a few thousand people every year.
Plague is caused by the bacterium Yersinia pestis, which lives in various wild rodents and is circulated by fleas. Transmission to people historically has been via fleas that jump from rats to people. However, plague isn't just a rat-human disease, as it can infect other animal species. Among domestic animals, cats seem to be most commonly infected, probably because of exposure while hunting.
The problem with plague and pets has been shown once again a case of plague in an Oregon man who likely picked up the infection from his cat. (Oregon is outside of the main range of plague in the US, where the disease is most common in the southwest). The man was bitten by the cat while retrieving a dried, decayed mouse carcass from its mouth. He developed septicemic plague (infection of the bloodstream), and then pneumonic plague (infection of the lungs), which is the worst case scenario. At last report, he was in critical condition and the prognosis for survival is probably guarded.
There's no mention of the cat's health. Most cases of cat-human plague occur in people taking care of sick cats (especially veterinarians). If a person is infected by a cat bite, I would expect the cat to have been sick with plague, although transmission has been reported from apparently healthy cats. Some other possible routes may need to be considered. If the cat in this case was exposed to plague, then plague's obviously in wildlife in the area, so you have to consider that the infected man might have been bitten by an infected flea (that came directly from an infected wild animal or that the cat tracked in) or from direct contact with wildlife, especially if his house had a rodent infestation.
Regardless, it's important for people in plague-endemic (and neighbouring) areas to be aware of plague and take measures to reduce the risk of exposure for themselves and their pets, such as:
- Avoid contact with wild rodents (and wildlife in general, since larger wildlife species can also be infected).
- Keep cats inside.
- Don't let pets with outdoor access roam unobserved, where they might be more likely to encounter wildlife.
- Have a flea control program for pets.
- Address any animal/household flea infestations promptly and aggressively.
- Make sure sick pets get prompt and appropriate medical attention, since diagnosing plague in a pet may be a critical factor in prompt treatment of people infected by the pet. Plague is an example of a disease for which diagnosing infection in the pet might save the owner's life.
From one of my grad students who, contrary to his claim, maybe does spend too much time on YouTube.
While I guess it's getting beyond the point where Hendra virus infections in horses in Queensland, Australia are considered "news," it's still a highly concerning situation. Infections caused by this fruit bat-associated virus continue to occur in the region and there's no sign that this problem is going to go away any time soon.
In the latest report, two horses from a farm where a horse recently died of Hendra tested positive for the virus. In another location, a dog is being re-tested after a weak positive test. This situation brings back memories of the debate that occurred last year after a healthy dog that tested positive was euthanized as a precautionary measure, despite no information about whether the dog could actually be a source of infection.
Hendra is resulting in profound changes in the horse industry in Queensland. Beyond being a major problem in horses, this virus can be passed from horses to people, resulting is tremendous concerns amongst horse owners and veterinarians. Many veterinarians are refusing to work with horses because of the risk and I assume that some people are selling horses for similar reasons.
Infection control practices can presumably reduce the risk of transmission of Hendra virus between horses and from horses to people, but there's no way to completely eliminate the risk. Fruit bat control strategies get discussed, ranging from removal of fruit trees from horse pasture to reduce fruit bat exposure (logical) to fruit bat culls (highly unlikely to have any longterm effect). At a minimum areas under fruit trees should be fenced off from horses, and it has also been recommended to keep water troughs covered to prevent contamination with excrement from the flying foxes. Ultimately, everyone's holding out for an effective vaccine, which has yet to appear, but work on the vaccine is well underway and the hope is that a commercial vaccine could be released as early as next year.
Local media are reporting an apparent case of West Nile virus infection in a horse in Northampton County, Pennsylvania. This is surprising since, while I know there are certainly mosquitoes emerging early with this mild weather, seeing active mosquito-borne infections at this time of year would be very unusual. That's particularly the case with West Nile virus, since it tends to be a late summer and fall disease based on the mosquito types that are predominant at that time of the year.
Information about this West Nile virus case is pretty sparse. The report simply says the horse was euthanized because it was "suffering from the virus." Knowing if and how it was actually diagnosed is important to determine whether it was truly an active infection or a false-alarm, like this winter's report of West Nile virus in British Columbia.
Regardless, it's still a good reminder that we are now heading into the time of year when we have to think about mosquito-borne diseases in various species (including people). Measures to reduce mosquito populations, such as eliminating standing water (see picture), and mosquito bite avoidance are always good, regardless of what diseases are currently being diagnosed.
Image source: www.saskatoonhealthregion.ca
Authorities in Hawaii are advising people in Oahu to eliminate standing water as a mosquito control measure. While it's always a good idea, it's of particular concern in this case bacause a rare type of mosquito, Aedes aegypti, was found around the Honolulu International Airport. This mosquito species is a highly effective vector for various infectious diseases, including dengue fever and yellow fever.
What does this have to do with companion animal disease? Well, nothing directly, but it's a good reminder of how infectious diseases can easily reach a distant area (even Hawaii) in a short period of time.
There are a plethora of mosquito-borne diseases out there, and presumably we don't even know about many of them. Mosquitoes don't fly very far, which helps contain these diseases to certain areas. However, mosquito-borne diseases can still spread over wide ranges if either the pathogen or the mosquitoes are hitch-hiking.
A common way for pathogens to travel is in various kinds of animals (especially birds) that can harbour the pathogen (usually a virus) and infect mosquitoes in distant areas.
Modern transportation can be an effective vehicle for pathogen-laden mosquitoes. Theoretically, all it takes is for a single infected mosquito to hop onto a plane and survive the flight to a new region. If the mosquito bites a susceptible host, it can cause a rare disease - that's of particular concern since it's unlikely that an exotic foreign disease in someone who has not left the country would be promptly diagnosed (and therefore promptly treated). Even worse, the disease could establish itself in the new region if a series of things happen:
- The mosquito has to bite something or someone.
- That something or someone has to be susceptible to the pathogen and that pathogen needs to grow inside the host's body to high enough levels that it can infect another mosquito.
- Another mosquito that can carry the pathogen must come along, bite the infected individual and acquire the pathogen.
- The new mosquito must then find another susceptible host to bite.
- The above needs to be repeated enough times that the pathogen establishes a foot hold in the area and starts causing disease.
Is this common? No.
Is it possible? Yes.
West Nile virus is an example of what can happen. This mosquito-borne virus came out of nowhere in North America in the early 2000's and caused widespread illness and death in humans, horses and various other species. Did it arrive via a mosquito on a plane? No one knows, but it's certainly a possibility.
Botulism outbreaks in horses are usually bad news. Horses are very susceptible to botulism, and outbreaks in horses caused by contamination of food often end up killing multiple horses on a farm. The recent botulism outbreak in Reddington, IN is another reminder of how deadly it can be.
The outbreak involved a family that lost five horses to suspected botulism. "Suspected" because this disease can be hard to confirm sometimes, although it's usually possible to make a pretty solid presumptive diagnosis based on how the horses look and by ruling out the few other possible causes. The details are pretty sketchy. Apparently there are some other sick horses, but how sick they are and how many isn't clear.
Botulism occurs in two ways. In adult horses, it almost invariable occurs after ingestion of the extremely potent botulinum toxin produced by the Clostridium botulinum bacterium. In foals, it usually occurs after ingestion of the bacterium, which then produces toxin in the foal's intestinal tract.
In adults, outbreaks are usually associated with contaminated feed. There are some high-risk feeds like haylage and silage (see photo) that we usually focus on first, but sometimes botulism toxin can be found in hay or other common feeds. Haylage, silage and other fermented feeds become a problem with they are improperly fermented, allowing the Clostridium botulinum to grow and produce its toxins. Sometimes, contamination of feeds can occur when an animal that has died of botulism (and has the bacterium and its toxins in its body) gets incorporated into hay or other feedstuffs.
When an outbreak is suspected, a key step is removing any potentially contaminated feeds to reduce further exposure, although often it's too late by the time the disease is recognized. Antitoxin (which is pre-formed antibodies that help neutralize the botulinum toxin) can be given to exposed horses, but it's extremely expensive and does not reverse any damage that's already been done. That's why these outbreaks are often so disasterous, because when the diagnosis is made the only thing left to do may be damage control to try to save some of the less affected horses. That's tough because botulism has a very high mortality rate in horses.
The farm owners in Reddington are urging local horse owners to be on the lookout for botulism. It's reasonable, but rarely do we see multi-farm outbreaks from botulism. They also state that botulism doesn't affect cattle, which is wrong. Cattle are more resistant than horses, but they certainly can get botulism.
A botulism outbreak in horses poses little risk to people. People are susceptible to this horrible disease as well, but to get it someone would have to ingest the same contaminated feed that the horse did. There's no risk of transmission of botulism from an infected horse to a person or another animal.
An interesting and frankly somewhat scary report in an upcoming issue of Veterinary Microbiology (Clegg et al 2012) provides further information suggesting that cats might be a source of canine parvovirus infection. This potentially fatal infection, which typically affects young unvaccinated (or inadequately vaccinated) puppies, is a major problem, and outbreaks occur (not uncommonly) in some high-risk populations like shelters.
In the 1970s, a new form of canine parvovirus, CPV-2, emerged and rapidly spread worldwide. That predates my veterinary career but I've heard stories of clinics where you couldn't turn a corner without stepping on a dog that was hospitalized for treatment of parvo, since it was a new disease and vaccines were not yet available. CPV-2 was shown to be able to grow in cat cells in the lab, but not in live cats, so it was generally assumed that dogs had CPV and cats had their own closely related virus, feline panleukopenia virus (FPLV). However, new variants of CPV-2 have emerged over time, and these seem to have a greater ability to infect cat cells in the lab, and disease caused by these strains has been reported in cats both experimentally and in limited real-world situations. However, it was still considered an uncommon event and the role of cats in parvovirus infection of dogs was largely thought to be inconsequential.
Or maybe not.
In this new study, researchers collected fecal samples from 50 cats in a cat-only shelter, and 180 samples from 74 cats at a shelter than housed both dogs and cats. Canine parvovirus shedding was identified in 33% of cats from the cat shelter and 34% of samples from the dog/cat shelter. A concern with a study like this is cross-reaction of tests for CPV and FPLV, but they went a few steps further to confirm that the virus was indeed CPV, not its feline relative. They also showed they could grow the CPV from fecal samples in cells in the lab, which means they were detecting live virus in the animals, not just dead viral bits working their way through the cats' intestinal tracts.
The results are interesting and concerning, since they showed that a pretty large percentage of cats in some situations could be shedding live CPV, making them a potential source of infection for dogs (and possibly other cats).
What makes this even more concerning is the duration of shedding that they identified when they collected samples from the dog/cat shelter over time: cats shed the virus for up to 6 weeks, despite appearing healthy.
This raises concerns about the potential role of cats in the spread of CPV. Cats and dogs don't tend to mix much in parks or outside, but CPV is a very tough virus that can survive for a long period of time in the environment. It's certainly plausible that cats could be depositing CPV-laden feces in the outdoor environment, and since the virus can survive the outdoor exposure and some dogs are notorious poop-eaters, it's a route of transmission that can't be dismissed. Cross-contamination within shelters is also a concern.
The true role of cats in canine parvovirus infection isn't known and it's probably quite limited compared to dog-to-dog spread. However, this study shows that we at least need to be thinking about it and considering cats when dealing with parvovirus problems in shelters and households.
Some things to think about:
- Young puppies should be kept away from cats, especially strays and cats from shelters, until they are properly vaccinated.
- Parvo is one more reason to have good physical and procedural separation between cats and dogs in shelters.
- If a parvo outbreak in underway in a facility, prevention of potential cross-contamination from cats is required.
- If a cat has been in contact with a dog with parvo, it should probably be considered potentially infectious and kept away from susceptible dogs for at least a few weeks.
- Canine parvovirus vaccination is highly effective in dogs. If a dog is properly vaccinated, the risk from cats (or other dogs for that matter) is minimal.
Pasteurella multocida is a bacterium that's commonly found in the mouths of dogs and cats. It's a common cause of cat and dog bite infections in people, but can also be spread through close contact with pets (without bites). It's logical to assume that the closer the contact, the greater the risk of transmission. A recent report in Clinical Infectious Diseases (Myers et al 2012) describes three people with life-threatening Pasteurella infections. A unique aspect was all three people got sick from nursing dying pets.
- A 55-year-old woman with sore throat, fever and difficulty swallowing was diagnosed with epiglottitis (inflammation of the epiglottis, a part of the throat region) and hospitalized. Pasteurella multocida was identified on a blood culture. It was subsequently revealed that she had provided palliative care to her dying dog. As part of this, she was dropper-feeding the dog honey, and also eating honey with the dog from the same dropper.
- A 63-year-old woman with sore throat, difficulty swallowing and hoarseness was diagnosed with uvulitis (inflammation of a different part of the throat region) and narrowing of her airway. As with Case 1, P. multocida was isolated from her blood. Her cat had died six weeks earlier and she had "continuously held, caressed, hugged and kissed her cat during its last 7 days of life."
- A 66-year-old woman was hospitalized with fever, chills, cough and difficulty breathing. She had severe pneumonia and P. multocida was grown from a sample of respiratory secretions. Two weeks before she got sick, she had provided palliative care for her dying cat, by "holding, hugging, and kissing the head of the cat and allowing the cat to lick her hands and arms."
Fortunately all three women recovered from their infections, but the severity of disease is certainly a concern. As is common, there was no attempt to see whether the implicated pets actually carried the same Pasteurella multocida strain as the owners, but here the authors at least had a good excuse, since all of the pets had died before the owners got sick.
There are some interesting points in the Discussion section of the paper.
"Our 3 patients’ histories of having recently provided palliative pet care to their dying animals were obtained only after P. multocida was identified in cultures and only after subsequent detail-oriented, animal contact histories were obtained."
- Pet contact (or animal contact in general) is still not asked enough by physicians investigating unknown illnesses. It's unclear whether it would have made a difference in these cases, but knowing more and knowing it earlier can help speed the path to the right diagnosis. Here, pet contact was only considered after a pet-associated bacterium was identified.
"Simply asking whether or not the patient had a pet would not have uncovered the defined association of these respiratory illnesses with palliative pet care. The patient with P. multocida uvulitis even denied having a pet (it had died 6 weeks previously) and only admitted to having provided palliative pet care when asked specifically if she had any animal contacts in the past 3 months."
- This shows some of the challenges and how care must be taken when asking about pet contact. Simply asking "Do you have a pet?" doesn't cover it.
"Only diligence and very detail-oriented, pet-related histories will likely uncover further patients with invasive P. multocida infection related to the pet owner’s provision of palliative pet care to dying animals."
- This shouldn't be focused on palliative pet care, since that's a minor component of pet contact. Many other people have close contact with their pets, even when the pets are healthy. It's something that should be considered at all times.
Although the weather in Southwestern Ontario seems quite confused lately regarding whether it wants to be winter or spring, at least we're still a few months off from having to worry about mosquitoes and the viruses they carry once again. Warmer parts of the world, however, are in the midst of their mosquito season, and some chickens are lending a hand to give people in the area a "heads up" about what's around.
The Health Department of Western Australia has detected Murray Valley encephalitis virus (MVEV) in chicken flocks in East Kimberley. The department has also tested and found the virus in its sentinel chickens in Wyndham and Kununurra. These sentinel birds play an important role as an early warning system when viruses like MVEV are circulating in the area. Just like West Nile virus, MVEV typically circulates between birds and the mosquitoes that like to feed on them, but problems occur when the same mosquitoes start to bite people (or other susceptible animals such as horses), particularly when there are a lot of mosquitoes, like when the weather is very wet or when there's been flooding. Although most people who are infected with MVEV or WNV fight off the virus with no difficulty, or may simply develop short-term, non-specific signs of illness like mild fever and malaise, in some people these viruses can cause severe infection of the brain (encephalitis) and may even be fatal.
Knowing that MVEV has been found in these "guardian" chickens lets people know (via warnings issued by the health department) to take extra precautions against mosquito bites, such as:
- Staying indoors during peak mosquito activity - dusk and dawn
- Wearing protective clothing including long-sleeves and long pants
- Applying insect repellent
In North America, you can pretty much substitute West Nile for Murray Valley in a case like this. Sentinel chickens have been used to provide early warnings of circulating WNV here, before cases are detected in people or horses. Another means of early detection that is also used is testing pools of mosquitoes directly.
It just goes to show you can still be an important part of the country's defenses, even if you're a little chicken :p
Pigeon fever is an equine disease that doesn't have anything to do with pigeons. It's an infection caused by the bacterium Corynebacterium pseudotuberculosis which results in the formation of abscesses, usually along the chest (pectoral region) and lowest part of the abdomen. The name "pigeon fever" comes from the swelling in the chest region that vaguely resembles a pigeon-breast. A recent report describes and outbreak of pigeon fever involving at least 30 horses in Louisiana, bringing the estimated number of cases in the state in 2011 to over 100.
Pigeon fever is a regionally (and to a lesser degree seasonally) variable disease. It predominantly occurs in California, but over recent years it has expanded its range in the western US, and from this report, it's obvious that it has a good foothold in some other areas in the south east as well.
Corynebacterium pseudotuberculosis lives in the soil, and causes infections in horses when it gets inoculated under the skin via wounds and perhaps sometimes through fly bites. Once it gets into the tissues, it starts to grow and causes painful (and potentially large) abscesses that often need to be surgically incised in order to drain them.
Infection control practices on farms can help reduce transmission of the bacterium between horses and to reduce the risk of injuries. These include:
- Quarantine of new arrivals and careful inspection for sign of infection.
- Isolation of known infected horses.
- Use of "contact precautions" when dealing with infected horses to prevent transmission of the bacterium via peoples' bodies or clothing. This involves the use of protective outwear (e.g. coveralls and boots that are only used for the infected horse(s)) and gloves.
- Proper use of handwashing / hand sanitizer by people handling infected horses (or any horses, really, from a broader standpoint).
- Prevention of cross-use of items like buckets between infected/quarantined horses and the general horse population.
- Use of fly repellent, especially on horses with open wounds or draining abscesses.
- Careful cleaning and disinfection of areas potentially contaminated by pus from draining abscesses.
- Inspection of stalls, paddocks and fields for things that could cause wounds that might subsequently become infected.
Pigeon fever is a good example of why it's important to know disease patterns in your region (and those to where your horses travel). Being aware of the possibility of a specific disease is an important step in diagnosis, and knowing there is disease activity in any area in which your horse may have been is a key part of that. This disease is also an example of why we need ongoing disease surveillance and reporting, because if a disease makes it into new regions, veterinarians and horse owners need to know about that as soon as possible to allow for quicker diagnosis and use of control measures. Unfortunately, organized disease surveillance and communication is sorely lacking in horses.
Photo: A Jiennense Pouter Pigeon, which has a very pronounced breast compared to other breeds. The swelling of a horse's pectoral region due to abscesses caused by C. pseudotuberculosis is the reason the disease is sometimes called "pigeon fever." (click image for source)
Today's Morbidity and Mortality Weekly Reports, published by the CDC, describes Campylobacter jejuni infection in two men. Campylobacter is a zoonotic bacterium that causes diarrhea (and sometime severe complications) in people after it's ingested. It's usually a foodborne disease, but any method that leads to the bacterium reaching the mouth and being swallowed can result in to infection. This report describes a rather unusual method of infection.
This summer, the Wyoming Department of Health investigated two cases of C. jejuni infection. Both people worked on a local sheep ranch and got sick at the same time. Both had typical campylobacteriosis disease with diarrhea, cramps, fever, nausea and vomiting. One was hospitalized but both recovered. The interesting part is how they got infected. It turns out the men were involved in a multiday "event" to castrate and dock tails of 1600 lambs. Ten other people were also involved and they didn't get sick. The difference between these two and the other ten? The two infected men used their teeth to castrate some of the lambs. Animal welfare issues aside, this is just stupid. (I doubt anyone's looking at this but these idiots shouldn't be allowed to care for animals.) I don't see how anyone with an iota of common sense wouldn't think this is a bad idea in the current day and age. A very long time ago, apparently the "bit and spit" technique of castrating lambs (see photo, click for source) was relatively common practice. But like so many things that people used to do, there are much better (and safer, and infinitely more hygienic) ways of doing this nowadays.
Hopefully, they learned their lesson. Additionally, hopefully the farm owner takes some responsibility to make sure their personnel don't act like idiots and that someone investigates the animal cruelty aspect.
Photo: In "the old days" during castration of lambs, after opening the scrotal sac with a sharp blade, the testicles were often removed using the teeth, because it was faster than attempting to do so with an instrument. This technique is (almost) no longer practiced (except for at least two men in Wyoming, apparently). Photo source: http://old-photos.blogspot.com (used with permission)
The scope of research that's being done these days is astounding. Somewhere, someone's working on a project that will lead to a Nobel Prize in medicine. Other research will gather less critical acclaim but still have a big impact on science. Some research is more basic but can result in important preliminary information. And some studies... well, they may have a serious side but they're not what people typically think about when envisioning medical research.
Here are a few highlights from the lesser-heralded group of people investigating bathroom behaviours:
- A study of toilet reading habits in Israeli adults (Goldstein et al. Neurogastroenterol Motil 2009) concluded that toilet reading is a common and benign habit. (I hadn't really thought of it as a potentially poor lifestyle choice, but I guess this confirms it's fine). While it involves more time spent in the bathroom, "It seems to be more for fun and not necessarily to solve or due to medical problems." (Perhaps a more relevant area of study would be hand hygiene practices by toilet readers and the impact of toilet reading on fecal contamination of reading materials.)
- A Korean group has established that frequent recreational cycling does not have a negative impact on urination or sexual function in men (Kim et al. Korean Journal of Urology 2011). Cycling enthusiasts around the world, including me, rejoice.
- Horseback riders can be similarly relieved (pardon the pun) that recreational riding isn't associated with increased risk urinary or sexual dysfunction (Alanee et al. Urology 2009).
- A study with the catchy title "Female bowel function: the real story" (Zutshi et al Dis Colon Rectum 2007) wasn't too thrilling but had tidbits such as older women and women with children report more flatulence.
What do these have to do with zoonotic or infectious diseases? Nothing, but a little potty humour lightens up the start of the work day. More "real" posts to follow.
One of the big doomsday scenarios of the past couple of decades has been an H5N1 avian influenza pandemic. Human infections with this virus have occurred in various parts of the world (mainly southeast Asia) and death rates are quite scarey (50% or higher). Fortunately, the virus does not transmit efficiently between people, so human cases are linked to contact with infected birds or very close contact with infected people, and the current form of the virus is unlikely to have a wide impact on people. The concern is that if this virus changes to become readily transmissible between people, like common human influenza viruses, then a pandemic similar to the devastating Spanish flu outbreak of 1918 could occur (see image).
This raises the question: Should researchers be tinkering with H5N1 to see what mutations make it more transmissible? Those in favour want to understand more about the virus and what has to happen for it to become more infectious, but obviously there are considerable risks involved and others think this is playing with fire. This debate has reached full swing following a report by a Dutch researcher at the 2011 ESWI Influenza conference describing lab-induced mutation of avian influenza virus to make it highly contagious between ferrets. Ferrets respond similarly to influenza viruses compared to people, so something that spreads quickly between ferrets probably also spreads quickly between people. Therefore, the researchers may have (rather easily, it turns out) already created the ultimate "superbug."
So, is this good or bad?
- This type of research provides more insight into avian influenza and gives us more of an idea of what has to happen for the virus to become more transmissible. This may help determine whether there's a realistic concern of this happening in nature, and also provide more general information about influenza viruses.
- Is it responsible to create something like this that could kill millions if it gets out of the lab, either accidentally or maliciously? We have enough serious infectious disease threats already - do we need to be making more?
- Is publishing information like this just providing a recipe for bioterrorists? Manipulation of microorganisms can be done quite easily by people with some training and equipment. Materials are a lot easier to access than for other potential weapons of mass destruction. Do we want to make it easier by publishing step-by-step instructions?
The research findings haven't been published, and they are being scrutinized by an independent committee (set up by the US government) that provides advice about situations like this where legitimate research might be used for nefarious purposes. The committee makes non-binding recommendations, but presumably those recommendations would carry a lot of weight if publication is being considered.
This is a complex area. Academic freedom to pursue scientific investigations is very important and has helped modern science advance as quickly as it has. However, it's hard to determine where the benefits of individual academic freedom are outweighed by the risk to society from information developed in those academic pursuits.
Image: Historical photo of the 1918 Spanish influenza ward at Camp Funston, Kansas (where the pandemic began), showing the many patients ill with the flu. (US Army Photographer, 1918)
A Kitchener, Ontario family is dealing with a household outbreak of ringworm, likely contracted from a new pet guinea pig. Ringworm is a fungal infection cause by a few different types of fungi. Some ringworm fungi are able to infect both people and animals, and those can be spread in households from direct contact with an infected person or pet. In this case, the Gross family purchased a new guinea pig from a local pet store, and unfortunately, ended up bringing ringworm home as a bonus.
As is common, the new pet was the centre of attention when it got home, and the Gross' three children, ages 8, 5, and 2, had very close and frequent contact with it. The next day, the family noticed an area of hair loss on the guinea pig, at which point they took it back to the store. Ringworm was subsequently diagnosed, though there's no mention of how this was done, nor is there any mention of what actually happened to the little critter afterward.
The big problems started a week later, when a red lesion was seen on their youngest child's back. This was also diagnosed as ringworm, though again there's no mention of how, or whether it was definitively confirmed as ringworm. The newspaper report goes on to say "More spots kept appearing on Matthew’s skin as Gross was given different steroid creams to try and contain the infection." You always need to take media descriptions of medical issues with a grain of salt. Hopefully, the child was treated with anti-fungal cream, not steroid cream, as the latter not only won't treat ringworm, they may make it worse if used alone. Steroid creams are often prescribed for non-specific skin issues (particularly if the skin is very itchy, which can certainly happen with ringworm), but in a case like this where there was known contact with an animal with ringworm, I have to hope that the physician was treating with an antifungal cream instead of, or in addition to, a steroid cream.
Anyway, whether despite or because of the treatment, more skin lesions kept appearing on the child. Then skin lesions were found on the family dog, and both the dog and cat ended up being treated for ringworm. The treatment for dogs and cats is relatively straightforward, but it's still a hassle and can be somewhat expensive, and often takes several weeks.
The family has contacted the pet store about paying for cleaning supplies, air purifiers and veterinary bills, but the company did not respond to the newspaper reporter's inquiries, citing an ongoing investigation. It's hard to say whether the company should be held responsible. It largely depends on the measures they take to reduce the risk that they are selling pets at increased risk of transmitting infectious diseases. There's always a chance of picking up something from a pet, so an infection does not necessarily indicate incompetence or liability. If a store had reasonable practices in place, it's probably the purchaser's responsibility to take proper precautions when they take the pet home, and it's an example of why prompt veterinary examination of new pets is always a good idea. It's rarely done, particularly for species that cost less than the price of a veterinary exam, and you never know whether it would have helped prevent anything in this case, but in many instances it can help identify potential issues and address them before problems occur.
Preventing outbreaks like this can be difficult. Ringworm can be found on animals in the absence of any skin disease, so you can't always tell an animal is infected by looking at it. (However, in this case if a large patch of hair loss was noticed by the owners the day after the guinea pig came home, it's likely that something was evident the day before). Ringworm is spread by direct contact, which is common between pets and kids, especially new pets that often get smothered with attention in the first few days. Good hygiene practices, particularly attention to handwashing, can certainly help, but some degree of risk will remain.
Overall, guinea pigs are relatively low risk for zoonotic diseases, but this report shows that even "low risk" pets can be sources of infection. Fortunately, while controlling ringworm outbreaks can take time and be frustrating, it's not a serious disease and it is controllable.
More information about ringworm can be found on the Worms & Germs Resources page.
Veterinarians at Michigan State University's College of Veterinary Medicine are warning of an upswing in leptospirosis in dogs in the Detroit area. More than 20 cases of leptospirosis have been reported in dogs in the Detroit area, and it's likely that many more unreported cases have occurred. Leptospirosis, a bacterial infection, can cause very serious disease, including potentially fatal renal failure. It can be vague and hard to diagnosis if people aren't thinking about the disease. The most commonly identified problem is kidney disease, and early diagnosis and treatment is critical for successful treatment.
The Leptospira bacterium can survive well in the environment, particularly in moist conditions, and dogs are often exposed through wet environmental areas that have been contaminated with leptospires from the urine of infected wildlife. The strain that has predominated in the latest Michigan cases is Leptospira Icterohemorrhagiae, a type most often associated with rats.
Prevention of leptospirosis involves avoiding exposure to the bacterium as much as possible (largely through avoiding contact with wet areas where lepto cases have been identified) and vaccination. Vaccines are available for dogs and they can reduce the incidence and severity of disease caused by four different lepto types, including Icterohemorrhagiae. Vaccination should be considered in dogs in regions where lepto cases are identified and in dogs at increased risk of exposure based on lifestyle and travel.
There have been a few large outbreaks of dead birds around Ontario lately, with botulism being the main suspect. In one area alone, up to 6000 dead birds have washed up on Georgian Bay beaches. While dramatic, it's not a rare situation at this time of year, and typically relates to birds ingesting fish that died of botulism. When birds eat enough fish with enough botulinum toxin inside them, they can develop botulism themselves and die. This pattern can continue if dead birds are eaten by other animals.
In response to these events, I often get calls about risks to dogs and people. When thinking about it, it's important to consider how botulism occurs. There are two main forms of botulism:
- Toxicoinfectious botulism involves growth of the Clostridium botulinum bacterium in the intestinal tract, and as the bacterium multiplies it produces toxin which can be absorbed into the body through the intestinal wall. This type of botulism is rare in adults (both people and animals), since the mature intestinal bacterial population usually prevents C. botulinum from overgrowing. It's mainly a risk in young individuals. )This is why you're not supposed to give honey to babies, since C. botulinum spores that can be present in honey can pose a risk to them.)
- The other form of botulism in from ingestion of botulinum toxin that's already been produced. This is the most common form. When birds eat fish that have died of botulism, they ingest both the bacterium and its toxins, but it's the toxins that make them ill and ultimately lead to death. Dead birds will probably have some C. botulinum in their intestinal tracts, but the main concern is the botulinum toxin in the rest of their tissues.
Dogs (and cats) are quite resistant to botulinum toxin, and reports of botulism in these species are rare. It would take a pretty large amount of toxin to cause disease (at least compared to many other species) but it's not impossible. Casual contact with areas where birds have died is of basically no risk. Eating dead birds could pose some risk to the dog, depending on the amount eaten and how much toxin was present in the bodies. Ingestion of some C. botulinum bacteria in the birds is of limited concern.
So, walking in an area where birds have died is very low risk. People should ensure that their dogs don't have uncontrolled access to areas where birds have died, so that they can't eat lots of dead birds.
I also get questions about whether dogs that get exposed to beaches where birds have died pose any risk:
- Even if a dog ate a lot of dead birds and got botulism, a person could only be exposed to that toxin by eating the dog - an unlikely event. The dog could ingest some C. botulinum bacterium, but this also poses minimal risk since the bacterium is pretty widespread and people can be exposed to it from many different sources. Even if a dog had some C. botulinum in its intestinal tract, avoiding contact with feces will reduce the risk of exposure. Even if there was some ingestion of C. botulinum from the feces, there's little risk, especially to adults. Perhaps the main public health concern (which is still very low) would be exposure of infants to C. botulinum from dog feces or perhaps from a dog's contaminated haircoat.
Bottom line: Keeping dogs and cats away from dead birds is a good idea, for several reasons, including botulism exposure, but there's limited public health concern.
Image: Dead birds washed up on the shore of Georgian Bay, on the eastern side of Lake Huron (click for source)
Infectious diseases are continuous challenges for animal shelters. Unfortunately, outbreaks are not uncommon. Sometimes they're the result bad luck and the inherent risks involved in bringing together lots of animals of questionable health status from different sources. However, if you compound these risks with things like inadequate facilities, overcrowding, poor training of personnel, poor adherence to protocols, bad protocols, lack of awareness about infectious diseases and failure to get expert help early in any outbreak, the likelihood of "badness" increases.
A few shelter outbreaks are underway at the moment, and they highlight some of the infectious disease challenges posed by different diseases in animal shelters.
- The Oakville and Milton Humane Society (in Ontario) is closed because of a ringworm outbreak that's been going on since early September. Ringworm, while of limited health consequences, is an important shelter problem because it's common, highly transmissible, can be hard to control and can infect people. At last report, 22 cats were confirmed or suspected to have ringworm, along with at least four staff members. It's not clear who's coordinating the outbreak response, but hopefully they're getting good advice and they've read the comprehensive report from the Newmarket OSPCA ringworm debacle.
- 72 kittens were euthanized in the Miami-Dade County Animal Services because of "cat plague," which is a common name for feline panleukopenia. This viral disease is preventable by vaccination, but it's a serious concern in shelters were there are often lots of unvaccinated or inadequately-vaccinated cats and lots of susceptible kittens. In this shelter, all cats with clinical signs consistent with panleukopenia are being euthanized. Euthanasia is always a tough decision, but with a serious disease like this, it's a reasonable response. Outbreaks like this highlight the need for excellent infection control practices to reduce the risk of spread of pathogens like this once they make it into a shelter.
- Upper respiratory tract infections have resulted in suspension of adoptions at the Bergen County Animal Shelter in New Jersey. News reports are calling it a canine influenza outbreak, and canine flu is definitely on the list of possibilities, but it doesn't sound like it's been confirmed. Respiratory infections are a common cause of problems in animal shelters because some causes (e.g. canine parainfluenza virus, canine influenza virus) are quite transmissible. Canine flu poses extra challenges when it moves into a new area, since few if any dogs have antibodies against the virus and therefore it can spread rapidly. The report also mentions transmission by dogs not showing signs of disease. That's a problem with some infectious agents. For example, with canine flu, dogs tend to be able to shed the virus before they show signs of illness. Therefore, there's a period of a couple of days after infection but before disease where you can have a silent reservoir of infection. That's why quarantine of new admissions is critical, since it gives animals a few days to show signs of diseases they may be brewing at the time of admission. (Unfortunately, it's not easy to find space in which to quarantine an animal in an overcrowded shelter.)
A common denominator in all of these outbreaks is the potential that something could have been done differently to prevent the problem. It's possible (although unlikely) that everything that was done perfectly, however it's a rare outbreak where you can't find multiple areas for improvement. A key aspect of outbreak management is, once the crisis is over, performing an investigation of what really went wrong and why, and taking measures to reduce the chance of it happening again.
Image: Ringworm infection in a cat is not always readily apparent, but in some cases can cause obvious patches of hair loss.
An outbreak of canine influenza is occurring in San Antonio, TX, as this virus continues its strange and unpredictable movement through the North American dog population. In an article published on a local San Antonio news website, Dr. Michele Wright, a San Antonio veterinarian, reports 20 confirmed and 70 suspected cases over the past month. It's not clear whether these are all from her clinic, nor is there any information about possible sources of the virus or the severity of disease. Dr. Wright also states that the virus has been identified in Austin and Dallas.
It's not particularly surprising that canine flu has been found in Texas. It's now been identified in at least 38 US states, as well as one Canadian province. An outbreak is not particularly surprising either in this case, because when a virus reaches a new area, it can easily cause widespread disease since it encounters a population of animals that don't have any pre-existing immunity (i.e. antibodies) against it.
What's strange about canine flu is how it has spread across North America. When it was first identified in Florida greyhounds in 2004, it seemed like it was going to spread widely across the dog population. It spread quickly at greyhound tracks and in clusters in Florida and in other states, but it's subsequent spread across the continent was quite patchy - it caused only localized outbreaks in different states, instead of the catastrophic continent-wide epidemic that was anticipated. Whether this relates to the amount and type of direct contact between dogs (e.g. dogs are only infectious for a short period of time and an infected dog has to meet a susceptible dog during that time to continue transmission of the virus, otherwise it dies out), specific aspects of the virus in dogs (e.g. how long it is shed) or lack of recognition of disease in some areas (e.g. mild disease that doesn't get diagnosed) is unclear.
We've been looking for canine flu in Ontario for a few years now, with no "success" (that is, we haven't found it yet).
Are we flu-free at the moment? Probably not. I suspect it's lurking out there, but it's possible that it really hasn't made it to Ontario - yet.
If it's not here now, will it make it here eventually? Almost certainly. It's taking longer than I expected but all it takes is one infected dog entering the country. With the amount of cross-border dog movement, it's probably inevitable.
What about vaccination for canine flu? It comes down to risk of exposure and risk aversion. If flu is in the area, vaccination is a good idea. If flu is in adjacent areas, it's also a good idea. If flu isn't recognized in the area, it's a matter of how much risk people are willing to take and thinking about higher risk situations, as described below.
What about vaccination in Ontario, or other places where the virus doesn't seem to be present? It's hard to say when to recommend canine flu vaccination. Certainly, vaccination of dogs traveling to areas where canine flu is or has been present is a good idea. Vaccination of dogs that engage in high risk activities such as going to shows or kennels is also prudent, since these are the places where we may see the firsts outbreaks if/when canine flu makes it here. Vaccination of low-risk dogs in the province is probably not necessary at the moment (unless people are very risk averse and don't want to take any chances).
Why vaccinate? It's just "the flu"... This is an attitude that the human public health field battles all the time. Most people who get human influenza (humans can't get the dog version of the virus) feel crappy for a few days and get over it. The perception that it's only and always a mild disease keeps some people from getting vaccinated. However, thousands of people die from flu complications, particularly the very young and elderly individuals. Vaccinating everyone helps reduce the chance that these high-risk people will get sick. Also, while rare, serious (including fatal) infections can occur in otherwise healthy people. In dogs, there's probably actually more indication to vaccinate if there is a realistic risk of exposure. Canine flu can cause classical flu-like disease, akin to the typical human case. However, severe (often fatal) pneumonia can also occur in otherwise healthy dogs. High rates of severe disease were reported initially when canine flu was first identified. It seems like severe disease rates have dropped, but it's still a concern. I wouldn't be surprised if severe disease is more common in dogs with canine flu than in people with human flu.
Whether or not to vaccinate is a discussion dog owners should have with their veterinarian, considering the risk of exposure, risk of severe illness and risk aversion. At the same time, people in areas where flu has not been identified need to be on the lookout for it, to ensure that it gets diagnosed promptly if it emerges, and that information gets communicated to veterinarians and the dog-owning public so that appropriate responses can be made.
The latest edition of Emerging Infectious Diseases (Berger et al 2011) describes a case of Corynebacterium ulcerans infection in a women that was likely acquired from her cat.
Corynebacterium ulcerans is a bacterium that's related to C. diphtheriae, the cause of diphtheria. Some strains of C. ulcerans can produce toxins that cause diphtheria-like disease, and with the success of diphtheria vaccination, C. ulcerans is now the leading cause of diphtheria-like disease in people in some regions. Typically, C. ulcerans infections are associated with ingestion of contaminated milk or dairy products, but reports of infections acquired from dogs and cats appear to be on the rise. As is often the case, whether this is because it's becoming more common or that people are simply looking more is unclear.
In this report, a woman from Germany developed diphtheria-like disease, including a sore throat, ear ache, hoarseness and nasal obstruction. A swab was taken from her nose and throat, and toxigenic C. ulcerans was isolated. She didn't report any livestock contact and had not traveled abroad, so other possible sources of infection were considered, particularly other types of animal contact. She had a cat, so nose and throat swabs were collected from her pet, and the same strain of C. ulcerans was isolated.
With this type of investigation, you can't prove that the cat gave the bug to the owner. Since the cat was healthy and tested after the owner was sick, you can't say for sure whether the cat was the original source or if it was infected by the owner. However, with a bug like C. ulcerans that has been associated with pets before and that can be carried by healthy cats, the conclusion that it came from the cat is reasonable. The cat was treated with antibiotics and C. ulcerans was not detected after treatment.
This is an interesting report. It's always good to see people thinking about the relationship between human and animal disease, but at the same time, it's important to put this into context. Yes, C. ulcerans is a potential zoonotic concern, but it's rare. Anytime you see a case report involving a single person in the medical literature, you know it's either something new or very rare. In this case, it's the latter, since we know from previous reports that this bug can cause human infection and be transmitted from animals. Rare doesn't mean never, and you can't dismiss it, but C. ulcerans is just one of many bacteria that can be found in cats and transmitted to people. It's part of the inherent risk of infection that comes with cat ownership. This relatively low risk is hopefully outweighed by the benefits of cat ownership, and the cost-benefit can be maximized by basic infection control and hygiene practices. This report also shows how it's important for physicians to query pet ownership when dealing with infectious diseases in their patients, something that still needs lots of improvement.
A paper in the Journal of Neurooncology (Redelman-Sidi et al, 2011) describes "kitten-transmitted Bordetella bronchiseptica infection" in a cancer patient. The patient in question had a brain tumour that was surgically removed. The 56-year-old man was then started on chemotherapy, which in addition to killing cancer cells can also cause significant impairment of the immune system, which puts chemotherapy patients at high risk for infections of many kinds. This particular patient developed a persistent cough during treatment and was eventually diagnosed with B. bronchiseptica infection. This bacterium is one of the causes of kennel cough in dogs, and can cause respiratory infections in other species, including cats.
The man had acquired a kitten three weeks before he developed the cough. The kitten had (at some undefined time) conjuncitivitis and signs of respiratory disease. Unfortunately, as is too often the case in reports of supposed pet-associated disease in the medical literature, the kitten was not actually tested. Bordetella bronchiseptica is classically an animal-associated organism, the kitten was newly acquired and it had respiratory disease. These factors strongly suggests the kitten was the source. However, without testing of the kitten and investigation of other potential sources of infection, it's hard to be as definitive as the title suggests. The suspicion of the kitten being the origin is reasonable nonetheless.
Some statements from this report are contrary to my typical recommendations for pets and immunocompromised individuals.
Getting a young animal
- Kittens and puppies are entertaining, but they are also higher-risk animals compared to adult dogs and cats. They are more likely to harbour a variety of infectious agents. They are also more likely to bite or scratch through playful or rambunctious behaviour, and it's harder to properly assess their temperament. If an immunocompromised person wants to get a new pet, getting an mature animal is ideal.
Source of the kitten
- The paper unfortunately doesn't mention from where the kitten was obtained and whether there was a respiratory disease problem in other animals at the source. Animals in shelters, humane societies and pet stores are more likely to carry various infectious diseases because they are densely populated facilities, often have infection control challenges, house many high-risk animals and are stressful environments. Getting new animals from these places is not ideal for a high-risk person.
- The kitten had signs of respiratory disease and was seen be a veterinarian. It doesn't appear that any testing was done and the kitten was just treated with antibiotics. That's pretty common, but in a situation where there is a high-risk person in the house, it's wise to be more aggressive with diagnostic testing to determine whether there may be any concerns for the person.
A pet can be a wonderful thing for a person living cancer, by providing social and emotional support, along with other benefits. Pet ownership always carries some risk of zoonotic infections, and the risk is higher in people with compromised immune systems. Rarely, if ever, is pet ownership inappropriate for a cancer patient, although certain pets and certain situations might be, and high-risk individuals need to think about possible risks and measures to reduce those risks.
People with cancer or other problems affecting their immune system should ensure that their physician knows that they own pets. Veterinarians need to play a role as a member of the overall healthcare team too. Optimizing pet health can help reduce the risk of human infection. Prompt and proper diagnostic testing can identify potential issues. Proper counseling can reduce risky situations from inappropriate pets, inappropriate contacts and other factors that might make exposure to a nasty infection from a pet more likely.
Close to a dozen dogs in the Big Bay area of Michigan's upper peninsula have been diagnosed with blastomycosis, an uncommon but regionally important disease. Blastomycosis is caused by a fungus, Blastomyces dermatitidis. It's a dimorphic fungus, meaning it exists in 2 forms:
- Normally, it lives in the environment in the mold form. This is the infectious form to which dogs (and people) can be exposed via inhalation, ingestion or contamination of wounds.
- The other form is the yeast form. This develops from the mold form once it gets into the body, and this is what causes disease.
Dogs that are infected with blasto are of minimal risk to others since they are carrying the yeast form, and the yeast form is not transmissible under normal conditions. There is only a risk of infection in rare situations, such as a bite from a dog that has the yeast form in its mouth, or if someone sticks themselves with a needle that was used to sample an infected site. The main issue with finding blasto in a dog is that it is an indication that the fungus is present in the environment in the area where the dog has been in the past few months. That means people who went to those areas may have also been exposed.
Knowing where blasto is present is important for diagnosing disease in people and animals. Blasto is also a great example of a disease when getting a travel history can be critical for diagnosis. In some regions, blasto is most common where people tend to vacation or have cottages. If a veterinarian doesn't know that a dog has visited a high-risk area, blasto may not be considered. Not asking about travel history (or not getting a clear answer) can significantly impact the ability to diagnose this disease, and early diagnosis and treatment are critical for getting a good response.
If you live in an area where blasto is present, avoiding it can be tough. Staying away from areas that have been associated with the fungus can help, but defining this is difficult because of poor reporting and the long incubation period. Staying away from soil is pretty tough to do as a routine measure, so people living in endemic areas have to be aware of the disease and ensure that proper veterinary care is provided if there are early signs of infection (e.g. respiratory disease, skin lesion, unexplained weight loss). People who travel to areas where blasto is present should make sure their veterinarian knows about the potential for blasto exposure in any animals that may travel with them.
Adding a new twist to the already very concerning situation in Australia, Hendra virus infection has now also been identified in a dog. It's been a bad year for Hendra virus in Australia, with larger numbers of cases of this highly fatal disease in horses in a geographic range that seems to be expanding. Spread by flying foxes (fruit bats), Hendra virus predominantly infects horses, but can be transmitted to people working with infectedhorses.
The Australian Animal Health Laboratory in Geelong has now announced diagnosis of Hendra virus infection in a dog. The dog is from a quarantined farm in Queensland where the virus has been identified in a horse. The dog was healthy and was tested as part of a standard policy to test dogs and cats on infected farms. It's great to see this approach being used, since it helps identify other potential sources proactively - something that is often overlooked in outbreak investigations that focus only on the main species that are already known to be involved.
In this case, the dog had antibodies against the virus in its blood. That means that it was exposed to the virus and mounted an immune response. It doesn't indicate whether it was exposed recently or in the past. Two tests for the virus itself were negative, suggesting that the dog's immune system eliminated the virus (or that the virus isn't really capable of surviving for long in a dog). This is a good news/bad news scenario.
- Dogs can be infected. It increases the range of known susceptible species.
- If dogs can be infected and shed live virus, then they could be a source of infection for other individuals, including people.
- The dog wasn't sick. This might sound like strange "bad news," but healthy carriers of infectious diseases are harder to spot and control than ones that are sick.
- The dog wasn't shedding the virus. That's critical since if dogs can be infected but not infectious (i.e. if they can carry the virus but not transmit it), then they are of limited concern.
- They have been testing farm dogs and cats as a routine measure, and this was the first positive. Infection of pets therefore must be relatively uncommon even on farms where the virus is active.
- The dog wasn't sick. While it's only one case and doesn't guarantee dogs won't be affected clinically, this might suggest that dogs just occasionally get exposed with no disease. Since it's highly fatal in other species, that's a good thing.
What should be done based on this?
- Probably not much more than should have been done before this finding, but it's a good reminder about the potential involvement of other species.
- Dogs and cats should be kept away from fruit bat roosting sites.
- Dogs and cats should be kept away from infected horses.
- If a farm is quarantined because of Hendra virus, dogs and cats should be tested and quarantined. Quarantining the animal while testing is underway helps reduce the risk of an infectious dog or cat (should that occur) transmiting the virus to people on the farm, or wandering away and exposing other people or animals.
- Animals of any type in areas where Hendra virus is active that get sick with signs that could possibly be consistent with Hendra virus infection should be tested.
This should also be taken as yet another reminder that infectious diseases are unpredictable. Considering the potential involvement of different species in a proactive manner as was done here is critical.
Image: Bay Horse and White Dog by George Stubbs (1724-1806)
This Worms & Germs blog entry was originally posted on equIDblog on 26-Jul-11.
As Australia faces a particularly bad year for Hendra virus, with possible expansion of the range of this serious disease, there have been calls for a mass cull of flying foxes (fruit bats). These bats are the reservoir of the virus but also a protected species. The virus lives in the bats and is spread mainly through their urine. Horses that are exposed to bat urine or feces (e.g. grazing under a tree where bats are roosting) can become infected and then serve as a source of human infection. Being a highly fatal disease for which there is no available vaccine, looking at ways to reduce exposure to the virus is critical. When you have a wildlife-associated disease, questions about trying to eliminate the wildlife source often arise. Any discussion of culling wildlife leads to intense debate, and this situation is no different. Some people support culling bats in areas around people and horses, while others are opposed on various grounds, including a lack of evidence that it will be effective.
Can fruit bat numbers really be decreased? A lot of bats would have to be killed to have a significant impact on the population. Bats can reproduce quickly and migrate readily, therefore a single cull may have only a limited and short-term effect. A good understanding of the dynamics of the bat population is required to determine how many would need to be killed in a given area to have any significant impact. As Biosecurity Queensland's chief veterinarian RIck Symons stated "Culling is against government policy. I believe in terms of biosecurity it's counterproductive, because it does stress flying foxes and they're more likely to excrete (the virus). It could be filled by another bat colony the next day and if you're moving them on, you're moving it on to somebody else and it's somebody else's problem, so that is not the solution."
Will a cull actually achieve anything? Even if effective at reducing bat numbers (probably just in the short term), culls don't necessarily have an impact on disease rates. All bats would not be eliminated, and it's unclear whether there is a critical mass of bats that is required to transmit infection or whether a small number of bats distributed across the same region would be as likely to result in infections. Small or temporary decreases in bat numbers may have no effect.
What unintended consequences might occur if a cull is effective at reducing bat numbers? Removing an animal from any ecosystem has an effect, and it's important to be confident that that effect isn't accompanied by problems of its own. I don't know enough about fruit bat ecology to say much here, but if this species is greatly reduced, are there other species that will come and occupy that ecological niche, and might they be associated with problems of their own? Careful scientific study can help to figure this out in theory, but you can never be certain.
Are other control measures, such as removing roosting sites from pastures and other bat avoidance measures, being adequately used? Culls should only be considered when other measures have failed, but it can be difficult to ensure or enforce compliance with these other measures. Certainly, people in endemic areas should remove trees in which bats roost from pastures. However, not all Hendra cases are associated with identifiable roosting sites. For example, one affected Queensland farm does not have any fruit bats residing on the property, but it lies along a common flight path for the bats.
It's easy to talk about avoiding a cull when you're not in the heart of the Hendra epidemic, and I understand the reasoning behind the calls for a cull. Hendra is a devastating disease that's a threat to both horse and human health, and it's unpredictable - and that's scarey for a lot of folks. People that have been exposed face an incredibly stressful period while they wait and see if they've been infected with a virus that kills in ~50% of cases. A vaccine is probably still a couple of years away, leaving a period of continued risk and stress. With such a serious disease, considering culling is reasonable. However, it can't be a knee-jerk reaction to public outcry. It needs to be based on sound science to ensure that if it's used, it will be effective. The impact on this protected species also can't be ignored.
This Worms & Germs blog entry was originally posted on equIDblog on 19-Jul-11.
When it comes to public health concerns about staphylococcal bacteria from pets, most of the attention gets paid to methicillin-resistant strains like MRSA. That's not surprising considering how important MRSA is in human medicine. However, staph that aren't methicillin-resistant can also be a problem, since they can cause the same types of infections that resistant types can (they are just easier to treat). Another issue that often gets overlooked is staphylococcal food poisoning.
Staphylococcal food poisoning is one of the most common foodborne illnesses and results from growth of certain strains of staphylococci in poorly handled or stored foods. If staph get into food and the food is kept at improper temperatures, the bacteria can grow. If the strain of staph that's in the food is one that can produce enterotoxins, these toxins can accumulate in the food at high enough levels to cause food poisoning when eaten. In most cases, people are probably the origin of enterotoxin-producing staph that contaminate food, but pets are another possible source.
A recent study in Vector-borne and Zoonotic Diseases (Abdel-moein et al 2011) looked at enterotoxigenic staph in 70 dogs and 47 cats. Swabs were collected from the mouth, nose and wounds. Nasal swabs were also collected from 26 people. The researchers isolated enterotoxigenic Staphylococcus aureus (strains of S. aureus that possessed genes for enterotoxin production) from 10% of dogs and 2.1% of cats, as well as 7.7% of people. Most of the positive samples from pets were oral samples.
This study shows that dogs and cats can be potential sources of strains of S. aureus that cause food poisoning. Since the staph are often in the animals' mouths (and therefore presumably shed in saliva), animals can potentially contaminate food with these enterotoxigenic staph fairly easily, but it's unknown how often this occurs.
Prevention measures are pretty basic but should be considered, including:
- Keeping pets off kitchen counters.
- Discarding foods that pets have licked.
- Washing hands after pet contact, before handling food.
- Properly storing food, so that even if it gets contaminated with staph, the bacteria don't get the opportunity to grow and produce toxins.
- Photo from http://www.wagreflex.com/2009/06/taking-cat-ownership-to-the-next-level.html
A Minnesota woman has died of Powassan virus encephalitis, a very rare neurological disease transmitted by ticks. Powassan virus is most often found in parts of Ontario, Quebec and New Brunswick, but there is evidence of it in many other parts of North America as well, and as far away as Russia. Human infections are very rare, but when they occur neurological disease is severe, mortality rates are high, and survivors often have residual neurological problems.
Powassan virus is a flavivirus, related to St. Louis encephalitis virus and West Nile virus, but unlike these, the reservoir of Powassan virus seems to be wild small mammals, with transmission via ticks (as opposed to a bird reservoir and transmission via mosquitoes for the others). The virus has been detected in mosquitoes but it's not known whether they can transmit the virus. Ticks are considered the major (and possibly only) route of infection.
The risk to animals in areas where Powassan virus can be found is very limited. Natural infections of dogs, cats or horses have not been reported, as far as I know. However, that doesn't 100% rule out the possibility of disease, since you have to look in order to find, and specific investigation of Powassan virus transmission is uncommon. Neurological disease has been reproduced experimentally in horses, but not dogs and cats.
Overall, the risk to pet owners and pets posed by Powassan virus is very low. Taking measures to avoid ticks is the key, and such precautions should be taken for many reasons beyond Powassan virus exposure.
An interesting study published recently in Veterinary Dermatology (Bartlett et al 2011) looked at bacterial contamination of ear cleaning solutions used on dogs at home. Ear cleaners are widely used by dog owners, but since the bottles the cleaners come in are used repeatedly and can have direct contact with the ear, there’s a chance for contamination of the bottle and/or its contents.
In this study, the researchers collected ear cleaner bottles from dog owners and cultured both the applicator tips and the contents. Bacterial contamination was detected on 10% of the bottle tips and in 2% of the solutions. The relative numbers make sense, since the tips are most likely to have contact with the ear. Regardless, this shows that a small but still reasonable percentage of bottles contain bacteria that could be inoculated into the ear.
Finding bugs is one thing, but determining if they are types that can cause disease is another. The researchers identified a few different bacteria, including Staphylococcus pseudintermedius, which is an important cause of ear infections. This isn't too surprising since the bugs that cause infection are typically those that are also normally found in (healthy) ears at low levels (and therefore the types of bugs with which cleaner bottles might have contact).
Expired ear cleaners were more often contaminated. This doesn’t necessarily mean that age leads to increased risk of contamination. It could just indicate that bottles that have been used more and over longer periods of time are more likely to become contaminated. Similarly, large bottles more often had contaminated tips, probably because of more overall use (and correspondingly more chance for contamination).
An interesting aspect was the finding that solutions containing Tris-EDTA had higher contamination rates. Tris-EDTA is a solution that is often included in ear cleaners as it has been shown to be useful for treatment of infections caused by Gram-negative bacteria.
What does this mean for people that clean their dogs’ ears? It’s hard to say. We don’t know whether a little bit of bacterial contamination poses a realistic risk. However, it’s reasonable to consider using smaller bottles and discarding them after they are used to treat a dog with an ear infection (as opposed to regular ear cleaning).
In trying to keep up with technology, my lab has started adding a QR code to posters presented at research meetings. The code links to a page on the Worms & Germs Blog Resources page that houses a collection of research posters that people can view and download. You can also go directly to the poster site by clicking Research Posters on the "Topics" bar on the left side of the Worms & Germs Blog homepage, or through the Resources tab at the top of the homepage. Check back regularly to see new additions to the list.
A California teen has been battling a chronic and severe infection acquired from a fish tank. Five years ago, Hannele Cox cut her hand when she pulled it out of an aquarium. It sounds like it was a pretty minor scratch, but it doesn't take much to cause an infection under the right circumstances.
A while after the injury, infection was apparent. A round of antibiotics didn't fix it (no word on whether any bacterial cultures were performed at that point). Eventually, a dermatologist diagnosed the problem: Mycobacterium marinum infection. One problem with infections like this is that they are sometimes not diagnosed until they are quite advanced. If the patient doesn't mention the aquarium exposure and/or the physician doesn't ask about pets, an infection like M. marinum might not be considered.
Mycobacterium marinum infection is sometimes called "fish tank granuloma" in testament to its common association with fish tanks. It can be found in both freshwater and marine fish (and the water in their tanks), and most often infected fish don't have any signs of disease. Therefore, you have to assume that any fish and any aquarium could be infected, and therefore a potential source of human infection.
Infections with M. marinum usually develop a couple of weeks after exposure and are characterized by small bumps (papules) on the skin that progress to shallow ulcers. Typically, infection is not very invasive and responds to treatment, although months of treatment may be required. Sometimes, the infection can spread to deeper tissues, making it much harder to treat. Unfortunately, that's what happened to Hannele Cox. Her infection has not responded well to treatment and has spread to deeper tissues, including bone. She's had two surgeries to try to save her hand, and at least one more is planned. Amputation isn't outside of the realm of possibility, but will hopefully be avoided.
Fish owners should be aware of the risk of M. marinum infection. While fish are often ignored as a potential causes of infection and the overall risk is low, there are simple measures that can be undertaken to reduce the risk of acquiring an infection from fish tanks. These mainly involve limiting contact with fish tank water and the use of good general hygiene practices:
- Contact with aquarium water should be minimized
- Never dump aquarium water into kitchen or bathroom sinks.
- Promptly clean up any aquarium water spills.
- Take care when putting your hands in the aquarium, especially if there are sharp surfaces (e.g. rock, coral) that might result in cuts or abrasions.
- Hands should be washed thoroughly after contact with aquarium water.
- People with compromised immune systems should not have contact with aquarium water. They should have someone else clean their fish tank.
As many of you know, there was a large ringworm "outbreak" at the Newmarket (Ontario) OSPCA shelter in 2010 that led to a public outcry in response to plans to depopulate the shelter. In the aftermath of the event, an independent investigation was launched, headed by Mr. Patrick LeSage (former Chief Justice of the Ontario Superior Court) and Dr. Alan Meek (former Dean of the Ontario Veterinary College). The investigation involved a comprehensive examination of activities pertaining to the outbreak and shelter operations, in conjunction with relevant experts (disclosure: I was one of those).
The report of the investigation is now available, and covers important aspects such as whether an outbreak was actually present (short answer: no) and whether there were major problems in shelter operation (short answer: yes). Most importantly, it provides a comprehensive set of recommendations to improve the operations of the Newmarket shelter and OSPCA as a whole.
The report, in its entirety, was released today by the OSPCA and is available for download on their website. The report is on the site in multiple files: the main report is listed as "Index" and contains the ~90 page overview and recommendations. The expert reports, which might also be of interest, are tables D1-3, E, F and G.
A 35-year-old UK man has died following a seemingly innocuous dog bite. He was nipped by the family's pet dog, not during an aggressive incident but just a playful, boisterous dog. Later, he developed a fever. He saw a doctor the next day and was told that he had influenza based on his clinical signs, but no testing was done. There's no mention about whether the doctor was notified about the dog bite or asked about animal bites or contact. (I wouldn't be surprised if that didn't happen.)
Unfortunately, the man's condition deteriorated and he was diagnosed with sepsis, which is an overwhelming infection of the bloodstream. A dog-associated bacterium, Capnocytophaga canimorsus, was identified as the cause. Both of the man's leg's were amputated because of the effects of the infection, after which he started to improve, but he later developed more complications and ultimately died.
A doctor explained, "These things are so unusual. It would have been like an unstoppable train – it just depends on how the body reacts." Infection with C. canimorsus is rare, and once it's underway, it can be difficult to control. However, this quote neglects the potential treatable aspect of the infection. For an aggressive infection like this, diagnosing it early is critical. If the doctor had asked about pet contact, asked about bites, noticed the bite, or if the person had mentioned the dog bite at the first visit, an astute physician may have thought about bite-associated infection and hopefully started proper treatment, before fulminant sepsis developed. This would be particularly true for certain high-risk individuals.
Capnocytophaga infections occur almost exclusively in high-risk people, particularly people without a spleen, but also in immunocompromised individuals or alcoholics. There's no mention of whether this person had any of these risk factors, but people who do should know that they are at high risk, see a physician if they are ever bitten by an animal (even if it seems like a very minor bite), and make sure their physician knows about pet contact.
Avoiding Capnocytophaga is essentially impossible if you have a dog. It's carried in the mouths of most (if not all) dogs, but it's typically not an issue. Human infections are rare but they are important because, like in this case, they tend to be very severe when they do occur. High-risk individuals need to know about this bug, make sure their physician knows about any animal contact they have, be proactive to avoid bites and other exposure to dog saliva, thoroughly wash any bites or wounds contaminated with dog saliva, and consult a physician after any bite, regardless of how mild it may seem. Pet owners shouldn't be afraid of Capnocytophaga, but they should be aware of it and various other bite-associated pathogens, do their best to reduce the risk of bites occurring (e.g. proper training of dogs (and kids)), and know how to take care of bites.
An important concept when dealing with infectious diseases is consideration of the risk that an animal has been, or will be, exposed to a particular microorganism. Some diseases vary greatly geographically, and something that's very important in one region may be rare or non-existent in another. Good veterinarians are aware of disease trends in their area and make informed decisions about vaccination and anti-parasitic treatments based on what's happening in the area. They also know which diseases are common and which are rare or non-existent.
But that only works if the pets stay in their "home" area. Traveling with pets can result in exposure to various infectious diseases they wouldn't normally encounter. If a veterinarian doesn't know a pet travels, they can't make proper recommendations for preventive medicine.
Additionally, travel history can be very important when evaluating a sick animal, since there may be diseases that need to be considered in a traveling pet that wouldn't be an issue with a local pet. However, it's easy to overlook or forget about travel history. Pet owners need to tell their veterinarians about "recent" travel with their pets. What does recent mean? It's hard to say. For some diseases, exposure within the past few days is all that's important. For others, it may be weeks or months. So, if you have a sick pet and have traveled any time in the past year with it, it's good to mention that to your veterinarian. It may have nothing to do with the current illness, but it never hurts to let them know anyway. In some situations, it may be the critical piece of information needed to trigger thinking about a specific disease.
Some examples of diseases that may be travel-related (at least to dogs in most parts of Ontario):
- Blastomycosis, a fungal disease, tends to occur predominantly in specific areas. It's not too common elsewhere, but travel to high-risk areas puts blasto on the list of possibilities in certain cases.
- Around here, there's no indication for heartworm preventive treatment during cold winter months, but that changes if the pet goes to areas where mosquitoes hang around all year.
- Some tickborne diseases have very specific ranges that correspond to their primary hosts and certain vector species (such as birds). In Ontario, ticks are currently quite geographically focused and many dogs have little risk of exposure. Travel to one of the tick hotbed areas changes that, and means that certain tickborne diseases need to be considered.
- Canine influenza currently seems like a non-entity in Ontario. We're still looking for it but haven't found it. It is present in some places in the US, and at times, is a big problem. Travel to a place experiencing a canine flu outbreak would be a good indication to consider canine flu vaccination.
What to do?
- If you travel with your pet, part of your pre-travel checklist should be an appointment with your veterinarian to go over anything that needs to be done, be it vaccination, deworming, flea control, heartworm preventive or anything else. (It's also a good time to make sure there's nothing else going on with your pet, because you don't want a pet health crisis en route.)
- If your pet gets sick and has traveled, make sure your veterinarian knows where you went and when.
- If you travel regularly, even if it's not long distances, it's good to discuss it with your veterinarian to see if anything is required for your pet. Even if you just go a couple of hours away to a cottage regularly during the summer, you may be exposing your pet to something different.
I received this question yesterday, pertaining to a potential therapy dog.
Valley Fever, also known as coccidioidomycosis, is a fungal infection caused by Coccidioides immitis or Coccidioides posadasi. These fungi live in the soil and are most common in the southwestern US, northern Mexico, and parts of Central and South America. They are part of an unusual group of fungi called "dimorphic fungi," meaning they exist in two forms. One form in found in the environment (soil). This arthroconidial form is the infectious form. The other yeast-like form is present in the body tissues during infection, but is not (or at least is very minimally) transmissible.
Disease from Valley Fever is rare in healthy people. These fungi are mainly a concern in people with compromised immune systems. When illness occurs, flu-like disease, respiratory disease, rash and joint pain are the most common signs, but disseminated infection (i.e. infection throughout the body) is a much more serious form of the disease that can occur.
Valley Fever is similar in dogs, with most dogs have mild to inapparent disease, and most sick dogs having vague signs and respiratory disease. Cats often develop skin lesion. Disseminated disease can also occur.
While coccidioidomycosis can occur in both humans and animals, the risk of transmission between humans and animals is extremely low. The fact that it occurs in both humans and animals is because both humans and animals get exposed to the same sources, not because they spread it between each other.
However, there is a slight risk that shouldn't be ignored. There are two situations that are of concern.
- Bites: There is one report of a bite-associated infection in a veterinary technician. The risk of infection after a bite from an infected animal isn't known, but anyone bitten by an infected animal should seek medical advice. Presumably, nothing would be done initially but there could be close monitoring for disease so that it can be treated early if problems develop.
- Veterinary procedures: Infection has been reported in a person performing a necropsy (autopsy) on an infected horse. It was thought that infectious endospores were aerosolized when an infected area was cut with a saw as part of the procedure, and inhalation of the fungus lead to disease.
There's also a theoretical concern with handling bandage material from infected animals. While the active infection would be caused by the minimally infectious tissue form of the fungus, it's possible that infectious arthroconidia could develop in a bandage.
People with infected pets have little about which to be concerned. The main risk (which is also very low) is infection from a bite from an animal with disseminated disease. Basic bite avoidance should minimize this risk, however medical care should be sought following any bite and people at high risk of serious infection (e.g. people with compromised immune systems) should take particular care when interacting with infected animals. If a pet owner has to change a bandage on an infected animal, they should wear gloves, double bag and immediately dispose of the bandage, avoid contamination of the environment during bandage changing and thoroughly wash their hands after completing the task.
Image: The infectious arthroconidia of Coccidioides immitis (source: CDC Public Health Image Library #476).
A bird specialty store owner wrote me recently, concerned about potential tuberculosis (TB) exposure. A client's bird had been diagnosed with "human TB" and that person had spent a lot of time with the bird. The source of the TB hadn't been identified, and the store owner was worried about the risk that he/she had been exposed as well.
Is it really TB?
The first thing to consider in a case like this is whether TB was really present. "Human TB" is caused by Mycobacterium tuberculosis. Birds can be infected by M. tuberculosis, but are more often infected by Mycobacterium avium complex (MAC), a related group of bacteria. Based on what the store owner wrote here, it seems that M. tuberculosis was the cause of disease.
Can TB be spread from birds to people?
Probably, but the evidence is sparse. Tuberculosis can be spread from people to birds, and it's likely it can go the opposite direction. However, close and prolonged contact is typically required for TB transmission. Human-to-bird cases tend to be birds owned by people with active TB who have close mouth-to-mouth contact with their birds (e.g. mouth-beak feeding).
What is the likelihood of transmission?
Being in the same room as a bird with TB is probably pretty low risk (just like casual contact with a person carrying TB is low risk). The risk also depends to a degree on the type of disease the bird has. If it has respiratory tract disease it is probably more likely to be shedding the bacterium in its respiratory secretions, which poses a greater risk of transmission than other forms of the disease.
Is there cause for concern?
I guess there's always some degree of concern when it comes to TB, but I assume the likelihood of transmission of TB from the bird to the store owner is quite low. The source of TB wasn't known, but most likely the bird was infected by its owner, and if so, being around the bird's owner is probably as (or more) risky.
Plague has been identified in a dog and cat from New Mexico. It’s not surprising, since plague is present in some wild animal populations in that region, but it’s still noteworthy because of the serious nature of the disease and the potential for transmission to humans.
Plague is a bacterial infection caused by Yersinia pestis. It’s carried mostly be certain types of rodents in different regions of the world, including parts of the southwestern US. It’s usually spread by fleas that bite an infected rodent and then bite a person or other animal, but it can also be spread by close contact with an infected animal. Cases in cats and dogs are uncommon, but occur in areas where plague is present in rodents, when pets have contact with infected fleas or close encounters with infected rodents (or rodent carcasses).
The latest two cases were in Santa Fe and Rio Arriba Counties in New Mexico. No details were provided about the form of plague (e.g. bubonic, pneumonic), the suspected source of infection or whether there is concern about human exposure. Finding plague in a pet is a concern for a few reasons. It indicates that plague is present in wildlife in the area, and people could be exposed from the same sources as the pets (i.e. fleas, contact with live or dead wildlife). Also, transmission of plague from pets to their caretakers can occur, particularly from cats with pneumonic plague (respiratory tract infection). Knowing that a person has had contact with a pet with plague is critical to making a prompt diagnosis. According to the World Health Organization, plague continues to infect more than 2000 people every year.
The New Mexico Department of Health has made the following recommendations:
- Avoid sick or dead rodents and rabbits, and their nests and burrows.
- Keep your pets from roaming and hunting and talk to your veterinarian about using an appropriate flea control product.
- Clean up areas near the house where rodents could live, such as woodpiles, brush piles, junk and abandoned vehicles.
- Sick pets should be examined promptly by a veterinarian.
- See your doctor about any unexplained illness involving a sudden and severe fever.
- Put hay, wood, and compost piles as far as possible from your home.
- Don’t leave your pet’s food and water where mice can get to it.
- Veterinarians and their staff are at higher risk and should take precautions when seeing suspect animal plague cases.
Photo: The vector of Yersina pestis: a flea (click image for source)
A Montreal pediatrics resident has expressed concern about rat bite fever in kids. Dr. Karine Khatchadourian described three cases of this bacterial infection in a paper called "The rise of the rats: a growing paediatric issue," published last year in the journal Paediatrics and Child Health. The article didn't really present any evidence that this is a "growing" issue, but it is a disease of concern.
Rat bite fever is a bacterial infection most commonly (but not exclusively) associated with bites from rats. Healthy rats often carry the bacterium that causes the disease (Streptobacillis moniliformis in North America), and infection can occur when the bacterium is inoculated into the body by a bite, or when it's spread to mucous membranes like the mouth through direct mouth-mouth contact with pet rats (yes, some people kiss their rats).
The disease can be serious, and even fatal, if not properly diagnosed and treated. It's also a classic example of why physicians need to ask their patients about pet contact and why people need to take bites from pets seriously. Knowing that a rat is in the house, and particularly if a bite has occurred, is a key factor in helping make the diagnosis. If the physician doesn't ask the question, this critical piece of information may be missed, along with the diagnosis.
Being concerned about rat bite fever (and other zoonoses) is good, and ways to educate pet owners and physicians about such diseases are needed. However, extrapolating "rat bite fever is bad" to "rats are bad" is a stretch. The statement in the paper "Should we, as health care professionals, advocate to have rats banned from being sold in pets stores?" is over the top.
Every animal carries many microorganisms that can cause disease in people, given the right circumstances. Similarly, every person you meet is carrying something infectious. The key things to consider are:
- What is the likelihood of infection?
- How severe is the disease that may occur?
- What can be done to reduce the risk of infection?
- What is the cost-benefit, i.e. how do the potential risks compare to the potential benefits?
How can the risks be reduced?
- Rat owners need to be aware of the disease.
- Good handling practices are needed to reduce the risk of bites.
- Any bites that occur should be promptly cleaned and a physician contacted if there are concerns.
- Contact of rat saliva with broken skin or mucous membranes (e.g. kissing the rat) should be avoided.
- Physicians need to know whether their patients own pets, including rats, and know what diseases may be associated with those types of animals.
With this type of approach, the risk of infection can be reduced and the ability to properly and promptly diagnose the disease, in the odd case that it occurs, can be maximized.
I don't want to downplay rat bite fever. It certainly can cause illness, particularly in children under the age of 12. A recent paper reported a fatal case in a 14-month-old boy, however in that case the infection was associated with ferrets, not a rat.
Parents of small children need to think about the risks of zoonotic diseases, as well as injuries (e.g. bites) when deciding whether to get a pet, and what type of pet to get. If people like rats, take care of them properly and communicate well with their physician (and if their physician is aware of the issues), then the risks of serious disease are quite low.
Dr. Khatchadourian suggests that parents "should stick to cats and dogs, and steer clear of rats." However, that's no assurance that a zoonotic infection will not occur. There's no evidence indicating the risk of disease is less with those species. It doesn't even eliminate the risk of rat bite fever, since Streptobacillus moniliformis can be found in the mouths of dogs too.
Rather than banning rats from pet stores, we should focus on educating pet owners, veterinarians and physicians about zoonotic diseases.
This isn't an infectious disease topic but I've had a few questions about it nonetheless, so I thought it would be worth making some comments here.
With nuclear meltdown concerns in Japan, some pet owners (particularly on the west coast of the US) are flocking to veterinarians looking for potassium iodide pills for their pets. Potassium iodide is given to people (and I guess it could be given to pets) who have been exposed to radiation or who are at high risk of exposure, as a way to reduce the risk of thyroid cancer.
For pets in North America, and other regions far away from Japan, the risk of radiation exposure from the damaged nuclear power plants appears to be basically non-existent. There's no evidence that, even with a major meltdown, clinically relevant levels of radiation would reach populated areas in North America or beyond.
- Even if something unexpected happened, there are intensive monitoring efforts underway downwind (i.e. east) of Japan to detect any spike in radiation levels. There's no need to take potassium iodide weeks in advance - at-risk individuals only need it at the time of exposure.
- Also consider that if potassium iodide treatment is indicated in pets, it's also needed in people in the same area. Given the available supplies, it'd be hard to justify treating pets if there's not a full supply for all the people who might need it.
- Potassium iodide isn't a benign drug. Overdosing can cause adverse effects, and we don't have good information about appropriate doses for pets. If it was clearly needed, it would be reasonable to make an educated guess from human doses, but with no indication of need, it makes no sense to take the chance.
- Compared to humans, pets are probably at much lower risk of adverse effects from radiation exposure, because pets have much shorter lifespans, but the effects of radiation exposure tend to cause disease over very long periods of time.
What about pets in Japan? That's a different story, since there is greater potential for risk of exposure now and perhaps through food and water in the future. Still, broad use of potassium iodide isn't being recommended in Japan in humans and there's no reason to treat pets any differently. If there are regions where treatment of people is recommended and where there are adequate supplies, treatment of pets may be a good idea.
The CDC's Morbidity and Mortality Weekly Reports has a short report about two plague cases in the US. Plague, while often thought of as a historical disease (the Black Death), is alive and well in wild rodents in some areas of the world, including parts of North America, and human cases continue to occur.
Here are highlights of the CDC report (in italics) with some extra comments.
Plague, caused by Yersinia pestis, is enzootic (present in the population, typically at a low level) among rodents in the western United States. Humans can be infected through 1) the bite of an infected flea carried by a rodent or, rarely, other animals, 2) direct contact with contaminated tissues, or 3) in rare cases, inhalation of respiratory secretions from infected persons or animals. In September 2010, the Oregon Health Authority reported the first two cases of human plague in Oregon since 1995 and the only two U.S. cases in 2010.
Both illnesses began on August 21. The patients, aged 17 and 42 years, lived in the same household and might have been exposed to plague by infected fleas from one of their dogs; that dog was found to be seropositive for Y. pestis by the passive hemagglutination-inhibition assay (dilution of 1:64). One patient acknowledged sleeping in the same bed with the dog during the 2 weeks before illness onset. Both patients had high fever and multiple bilateral inguinal buboes; one patient had hypotension, tachycardia, and acute renal failure and was hospitalized. A gram-negative rod with bipolar staining was isolated from a specimen of that patient's blood.
...25 days after specimen collection, the isolate was identified as Y. pestis... Both patients recovered uneventfully after empiric therapy with doxycycline and amoxicillin clavulanate potassium, respectively, although the latter is not considered effective in treating plague.
Plague is a Category A potential bioterrorism agent. Human infections are rare but can be life-threatening. The plague case-fatality rate depends on the clinical presentation (i.e., bubonic, septicemic, or pneumonic) and timing of antibiotic therapy initiation; if untreated, the case-fatality rate is >50% for bubonic plague and approaches 100% for pneumonic plague. Rapid laboratory identification can help guide therapy.
Sleeping in the same bed with dogs has been associated with plague in enzootic areas. Plague patients with no history of exposure to rodents can be infected by Y. pestis if their pets carry infected rodent fleas into the home. Veterinarians always should recommend flea control to dog and cat owners.
This is an example of a situation where pets can play a role in human infection while not being the direct source of infection. While direct pet-human transmission can occur, this typically involves situations where someone has close contact with a pet that is sick with the plague. Most often, this kind of transmission is associated with close contact with cats with pneumonic (respiratory) plague.
Key aspects of reducing the risk of pet-associated plague in areas where plague is, or may be, present, are:
- Preventing contact of pets with wildlife, living or dead.
- Preventing roaming of pets in the wild.
- Discouraging wildlife from living in or around homes.
- Keeping cats indoors.
- Routine flea control.
More information on plague and pets is available in our archives.
Glanders, a very serious disease of horses, donkeys and mules caused by infection with the bacterium Burkholderia mallei, has made the news again in a rather unusual manner – it has been reported as the cause of an outbreak in lions and a tiger at an Iranian zoo in Tehran.
The story goes that two Amur tigers arrived at the Tehran zoo from Eastern Russia in April 2010 as part of an exchange program between the two countries. The tigers were supposed to be used to help restore the tiger population in northern Iran on the Miankaleh nature reserve, but their living quarters there were apparently still not ready, and thus they were being kept at the zoo. One of the tigers died in December 2010.
And that’s were the story starts to get a little dicey. The Iranians claim the tigers were imported already carrying the disease, and that the last case of glanders at the zoo was 50 years ago. The tigers had already been at the zoo for eight months - although the incubation period for glanders can be months in some cases, it is normally only weeks. The Russians of course insist that the tigers were completely healthy when they were transferred – they’d been thoroughly examined and quarantined prior to being moved. (This makes the most sense to me, since transporting an animal such a long distance is a major stress and increases the risk of illness, and transporting an animal that is already sick would be even more risky. Not a chance I would take with two members of a species of which there are fewer than 900 individuals left in the world.) They also pointed out that a sick tiger from the cold regions of Russia would be much more likely to succumb to illness during the very hot Iranian summer, not during the winter.
Another report said that three lions at the zoo also died from glanders in the last two months, and subsequently another 14 lions were diagnosed with the disease, all of which were put down by the authorities. The main concern seemed to be the spread of the disease from the big cats to the feral cat population, and then to the human population. This second report states that “the tiger died after being fed contaminated meat, though it is possible it could also be related to the glanders.” Yet another report said that the tiger was infected with feline immunodeficiency virus (FIV - the feline equivalent of HIV).
Facts to keep in mind:
- Glanders is an highly contagious disease, and highly fatal (B. mallei is even classified as a Class B bioterrorism agent).
- Animals that do recover from the disease can become long-term carriers of B. mallei, and are a risk to other animals (and people). Prompt euthanasia of affected animals is therefore often the primary means of controlling outbreaks (but the bacterium is susceptible to antibiotics).
- The infection can be transmitted to other animals (and people), usually through close direct contact or contact with oral and nasal secretions and discharge from skin ulcers. It can also be transmitted by eating tissues from infected animals.
- The bacterium is killed by most disinfectants, and UV radiation (sunlight).
Glanders can affect species other than equids, including people and cats, however there is very little information available about glanders in any felids, let alone lions and tigers. Theoretically it might be possible for the disease to spread from the zoo animals to feral cats and then to people, but I don’t know how many feral cats are brave (or stupid) enough to wander into a lion enclosure. There’s also a possibility that a glanders-positive feral cat may have infected the zoo cats (but again, it would have to be very brave, or very stupid). It is also unclear what tests were used to confirm that the big cats were infected with glanders, and it is unknown if other animals at the zoo have been tested. Since this is typically a disease of equids (and has also been found in goats and camels), I would certainly be checking these animals first.
The big question is, where did the glanders come from in the first place? It seems unlikely that the tigers brought it from Russia, when the disease is actually endemic in Iran (even though they’d had no diagnosed cases at the zoo for many years). Is there a carrier animal in the zoo? Were the animals infected by eating contaminated meat? Was it brought in by feral cats? The source needs to be identified and addressed or animals will continue to be infected, which is particularly bad news for the kinds of rare species that may be found in a zoological collection. Some more details about the testing would also be appreciated – given the severity of this disease, and the severity of the consequences for positive animals (euthanasia), one needs to be as sure as possible that these animals are infected with B. mallei and not something else.
Photo: Amur Tiger (Panthera tigris ssp. altaica) (click image for source)
Cowpox virus is an example of a virus with a misleading name. It's place in history is from Jenner's observation that milkmaids who had been infected with cowpox were resistant to smallpox, leading to the use of cowpox (which causes very mild disease) to protect against smallpox (which is very, very bad). While cattle can be infected, they are not the true host of this virus, and infections in cattle are actually quite rare.
Various rodents are the true reservoir of cowpox. Other species can be infected from contact with infected rodents, including people and pets. Among pets, cats are most commonly infected, with most reports coming from central Europe. Cats may be infected more often because they may more often have close encounters with rats, but they are probably also inherently more susceptible to the disease than dogs.
Cowpox infections in dogs are very rare, but a case was recently described in Veterinary Dermatology (von Bomhard et al 2011). It involved a five-month-old Rottweiller from Germany that developed a very mild case of cowpox, with a single nodule on its muzzle. The dog recovered uneventfully, but it was an interesting case of a rare disease in a dog, and one that has some human health considerations.
People can be infected with cowpox from pets. In particular, infections from pet rats have been a problem in central Europe over the past few years. Outbreaks of human infections have been identified associated with widespread dissemination of infected rats from infected breeding or distribution facilities. Infections have also been reported from cats, and cats are a significant concern because of their ability to be a bridge between wild rodents and people, and because of the close contact they tend to have with people.
It's not surprising that disease was so mild in this Rottweiller puppy, and the risk to people in contact with the dog was probably limited because of the mild nature of the infection. No human cases were reported associated with this dog. Human infections from dogs have not been reported, largely because the disease is so rare in dogs and perhaps because when they are infected, dogs tend to have very mild disease. Cowpox is of minimal concern for most pet owners, but it something to be aware of when obtaining a new rodent, especially in regions where cowpox is an issue, and when dealing with cats in areas where cowpox is endemic in wild rodents. Some basic preventive measures include:
- Pet rodents and cats (especially newly obtained rodents) that develop skin lesions should be handled with care and be examined promptly by a veterinarian.
- Wild rodents should never be caught and kept as pets (for various other reasons, as well).
- Contact between domestic pets (particularly pet rodents and cats) and wild rodents should be prevented.
An upcoming article in the journal Emerging Infectious Diseases entitled "Zoonoses in the bedroom" has attracted some attention in the press. I haven't been able to access a copy yet, but will probably write about it soon. However, one article that was written about the paper had a pretty weak lead-in piece:
"Nikki Moustaki knew something was wrong when she got strep throat for the sixth time in a year. Her doctor wanted to take out her tonsils. But Moustaki, an otherwise healthy 30-something, was determined to uncover the source of the infection. "I saw a bunch of specialists, and one suggested my dog might be a carrier," said Moustaki, a New York City-based dog expert and trainer. "I had never thought of that. When you think of contagious diseases in dogs you think of rabies and ringworm, you don't think of strep." After four walks a day on the streets of Hell's Kitchen, Moustaki's dogs -- a schnauzer called Pepper and Ozzie, a schnoodle -- would curl up beside her in bed. Following her doctor's surprising suggestion, Moustaki started cleaning Pepper and Ozzie's paws with baby wipes after each walk. And she's been strep-free ever since."
While it's good to see the potential role of pets in human disease considered (since it's often overlooked), this is a example of the opposite end of the spectrum: implicating pets with absolutely no evidence, and actually, contrary to all available evidence. Saying that cleaning her dogs' feet prevented her from getting strep throat makes little sense on many levels. Firstly, if it actually made the difference, then she wasn't really getting strep from the dogs, it was coming into the house on the dogs' feet from the ground outside. There's no evidence the outdoor environment is a relevant source of strep. If strep was present on the dogs' feet, it would have to make it to her nose and mouth, and that degree of contact is hopefully unlikely (and if present, it would be associated with a lot bigger concerns that strep). Further, despite various studies, there is no evidence that dogs are even rare reservoirs of Group A Streptococcus, the cause of strep throat. Recurrent strep throat in people is caused by repeated exposure to infected people.
Like I said, it's good to see recognition of the potential role of pets. The next step, however, has to be looking for the evidence. It's not hard to find a few good references that talk about the role (or lack thereof in this case) of pets in human strep infections. Implicating the pet and recommending a rather bizarre foot hygiene regimen isn't really helping anyone.
Is it just coincidence that the infections have stopped in this woman? Probably. Recurrent infections don't tend to go on forever. However, maybe her increased attention to cleaning her dogs' paws also led to her paying more attention (consciously or otherwise) to her own hygiene practices, which would have probably played a greater role in disease prevention.
Pseudorabies is one of those diseases with a really bad name (although it's a pretty bad disease too). It has nothing to do with rabies. Rather, it's caused by a herpesvirus; porcine herpesvirus 1. The name "pseudorabies" presumably came into existence because it causes neurological disease that, in some cases, can look like rabies.
Pigs are the reservoir of this virus, and it's a very important cause of pig disease in some regions. Spillover infections can occur in many different mammals, including dogs, cattle and sheep, and infections in these species are typically fatal.
Pseudorabies is not as widely distributed internationally as rabies, but it is present in wild boars in many regions, including many European countries. Infections in dogs are sporadically reported, typically in hunting dogs infected by contact with wild boars.
Recently, a case of pseudorabies (also known as Aujeszky's disease) was diagnosed in a dog in Luxembourg, the first diagnosis of the disease in the country since it was identified in domestic pigs in 1999. (Infections in wild boars were suspected in late 2009 but not confirmed.) Few clinical details are provided in the report to the OIE, beyond the fact that the dog died. Contact with "wild species" was listed as the source of the infection, which presumably was contact with wild boars.
Unlike rabies, pseudorabies is not a significant concern in people.
A few days ago, I wrote about tuberculosis (TB) exposure in several people who performed a necropsy on an infected dog. As part of that investigation, a cat in the household was tested and was also positive for TB. It was euthanized because of the public health concerns. A logical question from a reader was "Is there no treatment for animals, as there is with humans?"
Diagnosis of tuberculosis in an animal often results in prompt euthanasia, and some individuals and groups have euthanasia as a standard recommendation.
- We have no data about how to properly treat an infected animal.
- We have no data about how effective (or ineffective) treatment may be.
- It's not easy to test animals before or during treatment to see if they are shedding the TB bacterium (Mycobacterium tuberculosis).
- It's such a concerning disease in people that the inclination is to err on the side of caution when it comes to public health.
Is it an appropriate response?
In some circumstances, it probably is. In other circumstances, treatment shouldn't necessarily be dismissed. A major problem is the knowledge gap.
- We don't know whether infected animals pose any risk to people. Human-animal transmission can occur, but it's unclear whether animals can transmit the infection back to people.
- If transmission between pets and people occurs, we don't know what circumstances are involved. TB is not readily transmitted even between people. Short term exposure is not a major concern. It's likely that close and prolonged contact is required for transmission from pets, but we don't know for sure.
- We don't know if certain infected animals are higher risk than others, although there probably are differences. A dog with respiratory TB and active disease is probably a much higher risk than a dog with a localized TB abscess.
- We don't have easy and accurate ways to test pets for TB exposure and shedding. In people, sputum cultures are tested by having people spit in a cup. Getting a sample like that is obviously difficult in dogs. Collecting a good sample for testing is much more involved in pets and not amenable to routine testing (for research or monitoring).
- We don't know for how long to treat a pet with TB, or which drugs are optimal for use.
Treatment might be reasonable when there is an animal with mild disease (or no signs of disease), when the animal was infected from a household contact (meaning that some degree of TB exposure has already occurred in the household and the dog would probably only be a secondary source of exposure), when there are committed owners who are willing to embark on time consuming and expensive treatment, when owners are able to keep the dog away from other animals and people during the treatment period, and when there is an understanding that treatment may not work.
When might treatment not be a good idea?
- When the animal is shedding the TB bacterium in respiratory secretions.
- When the owners cannot afford prolonged and expensive treatment and monitoring.
- When the owners cannot be relied on the administer every dose of medication and make every required follow-up appointment.
- When owners cannot be relied on to keep the dog away from other dogs and animals (and people) during the treatment period (or at least during the initial period).
- When there are high-risk people in the household, such as people with HIV.
- When serious disease is present, such that the chances of recovery are low.
Tuberculosis (TB) is a very important public health issue. Caused by the bacterium Mycobacterium tuberculosis, TB is likely the most widespread human infectious disease. Although it primarily affects people, it can rarely affect various animal species as well, including pets. The relevance of dogs to human TB is unclear: we know dogs can (rarely) be infected by M. tuberculosis, but it remains uncertain whether infected dogs pose a risk to their human contacts (presumably dogs become infected in the first place from one of their human contacts, who is therefore also a source of exposure to other people). There is little information available about this risk.
People working in the veterinary field are at increased risk of exposure to many infectious agents. For this reason, there are standard practices that are (or at least should be) used to reduce unexpected exposures. A good example of such an unexpected exposure and the consequences thereof is presented in a case report from Switzerland recently published in Veterinary Microbiology (Posthaus et al 2010).
The report describes a seven-year-old Ibizan hound that was referred to the University of Bern's small animal clinic because of lethargy and vague neurological abnormalities. The dog was originally imported from an unknown country in southern Europe and was adopted from a shelter at two years of age. The animal was ultimately euthanized after it became very ill, with severe neurological disease and respiratory arrest. On necropsy, masses were identified in the brain and liver, and infection with Mycobacterium avium complex was suspected. However, subsequent testing identified M. tuberculosis, triggering an investigation of all human and animal contacts.
Testing included a blood test called the IGRA, which detects people who are either infected or exposed. The test can't differentiate between a recent infection and a past infection/exposure, so a positive result needs to be interpreted in conjunction with an evaluation of the person's history, to determine if previous exposure is likely.
The Ibizan's two owners tested negative. None of the veterinary clinicians that worked with the dog before its death were positive (or more specifically, none were positive and the result thought to be related to exposure to the dog), including the three people who were involving in intubating the animal (placing a breathing tube - a potentially high-risk procedure in an animal with TB). In contrast, six pathologists who were involved with the necropsy were positive, including the three who were most closely involved. Two of these individuals had no apparent risk of previous exposure, so infection from the dog was suspected
Additionally, a cat that lived in the house tested positive. Because of the potential that the cat was infected and concerns about transmission to people, it was euthanized.
This case had some rather interesting findings:
- TB infection in a dog. Clinical disease caused by TB in dogs is rare, and signs can be quite vague, as in this animal. This was not a case of classical respiratory tract TB.
- Infection occurred in the dog well after its presumed time of exposure. The source of infection was unknown, but given the family's history, it is reasonable to suspect that the dog arrived in the country already infected. This shows how diseases like TB with potentially long incubation periods can catch you by surprise. The dog was treated with high doses of steroids initially, possibly triggering re-activation of dormant TB because of immunosuppression.
- Infection of people with TB while conducting a necropsy, demonstrating the occupational risks that can be involved in such procedures. The use of power tools to open the skull is commonplace in veterinary pathology, and may have played a role here by aerosolizing the bacterium. The institution has now changed standard necropsy practices to reduce the risk of subsequent exposures.
- There was no apparent infection of any people when the dog was alive. Presumably, it was not shedding much, or any, of the TB bacterium in its respiratory tract.
- Possible transmission of TB from the dog to a cat. However, it can't be stated with certainty that the dog and cat were not infected by the same unknown source after the dog was adopted. Testing was not performed on the cat after it was euthanized, so it is possible that it was not infected with TB, but with another related Mycobacterium.
This case doesn't indicate that we are dealing with a new issue. Rather, it is possible that there are many more dogs that are apparently healthy but infected with TB. These animals may pose little risk to people, especially if they don't have respiratory disease, but it's an area where information is limited. More attention needs to be paid to the risk of interspecies transmission of TB, how to identify it, how to reduce the risk, and how to manage infected animals. There's debate about whether exposed but healthy animals like the cat in this case should be euthanized because of the potential (but completely unknown) public health risk. Without good research data, we can't provide reliable answers to questions about the risks.
Image: Ibizan Hound (click for source)
Humane societies and shelters are often overwhelmed by the number of animals that come in. It's pretty uncommon to see much (if any) empty space in most shelters, and overcapacity shelters lead to increased risk of disease transmission, outbreaks and suboptimal care of the animals that are there.
One way of helping deal with overcrowding is fostering animals to people's homes for periods of time. Typically, foster homes take animals when shelters are at capacity, or take specific animals such as nursing cats, which are more difficult to care for properly in a shelter.
Most places have protocols for fostering, but they're not always very comprehensive and they don't always adequately cover some important areas. If you are thinking about fostering shelter animals, you need to think about the risks and whether you can manage them.
Are there people in the household that are at increased risk of infection?
Fostered animals should be assumed to be at higher risk of carrying and transmitting various infectious diseases. They can have high rates of carriage of various intestinal bacteria and parasites, along with a host of other microorganisms (e.g. ringworm). They may also be more likely to bite and scratch, not necessarily because they are aggressive, but often because they are young animals that may do so when playing. They may also be more likely to poop in the house.
Households with children under the age of 5, elderly individuals, pregnant women or people whose immune systems are compromised are at increased risk of various infections, both in terms of the likelihood of becoming infected and the likelihood of developing more severe disease. Households with these types of individuals should not foster animals. They are much better off having their own lower-risk pets.
Are there any "resident" pets in the household?
You might expect that someone willing to foster animals would also have their own pets, but that's not always the case. Non-pet owners are actually ideal, since this negates any risk of diseases being spread from or to household pets that live there long-term. However, it's more typical that foster homes also have such resident pets.
Are there any pets in the household that are at higher risk for infection?
As with people, there are some animals that are at increased risk of infection. These include the very young, very old, pregnant and pets with compromised immune systems. The latter group would include pets with chronic illnesses, those being treated with high doses of steroids for various diseases, animals with cancer, animals with diabetes, and a range of other issues. People owning a pet that fits into one of these categories should not foster animals because of the risk to their own pet.
How do you reduce the risks associated with fostering animals?
- May sure there are no high risk people or pets in the household.
- Make sure the shelter or organization knows what they are doing. Make sure they have a clear protocol that says who will be fostered and how it's done.
- Look at the animal before you get it. Visit it at the shelter. See if it looks healthy. If you have any questions, make sure it's examined by a vet before it reaches your home.
- Use good hygiene. Wash your hands regularly. Properly clean up feces and clean litterboxes regularly.
If you have pets of your own:
- Make sure they are vaccinated and on an appropriate parasite control program.
- Keep the new animal away from your pet at the start. That lets you find out more about the animal, and it gives you more time to see if there are potential infectious disease concerns.
- Do a controlled introduction of the new animal. Slow, supervised introduction of the animals can reduce the risk of bites or scratches.
Fostering is a good way to reduce pressures on humane societies and shelters, and to provide better care for some animals, like pregnant animals or those with young kittens/puppies. A good fostering program can be set up with limited risk to all involved, but infectious disease risks can never be completely eliminated. By accepting a new animal into your house, you increase the risk of exposing yourself and anyone else (human or animal) to infectious diseases. That's just a fact of life.
The Canadian Food Inspection Agency (CFIA) and the Public Health Agency of Canada (PHAC) have issued warnings about frozen beef pet food made by Surrey Meat Packers of Cloverdale, BC. The Beef Pet Food consisted of frozen 500 g blocks of beef (presumably raw) sold between October 8 and 23, that may contain E. coli O157.
This is a bigger concern that the periodic Salmonella recalls that have affected both raw and cooked pet foods. Salmonella is an important cause of disease, but E. coli O157 is a particularly nasty bug. This bacterium can cause very serious disease in people, including hemolytic-uremic syndrome (HUS), a life-threatening problem that can lead to kidney failure. The infectious dose is very low - all it takes is ingestion of a small number of bacteria for disease to develop. Risks to people from this recall mainly involve the potential for cross-contamination with human food or inadvertent ingestion of E. coli O157 from pet food via contaminated hands. Transmission of E. coli O157 from dogs to humans has been reported, but is probably quite rare.
The health impact of E. coli O157 in dogs is less clear. Experimental infection of dogs with the bacterium has resulted in disease, but studies of naturally occurring diarrhea have not provided convincing evidence that it is a significant cause of illness in dogs.
No illnesses have been reported in association with this batch of contaminated meat. Given that the contaminated meat was sold until October 23 (a few weeks ago), it's likely that most of the meat has already been consumed at this point. However, people who have purchased this product and still have some sitting in the freezer should check it. Affected product may not have a label indicating a packing or best before date, in which case you should assume it's contaminated (better safe than sorry). Any meat from that period (or of unknown history) should be discarded.
This is yet another important reminder of the fact that raw meat products can easily be contaminated with various pathogenic bacteria. People who choose to feed raw meat to their pets must ensure that they take careful precautions to reduce the risk of human infection from cross-contamination or contact with pet feces. More information about raw meat feeding can be found on the Worms & Germs Resources page.
British champion rower Andy Holmes has died of leptospirosis, which was suspected to have been acquired from the water during the annual Boston Rowing Marathon on the River Witham (UK) in September. The 51-year-old Holmes, an accomplished Olympic rower from the 1980s, started to feel unwell in the days after the race, and developed a fever. He was subsequently diagnosed with Weil's disease, a serious form of leptospirosis that can cause liver failure.
In some ways, this is being written off as a very rare and unfortunate event. It's always hard to determine how aggressive to be when making recommendations about avoiding infections that can be acquired from common recreational and occupational activities.
The race's welfare officer stated "Part of any rower's training is being warned about water safety. If you fall into water you must wash thoroughly and if you think you have ingested any water seek medical advice." The problem is, exposure to water during rowing and similar events is basically unavoidable. Splashes of small amounts of water into the eyes, nose, mouth or cuts/scrapes could be enough to inoculate potentially harmful microorganisms into the tissues. People aren't going to run to the physician after every potential exposure. Knowing whether or not the water source has previously been implicated in leptospirosis infections may be useful, but it doesn't tell you anything for certain.
General recommendations for people working around water include:
- Covering cuts and sores with waterproof bandages.
- Washing hands, particularly before eating.
- Avoiding contact of water with the eyes, mouth and nose, whenever possible.
- Avoiding ingestion of any amount of water.
- Ensuring their physician knows about the potential for water exposure should they become sick.
Obviously, complete avoidance of water exposure is impossible for many people, and the overall risk is very low. Weil's disease is a rare condition but it does occur, both as sporadic cases and large outbreaks. It's usually treatable but can be fatal, so it shouldn't be dismissed.
Issues with pets and leptospirosis are similar. Pets, mainly dogs, become exposed from contact with water that has been infected by Leptospira bacteria from the urine of infected wildlife. Infection can cause a broad range of disease in dogs as well, from subclinical to acutely fatal. Vaccines for certain strains are available for dogs who are at higher risk of exposure. Talk to your veterinarian about whether your dog should be vaccinated against leptospirosis. More information about leptospirosis in dogs and cats is available on the Worms & Germs Resources page.
Image: Andy Holmes sits behind Steve Redgrave after winning a gold medal for Britain at the 1988 Seoul Olympics.
An investigation is underway regarding mysterious deaths of dogs that have been walked in public areas of Sandringham, the Queen's 20 000 acre estate in Norfolk. Gastrointestinal disease, consisting of vomiting, diarrhea and lethargy, has afflicted an unknown number of dogs. One area veterinarian reports five deaths and four dogs with serious illness. No cause has been identified, but it's unclear how much testing has been done to date. There was also a cluster of sick dogs last year, but that outbreak was written off as a one-time event caused by a virus.
Outbreaks like this can have a wide variety of causes, including viruses, bacteria, parasites or toxins. Determining the cause of a diarrhea outbreak is often difficult, because of the numerous potential pathogens/toxins, significant gaps in knowledge about what's normally part of the dog's intestinal bacterial population, and limitations of existing diagnostic tests.
(Another possibility is that this isn't really an outbreak, but rather increased reporting of disease that has always been there. I doubt that's the case here, but it is a possibility - dogs get sick all the time. If the baseline level of gastrointestinal illness is just now being scrutinized, and public awareness is increasing because of news reports, you can get a spike in cases that have nothing to do with an outbreak.)
The Animal Health Trust has been called in to investigate. This will presumably involve several approaches, including getting more detailed information about the number of sick dogs, identifying any common links among sick dogs, comparing activities of sick dogs with those of healthy dogs, and testing of feces for various potential causes of disease.
There's no word about whether the Queen's corgis are being restricted from the area.
A large whooping cough (pertussis) outbreak has been ongoing in people California in 2010. This bacterial infection, caused by Bordetella pertussis, is a highly transmissible disease that can result in serious problems (including death) in young infants. At last report, there were over 6000 cases of whooping cough, making this the largest outbreak in 60 years. Over 200 infants have been hospitalized, and there have been at least 10 deaths. Nine of the 10 deaths were in infants less than two months of age. Infants in this age group have little to no immunity to the disease because they haven't been vaccinated, and they are more prone to severe complications.
Bordetella pertussis is a human bacterium. It does not infect animals and animals are not direct sources of infection. (Actually, experimental infection of neonatal puppies with large doses of B. pertussis can result in shedding of the bacterium by a small percentage of dogs, but that's not particularly relevant to the normal household situation). Therefore, people don't need to worry about infecting their pets and pets passing the infection on to other people. However, it's not impossible that pets could play an indirect role in transmission. A pet's haircoat could possibly become contaminated with the pertussis bacterium from someone coughing around it, or touching it with contaminated hands. The bacterium could survive on the haircoat for a while (probably days), and someone could potentially get the bacterium on their hands by petting it, and subsequently become infected.
What are the odds of this happening? Who knows. It's not something that anyone has investigated, as far as I know.
Could dogs and cats be important sources of pertussis in households? Probably not. I assume that if there is a person with whooping cough in a household, that person is more likely to be the source of infection for other people than a pet.
Could pets spread pertussis outside the home? That might be a more realistic concern. People with pertussis might keep themselves away from others and stay at home, but if they contaminate their dog's coat and the dog meets people on a walk or at the park (or at a veterinary clinic, or anywhere else), I have to wonder whether there could be the potential for spread of the disease.
What should we do about this? Common sense should prevail, and itt's important for pertussis as well as other diseases. If someone in the household has an infectious disease that is transmissible and for which a pet could potentially be a vector, some basic precautions should be taken. Good attention to hygiene might help reduce contamination of the pet's haircoat. This includes regular handwashing (especially after coughing and before petting an animal), avoiding coughing close to the pet and not letting the pet sleep close to the person's head. Keeping the pet away from people outside the house, or at least limiting it's contact with high-risk people might also be useful. In particular, keeping pets that might have been contaminated away from infants would be wise.
Overall, the risks are very low. We don't need to fear dogs and cats as potential pertussis vectors. However, in the absence of proof that there's no risk, and with a highly transmissible and potentially serious disease, use of some simple infection control measures makes sense.
The California Veterinary Medical Association has published recommendations for dog park safety. The document, entitled "Dog parks harbor risks as well as fun" emphasizes the benefits of park visitation but points out some risks and recommended precautions. Some of the risks associated with park visits include bites, scratches, and exposure to various infectious diseases.
Some basic and practical precautions that are recommended include:
- Ensure your dog's vaccination status is current.
- Make sure your dog is socialized and behaves well around people and other animals.
- Monitor your dog closely.
- Avoid mixing small dogs and big dogs.
- Bring water for your dog to drink.
- Clean your dog's paws when you leave the park (I'm not sure that one's very useful).
- Have your veterinarian check your dog regularly for parasites (and other infectious diseases or risk factors).
- Talk to your veterinarian about any (other) precautions you should take.
Overall, the document provides some useful and very practical information. A few things I would add:
- Keep your pet away from the park when it's sick.
- Make sure you promptly pick up dog poop and dispose of it properly.
- If it's an off-leash park, spend a few minutes watching the other dogs that are there before deciding whether to let your dog off its own leash.
- Make sure your veterinarian knows that your dog goes to the park if it becomes sick. There are some diseases that are more likely in dogs that visit parks, and outbreaks can also be associated with parks. Knowing that your dog has access to a dog park might be an important part of the diagnostic process. As well, knowing that you visit the park regularly might change your veterinarian's recommendations for vaccination and deworming.
A UK woman is both grieving the loss of her husband and battling illness she thinks came from a new pet parrot. The 67-year-old woman, who has chronic lymphocytic leukemia, obtained the bird to keep her company as her husband was dying of cancer. She says that she's never felt right since she obtained the bird. She is also upset that the bird is not very tame, saying "Jasper is clearly a wild bird, and they do carry all sorts of germs, so it is a worry for me."
Since her husband's death, the woman has had three rounds of antibiotics to treat a respiratory tract infection that refuses to go away. No more details are provided, and presumably (hopefully) her doctors have tested or treated her for psittacosis, a disease caused by Chlamydophila psitacii - a microorganism that can be acquired from birds, especially psittacine birds like parrots.
This story raises a few relevant questions:
Was it a good time to get a pet?
- That's a tough question. Getting a petting during a difficult time can help many people cope, and having the pet while a family member is sick can be very beneficial. On the other hand, bringing a new pet (with the associated new pet issues) into an already stressful situation can be a problem. Also, with both the woman and her husband being sick and having weakened immune systems, there are some infectious disease risks that need to be considered. The cost-benefit of getting a pet in a situation like this is hard to determine, and it varies greatly between households. At a minimum, anyone in such a situation who is considering getting a pet should learn about potential pet-associated disease risks first so that they can make an informed decision.
Was a bird a good pet to get for this household?
- Another question without a clear answer. Birds can be good companions, but they also carry a few diseases that are of concern, particularly for people with weakened immune systems. It's hard to say whether a pet bird is higher risk than a pet dog or cat. It probably is lower risk from some standpoints (e.g. bites, scratches) but higher risk for certain diseases. The key is, as mentioned above, being informed about potential disease risks and what can be done to reduce these risks. With that information, you can make a more educated decision about whether a specific pet is appropriate.
- Also, in high risk households like this, getting a new pet examined before it makes it to the household is a good idea. Such an exam provides an opportunity for a veterinarian to identify any concerns, ranging from obvious signs of disease to inappropriate behaviours. Identifying these problems before the pet makes it home allows them to be addressed quickly. This might involve treatment, prompt training, keeping the pet somewhere else for a short time while a problem is addressed, or a recommendation to return it to where it came from because of a major concern. It's much easier to do these things (especially returning the pet) before it has made it home and people have become attached.
Should you assume that a captive-bred bird is a disease-free bird?
- Absolutely not. Captive-bred does not equal disease-free. In fact, for some diseases, rates are higher in captive-bred birds. (I'm definitely not advocating getting wild-caught birds... just trying to make it clear that birds from breeders can carry various infectious diseases too). The point is, getting a bird from a reputable breeder is a good start, but it doesn't negate the risks. Healthy, well cared-for birds can carry a variety of microorganisms that can infect people. Risks are higher for people with compromised immune systems, such as the individuals in the household in this case.
Pet ownership always carries some risk of infectious disease transmission. Almost always, that risk is manageable and acceptable considering the positive aspects of pet ownership. However, thought needs to go into the process to ensure that the risks are minimized and acceptable in any given situation.
Image: Green Indian Ring-Necked Parakeet
Veterinarians are reporting a potential cluster of leptospirosis cases in dogs near Lake Aquitaine in Mississauga (Winston Churchill Blvd. & Derry Rd. area). Leptospira gryppotyphosa has been confirmed in one dog, with other cases being suspected but not confirmed because owners declined testing.
Leptospirosis is a bacterial infection caused by different types Leptospira spp. These bacteria like to live in water and in moist conditions, and infections in dogs most often result in kidney disease. The bacterium is shed in the urine of infected animals. Leptospira gryppotyphosa is mainly found in wild voles, raccoons, skunks and opossums, and these animals can infect various environmental areas. Any animals exposed to outdoor environments in endemic areas can become infected from ingesting infected water or from contact of infected water with the mouth, eyes or nose, or cuts or other broken skin.
People in the area where these cases have been found should take particular care and probably avoid letting their animals wander into the water or wet areas. A vaccine is available to reduce the risk of leptospirosis, including disease caused by this Leptospira type. Vaccination of pets that are exposed to water or wet habitats in areas where lepto is present is a good idea. People in the Lake Aquitaine area should be particularly vigilant and vaccination of pets would be a good idea.
The woman was admitted to hospital with a fever, headache, neck stiffness, confusion, difficulty speaking and nausea. These signs are suggestive of meningitis and a spinal tap was supportive of that presumptive diagnosis. Blood samples were also taken, and the same bacterium, Streptococcus zooepidemicus, was isolated from both blood and spinal fluid, confirming a diagnosis of S. zooepidemicus meningitis. She was treated and improved, but did not fully recover.
Streptococcus zooepidemicus is primarily associated with horses, although it can occasionally be found in other species such as dogs. After the diagnosis, the woman's family was questioned about her hobbies and it was revealed that she was an avid horsewoman. Further, she had been bitten by her horse the previous week. That was the presumed source of infection, but it doesn't appear that any further investigation was undertaken.
Associating the meningitis with the bite is reasonable, but it's not definitive. Streptococcus zooepidemicus infections in people have occurred in the absence of bites or other clear sources of exposure to horses, so the bite wasn't necessarily the problem. Regardless, it indicates the need to be proactive and properly treat any horse-associated wound, be it a bite or any another wound that gets contaminated with bacteria from the horse or its environment.
This was a very unusual case. People shouldn't be overly concerned about getting S. zooepidemicus meningitis from their horse. However, it should serve as a reminder that bad things can happen periodically and that proper attention to general hygiene practices and bite wound care is always important.
On a side-note, I thought the title "A horse bite to remember" was a bit crass, since the woman is now unable to live independently because of severe amnesia (memory problems) as a result of the infection. Maybe they were trying to be ironic, but it seems below a journal such as Lancet.
This Worms & Germs blog entry was originally posted on equIDblog on 10-Oct-10.
In response to a case of plague in prairie dogs in Saskatchewan's Grasslands National Park, park officials are dusting prairie dog burrows with insecticide to try to control fleas. A single case of plague, a serious bacterial infection caused by Yersinia pestis, was identified in a prairie dog in the park earlier this summer. Plague is present in some areas of North America, but it's rare in Saskatchewan. It circulates in wild small mammals, and prairie dogs are particularly susceptible to infection. The main mode of transmission is via fleas, which feed off infected animals, then bite and infect other animals.
Prairie dog numbers at the park have dropped by 50-70% this summer, however it's not known whether plague is involved in this, as there has also been a drought. It's fair to assume, though, that if there has been one case of plague found in the park, there have probably been many other undiagnosed cases. Whether or not plague is responsible for the large drop in prairie dog numbers, measures to try to reduce plague transmission are a good idea because of the impact it can have on the prairie dog population (and those of other wild mammals), as well as people or pets that may venture into the area. Anyone or anything walking through the area could plausibly be bitten by an infected flea. The odds are probably pretty low, but park officials are trying to keep people and pets out of the park to reduce this risk.
The world is certainly getting "smaller," especially in terms of infectious diseases. One example is the renewed controversy this month over the existence of Lyme disease in Australia. A Sydney man was recently diagnosed with the disease following his death, and now a doctor from Laurieton claims to have "absolute proof" of at least two other Australians with the infection.
Lyme disease is caused by infection with one of three species of Borrelia, previously all known as Borrelia burgdorferi. The disease is transmitted by a few specific species of ticks belonging to the genus Ixodes. It is relatively common in areas of North America (including some parts of Canada) and Europe where these tick species are also found. Ticks become infected by feeding on reservoir hosts, which are typically small mammals. Early signs and symptoms in people following a bite from an infected tick can include a rash, fever, headaches, tiredness and joint pain. The disease can be very difficult to diagnose because the initial signs are quite non-specific, particularly if the person does not report being bitten by a tick.
None of the tick species known to transmit Lyme disease are found in Australia, although there is one species of Ixodes tick there which some believe is a potential candidate for a vector. However, after testing some 12 000 of these ticks, evidence of Borrelia infection has still not been found. Also, none of the known reservoir hosts of Borrelia are said to live in Australia, and no other hosts have been identified.
The Laurieton physician, Dr, Mayne, claims he has "absolute proof" of Lyme disease in at least two of his patients, and says he has about 30 more patients with the disease as well. "Proof" is a very strong word. Not only is the disease hard to diagnose clinically, but there is also no perfect test that can detect infection for certain. Even the DNA test on which Dr. Mayne is hanging his hat can be prone to false-negative and false-positive results. The article also does not state whether or not the infected patients traveled outside the country and could have potentially picked up the disease in a Lyme-endemic area. Further investigation is needed before anyone can claim to have "proof."
So why am I writing about this situation on a zoonotic disease blog, when there hasn't even been any mention of pets, and the disease can't be directly transmitted between people and animals anyway? Because this is a perfect example of a situation in which physicians and veterinarians could potentially work together for the greater good, under the "one health, one medicine" banner. Dogs in particular can also be affected by Lyme disease. If the Australians really want to know if Lyme disease has made it to their shores - or perhaps some other tick-borne disease that mimics Lyme - then they shouldn't just be looking in people. By alerting veterinarians that Lyme disease or a similar condition is cropping up in humans, they can start to look for it in the animal population as well. If they're left unaware, Australian veterinarians may not consider Borrelia as a potential cause of illness in their patients and therefore not test for it. If pets also start testing positive for Lyme disease, then hopefully that would be communicated back to the human medical community to increase testing of suspect cases there as well. If more cases are identified, either human or animal, then further efforts could be taken to identify the tick source and reservoir hosts in Australia.
More information about Lyme disease and ticks in dogs is available in the Worms & Germs archives.
Image: The "classic" bulls-eye rash associated with a tick bite transmitting Lyme disease (source: CDC Public Health Image Library #9874)
Veterinarians are reporting an apparent spike in cases of leptospirosis in dogs in southern Michigan. Leptospirosis is considered a re-emerging disease in many areas of North America. This disease, caused by various types of the Leptospira bacterium, can affect many different species, including dogs and people. A wide range of illnesses can result, including fatal infections. In dogs, kidney failure is a common problem.
Classically, leptospirosis is diagnosed in dogs that spend time in the woods and similar areas, where they may be exposed to the bacterium from contact with the urine of infected wildlife. Different types of Leptospira have different animal hosts, and infected hosts can shed large numbers of bacteria in urine. These bacteria can survive in wet conditions for long periods of time, and other animals can be infected through ingestion of urine-contaminated water or contact of urine-contaminated water with broken skin (e.g. tiny cuts or open sores on their feet) or mucous membranes (eyes, mouth, nose).
Michigan vets have suggested that the recent spike in cases is the result of local highway construction, which may have driven rats out of their normal habitats and into areas that people and dogs frequent. That's possible, but it could also be increasing natural re-emergence of the disease, or increasing recognition of the disease, as more attention is being paid to it. Regardless, an understanding that this disease is a problem in the area is important to allow for prompt diagnosis (and proper treatment), as well as preventive measures.
A vaccine is available, but it is not 100% protective and only protects against certain strains of Leptospira. Nonetheless, it's still a good idea in areas where disease is caused by the strains present in the vaccine and when dogs have a reasonable chance of being exposed.
People can also get leptospirosis. Most often, they are exposed just like dogs: from the outdoor environment. However, pet-to-human transmission has been reported, mainly involving pet rats (since rats are an important reservoir host). People who have contact with an infected dog must take precautions to reduce the risk of transmission. This includes avoiding contact with urine, good attention to personal hygiene (especially hand washing), and proper cleaning and disinfection of any areas potentially contaminated with urine. Prompt diagnosis of canine lepto is very important because treatment rapidly stops the animal from shedding the bacterium. The earlier it's diagnosed, the quicker it can be treated, and the less contamination can occur.
"NDM-1 superbugs" have received a lot of press the last day or two. That's lead to questions about whether there may be any risks for pets.
It's good to see that people are thinking about how this might affect other animal species. That's a thought process that would have been rare a few years ago, and which was probably fostered by the emergence of MRSA in animals.
What it NDM-1?
- NDM-1 stands for New Delhi metallo-beta-lactamase 1. It is a type of beta-lactamase, an enzyme that inactivates certain antibiotics (those of the beta-lactam class). The concern with NDM-1 is that it inactivates carbapenem antibiotics, an important class of drugs that is often used to treat serious and life-threatening infections.
Where is it a problem?
- It's currently mainly a problem in India and Pakistan.
Will is spread to other regions?
- Probably. It's easy for people to travel around the world quickly, and it's easy for new microorganisms to travel with them. A bug that originates in one region can very easily spread across the planet. NDM-1 has been found in a few other countries, including Australia, parts of Europe and Canada. There is concern that the increase in health tourism (traveling to countries like India for cheap and quick procedures like elective surgeries) will result in spread of NDM-1, since people could pick up the bug in hospitals and bring them home. Transmission of NDM-1 in hospitals from patients that had healthcare procedures abroad has been documented in the UK. People traveling to regions where the organism is present for other reasons are also possible sources.
Can it affect pets?
- Probably. Two important types of bacteria, E. coli and Klebsiella spp, can carry NDM-1 (and probably other related bacteria can as well). These can cause infections in many different species. As more people carry bacteria with NDM-1, there's a greater chance that pets will be exposed, as we've clearly seen with MRSA. Dogs that visit human hospitals and pets owned by people who visit India for healthcare are probably at greatest risk, with pets of people who have been hospitalized and pets of healthcare workers likely also at increased risk.
What can we do to reduce the risks?
- Nothing specific. The most important factor here is control of NDM-1 in human hospitals. At the animal level, there's nothing in particular we can do about NDM-1 at the moment. The keys are prudent use of antibiotics (to reduce the likelihood that resistant strains will get established in pets), good general infection control in households and veterinary hospitals (to reduce opportunistic infections by bacteria that can carry NDM-1), and making sure that cultures are taken when infections are present (to find out if/when this becomes a problem).
How likely is E. cuniculi to be trasmitted from an infected rabbit to a dog? My sister has a positive rabbit and my dog was just diagnosed with kidney insufficiency. Now that the dog's kidneys are compromised, should we be concerned?
Encephalitozoon cuniculi is a strange little organism that is now classified as a fungus, but is also similar to some types of protozoal parasites. It is an important (and often overlooked but potentially treatable) cause of neurological disease in rabbits. It is quite common in healthy pet rabbits, and infected rabbits shed the organism mainly in urine.
Less is known about E. cuniculi in dogs. Neurological disease, stunted growth and renal failure are the most common problems that develop. Disease usually occurs in young dogs (less than 1 year of age, with most cases in dogs a couple of months old or younger). Some studies have reported antibodies against the organism in a large percentage of healthy dogs, indicating that they've been exposed at some point, but most studies have found antibodies in few or no dogs.
The risk of transmission from rabbits to dogs is not known. There are a few different types of E. cuniculi, including one type (type I) that is called the "rabbit strain" and another (type III) that is called the "dog strain." The ability of the rabbit strain to infect dogs, particularly dogs with normal immune function, is unclear. Considering the low incidence of infection in dogs (especially older dogs), the different types of E. cuniculi that predominate in dogs and rabbits, and the commonness of kidney disease in dogs, I doubt there's a link between the rabbit's infection and the dog's kidney disease in this case.
Recently, Kings of Leon canceled an outdoor concert after a pigeon (with very good aim, apparently) in the rafters above the stage managed to poop on band members, including one shot that hit the face of the band's bassist.
Besides, the "ick-factor," what are the concerns?
Various studies have found potentially nasty microorganisms in pigeon poop, including:
- E. coli
- Various microsporidia
- Various Cryptococcus species
- Multidrug resistant Staphylococcus spp
- Chlamydophila psittaci
- Mycobacterium avium complex
The risk of disease is pretty low for most people, and we are potentially exposed to many of those bugs on a daily basis. The risks increase with higher ingested doses (so direct-deposit of poop is a much greater concern that inadvertent contamination of your hands) and in people with compromised immune systems. It's unlikely but not impossible that someone would get sick from exposure to pigeon feces, and don't eat poop is a good general philosophy for life.
The internet can be a strange place at times. You can find great, reputable and unbiased information right next to complete garbage. Often, the garbage is pretty apparent, but sometimes it's dressed up well or mixed in with some good information. That's a problem with veterinary advice and information sites.
Among the creative myths identified in a couple of minutes of searching:
- Metronidazole is a proven treatment for parvovirus: No. Metronidazole is an antibiotic that doesn't have any effect on viruses. Antibiotics are sometimes used in the treatment of parvovirus, but they are drugs that are used to prevent or treat problems caused by bacteria from the gut entering the bloodstream as a result of the intestinal tract disease. Metronidazole won't do that.
- MRSA is a virus: You can't make much more of a basic mistake than confusing a virus and a bacterium. Anyone who says this when purportedly writing medical advice is completely clueless.
- If your dog gets an MRSA infection, your veterinarian will likely prescribe vancomycin: Only in extreme circumstances (if ever) should this ever happen. For more information on vancomycin and its use in treating animal and human infections, see our archives. (This gem is on a page that says it's information from infectious disease specialists).
-MRSA in dogs can easily become resistant to vancomycin so linezolid may be required: Fortunately, vancomycin resistance is extremely rare, having been found only a few times in people, in specific circumstances. It's never been found in a dog. Hopefully it will stay that way. (This site didn't even spell vancomycin correctly.)
- Cats can easily get a urinary tract infection if their litterboxes are not cleaned: No. There is no evidence of this and no reason to think it's an issue. Poor litterbox maintenance can lead to urinating outside of the litterbox or other problems like idiopathic cystitis, but not infection.
- In order to have a very healthy dog, it is often required to supplement your pet's diet to provide a high amount of probiotics: Nope. Certain probiotics might be useful in certain animals in certain situations, but we have no proof of this in dogs and cats, and they are certainly not needed for all animals.
There's no way to guarantee that a website is reputable or that the writers are knowledgeable, but here are some things I consider when scrutinizing information on the internet:
- Who set up the website? Is it clear who's in charge?
- Who wrote the information? Is it someone with actual credentials? For veterinary medical advice, is it a veterinarian? If it's a veterinarian, is it a specialist? If it's not a veterinarian, what expertise does the person have? Some people without veterinary degrees have expertise in some fields, but try to determine whether they truly have the qualifications to give advice on a particular topic. That's harder to do these days given the proliferation of mail-order "PhD" degrees, something that's not uncommonly encountered in unqualified people making poor veterinary recommendations.
- Why is the website there? Is it an educational site or is it there to make money? Commercial sites aren't necessarily bad but you have to consider any conflicts of interest or ulterior motives. If there is an article about something, and the last sentence tries to sell you a product to fix that problem, be careful.
- Does the information make sense and is it consistent with other websites? You can probably find a site somewhere to support any notion that you have, but does it really make sense?
- Is the site relevant to your geographical area? This is particularly important for infectious diseases since they can vary greatly between regions. A disease may be a big problem in one area, and a website might provide excellent advice... but only for that area. It may be completely irrelevant or inappropriate for other regions.
- Can they spell? The odd typo probably isn't a major issue (I do it myself). However, rampant and blatant abuse of the English language and an inability to spell important words properly should be red flag.
Searching the internet for pet health information is certainly not a bad thing to do. But, you have to critically assess what you read and remember that it's not always right. Use the internet as a resource but make sure that it's to supplement advice from your veterinarian, not to replace it.
Infection control is a constantly evolving and expanding area - for the good. Paying close attention to infection control in human hospitals is a relatively recent phenomenon, and the advances in infection control are now having an impact outside of hospitals. Pandemic H1N1 influenza drove a lot of changes, but there's been a general increase in awareness of the need for routine infection control in the greater community. This applies to veterinary clinics and living with animals, but is also evident in everything from protocols in workplaces to summer camps.
We're getting ready to send my oldest daughter to summer camp for 12 days. Back in my time, I doubt there was much of an infection control plan for summer camps. If anything, it was probably "don't puke on the other campers and try not to eat too much dirt."
Oh, how things have changed! Last night, we received an email from the camp reminding us to keep our daughter at home if she is sick and outlining their infection control program. Among the infection control measures are:
- Having 2 12-foot handwashing stations outside of the Dining Hall, with everyone required to wash their hands before eating
- Having sinks equipped with handwashing supplies present in all buildings
- Having hand sanitizers throughout the Dining Hall and in every cabin
- Training staff in infection control protocols
- Cleaning cabins every day, with daily inspections of cabins by their "Public Health Supervisors"
- Daily spraying down of surfaces like Dining Hall tables, door handles, toilet handles, taps etc. with disinfectant
- Screening of all kids by one of the Registered Nurses on the first day of camp
Pretty impressive effort, in my opinion. Like everything else, compliance is critical and having good facilities and plans doesn't guarantee good practices, but the efforts put into developing this program and communicating it suggest that they'll be paying attention to it. Even with a good program, camps are an excellent breeding ground for infectious diseases and are perpetually an outbreak waiting to happen, but a good infection control program should greatly reduce the risks.
Canadian singer Alanis Morissette wrote a song called "Ironic" that (ironically) doesn't really describe irony: Rain on your wedding day, a free ride when you already paid, a black fly in your Chardonnay... they all suck but they're not ironic. What is ironic is Dr. Ed Breitschswerdt, an internationally renowned veterinary internist and tickborne disease expert, getting bitten and infected by a tick.
Dr. Breitschwerdt has worked on tickborne diseases for decades and is a wealth of knowledge on the subject, in terms of both animal and human infections. He regularly provides advice about how to avoid tickborne illnesses.
Dr. Breitschwerdt wrote an article about his recent tick-encounter, and here are some excerpts:
"...I do "tick checks" after outdoor activity on my farm, but I recently missed one. When I discovered the tick, I followed recommendation I've given to hundreds of individuals in lectures on tick-borne pathogens. I placed the parasite in a vial of alcohol and wrote the date of its removal on the label. This is an important step, as there are at least four tick species that attach to animals and people in North Carolina, and each species can transmit different bacteria that collectively cause a spectrum of diseases. Knowing the species can help the physician or veterinarian understand which infectious agent has been transmitted...The small tick in my armpit remained attached long enough for my body to mount an inflammatory response (itching, swelling and pain) before I noticed and removed it. Not initially feeling an attached tick is the norm, since ticks have evolved the ability to secrete chemicals that block pain and decrease the body's inflammatory response."
- The fact that the tick was present for a while is critical, since it takes time after attachment before a tick starts feeding and can pose a potential risk for disease transmission.
"Nine days after removing my tick I developed severe chills. The next day my symptoms progressed to include fever, muscle pain and headache - classic symptoms of Rocky Mountain spotted fever and human granulocytic or monocytic ehrlichiosis, the three most serious and frequent tick-transmitted diseases of dogs and people in the southeastern United States.
"Typical of the early stages of these diseases, my white blood cell count (the body's first line of defense) was low. My bone marrow responded by sending new white blood cells to fight the infection. After blood was obtained for diagnostic testing, antibiotic treatment was started immediately. This is of critical importance, as a delay in diagnosis and initiation of antibiotics for 24-48 hours greatly increases the severity of illness and the chances of death."
- Testing was performed on the tick and Dr. Breitschwerdt's blood, and Rickettsia rickettsii DNA was found in both. In combination with his clinical signs, including a rash on his arms and legs (see photo), this confirmed the suspected diagnosis of Rocky Mountain spotted fever. This is a serious disease from which approximately 6% of infected people die. Early recognition is critical, but diagnosis is often delayed because of failure to identify or report a tick bite, or failure of physicians to consider the disease.
Dr. Breitschwerdt concludes "This recent experience enhanced my belief that tick-transmitted diseases deserve respect and enhanced, comparative biomedical research. The next time you walk in the beautiful fields and valleys of North Carolina, apply a tick repellent and remember to check carefully for attached ticks when you return home."
Photo: Child's right hand and wrist displaying the characteristic spotted rash of Rocky Mountain spotted fever (source: CDC Public Health Image Library #1962)
Streptococcus zooepidemicus is an important cause of infections in horses. This bacterium can also be found in healthy horses. When you consider the large number of horses that are infected and the larger number of healthy horses that are carriers, along with the close contact that people have with horses, it's pretty obvious that people are regularly exposed to "Strep zoo". This bacterium is not well-adapted to survive in people and cause infections, so human infections are quite uncommon, but they can occur. There are periodic reports of S. zooepidemicus infections in people, with varying degrees of association with horse-contact.
An upcoming edition of journal Epidemiology and Infection contains a report of S. zooepidemicus meningitis in a 51-year-old woman (Minces et al, 2010). This person had a mild upper respiratory tract infection, then developed signs of meningitis (including fever, unresponsiveness, respiratory distress). A spinal tap was performed and S. zooepidemicus was isolated. The woman fortunately responded to treatment and recovered.
Upon initial questioning of the patient's mother, no animal contact or ingestion of unpasteurized dairy products (another risk factor) was reported. However, it was later revealed that the woman's daughter had started horseback riding at a friend's farm approximately one month earlier. The type of contact that the woman had with horses (if any) at the farm was not reported, nor was there any investigation of S. zooepidemicus shedding by horses on the farm.
Based on the fact that this is typically an equine-associated bacterium and the history of contact (albeit potentially limited or indirect) with horses, horse contact was blamed for the infection. It's a reasonable conclusion but it's far from certain because of the nature of the contact, the lack of any proof of the same strain of S. zooepidemicus in horses on the farm, and previous reports of infections occurring in people with no contact with horses.
Exposure to S. zooepidemicus is an inherent risk of having contact with horses. It's nothing to lose sleep over and is probably relatively low on the list of potential health problems associated with horse contact. The risk is probably greatest in people with compromised immune systems and other general risk factors for disease such as advancing age and pregnancy. Good general hygiene measures, avoiding contact with sick horses and close attention to hand hygiene probably minimize these already low risks.
This Worms & Germs blog entry was originally posted on equIDblog on 25-May-10.
The recent ringworm outbreak in a Newmarket, Ontario shelter has focused a lot of attention on shelter outbreaks, outbreak prevention and management. A common question that I've been getting in the last couple of days is "Why do these outbreaks occur?"
There are many reasons why an outbreak can develop. I have no first-hand knowledge of the Newmarket outbreak, and don't know what prompted that outbreak, but here are some general causes of outbreaks.
- Shelters need clear and logical protocols for all things dealing with animal care. This needs to include aspects like where new animals go, what types of evaluation and monitoring are performed, vaccination and deworming plans, when animals need to be tested or treated, when they can be released from quarantine, how to record and report infectious diseases, how to clean and disinfect areas and items, personal hygiene, and protective clothing, among other things. These protocols need to be in writing and accessible to all personnel.
- Shelters often have large numbers of staff, many with minimal training in animal husbandry or medicine. Proper training is required to ensure that they know what to do and why. (The latter is important because if people know why they need to do something, they are more likely to do it.) Training programs need to be well-structured and formal, not casual, follow-someone-around-and-see-what-they-do training.
- Even with good protocols and training, the facility managers need to ensure that protocols are followed. They need to enforce protocols and address problems with compliance. They need to make sure their protocols are up-to-date and consistent with best practices.They need to monitor disease rates and concerning trends of illnesses, so that problems can be identified early. They need to know when to get advice and who to ask (see below).
- Some facilities (or actually, most facilities) are not well designed in terms of infection control. That makes it harder to prevent disease transmission and contain problems. Limitations in isolation/quarantine areas may result in mixing of new (and more likely infectious) animals with those ready for adoption. Few sinks may reduce handwashing, a key component of infection control. A facility that is too small for the animal load results in cramming in too many animals.
- If staff (from management on down) don't understand the issues, they may not act appropriately. Proper routine preventive measures and outbreak response measures may not be convenient, easy or cheap. There must be motivation to implement them. If there is little awareness of the problem, people are less likely to do what is needed.
Failure to act appropriately when the first cases are identified:
- It is much easier to contain a problem when you act early. If only a few animals have been infected or exposed, it's much easier to take aggressive measures. Once you get a large number of infected or exposed animals, it's much harder to do things like properly separate different groups (e.g. infected vs potentially infected vs non-infected). The more animals affected, the greater the chance of further transmission. Keeping your head in the sand and hoping things will go away can result in a small containable outbreak becoming a facility-wide, difficult-or-impossible-to-contain outbreak.
Failure to get good advice:
- People working in shelters can't be expected to be experts in all aspects of infectious diseases and infection control. That's why getting good advice (and following it) is critical. Sometimes, people don't ask for advice or don't go to the real experts. This can happen because they don't really understand the problem, don't know who to contact, don't want to admit they don't know everything or don't realize they are in over their heads. A little good advice, especially early, can make a world of difference.
- Ultimately, you can have an exceptionally run facility and still get an outbreak. By the nature of what shelters do, they bring in a lot of animals with potentially infectious diseases and have many animals that are at higher risk of getting sick if they get exposed. It's much less likely to occur with a good infection control program, but you can never 100% guarantee nothing bad will happen. You can't do much about this. All you can do is make the best program possible, and try to limit any problems that develop.
Never a dull moment...
This morning the Toronto Star published an article about the intended euthanasia of 350 animals at a humane society in Newmarket due to an ongoing ringworm outbreak. This was quickly followed by another article about the same event that gave a few more details, including some comments from the OSPCA chief executive officer Kate MacDonald, who confirmed that the euthanasias had begun. A "very aggressive strain" of ringworm and "human error" (related to a breakdown in protocols) are currently being blamed for this morning's actions. A lot of people are (understandably) very upset. No one ever wants to see an infectious disease outbreak come to something like this.
I’m hesitant to comment too much at this stage, because we still don’t have all the facts - apparently even the duration of the outbreak is unknown. No one has said if all 350 animals are infected (or what percentage of them are), nor how many other animals are present at the shelter. We also don’t know what’s already been tried in terms of controlling the outbreak.
A few facts about ringworm (dermatophytosis) that people need to remember:
- Ringworm is a skin infection that can be caused by several species of fungi. It is not a "worm" at all. It is also very easily transmitted by direct or indirect contact with infected animals - their fur, their cages, their blankets, or anything else that may be contaminated with infected skin cells or hair. Such infectious material can even be spread over short distances (e.g. room to room) in dust that is stirred up into the air.
- Ringworm is transmissible to people, so with a large outbreak there are also issues with staff safety, and concerns with adopting out infected animals. For most people ringworm infection may cause itchy, uncomfortable skin lesions, but for higher-risk people (e.g. very young children, the elderly or immunosuppressed individuals) the infection can be much more serious.
- There are also a lot of animals (particularly cats) that carry ringworm without showing any signs of infection. If the Newmarket shelter has 350 animals with clinical signs of ringworm (a detail about which we have no information right now), that’s pretty bad, but even the animals who don't appear to be infected may be carrying the fungus and could spread it to others.
- Crowding, close contact and warm, humid environments are all factors that increase the risk of ringworm transmission. These are also all factors that are very hard to control in a crowded animal shelter.
- Ringworm is treatable, but it is not cheap or easy. Animals typically require systemic therapy (usually oral medication, which can be very expensive particularly in large dogs) as well as whole-body topical therapy (e.g. dips, shampoos, sprays), and they need to be treated for several weeks. Decontamination of the environment at the same time is critical to prevent reinfection.
Cleaning up a ringworm outbreak at a shelter with at least 350 animals is no small undertaking. The second article in the Star also describes personnel at the shelter this morning wearing "white hazardous material suits, latex gloves and plastic covers over their shoes", which would be considered reasonable precautions for entering a highly contaminated environment.
I'm sure we'll hear more about this in the days to come, and hopefully that will include more details about why the mass euthanasia was deemed necessary by the OSPCA.
Photo source: yorkregion.ontariospca.ca via www.thestar.com
In 2007, there was a massive equine influenza outbreak in Australia. A large number of horses were infected in this country that was previously equine influenza-free, and there was tremendous economic disruption caused by containment measures. It turns out horses weren't the only animals infected. A report in the April edition of Emerging Infectious Diseases describes influenza infections in dogs associated with the equine outbreak.
In some ways, it's not too surprising. Canine influenza in North America is caused by H3N8 influenza that moved from horses to dogs. Similarly, H3N8 influenza of equine origin has been identified in dogs in the UK. So, while it's an uncommon event, we know that in some situations, the "standard" equine H3N8 influenza virus can infect dogs.
The first dog that was diagnosed lived near a large horse stable. The dog developed typical signs of influenza: decreased appetite, lethargy, nasal discharge and cough. After the first dog was identified, other dogs were noted to have similar signs, including dogs whose owners had contact with infected horses and dogs that had contact with other sick dogs. Some dogs had severe infections. Influenza was diagnosed through detection of antibodies in their blood, and the influenza virus was isolated from one dog. The virus that was isolated was the same as the one present in horses (and different from that in US dogs).
For influenza to jump between species a few things have to happen.
- First, the virus has to be able to infect the other (non-natural) species. This can happen because the virus is inherently able to infect different species or because of a random viral mutation that allows for infection of the new species.
- Second, the virus must encounter that host (in this case, dogs). It must then be able to multiply within the new host.
All this can happen with or without development of disease. For the virus to truly establish itself in the new species and spread (like canine flu did in the US):
- The virus must be able to multiply well in the new host, and adequate virus levels must be produced for the new host to be a source of infection to other individuals.
- The new host must come into contact with other susceptible individuals.
- The virus must be able to infect new hosts readily enough to maintain infection in the population, instead of dying out after a couple transmission cycles.
In these Australian cases, while it is apparent that equine flu was able to infect dogs, there was no clear evidence that perpetual dog-to-dog transmission occurred. Influenza virus was rarely detected in nasal secretions from infected dogs, making it unlikely that the virus would spread between dogs. Therefore, the virus was not able to establish itself in the dog population. This means it ended up being only an interesting situation that affected a limited number of animals, instead of the creation of a new, self-propagating infection that could continue to circulate in dogs in the country.
A 62-yr-old Italian woman has died from psittacosis, an infection caused by the bacterium Chlamydophila psittaci. Sometimes called "parrot fever," psittacosis is an uncommon but important disease linked to contact with birds, particularly psittacines (e.g. parrots, parakeets, cockatiels). In people, C. psittaci usually causes flu-like respiratory disease, but severe pneumonia and encephalitis (inflammation of the brain) can occur in some individuals. With prompt diagnosis and treatment, mortality (death) rates are very low (<1%), however mortality rates are higher when diagnosis and proper treatment are delayed. It's not clear in the this case whether psittacosis was considered early in disease nor when treatment was initiated.
Chlamydophila psittaci can cause illness in birds, but it's also carried by a variable percentage of healthy birds, mainly psittacines. This complicates control of the disease, since you can't tell which birds are carrying the bacterium without testing them all. In this case, the woman's parrot died a few days before she became ill. It's not clear from the brief report whether the bird was diagnosed with C. psittaci infection, however this is a good reminder of the need to consider pet and owner health in parallel. It also indicates why diagnostic testing is important when pets are sick, or even after they've died.
If a pet becomes sick, knowing what caused the disease might be of relevance to human health. Also, if physician's ask about illness of any other individuals in the house, this should include pets, as they might get some relevant information.
In a case like this, if the bird was diagnosed with C. psittaci infection and the owner developed flu-like illness shortly thereafter, it should have been a strong indication that the person might have psittacosis, allowing for early treatment. Alternatively, even without a diagnosis, knowing that the person had a pet parrot (a risk factor for psittacosis), and that the bird had died shortly before the woman got sick, could lead to recognition that both diseases could be linked, and could lead to earlier consideration of psittacosis.
This unfortunate event should be taken as yet another reminder of the need for veterinary personnel and human physicians to communicate more effectively, and that physicians need to know about pet contact and pet health when evaluating their patients.
Image: African Grey Parrot (Psittacus erithacus erithacus). (Photo credit: Eli Duke)
A recently reported outbreak affecting horses in Bahrain has been diagnosed as glanders, a very serious bacterial infection caused by the highly contagious bacterium Burkholderia mallei. So far, it has been reported that 8 horses were euthanized over the past 3 weeks because of the infection.
Bahrain's cabinet has allocated BD150 000 to fight the outbreak. Authorities have apparently stated that the outbreak can be "easily" managed, "We have sent samples from nearly 400 horses to a specialist laboratory in the UAE and the 10 results we have got so far give us the all-clear. We now know we can manage this quite easily and are taking appropriate action."
That's a pretty dangerous sentiment to be expressing (and believing) early in an outbreak, but hopefully it's true. "Easily" and "outbreak" aren't often uttered in the same sentence, and it's far from unusual to be fooled by an allegedly contained or controlled outbreak. I'd be very surprised if all of the positive horses have already been identified. Control of glanders involves widespread testing of horses, typically with euthanasia of any infected animals. It sounds like testing is underway and results of this will give a good indication of the extent of the problem. Ten negative samples don't mean that much to me. As more results come in (and if they continue to be negative), more confidence can be had in the assessment that this outbreak is truly contained. Glanders is not solely a concern for horses. It's a zoonotic disease that can cause rare but serious infection in humans, with a high mortality rate (almost 100% if proper treatment is not administered). People can become infected by direct contact with infected horses, with the bacterium gaining entry through skin abrasions, inhalation or contact with tissues of the mouth and nose. Pneumonia, bloodstream infections and other problems can develop. Burkholderia mallei is a Class B bioterrorism agent. Hopefully, people working around infected horses are using appropriate infection control precautions to reduce the risk of infection. Hopefully, more information will be available soon about this outbreak and results of ongoing testing. Image: A horse with glanders (Burkholderia mallei infection), exhibiting the characteristic infectious nasal discharge. Glanders is a reportable disease which has been eradicated from North America, Australia and most of Europe.
That's a pretty dangerous sentiment to be expressing (and believing) early in an outbreak, but hopefully it's true. "Easily" and "outbreak" aren't often uttered in the same sentence, and it's far from unusual to be fooled by an allegedly contained or controlled outbreak. I'd be very surprised if all of the positive horses have already been identified. Control of glanders involves widespread testing of horses, typically with euthanasia of any infected animals. It sounds like testing is underway and results of this will give a good indication of the extent of the problem. Ten negative samples don't mean that much to me. As more results come in (and if they continue to be negative), more confidence can be had in the assessment that this outbreak is truly contained.
Glanders is not solely a concern for horses. It's a zoonotic disease that can cause rare but serious infection in humans, with a high mortality rate (almost 100% if proper treatment is not administered). People can become infected by direct contact with infected horses, with the bacterium gaining entry through skin abrasions, inhalation or contact with tissues of the mouth and nose. Pneumonia, bloodstream infections and other problems can develop. Burkholderia mallei is a Class B bioterrorism agent. Hopefully, people working around infected horses are using appropriate infection control precautions to reduce the risk of infection.
Hopefully, more information will be available soon about this outbreak and results of ongoing testing.
Image: A horse with glanders (Burkholderia mallei infection), exhibiting the characteristic infectious nasal discharge. Glanders is a reportable disease which has been eradicated from North America, Australia and most of Europe.
This Worms & Germs blog entry was originally posted on equIDblog on 26-Apr-10.
A somewhat controversial study has just been published in the Journal of Veterinary Emergency and Critical Care (Savigny et al 2010). The study looked at the use of Tamiflu (oseltamivir) for the treatment of parvovirus infection in dogs. Tamiflu is best known as a potentially important influenza drug in humans. It's a neuraminidase inhibitor that can prevent replication of some viruses, such as influenza. It actually has no effect on parvovirus, but has been used by some veterinarians based on the hypothesis that it can have an effect on bacteria and perhaps prevent secondary bacterial infections, which contribute to the severity of parvoviral disease.
The study examined a relatively small number of dogs (35) with parvovirus infection. Some dogs received Tamiflu along with standard treatments, while the others received a placebo and standard treatments. There was no difference in major outcomes between the two groups, but control dogs lost more weight during treatment.
The study has some weaknesses and doesn't tell us too much, but it's the first objective investigation of this drug in dogs. There was no significant difference in relevant outcomes, but was that because the drug doesn't work, because the dose was too low (as has been suggested by some) or because the study was too small to detect a real difference? That's the big question.
Some veterinarians are completely convinced Tamiflu works for parvovirus infections and disregard any suggestion that it doesn't. Currently, there is no scientific evidence whatsoever supporting its use, and this study doesn't help much one way or the other. There are abundant anecdotes, and it's plausible that this drug could be useful for treating this disease, but there are a few concerns:
- We really don't know whether it works. Continuing to use a treatment in the absence of objective information is not necessarily a good idea.
- We don't know the appropriate dosage and duration of treatment for dogs. We also don't know which animals Tamiflu might or might not help. It is probably most effective (or perhaps only effective) early in disease.
- Tamiflu is an important human influenza drug, and resistance is emerging in influenza. Can we justify using a drug that is a part of pandemic influenza control for the treatment of canine parvovirus, without any evidence that it is effective or needed?
The article's abstract concludes by saying "Based on these results, the true role of oseltamivir in the treatment of parvoviral enteritis remains speculative, although it is believed that further investigation is warranted." Very true.
We need two things:
- Rational discussion about whether use of drugs like this is justifiable in animals.
- Better studies to tell us whether it works, and if so, how to best use it.
If we end up using it, we also need surveillance to make sure routine use of this drug in animals doesn't contribute to resistance in humans. Unfortunately, the Tamiflu debate is too often full of anecdotes and arguments as opposed to logical discussion and sound evidence. Hopefully that won't get in the way of someone doing a more definitive study.
On the way home from an MRSA symposium in the US the other day, I was (perhaps fittingly) listening to a podcast about new antibiotic development. The podcast, by The Lancet Infectious Diseases, discussed the small number of new antibiotics that are in the pipeline (about 15), particularly in contrast to the number of new anti-cancer drugs (about 800). There are many reasons for this, and development of new anti-cancer drugs is certainly important. However, we have definitely not "won the war" against bacteria, and resistance continues to be a serious threat to human and animal health.
The small number of potential new drugs (since many drugs in development will not ever make it past drug trials) is a concern if resistance continues to increase. The disparity in development between antibiotics and anti-cancer drugs is also concerning when you consider that good antibiotics are very important for cancer therapy - people with cancer often get infections, and often their infections are caused by multidrug-resistant bugs. As we develop more and better anti-cancer drugs, there will be more people who are susceptible to these potentially severe infections, and ways to treat them are needed.
Why are there so few antibiotics in development compared to other drug types?
- $$$ - Money. The potential return on investment for pharmaceutical companies is much greater for many other drug types. Huge amounts of money must be invested to develop, test and license drugs. Logically, companies are going to focus on the higher yield drugs, leaving some important areas with less research and development than would be desired.
What do we do?
Well, unless you own a pharmaceutical company or have millions of dollars to spend, you're probably not going to have an impact on drug development. Since we can't control what will be available to us in the future, we need to make sure that we delay, as much as possible, the emergence and dissemination of highly resistant bacteria.
Common sense practices such as only using antibiotics when necessary, using them properly (e.g. proper dose and route, giving the entire treatment course), good preventive medicine to reduce the risk of bacterial infections and good infection control measures are critical and often underused. While not as fancy as high-tech drug develop, these are the ways that we can have a positive impact in both human and animal health, and reduce our need for new drugs.
When the novel H1N1 influenza pandemic infected large numbers of people, it was not particularly surprising that the occasional infection was noted in pets, considering over 50% of North American households have pets, and the close nature of contact that many people have with their pets. While the few cases that occurred were highly publicized, in the end pet infections were rarely diagnosed (although that doesn't mean they were truly rare), and limited information about these cases has been available. Details regarding one H1N1-infected cat from Iowa (Sponseller et al. 2010) were recently published in Emerging Infectious Diseases.
Here are some of the highlights:
- The 13-year-old cat was an indoor cat that was admitted to Iowa State University's veterinary hospital because of depression, decreased appetite and signs of respiratory disease.
- Two of 3 people in the house had undiagnosed influenza-like illness a few days before the cat got sick. The cat was an affectionate pet and interacted closely with household members.
- Influenza was diagnosed in the cat by detection of H1N1 influenza virus using molecular diagnostic methods (reverse transcriptase PCR) on a sample of fluid collected from the lungs.
- The cat improved with supportive care alone (mainly intravenous fluids to correct dehydration).
Considering the cat lived indoors and people in the house had signs consistent with influenza, it's almost certain that the cat was infected by its owners. This isn't surprising, but it's a good example of how infectious diseases can move between people and pets, in either direction. There's no evidence that pets were a source of human infection, but if something can move from people to pets, there's certainly good reason to think that it could go back from pets to other people. This should be another wake-up call for the need to consider and investigate the potential role of pets in any emerging infectious disease, and to consider emerging "human" diseases in sick animals that might have been exposed.
The latest edition of the journal Emerging Infectious Diseases contains an article about a South African vet student that acquired West Nile virus from a pony while performing a necropsy. Occupational exposure to infectious diseases is an inherent risk in veterinary medicine. Veterinarians know that they are at higher risk of encountering various infectious diseases and take (or should take) precautions to reduce those risks. Sometimes infections occur despite the best precautions. Sometimes infections occur because of bad practices. This report highlights the latter.
In this case, a 4-month-old pony began showing vague signs of illness, then developed neurological abnormalities and was euthanized. A necropsy (post-mortem exam) was then performed by a veterinary pathologist with the assistance of two veterinary students. As part of the necropsy, the student removed the brain and spinal cord for testing, but gloves were the only protective gear that were used. No face or eye protection was used, which is quite astounding.
The pony was eventually diagnosed with West Nile virus. Six days after performing the necropsy, the veterinary student developed a fever, malaise, sore muscles, stiff neck and severe headache. West Nile virus infection in the student was confirmed, and the viruses from the pony and person were the same type based on testing. Fortunately, the signs of infection in the student subsided after approximately ten days.
Horses are considered "dead-end" hosts for West Nile virus, meaning they cannot naturally transmit the virus. This is because horses (even severely affected ones) only have very low levels of virus in their blood, so a biting mosquito can't pick up the virus and transmit it to other individuals. However, the brain and spinal cord, particularly in a clinically affected horse, may contain very large amounts of the virus. It's astounding that a veterinary school would have a student removing the brain and spinal cord of an animal that died from a neurological condition, especially without proper protective gear, since the procedure carries a risk of splashing or aerosol exposure to the virus. Anyone performing necropsies needs to be aware of the potential risks and take appropriate precautions. The paper states that after the incident, biosafety practices were improved to include the wearing of masks and eye protection during necropsies. Well, I guess it's better late than never...
This Worms & Germs entry was originally posted on our sister site, equIDblog, on 11-Mar-10.
Heartworm is an important problem in dogs. It's a parasitic disease caused by Dirofilaria immitis and is spread by mosquitoes. It can cause serious, even fatal disease, and routine testing and preventive medication is an important thing for dogs in areas where D. immitis is present. Dogs (wild and domestic) are the natural host for this parasite, but other species can be accidentally infected, including people and cats. People become infected by being bitten by a mosquito that is carrying the parasite, having acquired it from an infected dog. Human infections seem to be quite uncommon and, interestingly, while this is a serious problem in dogs, it tends to be rather innocuous in people. In fact, the biggest problem with heartworm infection in people is the fact that it can be confused with other, more serious problems, leading to invasive testing.
After infecting someone, D. immitis works its way to the blood vessels in the lungs. This can result in a small area of inflamed tissue in the area. If a chest x-ray is taken, a "coin lesion" (a small, usually 1-3 cm spot) is often present. The parasite infection usually doesn't cause any problems in people, but lung cancer and tuberculosis can look the same on x-rays. Usually, open-chest surgery ends up being performed to get a biopsy of the area because of the concerns about cancer. In heartworm cases,the biopsy identifies the problem as D. immitis, which is much better than cancer, but the risks associated with having undergone such an invasive procedure are much greater than that of the parasitic infection itself.
Typically, treatment is not recommended in people because the infection rarely causes problems and people are "dead end" hosts, meaning they cannot pass on the infection. (Unlike in dogs, infected people don't have the parasite microfilaria in their blood, which is how the infection is passed on to mosquitoes and other animals).
Heartworm is a rare and rather innocuous problem in humans - it's nothing to lose sleep about.
Image: A diagram of a very severe case of heartworm in a dog, in which there are so many worms in the pulmonary arteries that there is "back-up" of the parasites into the right side of the heart, which is how the parasite got its common name.
Antibiotic resistant bacteria are a huge problem in human medicine, and they're an increasing problem in veterinary medicine. In pets, we are seeing dramatic increases in multidrug-resistant bacteria, some as a result of transmission from humans and some that are developing in animals. Regardless of the source, infections caused by resistant bacteria are a major problem. As resistance increases and we have fewer and fewer treatment options for some infections, the potential need to use certain antibiotics that are important for serious infections in humans ("big-gun" antibiotics) increases. This is a very contentious issue because concerns have been raised over the use of these drugs in animals and the potential impact on humans.
There are two extremes to the argument:
- These are critically important drugs in human medicine and they should never be used in animals.
- These drugs are used thousands of times a day in people and very rarely in animals, so the impact of periodic use in animals should be minimal, and failure to use them would result in animal deaths from potentially treatable infections.
I take the middle ground here. I am very concerned about antibiotic resistance (in pets and people) and I want to make sure that what I do does not have a negative impact on public health. I also realize that very rare and appropriate use of these drugs will realistically be unlikely to have any negative impact on public health, and that withholding treatment could cause animal suffering, death and prolonged infections that could be transmitted to their owners. The key, to me, is ensuring that use of these drugs is truly very rare and appropriate. At the Ontario Veterinary College, we have strict guidelines for use of "big-gun" antibiotics to try to ensure that there are used rarely and properly. For example, vancomycin can be used, but only when:
- An infection is present and it is known that the bacterium is resistant to all other options and susceptible to vancomycin.
- Local antibiotic administration or other types of alternative treatment are not options.
- It's a serious infection that needs to be treated but it is treatable (i.e. no throwing a big gun drug at a patient that clearly has a terminal disease and does not have a realistic chance of surviving).
- Approval is obtained from the Chief of Infection Control (i.e. me).
With this approach, we've only had 1 case where vancomycin was used, and that was in 2001. That's a pretty good record for a busy referral centre with a tertiary care caseload that sees "the worst of the worst." There have been a few instances when vancomycin was requested but with discussion and review of the case, better alternatives were identified. I'm certain that these guidelines have reduced the use of vancomycin and increased awareness of the problem, but have had no negative impact on patient care.
Antimicrobial resistance isn't going away. We can control it but not eradicate it. Scrutiny of antibiotic use in veterinary medicine is also not going to go away, and in some ways, that's a good thing. It should provide impetus to make sure that we improve how we use drugs, from the big guns down to our day-to-day drugs. Realistically, it's the regular use (appropriate use, overuse and misuse) of less exotic antibiotics that is having a bigger impact on antimicrobial resistance, and we need to pay attention to that as much as to the high-profile drugs.
A Phoenix, Arizona man is suing a pet store after he contracted rat bite fever from a rat he had purchased. It's not surprising to see a lawsuit following a serious illness, considering people in the US often try to sue for just about anything, but I'm not sure it won't get very far. I don't doubt that the man had rat bite fever, or that he got it from the rat he purchased - the question is, is the pet store really liable? Specifically, did they do anything inappropriate?
"Rats being sold to people should not have rat-bite fever," Heitzman's lawyer, M.E. "Buddy" Rake Jr., tells New Times.
Actually, the rats don't have rat bite fever... rats are healthy carriers of the bacteria that cause rat bite fever. There are two different bacteria that can cause the disease, Streptobacillus moniliformis and Spirillum minus. Streptobacillus moniliformis is presumably the cause here since it's the main cause of rat bite fever in the US. This bacterium is very commonly found in healthy rats, with upwards of 100% of healthy rats being carriers. You have to assume that every rat is carrying this bacterium.
"It wouldn't be any different if they sold someone a dog with rabies," he says. "I'm not in the nuisance-lawsuit business - he was in rough shape."
It would certainly be a different story if the store sold someone a dog that had signs of rabies. It's possible that someone could buy a dog that had been exposed to rabies but which was healthy at the time of sale, but that's pretty unlikely. However, a big difference is that there is a highly effective vaccine against rabies. There is no such thing for rat bite fever. If a pet store sells an unvaccinated dog of unknown origin that could have been exposed, despite knowing the need for rabies vaccination, there certainly could be liability issues. Selling a rat that is carrying a bacterium that we assume most or all rats carry anyway is different.
PetCo did not immediately return telephone calls this afternoon, but in its defense, there is an information pamphlet explaining exactly how to avoid contracting rat-bite fever available on the company's Web site. ...though it seems the pamphlet's best suggestion is to not get bitten in the first place.
It would be better if everyone who bought a rat was given the information sheet, but it's a start. The fact is, the best way to avoid rat bite fever IS to avoid getting bitten by a rat! Proper rat handling is a very important aspect of disease prevention, since you can never rule out the possibility that a rat is a carrier.
Our suggestion: Don't have a disgusting rat for a pet.
Whoa. Rats can make excellent pets. They can also carry infectious diseases. However, EVERY animal can carry infectious diseases, and rats are probably no more risky than most other domestic pets. The key is to take common sense precautions to reduce the risk of injury and infection (though the risk can never be completely eliminated). For rats, this includes selection of a rat that is not aggressive or fearful, knowing how to properly take care of a rat, knowing how to take care of a bite should it happen and being aware of some diseases for which you might be at increased risk because you own a rat.
Image source: http://commons.wikimedia.org
The Associated Press is reporting a concern about botulism in dogs in Florida that might be linked to dead iguanas. The facts are pretty sparse at the moment, and it sounds like both the diagnosis of botulism and the link with iguanas are hypothetical, but it's an interesting story.
Botulism is a very serious, hard to treat and rare disease in dogs. It's also very hard to definitively diagnose, which is one of the problems in a situation like this. It seems that a veterinary neurologist first raised concerns after seeing paralysed dogs (and no evidence of typical causes) and a common history of exposure to dead iguanas.
The recent and prolonged cold weather in south Florida has apparently resulted in widespread death of iguanas (who do not tolerate cold weather). The iguanas presumably didn't die of botulism, but if they had Clostridium botulinum, the bacterium that causes botulism, in their intestinal tract (something that can be common in some animal species), then theoretically dogs could ingest the bacterium or (more likely) botulinum toxin produced by the bacteria in the iguana carcasses after death. Botulinum toxin is extremely potent, and ingestion of even minuscule amounts is enough to cause serious or even fatal disease.
Testing is pending on some of the affected dogs. It would be nice if someone would test some dead iguanas as well, to see if there is really a link. This type of outbreak, however, often passes without a definitive diagnosis because of the difficulties diagnosing the disease. Regardless, keeping your pets away from dead iguanas (and other dead critters) is a good general rule.
Image source: www.cafepress.com
The latest edition of the journal Emerging Infectious Diseases contains a paper describing the 2008 Australian Hendra virus outbreak in horses and people.
In this outbreak, there were five horses infected and two humans infected. The horses predominantly had signs of neurological disease, not respiratory disease like some other reports describing this disease. Four horses died. One recovered but was euthanized for public health reasons.
Two people became infected after working with the sick horses, which represents 10% of the total veterinary staff that were exposed to the infected horses. Both people started off with influenza-like illness, which seemed to improve initially, but then signs of severe neurological disease developed. They were treated with ribavirin, an antiviral drug, as part of an experimental treatment. One of them died after 40 days of illness, the other person survived.
The authors stressed that the effectiveness of ribavirin could not be determined, but they recommend it nonetheless because of the severity of Hendra virus infection and lack of other options. Ribavirin was also used in the 2009 outbreak, but it is clearly not 100% effective since one person died there also.
A number of concerning activities occurred that put people at risk of infection, including a "percutaneous blood exposure while euthanizing an infected horses" (they didn't explain exactly what this was, but it could have been a needlestick), low use of personal protective equipment, and contact with potentially infectious body fluids. This is unfortunately not surprising since the approach to infection control (particularly in terms of zoonotic infections) is often lax in equine medicine. That certainly has to change, particularly in areas where Hendra virus may be present.
Much more information about how to control this potentially devastating virus is needed. Fortunately, infections are uncommon and it is restricted to a fairly small geographic range in Queensland, Australia.
Image source: http://animalphotos.info/
This Worms & Germs blog entry was originally posted on equIDblog on 27-Jan-10.
Click here for a link to a presentation by an architect about veterinary clinic design. This video clearly shows why people that are designing clinics need to be thinking about infection control (and that some are clearly not doing so). This person talks about the trend towards not placing sinks in exam rooms. This is news to me, and a major concern, because one of my major points when consulting on clinic design is making sure there are sinks in all exam and treatment areas. The farther you have to walk to find a sink, the less chance you’ll wash your hands and the greater chance you’ll contaminate things on the way to the sink.
One of this person's arguments for not putting sinks in exam rooms is truly ludicrous. Basically, he says that pet owners are more and more in tune to hand hygiene, and if they see a sink and someone not use it, they get concerned that the vets hands are dirty. His reasoning is that not having a sink will prevent people from thinking about hand hygiene issues. For one thing, I think he’s underestimating the intelligence of pet owners - they don’t need to see a sink to think about hand hygiene. People are becoming much more aware of the need for healthcare providers to wash their hands, and this is filtering down to their perceptions of veterinarians as well. Instead of taking sinks out of exam rooms, if a vet is concerned their clients have a negative perception of their hand hygiene practices, there's a simpler solution: actually practice good hand hygiene (and do so where owners can see it so they can be confident it's being done!). The architect is correct that hand sanitizers are now more widely used, but he is incredibly wrong with his assumption that hand sanitizers replace hand washing. They don’t. Hand sanitizers are great but handwashing is still required in many situations.
Hopefully this architects assessment that sinks are disappearing is wrong. Vets and architects need to think about infection control when designing clinics. It’s easy to incorporate good infection control when building a clinic but very hard to retrofit a poorly designed clinic.
Just as I'm getting ready to go on vacation (that will hopefully involve some time on the beach), I read an article in the latest edition of Emerging Infectious Diseases about seagulls and beaches as reservoirs of multidrug-resistant E. coli (Simoes et al 2010). In this study, the researchers collected seagull poop from beaches in Porto, Portugal and tested them for the presence of extended spectrum beta-lactamase (ESBL) E. coli, a highly drug resistant form of this common bacterium. Thirty-two percent (32%) of the E. coli they isolated were ESBL, a pretty impressive rate in wild birds that would not be directly exposed to antibiotics. Various E. coli strains were present, including some that can cause severe disease.
In some respects this is pretty concerning, and in other respects not too surprising. We know that birds in various (including remote) regions can carry multidrug-resistant bacteria. The ability of wild birds to carry these bacteria, combined with the wide geographic range that some bird species have, raises concern about the role of birds in the spread of antibiotic-resistant bacteria, as well as the potential for contracting a nasty drug-resistant infection while on the beach. Birds certainly have the ability to help spread certain types of bacteria over wide ranges. However, their overall role is probably very limited compared to the role played by people and (domestic) animals. For birds to become carriers of these bacteria, they have to pick them up from somewhere, which presumably doesn't occur until the bacteria have built up to a good level in people and/or animals. I doubt that birds account for many human infections. Antibiotic exposure through antibiotic residues in water or food sources could also play a role in the presence of these bacteria in birds, but that's an area that's not well understood.
So, how does this influence my time on the beach? Not much. I wasn't really planning on having contact with seagull poop, and this paper just reinforces that basic precaution. Other basic measures such as keeping open sores covered, avoiding cuts by wearing shoes in rough areas or sand that might be contaminated with sharp objects, avoiding contamination of food with sand, avoiding areas with obvious bird poop contamination, and hand washing before eating and after leaving the beach are easy to do.
When we have a -30C windchill and snow on the ground, my first thoughts usually aren't about survival of bacteria in the outdoor environment. However, some microorganisms are well adapted for survival in various adverse conditions and we shouldn't assume that cold=dead for every bug of concern. Along that line, we received a question recently about survival of Leptospira and I passed it along to our lepto expert, Dr. John Prescott. Here's his guest post:
A reader in Ohio owns a dog that had leptospirosis, and had some questions about leptospirosis that may be of general interest.
Q1. Since the yard is likely contaminated with leptospires, she asked “How cold does the temperature have to get before the Lepto organisms are killed?”
A1. Once it’s frozen, as it is now in January, they’re dead. Leptospires are fragile bacteria that are killed by dry heat and by freezing. They survive well in moist or wet environments, with moderate temperatures. In some countries leptospirosis is called “mud fever” or “fall fever” since this description captures so well the environmental conditions under which they thrive.
Although leptospirosis in dogs can occur at any time in the year, it mainly causes disease in the fall, late September to December, peaking in November. The increasingly mild and prolonged falls that we have experienced in the last decade are thought to be an important reason that leptospirosis has resurged in dogs. Interestingly, there is often a “blip” of leptospirosis in dogs in March in Ontario (and likely Ohio), since this is when the snow melts and conditions are wet, even though we can still get freezing at that time. I suspect that this is also the time when the raccoons that are thought to be the main source of leptospirosis for dogs are again active after the winter, and are foraging for food for themselves and their babies.
Q2. Do dogs still shed leptospires after they’ve been treated?
A2. No. Leptospires are quickly killed by the antibiotics used in treatment, amoxicillin or doxycycline. There is no danger that dogs treated for a week with these drugs are a risk to people or other animals. You may read in otherwise very reputable textbooks that these antibiotics “do not eliminate the carrier state” but I have no idea where this misunderstanding comes from.
Q3. Where can I find out more about leptospirosis in dogs?
A3. I like the web site http://www.leptoinfo.com, which is maintained by a vaccine company. I was surprised how many web sites devoted to leptospirosis that there are, but like much on the internet some contain highly misleading information. The “Worms & Germs” site has good past blogs about canine leptospirosis and is usually (just kidding, Scott) a reliable source of information.
One very common entrenched misconception, which is very hard to kill, is that vaccination does not stop animals shedding the organism. This is quite wrong. I suspect this misconception came from an experimental study half a century ago when dogs with pre-existing kidney infection with a leptospiral serovar called Canicola were vaccinated. It would not be expected by anyone that these animals would stop shedding since antibodies don’t penetrate into the place in the kidney where the leptospires live and from which they are shed in the urine. What vaccination does incredibly effectively is to prevent leptospires from actually reaching the kidney and setting up home there. The leptospires are removed by antibodies in the blood, so they never reach the kidney.
A very poorly-written and confusing report suggests that another Streptococcus zooepidemicus outbreak is underway in dogs in a shelter in Ohio. Five of 175 dogs on the premises died suddenly of hemorrhagic pneumonia. The report variably mentioned a "virus that mutated from horses," that it's thought to be "not contagious" despite multiple dogs being affected, and that it's a "rare form of streptococcus" (a bacterium). Presumably, they are dealing with a group of dogs with Streptococcus zooepidemicus pneumonia (technically, Streptococcus equi var. zooepidemicus). This bacterium predominantly lives in horses but periodically causes infections in other species. Outbreaks in dogs are uncommon but have been reported in other shelters. I assume that cultures from the dead dogs identified the bacterium, otherwise other possible causes such as canine influenza would also have to be considered.
The statement about it not being contagious is bizzare. Obviously, it is contagious between dogs. It may have been referring to dog-to-human transmission, but while that's rare it has been reported.
The shelter is apparently treating all dogs with penicillin prophylactically (i.e. to prevent any more dogs from getting sick). There's no clear guidelines regarding management of S. zooepidemicus outbreaks in kennels. It's now known whether mass antibiotic treatment does anything helpful, but it has been used in other outbreaks. I think it's likely that these outbreaks stop on their own, rather than penicillin having a major impact, and that there's probably another underlying cause such as a viral infection to account for outbreaks of this rare disease. However, that's just speculation for now. Hopefully this outbreak will cease with whatever treatment and infection control measures they put in place (or on it's own). Hopefully a good review of routine infection control practices will be performed at the same time, as routine practices (or lack thereof) are often a major problem in shelters.
An article in an upcoming edition of Transplant Infectious Disease (Gisel et al) describes a case of Bordetella bronchiseptica pneumonia in a person who had received a kidney and pancreas transplant. This person had to board her dogs at a veterinary clinic while she was hospitalized for a bowel obstruction that occurred after surgery. The clinic required her dogs to be vaccinated against Bordetella bronchiseptica, a cause of canine "kennel cough." They were vaccinated intranasally (i.e. up the nose) with a modified live vaccine comprised of live B. bronchiseptica that is modified so it is unlikely to cause disease but can still induce a good immune response. The owner developed pneumonia after returning home and B. bronchiseptica was isolated. Specific testing was not performed to confirm that the vaccine strain caused disease, so it's possible that she was infected by the normal (i.e. "wild type") B. bronchiseptica (which still would have presumably come from the dogs).
Immunosuppressed individuals are at high risk for infection by microorganisms that usually don't cause disease in otherwise healthy people. Bordetella bronchiseptica is a good example of this. Care should be taken around pets by anyone whose immune system is compromised. Here are some recommendations pertaining to kennel cough vaccination:
- Immunosuppressed individuals should not receive modified live vaccines themselves, and it is probably prudent to extend this recommendation to avoid modified live vaccination of their pets with vaccines like the Bordetella (kennel cough) vaccine.
- If vaccination for kennel cough is required for entering a kennel or vet clinic, an exemption should be sought because of the potential risk to the immunocompromised person.
- If vaccination must be performed, injectable vaccination is preferred. It doesn't produce as good immunity in the dog compared with intranasal vaccination but the risks to the immunocompromised owner would be much less.
- If intranasal vaccination with modified live kennel cough vaccine is used, immunocompromised owners should not be in the same room during vaccination. They should avoid contact with the dog's mouth, nose and face for at least a few days after vaccination and should wash their hands (or use a hand sanitizer) regularly after contact with the dog.
- If respiratory disease develops in someone exposed to a dog recently vaccinated against kennel cough, the potential for vaccine-associated disease should be mentioned to the physician.
H1N1 influenza was diagnosed in two dogs in China, bringing increased calls to pay attention to other animal species when it comes to this disease.
I'm more surprised by this than finding H1N1 in a cat or ferret. Dogs are susceptible to influenza and have their own circulating influenza strain (H3N8, originally from horses) but they rarely get other types of influenza. It's just an example of "rare things happen rarely, but they do happen." As with cats, it is now apparent that dogs are susceptible to this virus, although presumably minimally susceptible given the very low incidence of reported canine infections. This doesn't change our basic recommendations for dealing with H1N1: infected people should reduce contact with all individuals in the household, human or otherwise. People should be aware but not worried about the potential for pets to acquire H1N1. The risk of animals transmitting H1N1 back to people is unclear. It's theoretically possible but in practicality, a pet that gets H1N1 most likely got it from its owner, who's already exposed the rest of the household members as well.
Vaccination against canine influenza will not provide any protection against H1N1.
Leprosy usually evokes images of deformed faces and hands and leper colonies. This disease, caused by Mycobacterium leprae, has been recognized for at least 4000 years, and is thought to have been one of the biblical plagues. While now treatable with proper access to healthcare, leprosy is still a problem in some regions.
Feline leprosy is a disease that is present in cats in certain areas of the world, especially British Columbia Canada, northern New Zealand and eastern Australia. It typically causes granulomas (firm fleshy, tumour-like masses) in the skin and tissues directly under the skin, These can become ulcerated and secondary bacterial infections can develop. Feline leprosy has some similarities to human leprosy, however it's not the same thing. It is caused by a related but distinct bacterium Mycobacterium lepraemurium. (It's also suspected that one or more other related bacteria can also cause this disease.) Mycobacterium lepraemurium also causes disease in rodents and can survive in the environment. Cats most likely become infected after being bitten by infected rodents. While the name may be concerning and the disease can be serious in cats, fortunately there is no risk to humans. There is no evidence that this uncommon disease in cats can be transmitted to people.
Image: A photomicrograph of Mycobacterium leprae taken from a leprosy skin lesion. (source: CDC Public Health Image Library ID#2123).
Campylobacter bacteria are important causes of disease in people. Many Campylobacter species exist, and these different species vary quite a bit in their ability to cause disease in people and animals. Campylobacter jejuni is one of the most common causes of diarrhea in people worldwide, and is most commonly associated with contaminated food. However, a few studies have reported that having pets (especially pets with diarrhea) is also a risk factor for Campylobacter jejuni infection.
Another Campylobacter species that may be of concern is Campylobacter upsaliensis. This species is primarily associated with dogs and cats, and a large percentage of healthy dogs and cats may be shedding this bacterium in their stool at any time. It doesn't seem to be a cause of disease in dogs and cats, but it may be an important and overlooked cause of disease in people. One study from the US reported that C. upsaliensis was the 2nd most common Campylobacter strain found in people with diarrhea (after C. jejuni). However, the true role of this species is unclear, partly because of common laboratory testing methods. Culture is the main method used to diagnose infection with Campylobacter, but this bacterium can be difficult to grow in the lab. Usually, culture media for Campylobacter contain antibiotics to inhibit other better/faster growing bacteria. Unfortunately, C. upsaliensis is often inhibited by these antibiotics, so it's likely to be missed in these cases even if it is there. Therefore, we might be underestimating the role of this Campylobacter species in diarrhea. This is an critical issue to investigate because C. upsaliensis is so common in dogs and cats, and it's important to determine what role pets play in human disease.
Avoiding Campylobacter infection involves some basic steps: avoid contact with feces, take care when handling diarrhea from pets, wash your hands regularly after handling pets and always wash your hands thoroughly after any contact with feces. Make sure your physician knows you have pets. In particular, if you have a pet with diarrhea or have recently acquired a new pet (especially a puppy or kitten), make sure Campylobacter infection is considered if you get diarrhea. Most infections are mild and go away on their own but some require specific treatment.
More information about Campylobacter can be found on the Worms & Germs Resources page.
Image credit: CDC/ Dr. Patricia Fields, Dr. Collette Fitzgerald
The topic of the potential for feral (stray) animals, particularly cats, to be sources of human influenza infection came up today. For feral animals to be a public health problem, the following sequence has to happen:
Feral animals need to be exposed to H1N1
- This is pretty unlikely. Influenza is spread through close contact, mainly through aerosols generated by an infectious person coughing, sneezing or breathing. Influenza only travels short distances in this manner. The likelihood of a feral animal being exposed to the H1N1 influenza virus is very low because it is rare for a feral animal to get that close to people. If there is close contact, it's probably very short term, and not high risk for exposure.
They need to become infected AND shed appreciable levels of virus
- Considering the number of infected people, how common pet cats are, and the fact that only one cat has been diagnosed with H1N1, the risk of actually transmitting the virus to a cat is very low even with close contact with an infected person. If tens of thousands of household pet cats have had close and prolonged exposure and only one infection has been diagnosed, this virus is pretty poorly transmissible to cats.
They need to be exposed to susceptible people
- As discussed above, there's not too much contact between stray cats and people. Close and prolonged contact is extremely rare. Influenza is only shed by infected individuals for a short period of time, unlike some other infections. So, the chance of an infected cat having close contact with a person during the relatively short infectious period is very low.
Each one of these events independently is very unlikely. When you combine them, it should be clear that the risks posed by feral cats are extremely low (probably about as close to zero as we get with infectious diseases).
A bigger concern might be someone infecting their indoor/outdoor cat, who would then infect a stray cat, which would then infect another indoor/outdoor cat, which could infect a family member. That's still a VERY unlikely situation - really it's nothing to worry about.
There are certainly public health issues with feral cats. H1N1 is not one of them.
One of the common questions accompanying the onslaught of calls I've taken today is "How do you diagnose influenza in pets?"
Clinical signs, such as sneezing, coughing, fever and lethargy, are not useful for diagnosis. Influenza can produce highly variable disease, ranging from almost none to very severe - so you can't look at an animal and say it has influenza just based on the clinical signs. We don't know much about H1N1 influenza in different animal species (including pets), but this type of influenza can probably cause a wide range of disease in animals as well (at least in those it can infect).
The presence of someone in the household with influenza should get you thinking about flu in a sick pet, but it is far from diagnostic. Many, many people have influenza, but very few pets do. There are many other diseases that can produce signs similar to influenza in pets. The health of people in the household is an important thing to know, but we can't jump to conclusions based on the household history alone.
Laboratory testing is required for the diagnosis of influenza, and there are a few options:
- PCR testing of nasopharyngeal (throat) or nasal swabs, or fluid collected from the trachea: This molecular test detects influenza virus RNA. This is the fastest test and it is most sensitive when samples are taken early in disease. This is the main option for diagnosis at this time.
- Serology: This involves testing blood for antibodies against influenza. Two samples are taken 10-14 days apart. If the antibody level rises 4-fold or greater, that is indicative of influenza infection. This is considered the most reliable method of diagnosis of influenza in many species but takes time. It is not currently a viable option for pets because tests for pets are not available.
- Virus isolation from nasopharyngeal or nasal swabs, or tracheal fluid: Samples are inoculated into eggs to try to grow the virus. This can take quite a while and isolation of the virus can be difficult. This is a method used by specialized labs with laboratory containment conditions appropriate for this virus and may not be readily available.
A report from Seattlepi.com is a textbook example of what can happen to certain people after dog bites. Mike Moore tried to break up a fight involving his two dogs and received a minor bite. It barely broke the skin. No big deal, eh? Well, perhaps for most people, but unfortunately not for Mr. Moore.
He cleaned the wound and didn't think much about it. Two days later, he thought he had the flu. The next day, he was worse and went to the hospital. By the time he arrived, "his face and body had a bluish tint" ...never a good sign. When he was being examined, he was asked about the scar on his abdomen and he told the hospital staff it was from his spleen having been removed. They then asked about the bandage on his hand and he mentioned the dog bite. (Insert big ringing bells here!) The article says that the medical staff couldn't pinpoint the problem right away, but hopefully Capnocytophaga was a leading thought. Mr. Moore was critically ill by this point with multiple failing organs. He was admitted to ICU, became septic (overwhelming infection in his bloodstream) and was put on a ventilator. His hand had to be amputated, as did both legs below the knee and three fingers on the remaining hand. But he survived. (Despite the obvious long-term problems, he's very lucky to be alive after such a severe infection).
People that have had their spleens removed or who have non-functional spleens are at much greater risk for various infections, such as Capnocytophaga infections. No one should be allowed to leave a hospital after having their spleen removed without a letter saying, among other things, if you are bitten by a dog, get thee to a physician (pronto)! If you don't have a functioning spleen, make sure you know the risks and how to protect your health.
Just when all those turkeys that managed to survive Thanksgiving weekend thought their troubles were over, there's new issue: H1N1 influenza (formerly known as swine flu) has been found in an Ontario turkey flock. The H1N1 virus was first reported in birds in Chile in late August.
This is not a reason to panic. No one can get the flu from eating a properly-cooked Thanksgiving turkey (nor from any other type of properly-cooked turkey). The producer has voluntarily (and very responsibly) quarantined the affected flock, and no birds or eggs have left the facility. There is no risk to the food chain.
Pigs can be infected by human, pig and bird flu viruses, and multiple infections can result in viruses trading genes and producing new viruses that can infect more species. So it's not too surprising that H1N1can infect people, pigs and now birds as well. This incident serves as an important reminder that we need to remain diligent about infection control and hygiene, even around animals. It's highly unlikely that these turkeys had contact with infected pigs - most likely the virus was spread to this flock by a person. Poultry producers may therefore need to consider getting vaccinated for H1N1 flu not only to protect themselves, but also their flocks, and anyone who may have the flu should definitely stay off these farms. Hopefully the virus does not become established in wild bird populations (like H5N1 has in some areas), as this would make it much harder to control.
Recommendations for avoiding the flu (H1N1 or other) remain the same:
- Wash your hands and/or use alcohol-based hand sanitizer
- Sneeze into your elbow
- Disinfect commonly touched surfaces
- Stay home if you are sick
- Get vaccinated!
Streptococcus equi subspecies zooepidemicus (usually just called Strep zooepidemicus) is a common cause of infection in horses. It is an "opportunist" that is often found in healthy horses, but which can cause disease in certain situations. While horses are the natural host of this bacterium, sporadic infections and outbreaks are occasionally reported in dogs at cats, particularly in shelters or other crowded situations. Severe (including fatal) pneumonia can occur, as was reported in a recent outbreak in a humane society in Ottawa. Rarely, S. zooepidemicus can also cause infections in people.
A report in the Journal of Medical Microbiology (Abbott et al) describes a serious S. zooepidemicus infection in a person, that was traced back to a dog. The dog lived on a farm that also had horses. It developed pneumonia and S. zooepidemicus was isolated from its respiratory tract. The dog was treated and recovered. However, the dog owner also became ill with fever, headache, a stiff neck and general malaise. Penicillin was prescribed, but the person's condition did not improve and he/she ended up in the hospital. Streptococcus zooepidemicus was also isolated from this person's nose and throat. When the dog and human strains were compared using molecular tests, they were related. An investigation of the farm was performed, and while all the horses present at the time were negative for S. zooepidemicus, the bacterium was isolated from a healthy dog.
This is a rare situation and one that shouldn't result in too much concern. It does highlight a couple points that are good to remember:
- Getting cultures is very important for obtaining a diagnosis.
- Animal contact and pet health should be considered whenever someone is sick with a potential infectious disease. Physicians need to know whether their patients have contact with animals. They need to be told if a sick animal is present so they can consider whether the pet and human illness might be related. Knowing to what someone may have been exposed might speed up diagnosis and appropriate treatment.
- Rare things are rare, but they happen. We shouldn't focus on rare events but we have to keep our minds open and recognize that strange things happen with infectious diseases.
When I talk about methicillin-resistant Staphylococcus pseudintermedius (MRSP), I usually say that the human health risks are low because human infections are very rare. However, rare doesn't mean it can't happen, as demonstrated by a case report entitled "Beware of the Pet Dog: A Case of Staphylococcus intermedius Infection" published in the American Journal of Medical Sciences (Kempker et al 2009).
This paper reports about a post-operative sinus infection in a 28-year-old woman. Cultures were taken and the bacterium was initially misidentified as a coagulase-negative Staphylococcus. It was then misidentified as S. aureus, and finally determined to be S. intermedius. In reality, that's probably another misidentification because the bug almost certainly was truly S. pseudintermedius. (It's become clear over the past couple years that S. intermedius is basically non-existent in dogs and that what has been called S. intermedius in the past is truly S. pseudintermedius).
It's important to remember that human infection with S. pseudintermedius is a rare event. Whenever you see a single case reported, you know it's a pretty uncommon or novel event. Further, this was a post-operative infection, not a spontaneous infection occurring in a low-risk person. At the same time, we need to make sure we don't completely ignore the potential risks. While the risk of transmission of S. pseudintermedius (including MRSP) seems to be very low, we shouldn't ignore it completely. Isolation and other strict measures aren't indicated when dealing with a pet with S. pseudintermedius infection, but general attention to basic hygiene practices and avoiding contact with the infected site is still a good idea.
The US Food and Drug Administration (FDA) has warned consumers about buying antiviral flu treatments over the internet. The FDA issued this warning after it tested "Tamiflu" purchased over the internet. Most of the products contained oseltamivir, the active ingredient in the original Tamiflu, but at varying concentrations. Some were pretty obviously a problem, such as one of the orders that arrived in an unmarked envelope with a postmark from India, and consisted of unlabeled, white tablets taped between two pieces of paper. These tablets contained talc and acetaminophen (the active ingredient in Tylenol), but no oseltamivir.
The commissioner of Food and Drugs, Margaret A. Hamburg, M.D, stated in the FDA press release that “Medicines purchased from Web sites operating outside the law put consumers at increased risk due to a higher potential that the products will be counterfeit, impure, contaminated, or have too little or too much of the active ingredient.”
Another issue is that a drug like Tamiflu needs to be given very early in disease to have any effect. If you think you're getting the flu and order Tamiflu over the internet, it's pretty unlikely to have any chance of working by the time it actually arrives (if they send you the appropriate drug in the first place). Then there's the concern that few people actually need to use Tamiflu compared to the number that do, and that viral resistance to Tamiflu may develop with unnecessary use.
Bottom line: if you really need medication, you should get it from a reputable source on the recommendation of a physician. If your pet needs mediciation, you should take the same approach. It's hard to be certain about what you're getting if you order it through the internet, especially from companies that are illegally selling prescription drugs. It might seem cheaper to buy drugs over the internet, but if it's not needed or it's fake, it's going to cost you more in the long run.
While in London (UK) last week, I went with a group of people to the John Snow pub. It's a bit of an epidemiologist pilgrimage, where you can sit in a pub named after one of the "fathers of epidemiology" and sign the guest book.
John Snow was a physician in London in the mid-1800's. Cholera outbreaks were a problem in Victorian London because of contaminated communal wells (for drinking water). Unlike many others, Snow did not believe in the miasma theory, which stated that noxious vapours in the air were the cause of many illnesses. While the "germ theory" of disease was not yet on the scene, Snow thought there must be some other way that diseases like cholera were transmitted, and he suspected (correctly) that the water supply was the problem.
During a cholera outbreak in 1854, he determined that a well in central London (Broad St, now Broadwick St) was a major source of the disease. Removing the handle from the pump (so that people could no longer use the well) stopped the outbreak. Although Snow himself suggested that the outbreak was already in decline, removing that source undoubtedly played a large role in saving many lives. Back then (and even still commonly today), getting people to accept and adhere to infection control measures was not easy. After the outbreak ended, public officials fixed the pump, despite the fact that it was clearly associated with the outbreak. In hindsight, it's not surprising that this well was associated with disease, since it was shallow and very close to a cesspool.
The John Snow pub is located at the original site of the Broad Street pump. You can see the location of the original pump from the window of the pub (there's a replica pump there and a marking on the ground at the exact site of the original pump). So, you can visit the source of a great cholera outbreak, peer out at the simple solution that helped stop it, and have a drink in the pub named after John Snow - something that's more than a little ironic, since Snow was also famous as a teetotaler.
Five more E. coli O157 infections have been linked to the Pacific National Exhibition's petting zoo, bringing the total to 18. It's very likely that the true number of infected people is higher, since mild cases are often missed because they don't go to the doctor or because testing is not performed. This situation follows a very large outbreak linked to a UK public farm and closure of some other UK petting zoos because of E. coli O157. Clearly, more effort needs to be put into proper management of these events, design of petting zoo facilities, scrutiny of animals and education of the public about infection control practices. Petting zoos shouldn't be banned, but they should be regulated and run responsibly.
Considering all of the disease outbreaks that have been attributed to petting zoos, including an outbreak in the UK this month that has sickened dozens and another in Vancouver that has affected at least 13 people, you would think that people who operate petting zoos would start to take the hint. Unfortunately, that's clearly not the case.
My family and I went to the Fergus [Ontario] Fall Fair today. Apart from the petting zoos, it was a great day, but the potential for ending up in hospital with a life-threatening infection shouldn't have to be a concern for fair attendees.
This fair had two petting zoos. One was also associated with a pony ride. We went there first and while my kids were looking at the animals, I noticed there was a table and a sign saying to use a hand sanitizer after touching the animals, but there were not actually any hand sanitizers available. I asked the attendant and he immediately started looking. They eventually found some, but we gave up after waiting a few minutes and went to the other petting zoo location because a handwashing station was set up there. Despite a large crowd around the first petting zoo, I didn't see anyone following our actions so presumably almost no one washed their hands after petting the animals. The good thing about this first petting zoo was they at least had a clean facility, appropriate animals and no major problems apart from the forgotten sanitizers.
Petting zoo number two was not as good. There were numerous problems, some of them very major.
- Inappropriate animals #1: As we walked in, someone held out a baby chick and tried to give it two my 2-year-old daughter to handle. Standard guidelines are that children under 5 should not handle young poultry, so these animals are inappropriate for any petting zoo.
- Inappropriate animals #2: The next thing we passed was a young calf. Calves are also considered a high-risk animal and should not be present in petting zoos.
- Inappropriate animals #3: The calf had diarrhea (see the diarrhea staining and hair loss probably associated with prolonged diarrhea in picture). It's very likely that this calf was shedding one or more infectious agents in its diarrhea, such as Cryptosporidium.
- Food for sale: Food was being sold and consumed inside the tent where the petting zoo was. This is inappropriate.
Petting zoos can be great events for kids. They can also be sources of large and serious outbreaks of infectious diseases. Hopefully nothing bad will come from this and we won't hear reports of illness in petting zoo participants. But, as I've said before, hope is not a proper infection control program.
Anyone running a petting zoo MUST know the issues, risks and proper preventative measures to take. Reading the Compendium of measures to prevent disease associated with animals in public settings would be a good start.
The Centers for Disease Control and Prevention (CDC) has released updated Guidelines for the Prevention and Treatment of Opportunistic Infections Among HIV-exposed and HIV-infected Children. A small but still important part of this document involves recommendations for contact with animals. It's a nice, balanced document that acknowledges the risk but doesn't make unnecessarily restrictive recommendations.
Among the important recommendations regarding animals:
- When getting a new pet, avoid dogs and cats less than 6 months of age or strays: These animals are at higher risk for shedding various infectious diseases and are more likely to have problems with biting and scratching.
- Avoid contact with animals that have diarrhea.
- Wash hands after handling pets.
- Avoid contact with pet feces.
- Avoid contact with reptiles, chicks and ducklings: These are very high risk for Salmonella.
- Avoid contact with calves or lambs at farms or petting zoos: These animals are high risk for various infectious diseases such as Cryptosporidium and Salmonella.
These recommendations also largely apply to other high-risk groups, including people (of all ages) with compromised immune systems and young children (especially less than 5 years of age). A key point is normal contact with common household pest using basic hygiene practices is considered a low risk. Infection control isn't rocket science. It involves basic and practical measures that can reduce risks associated with animal contact.
Skin and soft tissue infections increasingly caused by highly drug-resistant bacteria, along with various concerns about antibiotic use, have led to a desire to find non-antibiotic approaches to treatment of these infections. Tea tree oil has some potent antibacterial properties when tested in the lab, and there are some studies indicating it might be effective for the treatment of certain infections. Some work that we've done in my lab shows promising activity of a few different essential oils against MRSP. Some of these oil may be similarly useful treatments for certain infections.
However, as I've stated before, we need to make sure that we adequately investigate safety of any new drug or therapy. All natural does not mean safer. If something kills bacteria, we need to make sure that it doesn't also harm an animal's cells and tissues.
Tea tree oil can cause damage to skin and soft tissue cells, but it's unclear whether this is really a problem during short courses of treatment. Nonetheless, in humans it has been recommended that tea tree oil not be used for treatment of burns because of concerns about tissue damage.(Faoagali et al, Burns 1997)
Another concern is toxicity from ingestion. This isn't usually a concern in adults, but there are a couple reports of children that became seriously ill (neurological abnormalities, progressive unresponsiveness... fortunately temporary) after ingestion of small volumes of tea tree oil. This leads me to have concerns about ingestion of the oil by dogs and cats if they lick areas where it has been applied, or eat bandages soaked in oil. They probably wouldn't ingest that much, but it's possible.
At this point, the jury is still out on the usefulness of tea tree oil. There are some potentially beneficial aspects and some safety issues that need to be clarified. In the interim, if you want to use tea tree oil:
- Recognize it's not a proven therapy. Don't use it in place of conventional treatment recommended by your vet.
- Keep it out of the reach of children and pets.
- Be judicious about the amount you use, and make sure pets don't lick it off.
- If the infected site seems to get worse after tea tree oil is used, stop applying it and see your veterinarian.
Brucellosis can be a pretty nasty disease. Most people with brucellosis are infected through ingestion of contaminated food or contact with infected farm animals. Brucella abortus, B. melitensis and B. suis are the most common bacterial species involved. However, there is also another Brucella species, B. canis, which (as the name implies) is associated with dogs. Human infections with B. canis are much less commonly diagnosed than those caused by other Brucella species, but it is possible that this infection actually occurs more often than we realize.
Brucellosis can cause a wide range of problems, but most are rather non-specific such as fever, headache, body aches, sweating and back pain. Recurrent, undulating fever is a common sign and can persist for long periods of time. Disease caused by B. canis is similar to that caused by other Brucella species, but one reason this disease may be underdiagnosed is that screening tests for brucellosis do not cross-react with B. canis. Therefore, a physician might suspect brucellosis, but if the initial test (an antibody test) is negative, the physician is likely to move on to investigate other possibile diagnoses. Specific B. canis blood tests or culture of B. canis from blood or infected sites are required for diagnosis. Overall, it's probably still a very rare disease, but one that certain people should be aware of.
Many dogs that are infected with B. canis have no detectable signs of infection. The bacterium can circulate through the body continually or intermittently, and spread from the gentials (where it likes to reside) for years. Some infected dogs show signs of illness. Reproductive problems, including late-term abortion (miscarriage) and decreased fertility are major problems. Fever, lymph node swelling, diskospondylitis (infection in the spine) and other problems can also develop.
The risk of human exposure is highest in people in close contact with breeding animals, particularly people in contact with dogs that miscarry during pregnancy or kennels with reproductive problems. Most reported human infections involve people in close contact with dogs that miscarry. The risk to owners of household pets (especially neutered pets) is presumably very low.
- People who have been exposed to dogs that miscarry and who subsequently develop signs like fever and aches should make sure their physician considers B. canis infection.
- HIgh risk people (very young, elderly, immunocompromised, or pregnant women) should avoid contact with dogs that have miscarried, or dogs from kennels with reproductive problems or known B. canis infection.
- Care should be taken when handling dogs that have miscarried or are in the process of doing so. Gloves should be worn when handling the dog, aborted fetuses and any potentially contaminated items. Uterine (birth) fluids can have very high levels of B. canis.
- Hands should be washed regularly and after removal of gloves.
- If abortion or reproductive problems are identified in a kennel, testing for B. canis should be performed. If present, an eradication program should be started.
More information on brucellosis in dogs can be found in the Worms & Germs archives.
A paper in the July 1 edition of the Journal of the American Veterinary Medical Association (Muller et al) describes a case of encephalitis (brain inflammation) in a rabbit caused by human herpesvirus type 1. The owner had a severe herpes infection with genital and oral lesions five days before the rabbit got sick, and reported "intensive" nose-to-nose and mouth-to-nose contact with the rabbit. The rabbit started off with a decreased appetite and excessive tear production (epiphora) in one eye. Then other signs of eye and neurological disease developed. Despite aggressive treatment, the rabbit deteriorated and was euthanized after a week of hospitalization. Subsequent testing identified human herpesvirus type 1 in the rabbit's brain.
Human herpesvirus type 1, also called herpes simplex viruses type 1 (HSV-1), is a common sexually transmitted disease (STD) in people. It can cause oral, genital and ocular (eye) lesions. Humans are the primary host of this virus, but it has been found in species such as rabbits, rats, mice and chinchillas. In rabbits, it usually causes encephalitis, and is almost always fatal for these animals.
This case shows how viruses typically associated with one species can sometimes affect others. While we usually focus on microorganisms moving from animals to humans, they can also move in the opposite direction, as was presumably the case here. Close face-to-face contact with the infected owner was probably the source of the virus. This is an example of an uncommon event, but one that should not be ignored.
If you have an active herpesvirus infection:
- Limit close contact with rabbits (and, to be on the safe side, probably restrict contact with other pets as well). In particular, avoid contact with the mouth, nose or eyes.
- Wash your hands or use an alcohol hand sanitizer regularly, particularly after using the washroom or having any contact with infected sites/sores.
- Make sure herpesvirus infection is considered if your rabbit develops eye or neurological disease.
The risk of rabbits transmitting human herpesvirus is completely unclear. Common sense dictates that anyone hanlding a potentially infected rabbit should restrict contact with the eyes/mouth/nose, wear gloves, wash hands after contact (even if gloves were worn) and avoid contamination of clothing.
Tularemia has been diagnosed in five dogs and cats in Sioux Falls, South Dakota. At least one of the pets has died. Tularemia, sometimes referred to as "rabbit fever" is caused by the bacterium Francisella tularensis. Infections occur throughout much of the Northern Hemisphere but are much more common in certain regions, such as the central US. This bacterium has received a lot more attention over the past decade because of its potential use as a bioterrorism agent, but infections have been occurring in people and pets for a long time. In North America, the cottontail rabbit, wild hares and some rodents are the main reservoirs. People and other animals get infected through close contact with infected animals (e.g. rabbit hunting) or through bites from blood-feeding insects.
There was no mention of human cases in the recent report from South Dakota. One of the implications of identifying this disease in pets is that whatever infected the pet could also be a risk for people. If the pets were infected by contact with wild animals, people with similar contact with wild animals could also be exposed. If there is no chance the animals had contact with infected wildlife, then insect-transmission is most likely, and the same could happen to human members of the household (or elsewhere in the area). Therefore, diagnosis of tularemia in a person or pet should put both veterinarians and physicians on the lookout for further cases in all species.
Transmission of tularemia from infected pets to humans is also a concern. This has been reported in numerous instances, most often with cats. There are published reports of transmission from dogs to humans, but these are less convincing than the numerous cat-to-human reports. There's also a report of tularemia transmission from a hamster to a child. The overall risk of transmission is probably low, but tularemia can be spread from pets to people by scratches, bites, and perhaps regular close contact.
You can reduce the risk of your pet being exposed to tularemia by:
- Keeping pets indoors as much as possible. Cats should stay indoors. Dogs should not have uncontrolled outdoor access.
- Dogs should not be allowed to hunt rabbits in areas where tularemia is endemic.
- Animals that venture outside should be checked regularly for ticks and a preventive medicine program for ticks should be in place.
- Routine measures to reduce bites and scratches from dogs and cats should be taken.
I was reading an interesting old paper the other day about Q-fever in cats. Q-fever is a zoonotic disease caused by Coxiella burnetii. It is most commonly associated with contact with sheep, cattle and to a lesser extent goats, around the time they give birth. This bacterium is highly infectious - it only takes a small number of bacteria to cause disease. (That's one of the reasons it's classified as an important bioterrorism agent).
While most of the focus in on ruminants, there have also been many reports of Q-fever associated with cats, also mainly through contact with these animals around the time they give birth. Cats may be the most important Q-fever reservoir in urban areas.
The study I was reading, a 1988 article from the journal Chest, describes a Q-fever outbreak in a town in Nova Scotia. Thirty-three people were infected in the town of Baddeck (population 900, meaning 2.8% of the population was affected). Forty-two percent of infected individuals lived in four side-by-side buildings. Investigation revealed that most infected people had contact with a cat that have given birth to stillborn kittens (stillbirths are common in cats infected with Coxiella). The cat lived in one of the four buildings and regularly visited neighbouring buildings.
This is just one of many reports of Q-fever associated with cats. Almost all involve direct contact or being in the vicinity of cats around the time of birth. Since this bacterium is so infectious, and can even be spread through the air through aerosols (e.g.dust, tiny droplets of fluid), direct contact (e.g actually touching the cat) is not required for infection to occur.
That being said, cat-associated Q-fever is probably still pretty uncommon, but Q-fever can be a very serious disease. Since transmission mostly involves cats at the time of birthing, a few basic measures should be able to greatly reduce the risks:
- Avoid contact with cats that are giving birth or who have done so recently.
- Avoid contact with newborn kittens and areas contaminated during the birthing process.
- If your cat is going to give birth, try to have it do so in a well-ventilated area away from areas where people spend time and away from areas where food is prepared.
- If contact with the mother cat, kittens or areas/items contamination with birth fluids is likely to occur, gloves should be worn. Hands should be washed after gloves are removed.
- If a cat gives birth inside, the area should be thoroughly cleaned and disinfected afterwards. Gloves should be worn for this.
- The risks are probably higher with stray cats (who are more likely to be infected), so extra care should be taken to avoid contact with stray cats around the time of birth.
More information about Q-fever can be found in the Worms & Germs archives.
A canine influenza virus vaccine has recently been released. Canine influenzais a virus that originated from a horse influenza strain and is now circulating in some dog populations. (To my knowledge, we have yet to find it in Ontario. We didn't find any evidence of it in an earlier surveillance study). It typically causes mild disease, as with influenza in people, but can also cause serious (including fatal) infections. These cases are most common in densely-populated, stressful environments like shelters and racing greyhound facilities.
Like most vaccines, this canine influenza vaccine does not claim to provide 100% protection. Veterinary vaccines can get conditional licensing and be marketed with little evidence of effectiveness. The manufacturers have produced data "supporting product purity, product safety under normal conditions of use in field safety trials and demonstration that the product has a reasonable expectation of efficacy." That means they have shown the vaccine is produced with good practices, had no obvious adverse effects in a safety study, and there is a possibility that it could be effective (presumably from showing vaccinated dogs produce antibodies against canine influenza virus). During the conditional licensing period, the manufacturers "will continue to submit data obtained in support of the product’s performance, which will be evaluated by government regulators to determine whether a regular product license may be issued."
There's a good likelihood the vaccine will be effective at reducing the incidence and severity of disease, as with influenza vaccines in other species. Basically, if a vaccinated dog gets exposed to the virus, it should be less likely to get sick, and if it gets sick, it should be less likely to have severe signs. Reducing the incidence and severity of influenza also has the benefit of reducing the chances of developing a secondary bacterial infection, which can cause very serious disease.
Deciding whether to vaccinate your dog largely comes down to the risk of exposure and the implications of your dog becoming ill. In an otherwise healthy dog that is not in a high risk environment (e.g. kennel, shelter, greyhound racetrack), it's questionable whether vaccination is needed. If canine influenza virus is in the area, it's something to consider, but the virus seems to be rare (or at least rarely identified) in pets in most regions. Discussing the risks and benefits with your veterinarian is the key.
Canine influenza is NOT considered a zoonotic disease. There is no evidence that it can infect humans. Therefore, there is no public health argument for vaccination.
I recently wrote about Mycobacterium bovis, the cause of bovine TB and a pathogen that can be transmitted to people and rarely to pets. A reader made the following comment:
"Having come across your very interesting blog, I was questioning/wondering whether your statement regarding Mycobacterium bovis, "whose main natural reservoir is cattle", is in fact actually so any longer; if ever. . In the UK all cattle herds were once declared clear of this disease by testing and culling and the gassing of badgers, until the government protected the badger over here to appease animal rights activists and gain a few extra votes. Now it is rife again. These people somehow believe badgers have 'rights' to life above farmers' cattle.
I often wonder if the 'bovine' association is simply because the bacterium was first isolated in cattle as they were obviously captive and there to be investigated. Could it just as easily have been called Mycobacterium meles? As I understand it, Mycobacterium tuberculosis came first and originated in humans and then developed as Mycobacterium bovis in animals"
Good question. Just because a disease is named after a particular species does not mean that it's the main source or original source of the pathogen responsible. Cowpox virus is a good example - cows aren't actually the reservoir of this virus, rodents are. However, because cows are more closely observed or monitored than rats, it was originally associated with cows and thus named cowpox.
We are more likely to detect diseases in humans first, followed by domestic animals, followed by wildlife. Severe acute respiratory syndrome (SARS) is a good example of this. This disease was first found in people. It was then linked to civets and raccoon dogs. However, civets and raccoon dogs aren't the true reservoirs, nor where the disease originated. It appears that the reservoir is in fact bats. Bats are a lot harder to investigate than captive animals, so even though they are now the presumed reservoir, it took a while to figure that out.
Back to Mycobacterium bovis... It's impossible to say for certain where it originated. Since it is thought to have evolved from Mycobacterium tuberculosis, the reservoir of which is people, it makes sense that the evolution of M. bovis would involve a domestic animal species instead of a wildlife species. Cattle have much closer contact with people than do wildlife such as badgers, opossums and deer. So, since M. bovis has historically been most strongly associated with cattle, and cattle live in close contact with humans, I woudn't be surprised if they are the true orgin in this case. However, since M. bovis can infect a very wide range of species, we can never really know.
Tuberculosis (TB) is an incredibly important disease caused by Mycobacterium tuberculosis. It's a huge problem internationally, and the problem is getting worse in many areas. Another cause of "tubercular" (or tuberculosis-like) disease is Mycobacterium bovis, a related microorganism whose main natural reservoir is cattle.
Mycobacterium bovis is cause of bovine TB. It can also infect people (usually through drinking or eating unpasteurized dairy products) and pets. Pets can be exposed by a few different routes, including eating contaminated dairy products, eating infected animals (e.g. snacking on carcasses of wildlife like deer that have died of the disease), and perhaps from direct exposure to wildlife carrying the organism. Mycobacterium bovis is an important problem in some areas, typically because of its presence in a wildlife reservoir like deer or the European badger (a major problem in the UK).
Mycobacterium bovis can cause serious disease in pets. It often causes non-specific signs that makes it hard to diagnose until disease is very advanced (and unfortunately likely beyond the point of successful treatment). Some groups recommend prompt euthanasia of infected pets without considering treatment because of the potential for infection of people. The risk of pet-human transmission is completely unclear, but it's such an important disease that some people think any risk is unnecessary and unjustifiable. So, the key is avoiding infection in the first place (for both people and pets). This is of particular concern in regions where M. bovis is present in wildlife and cattle. In areas where it is not known to be present, there should be little to worry about.
Here are some simple steps that can help you reduce the risk of your pet becoming exposed to M. bovis:
- Keep cats indoors.
- Don't allow dogs to roam free outdoors.
- Don't allow animals to have access to unpasteurized dairy products or dead animals.
Pretty basic, isn't it?
A paper in the Journal of Clinical Microbiology back in 2000 described a case of Pasteurella multocida meningitis in a one-month-old baby that was linked to a pet cat. Pasteurella multocida is a bacterium that can be commonly found in the mouth of healthy dogs and cats - 90% or more of healthy cats may have it in their mouth. The organism can cause infection in humans. These cases are usually associated with close contact with animals, such as bites, scratches and licking wounds. In this case, there was reportedly little contact between the baby and the cat, yet the same P. multocida strain was found in both. The cat was healthy and the bacterium was found in its mouth. There was no clear route of transmission (like a bite or a scratch), however unidentified contact with the cat or (more likely) indirect transmission of the bacterium from the cat to the baby by another person are possible.
This is a good example of the unpredictable nature of zoonotic infections. There was no reported underlying disease that made this baby more susceptible to infection. It's just that being very young (or very old, or immunocompromised) means you're more likely to develop infections from the myriad bacteria that are present all around us. While this infection might not have been preventable, we need to think about good routine precautions involving contact of pets with babies.
- Keep them apart (but not completely). Pets should not be allowed to lick or have other close contact with a young baby. That being said, household pets need to be around the baby to learn to interact with the child safely, and recognize the baby as a member of the family, but supervision is needed and direct contact should be avoided.
- Good hygiene should be used around pets and babies (individually and together). Hands are the main source of disease transmission and regular hand washing is a great infection control tool.
A reader posed this question, with respect to having raccoons living around the house:
"One thing that causes me concern with the raccoon roundworm is the possible danger of infection to my pets and myself through the feces left behind from the raccoons in the yard and possibly in my vegetable garden. Can I acquire the roundworm from working in the soil and/or from my root vegetables etc? My cats mingle near the raccoons, they don't bother each other, should I get my cats tested?"
Certainly, working outside (particularly in soil) leads to the potential for exposure to many disease-causing agents, including Baylisascaris, as well as dog and cat roundworms (Toxocara spp.). Eating unwashed/uncooked vegetables is also a risk. However, in the grand scheme of things, the risks to the average person (not very young or very old, functional imune system) are minimal, especially if basic hygiene measures are used, such as washing hands after working in the garden, and thoroughly washing vegetables. Raccoons tend to defecate in the same specific areas most of the time (raccoon latrines), so in general gardens probably aren't common sites for raccoon feces, although it certainly can occur. Cats are probably more likely to defecate in gardens. We shouldn't take concerns about Baylisascaris lightly, because even though disease (larval migrans) is very rare, it can be very severe.
Now, about testing cats for Baylisascaris - there's not much use, for several reasons:
1) The likelihood of a positive result is very low. The prevalence of Baylisascaris in dogs is very low. Little is known about the prevalence in cats specifically, but it is presumably very uncommon there as well.
2) It can be difficult to differentiate Baylisascaris from the feline roundworm, Toxocara cati. Unless the lab has experience with this, they may not be able to tell the difference. Therefore, you might get a misleading result.
3) What does a positive test tell you? It tells you that the cat is shedding this parasite or that is has ingested eggs that are just passing through the intestine. The risk to people is still minimal if litterboxes are cleaned regularly. Contaminated stool is not infective until it has sat around for days to weeks, so regularly cleaning the litterbox and good handwashing can control the risk.
4) What does a negative test tell you? It tells you that the parasite was not detected on this single sample. It could have been there but not been identified. It might not be there today but could be there tomorrow (though this is still unlikely). A single negative test today does not tell you too much.
5) What would you do with the results? Probably not much. In the very unlikely chance that results were positive, it would likely be recommended to repeat testing to see if eggs are just passing through or whether the animal truly is infected with the parasite. That would determine whether treatment is needed. Otherwise, recommendations would be pretty much the same in both cases (good regular deworming program as directed by your veterinarian, proper handling of cat feces...).
The best way to prevent exposure of your cat to Baylisascaris (as well as other pathogens, predatory wildlife, vehicles, etc.) is to keep it inside.
Another surge in the number of cases of Q fever in people in the Netherlands has been reported. Prior to 2007, the average number of cases of Q fever per year in the country was only 15. In 2007 there were 192 cases, and last year there were 958 cases, making this the largest community outbreak of Q fever ever reported. At the beginning of May 2009, another jump in the number of cases - over 200 - was reported by the dutch newspaper de Volkskrant.
Q fever is caused by a highly infectious organism called Coxiella burnetii. The organism can be carried by many different animals, but particular sheep and goats, and sometimes cattle. Most of the time it does not cause a problem in these species, but it has been linked to abortions and abortion storms (i.e. when many animals in the herd abort in a short period of time). It can be shed in manure, urine and milk, but the largest numbers of organisms are found in birth fluids and tissues (e.g. aborted fetuses, placentae). When the tissues and fluid dry out, the organism can be stirred up into the air over short distances in dust. Humans are highly susceptible to C. burnetii, and inhaling even a single organism can cause infection. Most of the time people who get sick have signs very similar to the flu, but severe pneumonia and liver disease can develop in a small number of cases.
A definitive link between sheep and goats and the Q fever outbreak in people in the Netherlands has not yet been established, but it is highly suspected that many of the cases are associated with infected goats (and some sheep). In the last two years numerous outbreaks of Q fever have been reported on dairy goat farms and one dairy sheep farm in the Netherlands. This has lead to a cooperative arrangement between the Dutch agricultural ministry and the Dutch public health ministry - these two goverment branches have come together to help cover the costs of vaccinating sheep and goat herds in the country, in order to help stem the tide of disease and ultimately prevent more human cases. This is a great example of the "one medicine" concept, whereby groups on both the human health and agricultural/animal health sides are working together on this problem.
Manditory vacciation is now required for sheep and goats on larger farms in the hardest-hit areas, as well as any farms reporting any cases of Q fever since 2005, and any sheep or goats that have a "public function" (e.g. petting zoo animals or occupational therapy farms). It is very important that this last group is included under the manditory vaccination, as these animals have a large amount of contact with people. Steps have also been taken to improve hygiene, restrict spreading manure from sheep and goats, restrict visitors to infected farms, and to make abortion storms on sheep and goat farms reportable, so they can be investigated for Q fever. It will be interesting to see how effective these measures are at controling the outbreak in 2009.
More information on Q fever can be found in our archives.
The latest issue of Oprah's magazine "O" features the icon talking about her recent puppy dog adoption drama involving canine parvovirus. It just goes to show that even the pets of the biggest celebrities in the world are not beyond the reach of common microscopic infectious pathogens.
A couple of months back, Oprah adopted two cocker spaniel puppies from a shelter in Chicago. Unfortunately, within two weeks they both came down with parvovirus infection and had to be hospitalized. I'm sure both dogs received top-of-the-line care with no expense spared, but even so one of the puppies died. The other puppy came very close to dying as well, but happily she apparently has now recovered completely and is doing just fine (or quite likely better than fine, considering who her new owner is!).
Oprah also mentioned how one of her other dogs, Solomon, also suffered from a parvo infection years ago, but that dog was over a year old when he became ill. It's actually quite unusual for any dog to get parvo beyond one year of age - most adult dogs are not affected by the virus, unless perhaps their immune system is compromised for some reason.
These stories bring up a few interesting points to ponder:
It's great to adopt an animal from a shelter and give a homeless animal a home. It is an act of great kindness that I don't want to take anything away from in the least. However, it's important to realize that you never know what shelter dogs may be carrying, nor how well vaccinated they are.
- Even if the animals are vaccinated once at the shelter, the protective effect may be less than ideal if a properly timed vaccination series is not completed.
- In this case the pups may have been exposed to parvo after leaving the shelter, but they could have just as easily been exposed at the shelter, which begs the question of what else might they have been carrying? Bacterial pathogens such as Salmonella and Campylobacter are also particularly common in young dogs and cats (even healthy ones), and these are potentially zoonotic agents.
Young animals, particularly from shelters, are higher risk in terms of the infectious diseases they can carry and transmit. That doesn't mean they shouldn't be adopted, but it does mean taking some extra precautions for the first several weeks they're in their new home. These include being very diligent about controlling stool contamination of any kind (which can be easier said than done during the house-training phase), preventing contact with high-risk individuals (e.g. young children, the elderly, anyone with a weakened immune system) and lots of handwashing on the part of everyone involved with the puppy (or kitten!).
Parvo is a very serious disease in puppies, yet people sometimes become a little complacent about vaccinating for parvo and other puppyhood diseases. Remember, though, that the reason parvo has become so much less common than it used to be is largely because of widespread and effective vaccination. I have to wonder about how well vaccinated Oprah's dog Solomon was to get the disease at the age he did, but there could easily be other factors involved as well. The virus is still out there, and if we become lax in our infection control practices - including decreasing exposure of puppies to the stool of other dogs, as well as vaccination - it's waiting in the wings for its opportunity to move in. Even with the very best care the infection can still be fatal.
It's also relevant to note that, as demonstrated by Solomon's case, just because parvo is very uncommon in adult dogs doesn't mean it's impossible for them to get it. It's important to always remain diligent.
Parvoviruses are quite species specific, so thankfully people cannot get parvovirus from dogs, but remember that puppies can get diarrhea from pathogens like Salmonella, which can be transmitted to people. There is also a human parvovirus which is the cause of Fifth disease. Just like the dog virus cannot infect people, the human virus cannot infect dogs.
Image source: http://omg.yahoo.com
ProMed recently reported about an outbreak of canine brucellosis at a "puppy farm" in Ireland. Farm is definitely the appropriate word in this case, since this operation had about 700 breeding females. The picture on the right is not from this farm, but I imagine it's a similar operation. Beyond the concerns about humane management of dogs under these conditions, such a large operation creates perfect conditions for various infectious diseases.
"The farm's owner has refused to sign an undertaking not to move the dogs off-site before an official inspection can take place to investigate the extent of the [brucellosis outbreak]."
Lack of cooperation makes any disease investigation much more difficult. It's not surprising this person doesn't want to cooperate, given the type of operation he's running.
"Someone from the farm told the Irish Times that the 2 animal welfare agencies were involved in acts of "intimidation" against the establishment."
I suspect that "intimidation" in this case means the agencies were doing their job, because I can't see how there wouldn't be significant welfare problems at a farm of this type and size.
"'We got accurate information on Friday [2 May 2009] that this man was intending moving and selling these dogs and we acted on it,' according to Jimmy Cahill, chief executive of the DSPCA [Dublin SPCA]. 'The guards were very helpful but the owners refused to let us see the dogs or any of the carcasses.' "
The reference to "carcasses" implies that deaths have occurred. Death from B. canis in dogs is very rare but it is possible. However, a poorly managed operation with hundreds of dogs is bound to have multiple issues that could cause deaths.
Canine brucellosis is caused by the bacterium Brucella canis. This main problem with this bacterium in dogs is reproductive disease, including abortion and infertility (in both males and females). Discospondylitis (inflammation of the discs between vertebrae in the back) can also develop.
Brucella canis is a zoonotic organism. Human infections are rarely reported but it is possible that some go undiagnosed. Brucella canis can be transmitted from dogs to people through contact with body fluids from infected dogs, including urine and vaginal fluids. The risk of transmission is likely highest when handling animals during breeding or birthing. While the bacterium can be shed in nasal secretions and saliva, levels are low in these fluids and the risks are probably correspondingly low.
One problem with preventing B.canis transmission is that infected dogs do not necessarily show any signs of disease. In people, B. canis infection can cause flu-like disease, loss of appetite, weakness, joint and back pain, vomiting and diarrhea and various other symptoms.
To control the outbreak on this "farm," quarantine and repeated testing of all dogs is needed, and positive animals must be removed from breeding. Given the information provided above, it's pretty unlikely this will happen voluntarily. I suspect this person would likely either just get rid of these dogs and get more poor-quality breeding animals, or try to continue breeding these dogs and hope people get sick of looking into his operation.
The new H1N1 influenza virus has been found in pigs in Alberta, Canada. This marks the first time this virus has been found in pigs, or any other non-human species. It's not surprising - genetically speaking, the virus is most closely related to other swine influenza viruses (which is why it was originally referred to as "swine flu"), so it should be able to infect pigs. However, this is still a disappointing development because if the virus becomes established in the pig population, the pigs could become a potential reservoir for human infection.
In this case, the source of the pig infections is presumed to be a person - a farmhand that contracted the infection in Mexico. He became ill upon returning to Canada, and the pigs started showing flu-like signs about ten days after he returned to work. Various swine industry and health organizations sent out reminders to pig producers that sick people and/or people returning from Mexico should avoid contact with pigs, however the farmhand in question here returned from Mexico before much of this information became available.
I assume that much more information about this situation will soon become available. A close review of biosecurity practices on this farm is needed to determine if transmission occurred because of defiicient infection control protocols, or whether transmission occurred despite the use of standard practices. The farm is under quarantine and the pigs are being closely monitored to determine what effects this virus will have on them and how long is will stay in the herd. Undoubtedly, close monitoring of other pigs farms (both in Canada and many parts of the world) will continue, with particular emphasis on farms where individuals potentially exposed to the H1N1 virus may have had contact with pigs.
The World Health Organization (WHO) has provided the latest update about H1N1 influenza numbers internationally. (People are still often calling this "swine flu", but it has yet to be found in pigs and is clearly being transmitted human-human now, therefore some have recommended it be called "Mexican flu" or "North American flu" instead. This also decreases the negative associations with pork products, which are totally unfounded because the virus is NOT a food safety concern). Regardless of the name, this pathogen continues to move across the planet. The WHO is reporting 148 laboratory confirmed cases. Ninety-one have been confirmed in the US with 26 confirmed in Mexico.
It's important to remember that confirmed cases are very much the "tip of the iceberg". It's likely that there are thousands of cases in Mexico, despite only 26 having been confirmed by laboratory testing. For a case to make this list, the sick person has to go to a doctor AND samples have to be collected for testing AND the testing has to be appropriate for identification of swine flu versus other types of influenza. Areas with more diagnostic testing capacity and public health infrastructure (like some places in the US) will end up reporting more cases, even if they actually have fewer sick people. So, we shouldn't become complacent when reading about relatively small numbers of confirmed cases, and we must take care when comparing regional rates.
Confirmed cases have also been reported in Austria (1), Canada (13), Germany (3), Israel (2), New Zealand (3), Spain (4) and the United Kingdom (5). Deaths have only been reported in Mexico and the US, with the single (to date) US death being a child that was visiting from Mexico.
We've been talking a lot about the swine flu outbreak the last few days, but so far all we've really talked about are the human aspects. The reason we're blogging about it on this site is that it's a zoonotic disease - so where do the pigs fit in?
There's a distinct lack of information about where this strain of the influenza virus actually came from. I heard on the news this morning that one person who was interviewed by a CNN reporter was even trying to blame Canada for the outbreak, claiming that it was Canadian tourists that introduced the disease to Mexico in the first place! While I'm sure there will eventually be a great deal of investigation into how the outbreak got started (for the moment I think everyone's more worried about trying to just keep it under control), it's quite possible that we'll never find the "index case" or know exactly from where it came. But one thing's for sure: somewhere along the way, there has to be some pigs involved.
Pigs are the great "mixing pot" of influenza viruses, particularly with regard to avian, human and swine versions of the pathogen. Pigs can be infected by strains of all these different types, and coinfections (infection with more than one influenza virus at the same time) provide the viruses with a prime opportunity to trade RNA and recombine to form new influenza strains with new properties - more infectious, more virulent, or perhaps better able to infect another species, for example. In this case we appear to have a swine influenza virus that is not only capable of being spread to people (as occasionally happens with "regular" swine influenza viruses), but also between people, and hence the developing human outbreak.
But what about the pigs? There isn't a lot of information out there at the moment, with all the focus on the human aspect, but so far Mexican authorities have found no infected pigs in Mexico (at least no where they've looked - so far). Influenza in pigs is really nothing new, and other swine influenza strains are commonly found in pigs around the world. Highly pathogenic strains, like those that cause massive devastation of poultry flocks, don't occur in swine. If an influenza virus gets into a pig barn, however, it's like putting a person with the flu in a crowded room - the virus spreads very quickly through the air over short distances and soon everyone (or every pig) has the flu. Thankfully the virus generally also moves on quite quickly, and after a few days the animals generally start to recover. While such an outbreak certainly affects their growth efficiency, very few (if any) pigs die.
Yesterday the Canadian Veterinary Medical Association (CVMA) distributed a fact sheet on swine flu from the Canadian Food Inspection Agency (CFIA) for all Canadian veterinarians and swine producers. The CFIA is encouraging increased vigilance with regard to monitoring and diagnosing disease in Canadian pigs, to prevent the disease from spreading through the swine population. In addition to emphasizing vaccination, good hygiene practices and biosecurity, particularly around sick pigs, they also point out that it's equally important (especially now) for anyone who may have the flu to avoid contact with pigs (be they Canadian pigs or pigs in any other country), in order to avoid spreading the virus to them. Hopefully people in other countries will take the same precautions.
Another very important point is that swine influenza is NOT a food safety concern. The virus does not survive well in the environment for very long, and therefore cannot survive on pork products, and certainly cannot survive proper cooking (which is always very important for any kind of meat). The fact that some countries are banning pork imports is really not going to do anything to help control the outbreak - the concern should only be about live pigs (and people). So you can still have pork sausages at your next spring barbeque, just ask anyone who's feeling "under the weather" (or a little flu-ish) to please stay home!!
GoogleMaps has an interactive swine flu map that is quite interesting. The map indicates where cases of the disease have been diagnosed or are suspected, and it's updated frequently. Clicking on a marker gives you more information about what is happening in that particular location. Many of the pink "suspected" markers will probably turn out to be negative, but I fear the map's going to get a lot more crowded over the next couple of days. The picture below is a captured image of the map, but click here for the live interactive version.
A few years ago, I wrote a commentary in the journal Emerging Infectious Diseases about pets and household quarantine. It was written after SARS (severe acute respiratory syndrome) had caused tremendous problems in many areas, including Toronto. The point I was trying get across was that while there was a strict household quarantine implemented for exposed people, there was no consideration of pets. We now know that cats can become infected with the SARS coronavirus, and can transmit it to other cats. However, when people were quarantined, there were no recommendations for pets - pets could interact with quarantined people, then visit non-quarantined family members, or interact with other animals or people outside. From my standpoint, this was a significant concern. If cats had become infected with SARS, they could have been a source of transmission in households and potentially beyond. If SARS had infected the feral cat population in Toronto, it might have been very difficult to eliminate. I encouraged groups to ensure that pets are included in household quarantine guidelines.
The topic is front and centre again with swine flu. We don't know whether dogs and cats can be infected with this particular swine flu virus, but we DO know that cats can become infected with H5N1 avian flu and shed the virus. In my mind, that means that we should consider pets susceptible until proven otherwise.
So what should we do if people are being quarantined?
- If you are quarantining the family, quarantine the WHOLE family, including pets.
- Quarantined cats must be kept in the house. Quarantined dogs must be kept in the house as much as possible. They should only be taken outside to urinate/defecate, and this should be in a "remote" area where they can't have contact with other people or animals. They should always be under physical control (e.g. on a leash) when outside.
- If a quarantined pet gets sick, a veterinarian should be called first. That way, it can be determined if the pet needs to be examined, and if so, the clinic can know when it's coming and have protocols set up to handle it with infection control precautions.
The European Union's Health Commissioner has recommended that Europeans avoid all non-essential travel to the US and Mexico (Canada's apparently under the radar so far) as a measure to contain the spread of the emerging swine influenza virus. This has been met with some disdain by US officials, who emphasize the small number of cases (so far) in the US, and the much, much larger numbers of people that die in various countries every year from classical human influenza.
It's hard to say what type of restrictions are appropriate at this point in the outbreak. In general, it's better to be prudent and excessive (within limits) when dealing with a developing problem. The lack of information about the true scope of the problem, and the delays from transmission to definitive diagnosis of new cases, complicate assessments about whether the problem is truly contained, or containable.
Swine flu was most recently confirmed in Spain, and it has probably reached many different countries. It is also suspected in a group of students in New Zealand that recently visited Mexico. Considering the massive volume of travel between North America and much of the world, and the wide geographic range of cases in North America, it's hard to envision keeping this localized.
The fact that this outbreak is going to be difficult to contain, however, should not be taken as an excuse to not try to contain it. Even if this virus spreads to many different countries, good infection control and surveillance measures can help limit the impact of the disease.
Photo: Chichen Itza, one of the major tourist attractions on the Yucutan Peninsula in Mexico (credit M. Anderson)
Not surprisingly, swine influenza has been confirmed in Canada: 4 cases in Nova Scotia and 2 cases in British Columbia. More cases are certain to follow. As in the cases reported from the US so far, all Canadian cases have been mild.
The 4 cases from Nova Scotia were from the same high school. One of the affected students had been on a school trip to the Yucatan Peninsula in Mexico recently. Presumably, he or she picked up swine flu in Mexico and other students were infected by that student or others that went on the field trip. This is similar to a cluster of cases from a high school in New York. Eight students from that school were diagnosed with swine flu while more than 100 students had flu-like disease (it's unclear how many of these were tested). The two cases from BC were both in people who recently returned from Mexico themselves.
I imagine that we're going to see almost hourly reports over the next few days describing swine flu cases in people in various regions. Lets hope the pattern of mild disease that has characterized the Canadian and US cases persists.
In response to increasing numbers of confirmed or suspected cases of swine flu in the US, plus a still relatively unknown number of cases and at least 81 deaths in Mexico, the US government has declared a public health emergency.
This H1N1 swine influenza virus has many of the hallmarks of a virus with pandemic potential. It is of animal origin but has a unique combination of gene sequences that has not been found previously in swine or human influenza strains. People don't have pre-existing antibodies because they have not been exposed to it before, which leads to the chance for widespread disease. A big concern is that it seems to spread at least somewhat efficiently between people (unlike the H5N1 avian flu virus which is not efficiently transmitted between people). Fortunately, while it can cause death, this swine flu virus does not seem to be as deadly as avian flu, which kills approximately 50% of the people it infects. Therefore, while swine flu appears to be much more transmissible, it's probably not as fatal. (However, the large number of reported deaths in Mexico and early stage of the outbreak at this point means we need to be cautious making such statements).
It is clear that this swine flu strain is spreading in the US. It's been found in multiple US states and it is probably going to be found throughout the country. Mild cases have already been confirmed in Canada, and there are suspected cases in other countries. The number of cases in different regions and the amount of international travel makes containment of a reasonably-transmissible virus very difficult.
Some tips to reduce the risk of catching (or spreading) swine flu:
- Wash your hands regularly, particularly after contact with other people or common-contact sites (e.g. public door handles, public transit).
- If you are sick, STAY AT HOME. The era of "sucking it up" and going to work when you are sick should be over. All you're doing is putting others at risk.
More information about swine influenza can be found on the CDC's swine influenza website.
Image from http://www.nydailynews.com
Recently, I made a few comments about climate change and the potential impact on infectious diseases in horses on our sister site, equIDblog. A recent news article in New Scientist discussed concerns about climate change and pets. The main infectious disease concern regarding climate change is changes in patterns and spread of insect-borne diseases, because different insect vectors may expand their normal ranges or change their seasonality in response to climate change. Some of the examples cited in the article include:
- Babesiosis, a blood-borne disease spread by the European dog tick, is being found in areas of Europe where it was previously rare.
- Increasing populations and ranges of ticks have been reported in many countries, which is a significant concern based on the number of different diseases these ticks can carry and transmit.
- Leishmaniasis has been identified in dogs in the southern UK. If climate change allows sandflies (the insect vector of this disease) to become established in the UK, then spread of this disease could become a major problem.
- Milder winters may result in longer periods of activity of some insects that transmit disease, thereby extending the times of the year when there is a risk of disease. In some areas, year-round risk could develop for diseases that were previously seasonal.
Climate change is a complex and still rather controversial topic. Predicting the infectious diseases implications of climate change is difficult. Information that is already available for some diseases, combined with general knowledge about microorganisms and their hosts, can help us make some educated guesses about what may happen. While the full scope of the impact cannot be predicted, it is almost certan that climate change will result in infectious disease challenges in both veterinary and human medicine.
Plague has been diagnosed in a dead rabbit found on a private residence in New Mexico. Plague, also known as the black death, is a highly fatal disease of humans and many animals caused by the bacterium Yersina pestis. While often considered a disease of mainly historical interest - having killed a large percentage of people on the planet during a few pandemics over the centuries - plague is actually still alive and well in some regions. In North America, most cases occur in New Mexico, Arizona, Colorado and California.
Yersinia pestis primarily lives in wild rodents and is transmitted by fleas. Many different animal species, including cats, dogs, rabbits and people, can be infected if bitten by a flea from an infected rodent (hence the historical association of the disease with rats). Predatory species (like dogs and cats) can also become infected by eating infected animals. Dogs are relatively resistant to plague and usually only develop mild disease, while cats and rabbits are as susceptible as people, and can develop bubonic, septicemic or pneumonic plague. Transmission of plague from pets to people can occur, and most often involves cats. People can become infected by close contact with sick pets, or being bitten by a flea from such a pet.
Preventing plague in animals involves flea control and reducing exposure to infected wildlife. In areas where plague is active, all pets should be on a flea control program. Cats should be kept indoors to reduce the risk of exposure (e.g. keeps them from hunting infected rodents). Dogs and cats should not be allowed to have contact with dead animals of any kind. Measures to reduce rodent infestations in and around the house are also important.
More information on plague is available in the Worms & Germs archives.
A recent edition of the Veterinary Record contains a case report of Weil's disease in a person that adopted a feral (wild) rat (Strugnell et al, 2009). Weil's disease is a severe disease of the kidneys, liver and other body systems that can develop after acute leptospirosis (infection by Leptospira bacteria). This group of bacteria can infect a wide range of animals and is typically shed in the urine. The person that was affected adopted the rat after it was caught by her neighbour's cat. The paper says that the rat was "urinary incontinent" - not something we usually notice about rats since they are not typically litter or house trained. I presume this means the rat was urinating frequently when out of its cage, including when it was being handled. Because of this, the owner reported that she "aimed" to wash her hands after every time she touched the rat.
A couple of weeks after adopting the rat, the woman was admitted to hospital because of lethargy, muscle aches, mild abdominal pain, cough and a bloody nose. Blood tests showed that she had decreased levels of white and red blood cells, as well as liver and kidney disease. After further testing she was diagnosed with leptospirosis. She had to be treated in the ICU, but eventually made a complete recovery. The adopted rat and the other rat that she owned were euthanized by the owner's partner shortly after she was admitted to hospital. Testing of the adopted rat identified Leptospira in the kidneys.
This is another example of why wild animals should be left in the wild, and another case highlighting the need for veterinarians, physicians and public health personnel to work together.
People that work with animals are at increased risk for certain infectious diseases. That's pretty clear. Pet shop employees fit into this group as well, and they may be at particular risk for specific diseases because of their close contact with young animals, birds, rodents and reptiles. A suspected case of psittacosis in a Toronto pet shop worker is an example of this.
A bird in the pet store where this person worked supposedly died of avian chlamydiosis in mid-March (although the initial test results have been called into question). Avian chlamydiosis is caused by the bacterium Chlamydophila psittaci. This organism is relatively common in psttacine birds (parrot family), especially in breeding colonies, but can also be found in other types of birds. It can cause serious disease in birds, but it is also commonly carried by healthy birds. People can become infected from breathing in the bacterium, often from aersolized dust containing dried bird droppings. The disease in people is called psittacosis. The pet store worker developed signs that could be consistent with psittacosis: cough, lethargy and difficulty breathing. However, these signs are still fairly non-specific and could also be caused by numerous other respiratory pathogens. Test results are still pending.
People that have close contact with pet birds, especially psittacines, need to know that they may be at increased risk of psittacosis. They also need to ensure that their physicians know about their increased risk. This is important because early signs of psittacosis are very vague, such as fever and cough. Psittacosis would presumably not be high on the doctor's list of possible diagnoses for the average person coming in with fever and a cough. If the doctor knows a person has contact with birds, hopefully psittacosis would be considered earlier so prompt diagnosis and appropriate treatment can be given. This disease is readily treatable if diagnosed early, so awareness of the possibility on the part of the patient and physician are important.
This report also demonstrates why determining a final diagnosis for sick or dead pets is critical. While the diagnosis may not help the animal (especially if it's already dead), it may play an important role in protecting the health of people or other animals. If the bird in this case was not tested, it's hard to say how long it would have taken for psittacoiss to be considered in the case of the pet store worker.
More information about psittacosis can be found in a document from the National Association of State Public Health Veterinarians. More information about good management practices to reduce the risk of disease transmission from birds can be found in the information sheets on pet birds on the Worms & Germs Resources page.
Helicobacter species are a fascinating group of bacteria. They live in the stomach of humans and many animals, an environment that was previously thought to be completely inhospitable to bacteria. We now know that Helicobacter bacteria are beautifully adapted for survival in the stomach and are very common. In people, Helicobacter pylori is an important cause of gastritis (inflammation of the stomach), stomach ulcers and stomach cancer.
Studies looking at bacteria in the stomachs of dogs and cats have found that Helicobacter species are extremely common, with some studies finding one or more species of Helicobacter in every dog or cat that was tested. Since Helicobacter is an important problem in people, does that mean that we need to be worried about pets as a source of infection? Probably not. Here's why:
It could be a problem because:
- A few studies have found the same Helicobacter species in infected people and their pets.
It's probably not a problem because:
- Studies looking at risk factors for Helicobacter infection in people have not identified pet ownership as a risk factor.
- A study comparing one Helicobacter species that has been mentioned as a possible zoonotic concern, H. heilmannii, reported that H. heilmannii strains from people were generally different than those from animals.
- While other Helicobacter species are common in dogs and cats, H. pylori (the main cause of problems in people) is rare in pets.
- While finding the same Helicobacter species in a person and his or her pet raises concern, studies have yet to demonstrate whether such findings are due to animal-to-human transmission, human-to-animal transmission, or infection of both person and pet from the same source.
Overall, the risks of pet-associated Helicobacter infection are probably very, very low. If there is any involvement of pets in this disease in people, it's probably sporadic at most. Avoiding contact with stool from pets and paying good attention to handwashing should decrease the risk even further.
One question that is currently unanswered is whether the mouth of a dog or cat can be a source of Helicobacter infection, because the bacterium can be found in saliva. We really don't know whether this is a risk - it's probably minimal at most, but avoiding contact with pet saliva (e.g. no sloppy wet dog kisses!) is a good idea anyway.
A study published recently in the Journal of Hospital Infection (Lefebvre & Weese, 2009) looked at contamination of the haircoat of animals used in hospital visitation programs. In the study, Dr. Lefebvre petted animals that were going into a hospital and we cultured her hands. Then when the dogs finished their visits she petting them again and we re-cultured her hands. We tested for MRSA and Clostridium difficile, two important causes of hospital-associated infections. The goal was to see if the dogs' coats could become contaminated, presumably by patients' hands, during regular visits. The dogs' paws were also tested before and after to see what they picked up walking around the hospital.
After being in the hospital, one dog (4%) was found to have C. difficile on its feet. The strain that was recovered (ribottype 027/NAP1) is a strain of great concern, being it has caused outbreaks of illness internationally. The fact that there was C. difficile on the dog's paws, which was presumably picked up from the floor in the hospital, isn't exactly surprising. It shows that contact with dogs' feet (e.g. shaking a paw) could be a source of exposure to people in hospitals, and at home, and that dogs could be exposed to C. difficile after hospital visits by licking their paws. We previously demonstrated in another study that visitation dogs are at high risk for picking up C. difficile during visits.
The more important aspect of the study was what ended up on Dr. Lefebvre's hands after petting the dogs - a very common type of contact with dogs in hospitals and at home. She picked up MRSA from the coat of one dog (4% of dogs overall) after it had been in the hospital. The dog was not an MRSA carrier, and it did not have contact with anyone known to be carrying MRSA during its visit. Presumably, there was someone in the hospital that was an unknown carrier. If MRSA was on the person's hands, they could have transfered the MRSA to the dog's coat. The important part is that this MRSA was then able to spread to someone else's hands (Dr. Lefebvre's, in this case). This is a potential route of transmission of MRSA to patients during hospital visitations, and to other people these dogs might encounter outside of hospitals. The same thing could presumably happen with other infectious agents, including bugs like norovirus and influenza. These can't infect dogs, but dogs could potentially be short-term vectors of these viruses and spread them around a hospital.
The good thing about all this is that some basic guidelines can greatly reduce the risk of transmission:
- Patients should wash their hands or use an alcohol-based hand sanitizer before (to reduce the risk of depositing something on the pet's coat) and after (to reduce the risk of picking something up from the pet's coat) touching a pet.
- Pets should be kept off beds unless a disposal/washable barrier (e.g. drape, towel) is kept between the pet and the bed sheets, to prevent dirty feet from infecting the patient's living space/clothes/sheets.
- People should not "shake-a-paw" with pets in hospitals.
All these precautions can be taken without compromising the benefits of hospital pet visitations. More details about guidelines for hospital visitation aniamls can be found in an earlier post. More information about Clostridium difficile and MRSA can be found on the Worms & Germs Resources page.
Escherichia coli (E. coli) O157 is a particularly important bacterium that can cause very serious disease in people, including diarrhea and a severe kidney disorder called hemolytic uremic syndrome (HUS). Infection in people typically results from ingesting the bacterium from contaminated food products. The main reservoir of E. coli O157 is in the intestinal tract of cattle. There have been a few reports of suspected transmission of E. coli O157 from pets, but overall pets are thought to play a very minor role in the spread of this disease.
However, minor role does not mean no role. A recent report in the journal Veterinary Record described suspected transmission of E. coli O157 from dogs to people. Three children and two adults in a household developed diarrhea, and E. coli O157 was isolated from their stool, as well as from the stool of a healthy sibling in the house. Molecular testing showed that all the people were infected with the same strain of E. coli. An "outbreak response" was initiated by the UK's Health Protection Agency to determine the source of infection. One of the affected children, the first to get sick, visited a farm five days before developing diarrhea, so the investigation focused on that farm.
The same E. coli strain was found in 7/29 samples collected from the farm: three samples from calves, two from dogs, one from a manure pile and one from a calf pen gate. Finding E. coli in samples from the calves was not surprising, as it is commonly found in healthy cattle. However, the visiting child did not have direct contact with the calves. Finding the bacterium in the dogs was somewhat surprising. Since the child had contact with both dogs, this was thought to be the most likely source of infection. Cattle were probably the source that infected the dogs, the dogs were then probably able to transmit the infection to the child, and the child then infected other people in the house. Infection from contact with E. coli in the environment is also possible, but considering there was confirmed contact with dogs who were carrying the same strain, the conclusion that the dogs were likely the source is reasonable.
Like many of the other bacteria we worry about, E. coli is transmitted by the fecal-oral route - infection is spread by swallowing feces/stool/manure (even in minute quantities) that contains E. coli. This can occur more easily than people think, as low-level fecal contamination of hands and other surfaces is common. Identifying animals that carry this bacterium is not practical. The most important protective measure is close attention to handwashing after contact with animals, especially farm animals or pets exposed to farm animals.
This study provides more information about dogs as potential sources of E. coli O157 and the need to include testing of pets during outbreak investigations. However, dogs are probably still a minor source of this important pathogen, and it's most likely only of concern in dogs with close contact with cattle.
The following is a post by guest-blogger, Dr. David Waltner-Toews.
For North American veterinarians, the term “companion animals” covers a wide territory, from dogs, cats, and caged birds, to a variety of rodent and porcine escapees from barnyards and burrows. But when does a companion become something else? In my work with Veterinarians without Borders/ Vétérinaires sans Frontières – Canada, I find that I sometimes have to change my ideas of what companion animals are.
We have all heard about bird flu, and the fear that it might become a global pandemic. We know that wild water birds are the main reservoir for all the different kinds of influenza viruses that emerge every year from Southeast Asia and circle the world. The viruses are unstable, and historically haven’t caused many problems in birds. The disease in people can be serious, especially in older people, but large scale vaccination programs have helped. The big concern is that a new variation of the virus has evolved and has spilled from water birds into domestic poultry. A virus that not only kills birds, but also kills a high percentage of people – and other animals such as cats. Fortunately, it is difficult to contract – you pretty much have to be the one killing and cleaning the bird.
To some people, the way to stop a global pandemic is easy. If you suspect bird flu on a premise, kill all the birds and disinfect the area. Easy, isn’t it? They are, after all, “just chickens”. Or are they?
When my wife and I recently visited a part of the island of Java, Indonesia, where this new virus is thought to be endemic, that is, a lot of birds are carrying it, I already knew it was more complicated than just killing chickens. Often, poor people will “salvage” sick, dying or even already-dead birds by cooking them up and eating them before the authorities discover them. If you are hungry, it seems such a waste not to. As a result of such situations, about 120 people in Indonesia have died of bird flu since 2003.
But, we discovered, poverty is not the only “complication”. We held a town hall meeting in one village, in the middle of this endemic area, to explore how they were coping with the disease. They told us that they didn’t have any bird flu. Certainly, sometimes, they had some sick birds, which they threw into the river, but no bird flu. They attributed their disease-free status to the fact that they fed their birds a warm porridge made from snails and papaya leaves.
After our town hall meeting, we trundled through the rain to one of the nearby chicken-owners. When we entered the well-kept concrete-walled yard, a young boy proudly showed us his pet pigeon. His father, however, did him one better. It turns out that this family raised singing roosters, so-called Ayam Pelung, beautiful birds, about a metre high. I knew that wild jungle fowl had first been domesticated in Southeast Asia tens of thousands of years ago as fighting birds, now referred to in Indonesia as Ayam Bangkok.
I had heard about the singing birds, and had seen them in their cages at a competition at the veterinary college in Yogyakarta when I worked there in the mid 1980s, but this was my first close-up view. The men who owned them proudly crouched next to them for pictures. Periodically, one of the roosters would stand still and give a long, drawn out, low, throaty call, an avian version of some sultry lounge singer. These birds, if they win competitions throughout the country and region, apparently bring in up to 500 to 1000 U.S. dollars each. In a country where the average annual income is between $3000 and $4000, a few birds can represent a huge investment. Are these birds companion animals? Are they friends, workers, threats… or just chickens?
When is a dog or a cat or a bird more than a companion? When they sing? Race? Fight? When they are worth lots of money? In Thailand, where fighting cocks are common, and are valuable, the authorities have issued “vaccination passports”, with pictures of the roosters, indicating vaccination with a reputable influenza vaccine. When, in trying to control a disease, do we cross the line from “culling” economically important “units” to killing companions? When do we hand out passports?
If you had an amazing purebred dog worth tens of thousands of dollars, and the public health authorities threatened to kill it if it was found to be harbouring some virus which might or might not make you sick, what would you do? What if that dog was not only your companion, but your retirement investment?
Suddenly controlling a bird flu pandemic is a lot more complicated than killing “just chickens”. Welcome to the real world.
David Waltner-Toews is the founding President of Veterinarians without Borders/ Vétérinaires sans Frontières – Canada (www.vwb-vsf.ca) and a Professor in the Department of Population Medicine at the Ontario Veterinary College.
The latest edition of the Centers for Disease Control and Prevention (CDC)'s publication Morbidity and Mortality Weekly Reports consists of the revised Guidelines for Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents.
Among the highlights relevant to pets:
- HIV-infected patients should be advised to wash their hands after handling pets or other animals.
- They should avoid direct contact with diarrhea or any stool from pets, particularly stray pets or dogs and cats less then six months of age.
- Gloves should be worn when handling stool or cleaning areas that might have been contaminated with stool from pets.
- Contact with calves or lambs (e.g. on farms or at petting zoos) should be limited or avoided. Attention should be paid to hygiene and avoiding direct contact with animal manure when visiting such premises.
- Contact with reptiles, chicks and ducklings should be avoided because of the risk of Salmonella.
So, nothing earth-shattering or nothing we and others have not been saying all along. That's because basic measures, while not flashy, are the most useful tools. Use common sense, avoid contact with stool and high risk animals, and above all wash your hands.
The spleen is an important part of the immune system. It is especially important for fighting off certain types of infections. People who have had their spleen removed or whose spleen is not working properly are therefore at greater risk of some infectious diseases. The risk of infection is highest in the first few years after the spleen is removed or stops functioning, but the risk remains increased for life. In general, people who are immunocompromised (i.e. have a weakened immune system (including lack of a working spleen)) can get sick from microorganisms that would not usually cause illness in other people, and bugs that would only make most people mildly ill can cause severe infections in immunocompromised individuals. This is a particular problem in children. Kids that have their spleen removed are often treated with antibiotics for a few years to help prevent infections.
Infection with Streptococcus pneumoniae and Haemophilus influenzae, which are both common pathogens of humans, are two of the major concerns in people without a functioning spleen. The most commonly discussed zoonotic disease threats in these individuals are the bacterium Capnocytophaga canimorsus and Salmonella. Capnocytophaga lives in the mouth of a large percentage of healthy dogs. Infection in immunocompromised people typically occurs as the result of a bite, but is very rare in other people. There is no indication to test dogs for Capnycytophaga, because it is difficult to identify and we do not know how confident we can be about a negative result (e.g. it may be in the dog's mouth even though it doesn't grow from a sample in the lab).
Here's some general advice for individuals who don't have a working spleen:
- Talk to your physician or an infectious disease specialist about the risks associated with animal contact (including pets).
- In general, you do not need to give up your pets. The risk of infection may be increased, but the risks can be minimized in most situations, and the risks are often outweighed by the beneficial aspects of pet ownership.
- Be wary of any possible exposure to an infectious disease, and be diligent about infection control precautions. If you are bitten by an animal (of any kind), see a doctor as soon as possible.
- Make sure your pets do not touch any open wounds you may have. In particular, do not let a dog lick skin that is damaged in any way. Since Capnycytophaga is commonly carried in the mouths of healthy dogs, licking in general should be discouraged.
- Don't feed your pet raw meat or raw treats, because this increases the risk exposure to Salmonella from your pet's stool.
- Be very careful when handling stool to avoid contaminating yourself or other objects/surfaces. If you have a cat, ideally its litterbox(es) should be changed by someone else.
- Always wash your hands well (and frequently) after contact with pets and pet foods, including dry commercial pet food (kibble).
A reader asked this question the other day:
"I was walking with my dog, when it got hold of a used condom. Is it possible that my dog got HIV or AIDS or something?"
The short answer is NO. Dogs cannot be infected by HIV, nor can dogs transmit the virus (although there is a theoretical concern that a dog could transmit HIV from one person to another if it bit someone with HIV, got blood from the person in its mouth, and then immediately bit someone else). The virus that causes HIV/AIDS does not survive long outside the human body and would quickly die in a dog's mouth. So HIV infection in a dog from chewing on or swallowing a used condom is not a concern.
Dogs are not susceptible to the other important sexually transmitted diseases in people either. The biggest potential problem in this situation (and a slim on at best) is if the dog swallowed the condom, it could cause a blockage in the dog's intestine. Most likely, though, the dog would pass the condom in its stool and nothing untoward would happen.
(The "ick" factor with dogs eating things like this furthers my objections to being licked in the face by any dog, however!)
Methicillin-resistant Staphylococcus pseudintermedius (MRSP, sometimes misidentified as methicillin-resistant S. intermedius (MRSI)) is an increasing problem in dogs and cats. This highly drug-resistant bacterium is a particularly problem in skin and ear infections, and the number of infected animals appears to be increasing significantly. A related bug, methicillin-resistant S. aureus (MRSA) has been a major problem in people for decades, and MRSA is now being found with increasing frequency in animals as well. Sometimes people get confused when they are dealing with methicillin-resistant staph, and it's important to realize some of the differences between these two related bugs:
- MRSA is a huge problem in people and can be transmitted between animals and people. The role of animals in human disease is unclear, but there is concern that people can develop infections due to contact with infected or colonized animals.
- MRSP is rarely identified as a cause of infection in people. Transmission of MRSP between animals and people has been reported. However, this is much less concerning than with MRSA because people are much less likely to carry, transmit or develop infection from MRSP than MRSA.
- The recommendations that have been made for management of animals with MRSA largely involve improving general household infection control practices. These guidelines are only based on expert opinion (i.e. there are no studies (yet) to back them up), but they are reasonable and practical.
- Even less information is available regarding MRSP, mostly because it's not considered a major human health issue. That being said, you don't want to get a multidrug-resistant bacterial infection, even if it's uncommon. Therefore measures to reduce the risk of transmission of MRSP from pets to people is should still be considered.
- Strict isolation of infected pets is probably excessive. General infection control practices (e.g. handwashing after contact with the animal, avoiding contact with the infected site, limiting contact overall) are probably adequate, especially in households with no high-risk people (e.g. people with weakened immune systems, infants, elderly individuals).
More information on both MRSP and MRSA can be found on the Worms&Germs Resources page.
Cowpox is a disease caused by cowpox virus. This virus is most famous for being used by Edward Jenner to vaccinate people against smallpox (which is caused by a related virus). However, despite the name, rodents are the natural host of cowpox virus, not cows. Most human cases of cowpox are associated with contact with rodents. Cats are another important source of human cowpox infection in some areas.
Cowpox infections in people are uncommon. Most cases occur in Europe, western parts of the former Soviet Union and parts of Northern and Central Asia. Outbreaks of cowpox can be associated with infection of pet rats at central breeding or large housing facilities, which results in large numbers of infected rats that are then shipped to many different places. Recently, outbreaks of rodent-associated cowpox have been reported in Germany and France. It is suspected that these infections are associated with a large rat breeder in the Czech Republic, however this has not been confirmed.
Cowpox causes typical "pox" lesions, like those that are seen with chickenpox. Only a single lesion is present in most cases, but multiple lesions can develop. Flu-like symptoms such as fever and fatigue, as well as enlarged lymph nodes, are also common. Severe, even fatal, disease can occur in individuals with a weakened immune system, but in most people cowpox infection causes only mild illness and resolves without treatment.
Cowpox is not a concern in many areas of the world. In regions where it is present, basic, common-sense precautions can reduce the risk of infection.
- Contact with infected animals should be avoided. Cats are an important source, and cowpox should be considered in any cat with appropriate skin lesions in an endemic area. The same should apply to rats with skin lesions.
- Gloves should be worn when handling cats and rats with skin disease, and hands should be washed immediately after glove removal.
- If skin lesions are identified on a rat, particularly over the feet, ears or tail, the animal should be examined promptly by a veterinarian.
- Don't buy any rat with skin lesions, and if possible, avoid buying rats that were bred and/or housed in facilities with a very large number of other rats.
In contrast to dogs, urinary tract infections (UTIs) are uncommon in cats, although urinary tract disease is very common. The vast, vast majority of cats with signs of feline lower urinary tract disease (FLUTD) (e.g. straining to urinate, frequent urination, bloody urine) do not have an infection. However, many cats with urinary tract disease are treated - unnecessarily - with antibiotics. That's a problem, for several reasons:
- Antibiotics are not effective if there is no infection, and treating with antibiotics delays addressing the animal's real problem.
- Use of antibiotics in these cases unnecessarily increases the risk of antibiotic resistance emerging. Even if there is no infection in the bladder, resistant bacteria may emerge elsewhere in the body. Antibiotics don't just go where we think the infection might be - they also go to areas where there are always bacteria, like the intestinal tract, and resistance can emerge there.
- Adverse reactions to antibiotics can occur. Vomiting and diarrhea are most common.
- Proper diagnostic testing should be performed in every cat with urinary tract disease. This includes evaluation of a urine sample under a microscope to look for signs of infection (such as white blood cells) and a urine culture.
Urinary tract infections (UTIs) are a common problem in dogs, especially female dogs. UTIs are also a common reason for antibiotic use in dogs. Unfortunately the use of antibiotics for canine UTIs is commonly inappropriate, in one way or another - in some cases the drug selected is inappropriate, while in others the length of treatment may be the problem. These mishaps may occur for many reasons, including failure to perform urine cultures, stopping treatment too early because the animal looks better, or not being prescribed an appropriate duration of treatment.
Urine culture is very important. Culture can confirm that an infection is present and help guide antibiotic therapy so the infection gets treated as effectively as possible. Urine culture should be done on every animal with a UTI, not just those that have not responded to initial treatment. If a culture is taken when the animal first develops the infection, there is probably less chance that the infection will recur. If it does recur, another culture can determine whether the same bug is involved - sometimes animals will have repeated infections with different bacteria, indicating that there may be an underlying condition making them extra susceptible to infection (e.g. diabetes, Cushings syndrome). Repeated infections with the same bacterium suggests that the infection was never completely eliminated, and that a longer course of treatment might be needed, or that there might be something reducing the effectiveness of the treatment, such as a bladder stone.
A major problem with treatment of UTIs is stopping treatment too early because "the dog looks better." In animals with a UTI, the signs of disease (e.g. frequent urination, straining, bloody urine) may resolve before the infection is completely eliminated. Stopping treatment too soon can allow the infection to come back. That means the animal will be sick longer, and it will be more expensive (another visit to the veterinarian, more antibiotics, and (more) urine culture(s)).
We don't really know how long to treat UTIs in dogs. Dogs are often initially treated for 7-14 days for a UTI. Standard recommendations for treating UTIs in people used to be 7-10 days, but nowdays only short courses are used (and appear to be effective). It's unclear whether we should change the way we treat dog UTIs in a similar manner. In an otherwise healthy dogs with a first-time UTI, shorter treatment is probably reasonable. Too short of a treatment period can cause its own problems, however, as discussed above.
Early diagnosis and treatment are important. The longer the infection festers, the greater the chance of a deeper infection in the bladder (which may be harder to eliminate) and the greater the chance of complications such as bladder stones. Not to mention it's no fun for anyone (dog or owner) to have a bladder infection, so don't let it get any worse!
Some dogs have recurrent UTIs because of issues such as bladder stones and neurological dysfunction. Typically, all the antibiotics in the world won't fix these problems. If there is an underlying cause, that needs to be addressed first. There's no use continuing to use antibiotics when treatment will be ineffective and antibiotic resistance will possible emerge.
Rats can be really interesting pets. They can be quite social and are interesting to watch. Being larger than hamsters and gerbils, they can also be more easily and safely handled. They can still bite, however, particularly if they are not properly socialized and/or they are handled by people who don't know how to do it properly. Even though rats have tiny teeth, bites can still cause problems. One concern is rat bite fever. This disease is actually caused by two completely separate bacteria. Streptobacillus moniliformis is the most common cause in North America and Europe, while Spirillum minus is the main cause in Asia.
I'll focus on Streptobacillus moniliformis today. This bacterium is very commonly found in the mouths of healthy rats. Up to 100% of rats can be carriers. It doesn't cause disease in the rats, but it can be transmitted to people by bites or scratches. It can also be spread simply by handling rats (especially if a person has any cuts or broken skin), and through close contact with rats' mouth, such as kissing and sharing food (yes, some people do).
In most people, rat bite fever causes a high fever, headache, chills, vomiting, joint and muscle pain and a rash, most commonly over the soles of the feet, palms of the hands and the extremities. While the disease will resolve on its own in many cases, treatment with antibiotics is indicated because severe complications such as inflammation of the heart, pneumonia and meningitis can also develop.
Common sense can help reduce the risk of rat bite fever.
- Assume all rats are carrying S. moniliformis in their mouths.
- Only handle rats if you know how to do so properly, and if you know the rat is amenable to being handled. Avoid contact with the rat's mouth (e.g. kissing).
- If you have open sores or cuts on your hands, avoid handling rats or wear gloves.
- Always wash your hands thoroughly after handling a rat or cleaning its cage.
- Thoroughly clean any bites from any rodent immediately with lots of soap and water.
- If you develop signs consistent with rat bite fever after being bitten, consult your physician as soon as possible, and be sure to let your physician know about the bite.
I used the think the New York Times was a reputable newspaper and source of reasonable information. However, considering some of the articles I've seen, I no longer have a good opinion of this newspaper. One example from a few years ago came across my desk recently. The article is basically an infomercial for an unqualified person that sells pet health products. The person in question is an industrial designer by training - you'd think a reasonable news source would look for someone with training in veterinary medicine, nutrition or pharmacology when discussing pet health. (Given the level of expertise they require, I guess I'm qualified to comment in the New York Times about how to solve conflict in the Middle East or fix the economy). Among some of the gems in this article are:
- People "have to include raw and whole foods in their pets' diets..." and "[Pets] don't get E. coli or Salmonella." Tell that to the dogs and cats that get sick and die from Salmonella. I can't believe people that sell raw foods continue to falsely claim that pets can't get Salmonella. Outbreaks of salmonellosis associated with raw foods have been reported. Dogs have even been sickened in the recent peanut butter Salmonella outbreak.
- The big problem with the pet food industry is that people treat pets like televisions and get a new one if they're sick. Apart from the last part being ludicrous, what does that have to do with the pet food industry?
- The alley dogs this guy grew up with in the Bronx lived a long time. Now, a dog is considered old if it lives past 7 years. Show me any evidence that feral dogs live longer than household pets. Not a chance.
- Pets are dying younger because of low grade nutrition and pharmaceuticals. Again, show me evidence that pets are living shorter lives. I'm certain it's the exact opposite.
People need to make sure that they critically assess things that they read about pet health and diseases. Just because something is written in a high profile newspaper doesn't mean it's necessarily correct. In the internet era, volume overload and differentiating good sources from bad sources can be difficult. Here are some tips:
- Look for advice from qualified individuals. That's not a guarantee, but I'd rather have my car fixed by a mechanic than a gardener.
- Beware of advice from people that are in a conflict of interest, such as people selling a product. For most reputable companies, representatives can be sources of good information, but unfortunately it's not always true.
- Ask your veterinarian about questions relating to animal health and nutrition.
- Use common sense. If something seems too good to be true, it probably isn't. Something that claims to cure all that ails you probably cures nothing.
Plague (aka the "black death") is a fascinating disease. It is one of the most important diseases in human history because it had a devastating impact of the human population during various outbreaks. Many people may not realize it, but plague is not just a historical problem - it is still alive and well in some areas of the world. Plague is caused by the bacterium Yersinia pestis, which tends to circulate in rodent populations and can be spread by fleas. In North America, plague is most common in some regions of the southwestern US, particularly New Mexico, Arizona and Colorado. We're heading into the high-risk season for plague in those areas: March to October.
Plague can infect domestic pets, and pets can be a source of human infection. Cats are quite susceptible to plague, whereas dogs are quite resistant. Cats can transmit plague to people. Pneumonic plague (infection of the lungs with Y. pestis, not to be confused with bubonic plague which is primarily infection of the lymph nodes with Y. pestis (see picture left)) in cats is of particular concern, because in this form the bacterium can be spread through the air over short distances.
A paper in Clinical Infectious Diseases a few years ago (Gage et al, 2000) described 23 cat-associated cases of plague in people, five of which were fatal. People were infected by face-to-face contact, bites, scratches or simply caring for an infected cat. Most affected people were cat owners, but some were veterinary clinic personnel. Plague is treatable with antibiotics, but the disease can progress rapidly, so it's important to determine the diagnosis and start treatment as soon as possible.
Here are some things to consider if you live in an area where plague exists:
- Keep pets indoors as much as possible to help prevent exposure to infected wildlife.
- Use routine flea control measures as directed by your veterinarian.
- Consider any cat that develops a fever of unknown origin or enlarged lymph nodes a plague suspect.
- Don't let cats and dogs hunt wild rodents, and don't let them have access to rodent burrows.
- If your pet has been diagnosed with plague, you need to seek medical attention promptly in case you have been exposed. If a person in the household is diagnosed with plague, pets should be investigated as possible sources and should be treated prophylactically in case they have been exposed.
Lower photo: Bubo in the leg of a person infected with bubonic plague (source: Centers for Disease Control and Prevention)
I received the following question from a reader the other day: "I'm currently pregnant and was bitten by my grandmother's German Shepherd. The bite was on my ankle and broke the skin in several places. I went to the doctor and was prescribed antibiotics and the wound has seemed to heal fine. This is my second pregnancy and I have been diagnosed as group B strep positive, which I wasn't with my first child. I know that dogs can't spread strep throat to humans, but is it possible that I picked up group B strep from the bite?"
The short answer is that it's extremely unlikely there's an association.
Group B Streptococcus is predominantly a problem in people. Most people that carry this bacterium have no problems, although it can cause infections in some situations. It is of particular concern in pregnant women, because in 1-2% of exposed newborn babies the bacterium can cause serious infections such as bloodstream infections, meningitis and pneumonia. That is why pregnant women are often screened for Group B Streptococcus shortly before their due date, by taking a swab from the vagina and rectum. Approximately 10-30% of pregnant women carry Group B Streptococcus. Pregnant women that are carriers are usually given antibiotics shortly before delivery to reduce the risk of infection of the baby.
What about the role of pets? Group B Streptococcus is mainly found in people, and is quite common in healthy people. It is rare in pets, although it can cause various types of infections in animals too. Group B Streptococcus infections in dogs might actually represent human-to-dog transmission, although this hasn't been proven. In the case described above, a dog bite on a person's leg would not be a high risk for transmitting this bacterium to the intestinal tract or vagina. If a dog was carrying this bacterium in its mouth, it could cause a bite wound infection, but it is very unlikely that the bacterium would spread to other parts of the body in a healthy person. Other bacteria in the dog's mouth would be more likely to infect such a wound, even if Group B Streptococcus was present. If dogs were common carriers of this bacterium (which they are not), the main risk of transmission would be from regular contact, not bites.
So don't blame the dog... at least not for the Group B Streptococcus. The bite itself is another issue.
I came across an interesting (and somewhat bizarre) paper in the journal The Lancet from 1988. It described a case of listeriosis in a baby. Listeriosis is caused by the bacterium Listeria monocytogenes. Human infections are usually acquired from eating contaminated food. I made some comments about the risk of listeriosis to household pets in an earlier post during the recent foodborne outbreak of listeriosis in Canada that was associated with contaminated meat
The paper from 1988 puts a "new spin" on potential sources of infection for pets.
The baby described in the report was not breastfed for the first three days of life because her mother had some post-delivery complications. The surplus milk that was collected over those three days was reportedly fed to a litter of Doberman puppies. All three puppies in the litter became sick the day after the child began showing signs of illness. Listeriosis was diagnosed in both the baby and the puppies. Listeria monocytogenes was cultured from the mother's milk. Apparently the baby and the puppies were all infected by drinking the mother's milk. The baby, and two of the three puppies, survived.
Certainly, human-associated listeriosis in pets is extremely rare, and (presumably) so is feeding puppies human milk. This case just shows how infectious diseases can do strange things, and that diseases can move between people and animals in both directions. It also highlights that knowing the health status of both animals and people is important for physicians and veterinarians to make informed decisions about diagnosis and treatment of some diseases.
I have a small flock of Soay sheep and lambing season started today (too early, but better than the -30C weather from a few days ago). For someone like me, lambing season inevitably triggers thoughts about Q fever, a zoonotic disease that is most commonly associated with contact with small ruminants like sheep and goats (especially sheep). The disease is caused by the bacterium Coxiella burnetii. This organism is highly infectious - very few bacteria are required to cause infection - and is considered a potential bioterrorism agent. Coxiella burnetii can be transmitted by direct contact with an infected animal, or by inhalation of organisms in dust or dirt that get blown into the air. It can be carried by healthy animals several species, but the greatest risk of transmission is from sheep and goats around the time of birthing (lambing and kidding, respectively). At that time, large numbers of C. burnetii can be shed with the placenta and fetal fluids, and can also be found on the newborn animals. Close contact with the animal and these tissues during lambing, such as with our first lambing this morning - a stillborn lamb that was stuck at the shoulders and required some manipulation to free it - can result in transmission of C. burnetii.
On a happier note, the second lambing in our flock was unassisted, although I still handled the little guy to make sure he was okay.
Q fever can affect people of any age or health status. Disease can range from mild to life-threatening. More information on Q fever can be found on the websites of the Ontario Ministry of Health and Long-Term Care and the Centers for Disease Control and Prevention (CDC), as well as the previous Worms & Germs post entitled "Q Fever - From Goats to People (and Pets!)". The disease can cause miscarriage in pregnant women. People with heart valve disease or vascular grafts are also at high risk for serious disease from this infection.
- It is prudent to consider all sheep and goats Q fever-positive unless proven otherwise (which is difficult to do).
- Contact with newborn lambs and kids, placentae and fetal fluids of sheep and goats, and any area contaminated by these tissues should be avoided as much as possible. If contact is necessary, it should be done by low-risk people, and careful attention should be paid to hygiene, especially handwashing.
- Pregnant sheep and goats should not be used in petting zoos. Unfortunately, this is actually a common occurence.
- Live birthing exhibits, where sheep or goats give birth in public during fairs or similar events, should not be held. If they are held, they should be in an area where there is no direct or indirect contact with the public, unlike this picture (right).
- While we focus on sheep and goats, many different species can shed Coxiella burnetii, including cattle and cats. It is reasonable to consider all animals a risk around the time of giving birth, and ensure that hygiene practices are optimal.
- At my place, Q fever control consists mainly of careful attention to hygiene around newborn lambs and their ewes, and not allowing my kids to handle newborn lambs.
- Like most zoonotic diseases, hand hygiene is a critical infection control measure.
One of my favourite stories about surgeons comes from a book by Irwin W. Sherman called "The Power of Plagues." In the pre-anesthesia and pre-antibiotic era, speed was considered the sign of a good surgeon. One surgeon, Robert Liston, was particularly renowned for his speed. However, speed sometimes lead to problems. In one surgery, he amputated a leg in 2.5 minutes, but the patient died of infection after surgery (a common event those days). During surgery, he accidentally amputated the finger of his assistant as well, who also subsequently died of infection. To top it off, he slashed the coattails of a surgeon who was watching, who "died of fright" thinking his organs had been slashed too. He's the only surgeon on record with a 300% mortality rate for a surgery.
These days, surgery is a lot more humane and safe. However, problems like surgical site infections still occur. They occur following a much smaller percentage of surgeries than they used to, but they can still be very serious. Nowadays, more of these infections are being caused by multidrug resistant bacteria, which can affect and be transmitted between both animals and people. It's been stated that the time of maximal influence on surgical site infections beings and ends in the operating room (e.g. the most critical time for preventing infection is during the surgery itself). However, there are things that can be done at home to help reduce the risk of infection.
- Antibiotics are usually NOT required after surgery, depending on what procedure was performed. But, if antibiotics are prescribed by your veterinarian, make sure you give the full course and follow all instructions carefully.
- Keep your pet from licking the surgery site. Trauma from licking and chewing, and bacteria from the mouth can help start an infection. If your pet is licking or chewing its surgery site, consult with your vet about ways to stop this.
- Keep an eye on the surgery site. If you see signs of infection such as excess heat, pain, redness, swelling or discharge from the site, talk to your vet as soon as possible.
- Don't touch the surgery site. You could contaminate the site with bacteria from your skin that could start an infection. Also, if an infection is present, bacteria could spread to you. If you must touch the surgical site (e.g. if you need to change the bandage over it, or your veterinarian has instructed you to clean the site), you should wear disposable gloves.
An outbreak of E. coli O157 - the particularly nasty strain of E. coli that can cause hemolytic uremia (a serious kidney disease) and death - has been identified in Colorado, and signs are pointing toward a livestock show as the source. So far, 20 people have been identified as infected, including 19 children. The exact source of the infection is not clear, and could be food, water or contact with animals. However, considering the high percentage of children, the petting zoo is a likely source.
As we've discussed previously, petting zoos can be fun and educational events (particularly for children) but are always associated with some degree of infectious disease risk. Petting zoos are often poorly equipped to handle these risks, as we reported in a paper in Clinical Infectious Diseases a little while ago. Petting zoos are a risk because animals that appear healthy can still carry infectious diseases. This is particularly true for E. coli O157, which can be carried by perfectly healthy cattle. Despite the possibility of exposure to E. coli and other potentially harmful microorganisms, the potential for disease can be greatly reduced with some very basic measures, like handwashing, not eating in the petting zoo, handwashing, keeping baby bottles and other items out of the petting zoo, handwashing, and having signs encouraging people to wash their hands. The people in charge of this event stated that they had a well organized petting zoo with handwashing stations available, and that may very well be true. Having access to handwashing facilities is a critical step, but it doesn't do anything if people don't use them. Unfortunately, poor compliance with handwashing is very common and is one of the weakest links in infection control at petting zoos.
- Always wash your hands after leaving a petting zoo.
- Don't eat in a petting zoo area.
- Don't take items into the petting zoo that will go into a child's mouth, like bottles, cups and soothers.
If your veterinarian suspects your pet may have ringworm, there are several different ways he or she may test for the causative fungus (a dermatophyte) on your animal's fur and skin. Some of these techniques are more useful than others in different situations.
- Wood's lamp: A Wood's lamp is simply a special ultraviolet light. Approximately half of all Microsporum canis strains (the most common species of dermatophyte that causes ringworm in cats and dogs) will fluoresce blue-green under such a light. This type of testing is obviously very easy to perform. However, other debris in an animal’s hair coat may fluoresce as well, and other species of fungus that cause ringworm do not fluoresce, so this test is not useful by itself in most cases.
- Microscopy: Sometimes ringworm fungus can be seen on hair shafts from an infected pet when examined under a microscope. However, it is easy to confuse other debris and structures for dermatophytes. Also, not every hair on an infected animal will carry the fungus, so it's possible to miss the infected hairs altogether with this test.
- Fungal culture: The best way to diagnose ringworm is to culture the fungus from the infected individual (person or animal). In animals, one of the best ways to collect a sample for culture is to comb over all the fur and skin with a new toothbrush, and then try to grow dermatophytes from the toothbrush. This allows the fur from all over the animal to tested, rather than just one little clump of fur plucked from one area. It can also make it easier to get a sample from the face and paws of cats, which is where these animals often carry the fungus. Although fungal culture is the best way to diagnose ringworm, remember that fungal culture takes much longer than bacterial culture – instead of days, it may take up to three weeks to grow some dermatophytes.
It's also important to remember that dogs, and more often cats, may carry dermatophytes on their fur even when they look healthy. A positive fungal culture from an animal with skin disease, particularly a cat, does not necessarily rule out other diagnoses, so your veterinarian may still recommend other tests as well. However, any animal with ringworm should be treated to prevent spreading the infection to other animals and people.
I did a presentation at a conference last week with a physician on the topic of "Pets and Immunocompromised Owners". It led to some interesting discussion. People with suboptimal immune systems are becoming more common in households and they often own pets. These individuals are susceptible to infections caused by microorganisms that would not typically cause disease in healthy people, and they are also more susceptible to severe (including fatal) disease caused by microorganisms that would only otherwise cause mild disease. Therefore, there's a lot of concern about pets transmitting infection to immunocompromised people. Rarely is removal of pets from households of immunocompromised people necessary, but precautions should be taken to reduce the risks of disease transmission.
One topic that comes up periodically is testing for Bartonella henselae. This bacterium is the cause of cat scratch disease, which is spread by cats through scratches (obviously) but also through bites and by fleas. Cats that carry Bartonella henselae hardly ever have any signs of disease. In healthy people, cat scratch disease typically causes fever, local lymph node swelling, headache and fatigue. Immunocompromised people, particularly people with HIV/AIDS, are at higher risk for severe disease, which can be fatal if it is not identified and treated promptly. Similar disease can also be caused by other species of Bartonella that are not carried by cats.
Tests for Bartonella are not 100% accurate. Some tests just indicate exposure which does not tell you whether the cat is still carrying Bartonella or if it was previously exposed but already eliminated the bacterium from its body. False negative tests (e.g. the cat has been exposed but the test comes back negative anyway) can also occur. When considering screening tests, or any diagnostic tests in general, only do a test if there's a reasonable chance that the results will affect what you do.
- If a cat is positive, I wouldn't recommend removing it from the house. It may or may not be shedding Bartonella, so the key points for avoiding cat scratch disease are reducing the risk of bites and scratches, and controlling fleas.
- If a cat is negative, it's probably (but not guaranteed to be) free of Bartonella, but it could be infected later in life, and the key points for avoiding cat scratch disease are reducing the risk of bites and scratches, and controlling fleas.
So, if the recommendations are exactly the same in both cases, save your money and spare the cat the blood sample. I don't recommend testing for Bartonella henselae. The Infectious Disease Society of America also does not recommend testing (or treating) cats for Bartonella in their guidelines for HIV/AIDS patients.
I've had this question a lot lately. Methicillin-resistant Staphylococcus pseudintermedius (MRSP), which is sometimes misidentified as methicillin-resistant S. intermedius (MRSI), is an important and increasing cause of infections in dogs and cats. After an animal has had an MRSP/MRSI infection, a question people often ask is how long they will carry the bacterium?
MRSP can be carried in the nose, intestinal tract or on the skin of a small percentage of normal animals. The implications of this are not clear, but it is reasonable to assume that carriers are more likely to develop infections in certain situations (e.g. if they sustain a wound or need to have surgery), and can transmit it to other animals (and possibly people, but that's much less of a concern with MRSP than with MRSA).
Back to the question... To be perfectly honest, we really don't know. However, I think it's reasonable to assume that some animals could carry MRSP for a long period of time - certainly weeks or months, maybe even years. Staphylococcu pseudintermedius is a common bacterium in healthy dogs and cats, and has basically evolved to survive on these animals. The methicillin-resistant versions are likely no different in this respect, so it's reasonable to assume that some animals could be long-term carriers. This makes controlling MRSP more difficult. In contrast, MRSA appears to be only transiently carried by dogs and cats, probably because it is better adapted to living on humans than pets.
What you should do in the meantime if your pet has MRSP:
- Treat any infection as per your vet's instructions.
- Always complete the full treatment course.
- Wash your hands after contact with your pet, healthy or not.
More information about different types of staph bacteria can be found in the previous Worms&Germs post entitled Methicillin-Resistant Staph - What's In A Name?
Particularly when the mercury is well below zero (like it has been recently here in Ontario), many people dream of warmer places, and some of the luckier ones even get to jet off to regions closer to the equator to thaw out for a while. Before you set off for a tropical destination, it's always good to do a little research so you know what you're getting yourself into, which includes being familiar with local endemic diseases.
For today's example, take African trypanosomiasis, also known as sleeping sickness. This disease is caused by a protozoal parasite called Trypanosoma brucei, which is transmitted by the bite of tsetse flies. The disease only occurs on the African continent, but it is endemic in 36 countries and poses a risk to approximately 50 million people. There are actually two subspecies of T. brucei that cause disease in man. Trypanosoma brucei gambiense tends to cause more chronic disease and has caused massive epidemics of sleeping sickness in the past. Trypanosoma brucei rhodesiense causes more acute disease, tends to occur sporadically and is more common in tourists and travellers in Eastern and Southern Africa. What a lot of people don't realize is that T. brucei rhodesiense is actually a zoonosis - the main reservoir of the organism is livestock, whereas the main reservoir of the gambiense subspecies is infected people.
The World Health Organization (WHO) places human African trypanosomiasis (HAT) on its list of seven neglected endemic zoonoses. Some of the other disease on this list have also been discussed on the Worms&Germs blog, including rabies (one of our favorites), brucellosis and echinococcosis. In the early 1960s, efforts to control HAT brought the prevalence of the disease down to less than 1 case/10 000 people. Unfortunately, for a lot of reasons, the control efforts could not be sustained, and the African continent is now facing its third major epidemic of sleeping sickness. Better and ongoing surveillance, treatment of infected animal reservoirs, and control of the vector tsetse flies are all important components of the WHO's control strategy for HAT on the African continent.
Dogs can be infected by both T. brucei gambiense and T. brucei rhodesiense, but they are not considered significant reservoirs of disease. Dogs may be more important as sentinels for human disease in endemic areas. There are, however, other Trypanosoma species that occur in dogs and people in North and South America, including T. cruzi, which causes American trypanosomiasis or Chagas' disease.
More information about zoonotic sleeping sickness is available on the WHO website, and more information about Chagas' disease in people is available on the CDC website. Keep watching the Worms&Germs blog for more posts about trypanosomiasis in pets.
Mumps is a common (and highly infectious) viral disease in people, particularly children. Typically it causes flu-like symptoms (fever, headache, aches and sore muscles) as well as painful swelling of the parotid salivary glands. These glands are located within the cheeks near the angle of the jaw, just below the ear. Illness usually lasts for about ten days, but in young adults the infection can cause serious complications, including meningitis and deafness. Because the disease is so infectious, it is recommended that anyone with the mumps be isolated for nine days - that means no going to work, school, the store or anywhere else!
Dogs may actually be able to get mumps too, but it's very uncommon. Dogs living with recently affected children have been reported to develop similar signs of illness to humans, including fever, not wanting to eat and swollen parotid salivary glands, and antibodies to mumps virus have been found in some dogs. It's also been shown that the virus grows well in canine cell cultures in the laboratory. However, there are no experimental trials that have definitively demonstrated transmission of mumps to dogs.
Because mumps is caused by a virus, antibiotics are not useful for treating the infection. In dogs suspected of being infected, specific treatment is usually not needed - just some TLC and most dogs recover within 5-10 days. There are no reports of people getting mumps from a dog - this is primarily a disease of humans.
People, but not dogs, can be vaccinated for mumps. The vaccine is part of the MMR (measeles, mumps and rubella) vaccine, which many people receive when they are children. For more information about this disease and vaccination, see the website of the Ontario Ministry of Health and Long-Term Care.
A report in the latest newsletter from the University of Guelph Animal Health Laboratory describes a case of tuberculosis (TB) in a pet dog. The dog was a seven-year-old Bichon Frise that had an abdominal mass, low-grade fever, nasal discharge and pneumonia. Tuberculosis was diagnosed by testing a sample of the mass that was obtained during an exploratory surgery. The dog was euthanized because of the poor prognosis and because of concerns about transmission to people in the household.
Tuberculosis has historically been one of the most important infectious diseases in people and has re-emerged as a huge problem in human medicine, particularly because of the development of highly drug-resistant strains. The disease is caused by the organism Mycobacterium tuberculosis. It can be spread through the air over short distances by minute droplets when someone with active TB coughs, sneezes, speaks or sings. Other individuals become infected by breathing in the bacterium.
Tuberculosis is primarily a human disease. It has been reported in various animal species, but only rarely. Dogs are considered relatively resistant to TB, even so there are several reports in the scientific literature of TB in dogs. The source of the dog's infection in this case was not discussed. Presumably, the dog was infected by close contact with an infected person.
One of the reasons for euthanasia of the dog in this case was the risk to household members. At this point, we have little information about the risk that infected animals pose to their human contacts. This makes providing evidence-based advice difficult. Many people may err on the side of caution by euthanizing the animal to prevent transmission. Important aspects that need to be considered include whether the owner can afford to attempt treatment of the animal (with no clear evidence of what works and longterm treatment being required), whether the disease is potentially treatable (i.e. what are the chances the animal will recover if it is treated), and the status of other household members with respect to TB disease or exposure. Of course, these consideration are all in addition to that of the animal's condition and quality of life, which may warrant euthanasia regardless - tuberculosis can be a devastating disease, and it is often not detected until it is quite advanced.
There's no correct answer. Our poor understanding of this disease in dogs and the significant health risks of TB in people unfortunately make euthanasia a reasonable decision.
Bartonella henselae is a small, Gram-negative bacterium that is host-adapted to cats. It may rarely cause mild illness in cats, but most felines, from tiny house cats to the king of the beasts, carry the bacteria with no clinical signs whatsoever. Unfortunately, when B. henselae infects a person it can cause any of several serious conditions (most of which have very long names!). These include bacillary angiomatosis (formation of masses of abnormal blood and lymph vessels), endocarditis (infection of the lining of the heart), chronic lymphadomegally (enlarged lymph nodes), and pyogranulomatous lymphadenitis, better known as cat scratch disease. There are at least four Bartonella species (among many, many other Bartonella species) that can infect cats, but B. henselae is the most common. There are at least nine Bartonella species that can infect humans, seven of which are zoonotic.
Between 5% and 40% of cats in the USA have B. henselae in their bloodstream. It is most common in cats from temperate areas, and is much less common in Canada. Bartonella spp. live in the red blood cells of their host – quite a clever strategy really, because it makes the bacteria readily available to be picked up by vectors like blood-sucking fleas, it protects the bacteria from the hosts immune system so it can live there for a long time, and it may even partially protect the bacteria from antibiotics. Cats can maintain a waxing and waning infection for months or even years. The bacterium is transmitted between animals by the cat flea (Ctenocephalides felis felis). Studies have shown that transmission does not occur between cats kept in a flea-free environment. Some ticks may also be able to transmit the disease. Diagnosis in cats is difficult – blood culture is the most reliable means, but it is not always sensitive. Antibody production only confirms exposure but not active infection. Polymerase chain reaction is often faster but no more sensitive than blood culture. An effective treatment regimen to eliminate B. henselae infection in cats has yet to be determined.
Transmission of B. henselae from cats to humans is thought to occur through contamination of scratches and bites (broken skin) with flea dirt (i.e. partially digested blood from the infected animal that is excreted by fleas = flea poop). Infection in individuals with weakened immune systems can be extremely serious or even fatal. In otherwise healthy people, the infection tends to remain localized, but can still cause massive swelling and abscessation of local lymph nodes. The type of disease that occurs may depend on the strain of Bartonella involved.
There are a few simple steps people can take to decrease the risk of cat scratch disease. These are particularly important for individuals with compromised immune systems, in which infection can be much more severe:
- Keep your pets flea- and tick-free. Effective treatment and prevention products are available from your veterinarian.
- Avoid or prevent situations that may result in bites and scratches from your pet. There is more information about this on the Worms & Germs Resources page and in our archives. If you do accidentally get scratched or bitten, be sure to clean the wound thoroughly. Consider seeking medical attention for bites in particular.
- Be aware of where cats come from. Stray or shelter cats less than one year old are most likely to be infected with B. henselae.
It is also important to note that there is NO evidence that declawing cats decreases the risk of transmission of B. henselae to humans!
As a point of interest, Bartonella quintana (a human-adapted Bartonella species) was the cause of trench fever in World War I, and was transmitted by lice.
A recent article in the journal Avian Pathology describes a case of Mycobacterium tuberculosis, the cause of tuberculosis (TB), in a pet bird (African Grey parrot) and its owner. Mycobacterium tuberculosis mainly causes disease in people, but can sometimes be found in other animal species, including birds. In this case, the bird was presented to a veterinarian because it had a decreased appetite and nodules under its tongue. The bird was wild-caught in Africa 11 years earlier. The owner was treated for TB two-and-a-half years earlier. Apparently, the owner usually fed the bird pre-chewed food (don't ask me why), and the vets suspected TB because of this close exposure. Because of the severity of the disease, the bird was euthanized and TB was confirmed by culture and PCR.
Often, we get to a point like this where both an animal and person have been diagnosed with the same disease, and can't go any further in terms of determining how each of them got the disease, and if it was transmitted between them. Fortunately, the Mycobacterium tuberculosis isolate from the owner had been saved, and they were able to compare it with the strain found in the bird. They were same. This strongly supports the theory that TB was transmitted between the owner and the bird. However, that's as far as we can go with confidence. The authors hypothesized (reasonably) that since the owner was diagnosed first, and since TB is mainly a human issue and is rarely found in birds, that the person acquired TB from some source then infected the bird. Additionally, two other reports of TB in birds also stated that the owners pre-chewed the birds' food.
TB in birds (and pets in general) is rare, and people shouldn't panic about it. However, it is apparent that transmission between species can occur. Transmission from an infected person to a pet is more likely than the other way around, but both are certainly possible. It's a good reminder that people with TB who are considered infectious should take precautions around their pets, just like they do around other people.
...and pre-chewing food for your bird is probably not a good idea, either.
I've never been one to make New Year's resolutions. I figure if it's important and something I should do, why wait until January 1 to start? However, New Year's resolutions can be a good way to get people thinking about ways to improve their health. NovaNewsNow.com has a good idea for a practical and useful resolution: better hand hygiene. The article contains some good tips on when hand hygiene is needed. Hand hygiene is the term used for hand washing or use of alcohol-based hand sanitizers, and hand hygiene is one of the most (if not the most) effective and important infection control tools in hospitals, and in the community. Despite this, most people don't perform hand hygiene often enough (or properly), resulting in unnecessary risks of disease transmission.
Have a Happy New Year, and clean your hands.
My wife has a lousy immune system. She's a good indicator of whatever infectious diseases are circulating in the region. After running through a stretch where our whole family was biohazardous (baby with a cold, older two with two different bugs that they then spread to each other), Heather developed strep throat. This common bacterial disease is caused by Group A Streptococcus. I've previously posted about issues regarding strep throat and pets, and the fact that there is little evidence supporting pets as sources of strep throat in households. However, I still get asked about this, and I still see recommendations on the internet to test or even treat pets to try to contain strep throat in a household (for example, see these posts on medhelp.org and justanswer.com).
As a veterinary infectious disease specialist who runs a microbiology research lab (and someone who likes to play around and look for strange things), I'm in a perfect position to start culturing my pets to look for a link, but I don't bother. We've not found any convincing evidence, and neither have other groups, that pets are a source of strep throat for humans. There are a number of zoonotic disease concerns involving household pets, many of which dont' receive adequate attention, but this isn't one of them. More information about "Pets and Strep Throat" can be found in the previous Worms & Germs post of the same name.
I had an advice call the other day about control of Tritrichomonas fetus in cats. This protozoal parasite is being recognized as an important cause of diarrhea in cats, particularly in crowded situations such as catteries. In addition to the standard discussion about control of this parasite in cats, the question about human risks was raised. Tritrichomonas fetus is passed in the stool of infected cats, and other cats become infected by ingesting the organism. It is certainly possible that someone with an infected cat could be exposed to this parasite through inadvertent ingestion of the parasite following contact with infected surfaces (e.g. the cat's fur or litter box). Although this sounds gross, it probably occurs more often that we think. We encounter bacteria of fecal-origin regularly throughout the day. Keep that in mind the next time you don't want to be bothered washing your hands.
The risk of human infection with T. fetus is unclear, but is probably quite low. There is only one report of human infection by this parasite, and the person was immunosuppressed. Risks to healthy people are probably very low but we can't say there is no risk. Basic hygiene measures (especially hand hygiene and good litter box management) should reduce the risks even further. People with weakened immune systems should take greater care (because of the risks from this organism and many others), but still, common sense practices are the key. More information about household infection control and litter box management for cat owners is available on the Worms & Germs Resources page.
Some excellent information on Tritrichomonas fetus can be found on the website of Dr. Jody Gookin, a leading researcher in this field.
Infections caused by methicillin-resistant staphylococci are an increasing problem in veterinary medicine. Staphylococci are a group of bacteria that can cause various infections in many different animal species, including people. The one that gets the most attention is methicillin-resistant Staphylococcus aureus (MRSA). There is more information about MRSA in animals on the Worms & Germs Resources page and in our MRSA archives.
While MRSA gets most press, infections by methicillin-resistant Staphylococcus pseudintermedius (MRSP) are more common in dogs. (More information about the issues with naming staphylococci (particularly MRSI vs MRSP) can be found in the post "Methicillin-resistant Staph: What's in a name?"). These canine MRSP infections creat many frustrating and concerning situations. They can be very difficult to treat because they are resistant to a large number of antibiotics. However, with the proper testing we can usually identify an effective antibiotic to treat these infections, and the prognosis for dogs with MRSP infections is usually good, unless they have a very severe or invasive infection.
I get advice calls about management of MRSP on almost a daily basis. The first question is usually what treatment should be used. Almost inevitably, the second question is about human health concerns, because of the awareness of MRSA in people. MRSA can be transmitted from pets to people, although it probably more often goes from people to pets. MRSP can also be found in people, but it is very rarely identified as a cause of disease in humans. Someone in contact with an infected dog is probably more likely to carry MRSP in their nose, but they are unlikely to develop an MRSP infection. However "unlikely" doesn't make it impossible.
If someone has a dog with an MRSP infection, it's important to know that this is different than MRSA. The risks of human infection are likely much lower. Nonetheless, the last thing you want is an infection with a multidrug-resistant bacterium, so some basic measures should be employed to reduce the risks:.
- Avoid direct contact with the infected site(s). If you have to touch infected site (e.g. when applying ointment or changing a bandage), wear disposable gloves and always wash your hands well when you take the gloves off.
- Keep infected sites covered with a bandage if possible.
- Wash your hands or use an alcohol-based hand sanitizer regularly after contact with the dog, and always after contact with the infected site (even if gloves were worn) or the dog's nose or hind end. Remember that MRSP can be carried in the dog's nasal passages and intestinal tract.
- Avoid contact with the dog's stool.
- People with weakened immune systems, very young children and elderly individuals are probably at higher risk for infections, and should therefore avoid contact with infected dogs whenever possible.
- Don't let infected dogs sleep on the bed or on other areas where people have close and frequent contact (e.g. couch).
- While the risks are low, if you have any concerns, talk to your physician.
I just received this comment from a reader of an earlier post about blastomycosis:
What should be done if a person was bit by a dog with blasto? I was trying to pill a dog who has blasto and the dog just out of reflex shut her mouth on my finger. What are the chances of the blasto being transmitted to me?
It's a reasonable question and one that I get periodically. If the bite didn't break the skin, the risk is essential nil. If the bite broke the skin, the risk is still fairly low, but certainly not zero.
Simple contact with an infected dog cannot result in transmission of blastomycosis because Blastomyces is a dimorphic fungus, meaning it can take the form of either a mold or a yeast. The highly infectious mold form is found in soil at ambient temperatures, while the minimally transmissible yeast form is present in the body of an infected animal or person. However, bites can be a different story. A bite from a dog with advanced pulmonary blastomycosis (e.g. fungal pneumonia due to Blastomyces) can result in localized blastomycosis at the site of the bite (e.g. only the person's finger might get infected).
Considering the dog in this case was already being treated for the infection (and therefore hopefully was not shedding much of the fungus), and that there are very few reports of bite-associated blastomycosis, the risk is probably quite low. However, any bite that breaks the skin can result in infection from the multitude of bacteria in an animal's mouth. Any bite on the hand should be taken seriously because it's easy for sensitive structures like joints and tendon sheaths to become infected. Consulting your physician or getting medical attention is recommended.
More details about general issues regarding animal bites are available in our bites archives. Relevant information is also available in the Cat Bites information sheet on the Worms & Germs Resources page.
Photo: Light micrograph of the budding yeast form of a fungus.
Encephalitozoon spp. are single-celled microsporidian parasites that can cause infection in the intestinal tract of animals and people, and sometimes infection in other parts of the body (systemic infection). Cases of infection with these parasites (encephalitozoonosis) have been reported in countries all over the world. The species E. bieneusi and E. intestinalis are the most common. A much less common species, E. cuniculi, is thought to be one of the most virulent microsporidia that infects humans (i.e. it causes the most severe infections). Encephalitozoonosis is rare in healthy people, but it is a common complication in patients with weakened immune systems. Encephalitozoon cuniculi can also be found in many animal species, particularly in rabbits. Most infections in rabbits do not cause illness (i.e. subclinical infections), but when disease occurs it typically causes neurological signs. In these cases the parasite tends to attack the brain and kidneys. The primary means of transmission between rabbits is E. cuniculi spores shed in the urine. Organ damage in the few human cases that have been reported have also been primarily in the brain and kidneys.
Direct transmission of this parasite from rabbits to humans has not been reported, but because there is also no evidence that it can't be transmitted from rabbits, the disease is so severe when it does occur, and the parasite is so common in rabbits, it is still prudent to take a few simple precautions. This includes washing your hands after handling rabbits, and keeping rabbits away from food preparation areas and food meant for human consumption. Anyone with a weakened immune system should be particularly careful, and ideally should have someone else clean out their rabbit's enclosure on a regular basis.
In general, the risk of illness in a rabbit and zoonotic transmission can be reduced by proper handling, good management, personal hygiene and routine healthcare. A rabbit that is not stressed and is well cared for is less likely to be susceptible to infection, and therefore less likely to transmit infection to a person. More information about rabbits is available on the Worms & Germs Resources page.
Back in the 1980s, Vietnamese Pot-Bellied Pigs were a popular fad pet. These stout little oinkers are still out there, though they're not quite as popular as they once were. Potbellied pigs are cute (at least to some people... to each their own!), supposedly quite smart, and can even be house trained/litter trained. As with any new pet though, it's very important to do your research before going hog-wild and getting yourself a pot-bellied pig. Talk to your veterinarian about what your pig will need in terms of medical care - vaccines, deworming, spay/neuter, hoof trimming, tusk trimming... Because they are uncommon pets, some veterinarians may not be comfortable treating a pig. Make sure you ask ahead of time so you know to which veterinarian(s) in your area you can (and will!) take your pig.
We recently received a question about vaccination of pot-bellied pigs. Just like dogs, in some areas pigs need to be licensed by the city, and certain vaccines are required in order to obtain a license. In this particular case, pigs are required to be vaccinated against rabies, swine erysipelas and leptospirosis. Regular visitors to this site are no doubt familiar with the issues around rabies and why it's important to vaccinate for this deadly disease. (More information about rabies is available on the Worms & Germs Resources page and in our archives.) Swine erysipelas is a systemic bacterial infection caused by Erysipelothrix rhusiopathia, which can rarely cause a skin infection known as erysipeloid in humans. This is not to be confused with human erysipelas, which is a skin infection caused by various species of Streptococcus (particularly Streptococcus pyogenes).
But the question was about leptospirosis vaccination in pot-bellied pigs. Pigs are susceptible to infection by Leptospira interrogans, just like dogs and people, and if infected a pet pig would be equally capable of shedding the bacterium in its urine and potentially transmitting the disease. The issues around requiring vaccination of pigs for leptospirosis are very similar to those around making leptospirosis a "core" vaccine in dogs. More information about this is available in the Worms & Germs post entitled "Should all dogs in Ontario be vaccinated for leptospirosis?" A pet pig would likely be exposed to the same serovars of Leptospira as a dog kept in the same area, typically by coming in contact with urine from infected wild animals such as raccoons and skunks when they go outside. However, the risk of exposure for a pig that rarely or never leaves the house would be extremely low compared to a pig that has outdoor access. Another important consideration is whether or not the pig vaccine is against the same serovars that a pet pig, instead of a commercial pig, might encounter. This will also vary depending on in what area the pig lives. The Leptospira servoars pomona and bratislava are actually host-adapted to pigs.
It is also important to vaccinate an animal with vaccines that are labeled for use in its own species. Vaccinating a pig with a vaccine meant for dogs could have unpredictable results - it may increase the risk of an adverse reaction, or it may not adequately stimulate an immune response, thereby leaving the pig essentially unvaccinated. Your veterinarian can discuss the pros and cons of vaccination in your pet with the available vaccine products.
More information about leptospirosis is also available on the Worms & Germs Resources page.
Most of the infectious disease topics that we've covered on Worms & Germs involve bacteria or viruses. Fungal diseases (other than ringworm) are often overlooked because they are less common, and because they tend to be more of a concern in certain areas only. However, when fungal infections occur they can cause serious problems.
Blastomyces dermatitidis is a dimorphic fungus (meaning it can exist in the form of a mold or a yeast) that lives in the soil in some areas. It is more common in wet, sandy, acid soils that have a high organic content. Animals (and people) can become infected by exposure to the mold form of the fungus in the soil. If the fungal spores are inhaled, it can result in severe pneumonia. Blastomycosis (infection with Blastomyces) can be difficult to diagnose and very difficult (and expensive) to treat. So while blastomycosis is rare in general, it is still an important disease, especially in areas where it is more common.
Recently, a study was published in the journal Medical Mycology (Chen et al, 2008, 46: 843-852), regarding blastomycosis in dogs in Tennessee. This was a case-control study that compared dogs with blastomycosis to dogs that did not have the disease. Here are some of the results:
- Male dogs were 2.7 times as likely to be affected as females.
- Working and sporting dogs were at higher risk (4.6 and 6.2 times as likely, respectively).
- Dogs 2-4 years of age were at highest risk.
- Close proximity to water was also a significant risk factor for infection.
In Ontario, blastomycosis seems to be most common around Georgian Bay. In the US, it is more common in central and northern states, with most cases reported in Wisconsin, Tennessee, Mississippi, Kentucky and Arkansas.
Blastomycosis can also occur in people, but blastomycosis cannot be transmitted from dogs to humans (or between any animal species). Only the mold form of the fungus that lives in the soil is infectious.
The weather outside is frightful (at least up hear in Canada!) - it’s getting colder, the weatherman now warns us about “flurries” instead of “showers”, there’s frost on the cars in the morning, and we’ve all had to start putting on those extra bulky layers before leaving the house in the morning. There's lots of grumbling about the oncoming winter weather. Let’s take a look at the silver lining though – people who live at more northern latitudes often don’t appreciate what a few months of cold weather does for us!
Insects in particular, including mosquitoes, ticks and others that transmit various diseases, are almost entirely inactive outdoors when it’s cold outside. Many insect species can’t even survive Canadian winter weather, which is why they are only concerns in more southern climates. For example, the brown dog tick (Rhipicephalus sanguineus), which can transmit many diseases including canine babesiosis, anaplasmosis, and Rocky Mountain Spotted Fever (RMSF, which can also be transmitted to people), doesn't exist in Canada except on dogs that have travelled to the south. The cold weather also helps keep heartworm in check through mosquito control - the prevalence if heartworm in North America decreases dramatically the farther north you go. Bacterial pathogens are often good at surviving in the cold, but many are killed by freezing, and even if they can survive, it is almost impossible for bacteria to grow and multiply in the cold. Winter provides a reasonable knock-down effect for a lot of pathogens and parasites that often thrive in the outdoor environment during the summer months.
Of course, microbes and insects can still survive in the same environments where we do over most of the winter – indoors, where it’s nice and warm. So it’s still important to do things like wash your hands after handling your pet and before you handle food. And, as always, come spring we’ll have to be prepared for the return of all those worms and germs as we venture back to our favourite warm-weather outdoor activities.
In the meantime, grumble though we may, try not to give old man winter too hard a time – a few months of freezing temperatures isn’t all bad afterall.