Study Seeking "Superbugs" In Horses
A two-part study (Maddox et al. 2011) was recently published online in the Equine Veterinary Journal looking at antimicrobial resistant "superbugs" in horses in the UK. The first part of the study had the simple objective of estimating the prevalence of both MRSA nasal colonization and fecal shedding of antimicrobial resistant E. coli in the UK horse population. The reason they were looking at E. coli is because this bacterium is part of the normal intestinal flora of most animals (including horses), so it's easy to find, and it is frequently exposed to antimicrobials whenever a horse is treated systemically (i.e. with either oral or injectable antibiotics), so researchers use it as an "indicator" for resistance that may develop in other bacteria as well. E. coli doesn't typically cause gastrointestinal disease in horses like it can in people, nonetheless E. coli is a common cause of uterine, urinary and wound infections in horses, as well as septicemia in foals, and antimicrobial resistant infections in these situations can certainly be a big problem.
Out of 678 nasal swabs (taken from horses on over 500 premises), only 4 (0.6%) were positive for MRSA. That's good to see, as it's very easy for MRSA to spread in a horse population "under the radar," because colonized horses do not have any outward signs that they are carrying the pathogen. The overall low prevalence in the community setting is similar to previous community studies in the UK and other areas. Out of 650 fecal samples, 452 (72.2%) were positive for an E. coli that was resistant to at least one antimicrobial. That's not too surprising. The bigger concern is that 233 (37.6% - over one third of all horses tested) samples contained multidrug-resistant E.coli (defined in this study as resistance to more than three antimicrobial classes) and 42 (6.3%) samples contained an E. coli that produced an extended-spectrum beta-lactamase (ESBL). ESBLs are particularly problematic because they can be relatively easily transferred between bacteria, they confer resistance to a large number of commonly used antimicrobials in the beta-lactam class (which includes penicillins and cephalosporins), and are frequently associated with genes that confer resistance to other antimicrobial classes as well. Bacteria that produce ESBLs are a significant problem in human medicine and have been reported to cause infection in horses as well.
The second part of the study used information collected from questionnaires filled out by the horse owners to try to determine risk factors that affected the odds of a particular horse shedding antimicrobial-resistant E. coli. They used some pretty heavy-duty statistical analysis because they were looking at so many factors and different outcomes, and any time that happens you have to take the final numbers with a grain of salt. Nonetheless, the results can help point the way for future studies to help determine which factors may have the biggest impact on the risk. The authors found recent hospitalization and veterinary treatment for various conditions over the last six months were associated with higher odds of shedding multidrug-resistant strains of E. coli, and the type of farm/facility also affected the odds. In addition, having a recently hospitalized horse on the premises (among other things) increased the odds of a horse shedding ESBL E.coli.
What does all this mean for the average horse owner? The results really aren't new or startling. We already know that antimicrobial resistance is a growing problem in equine medicine, as it is in veterinary and human medicine in general, and this is one more set of studies that provides evidence to that effect. I have no doubt that if a similar study was performed in North America the same kinds of resistant bacteria would be detected, although the numbers may vary somewhat one way or another. The second part of the study also re-emphasize the role that antimicrobial use plays in promoting development of and selection for resistant bacteria, and the potential for the treatment of certain horses to affect the microbes being carried and shed by the animals around them. In the end, it comes down to being responsible about how we use antimicrobials in order to curb the development of resistance, so that these important drugs remain effective for treating serious infections in the future. This applies equally to their use in people and animals of all kinds.
Weird pets and weird infections
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One problem with keeping uncommon animal species as pets is that we don't know much about them from an infectious disease standpoint. Some species end up being pretty low risk while others end up causing unexpected infectious disease challenges.
A Texas family found this out the hard way, after their 16-year-old daughter got sick after being bitten by a kinkajou. Kinkajous are strange little critters that are somewhat related to raccoons. Paris Hilton helped fuel the kinkajou fad a few years about after she adopted one (and was bitten by it shortly thereafter). They tend not be be good pets because they are nocturnal and can be antisocial or aggressive during the day (like a lot of people that are kept awake when they want to be asleep).
I wrote earlier this year about concerns regarding the raccoon roundworm, Baylisascaris procyonis, in kinkajous. This more recent report involves an infection that set in after the Texas girl was bitten by her aunt's six-week-old kinkajou. Within 24 hours of being bitten, the girl was severely ill and ended up in hospital for six days. She was treated with antibiotics and responded to treatment.
Because "kinka-what?" was the response to being told that the girl had been bitten, the family and their doctors researched diseases that might be associate with kinkajou exposure. One thing they found was a bacterium called Kingella potus, which was recently found in kinkajous (and subsequently in people with kinkajou bites). Nowhere in the news report does it actually say that this bacterium was identified in the girl, so it's unclear what really happened.
This is yet another example of what can happen when people buy pets that neither they nor the veterinary and medical communities know much about. The recent debacle in Ohio that culminated in the deaths of a large number of exotic animals was a high profile example of the weak to non-existent laws (or enforcement) pertaining to exotic animals in many areas, something that continues to put both animals and people at risk.
Dead birds, botulism and dogs
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)
Canine papillomavirus
We seem to be seeing more canine papillomavirus cases in dogs in the area as of late. It isn't a high profile disease - the virus doesn't typically make dogs sick, it usually just causes warts. Whether there is actually an increase in cases or we're simply looking for them more carefully is unclear, but it may genuinely be on the rise.
Canine papillomavirus can cause a range of skin problems in dogs, typically warty lesions (papillomas) that go away over time without specific treatment. Usually, a small to moderate number of warts are found in the mouths of infected dogs (see picture right). Sometimes, the lesions can be large and extensive, causing problems and requiring surgical removal. Most often (like warts in people), it's merely a cosmetic issue that goes away eventually, but it may take months. Depending on the size and extent of the lesions, and whether they are growing or causing problems, treatment may be recommended. This can include crushing a wart to try to stimulate the body's immune response, or topical administration of certain drugs. Complete removal of the lesions surgically should be curative.
Canine papillomavirus is spread by direct contact between an infected dog and a susceptible dog. However, because it tends not to cause severe disease, this virus doesn't get a lot of attention in the research world. However, a recent study (Lange et al J Clin Microbiol 2011) has provided more insight into the virus. In the study, researchers evaluated different ways to identify the virus. They then tested 95 healthy dogs at the University of Zurich and identified viral DNA on the skin or in the mouth of over 50% of the dogs. Whether these healthy dogs pose a risk to others is currently unclear, but it suggests that the virus could be transmitted not only from dogs with skin lesions, but from a large number of normal, healthy dogs. If that's the case, control will be a lot harder, since focusing on just the "sick" dogs (the ones with skin lesions) would miss a big pool of potentially infectious animals.
It's important to note that people cannot be infected with canine papillomavirus, nor can dogs be infected by papillomaviruses from other species.
Image from: www.marvistavet.com
Raccoon invaders and roundworms
Here’s a recent question I received:
"My problem is that the raccoon broke a window, came into my house, ate the cat food and then defecated on the kitchen floor. Since they went a day without food, the cats may have eaten the few bits of food that were left behind. How can I tell if they got the roundworm?"
It’s a reasonable question given the concerns about Baylisascaris procyonis, the raccoon roundworm. However, there’s basically no risk. While it is very likely that the raccoons were shedding roundworm eggs in their feces, those eggs are not immediately infective. Ingesting a "fresh" roundworm egg isn't a risk. Eggs have to sit around in the environment for at least 11 days (typically 14-28 days) before they become infective. Therefore, unless the feces are allowed to sit around in the house for a couple of weeks, roundworm infection isn’t a concern in such a case.
NDM-1 in Salmonella...ugh!
NDM-1 (New Delhi metalloproteinase 1) is a little bacterial gene that's attracted a lot of attention (and controversy, due to its name). NDM-1 can be picked up by certain types of bacteria, making them resistant to a whole lot of antibiotics. Some bacteria that carry NDM-1 are resistant to virtually every available antibiotic, which raises the spectre of the "untreatable infection."
Since it's discovery, NDM-1 has been found in multiple countries, often in people that were in India as tourists (or "medical tourists" who traveled to India for medical procedures they couldn't have done in their own countries), and in a few different types of bacteria. Recently, NDM-1 was found in an American upon his return from India, this time in Salmonella (Savard et al. 2011, Antimicrobial Agents and Chemotherapy).
The 61-year-old man was hospitalized in India in late December 2010 following a severe bleed in his brain. He was transferred back to the US on January 25, 2011. Upon arrival, he developed a fever and a multidrug-resistant bacterium, Klebsiella pneumoniae, was isolated from his breathing tube. This was concerning by itself, but later, Salmonella Senftenberg was isolated from the man's rectum. The strain was highly atimicrobial-resistant and was determined to carry the NDM-1 gene.
There have been complaints from people in India about the stigma associated with the "New Delhi" component of the name. In hindsight, many people wish it had been named differently because of this, but at least at the moment, it's undeniable that India is a (or the) hotbed of NDM-1. It's been found in various bacteria from water and seepage samples in New Delhi, but this is the first report in Salmonella. It's concerning because of the difficulty that would be encountered treating highly resistant Salmonella in infected people. Usually, antibiotics aren't needed when someone has salmonellosis, but when they are needed, it's important that they work. Highly drug resistant strains increase the chance of a bad outcome if ineffective antibiotics are used initially (before it's determined that the strain is resistant).
NDM-1 has not been reported in animals... yet. I assume it's inevitable that it will occur, since this gene appears quite able to move between bacterial species. If it increases in humans and in human-feces-contaminated sources like water, exposure of animals will certainly occur. If NDM-1 containing bacteria establish themselves in the intestinal tracts of healthy animals, it's going to be much harder to control.
Botulism Suspected In Aussie Outbreak
A couple of days ago, I reported about a deadly outbreak on a Queensland farm that had killed a significant number of horses. A definitive diagnosis has still not been made, but it is starting to look like botulism might be the cause. In my previous assessment, I said botulism was a potential cause of an outbreak like this, but that this particular disease has a pretty consistent clinical presentation so it was probably unlikely if no one was talking about it as a leading option. It looks like now they are, with the owner stating "I've been talking to vets all over Queensland and they're saying the symptoms are spot-on for botulism." It's unclear whether the first vet(s) didn't consider it or whether there wasn't much veterinary involvement at all initially. Regardless, botulism makes sense, particularly with the description of the type of illness that's now being provided.
Botulism testing is underway, but it's often hard to get a positive lab test for this disease in horses. Often, it's a presumptive diagnosis made based on the clinical appearance and lack of any other identifiable cause. Botulism outbreaks on horse farms can be devastating, as in this case. They are often associated with feeding improperly fermented silage or haylage, but there are a variety of ways horses can ingest feed (or water) contaminated with the toxins produced Clostridium botulinum.
The good thing that comes out of this, if botulism is diagnosed, is that there's not much risk to other horses in the region, or at least not any higher risk than is always present. Whenever a large number of horses die from an unknown cause, it's always a concern that a new disease might be involved, something that fortunately does not seem to be likely here.
Image: Poor tongue tone is one of the classic signs of botulism in horses, which results in difficulty eating and drinking (click image for source).
Animal shelter outbreaks
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.
Queensland Horse Deaths Being Investigated
There's still no confirmed cause of death for 19 horses that died within a short period of time on a Kooralbyn, Queensland (Australia) farm. Sudden death and Queensland invariably conjures up thoughts of Hendra virus, considering the large number of Hendra cases that have occurred in the area this year, but that particular disease has already been ruled out.
Large numbers of horses dying on a farm around the same time obviously raises a lot of concern. Often, diagnosis is difficult and takes time. One problem is even deciding where to start. For an outbreak like this there are various considerations:
- The usual (infectious) suspects: Common things occur commonly, and strange things are often caused by atypical presentations of common diseases. Hendra's been ruled out but other infectious causes can't be ignored.
- Toxin-associated bacterial diseases: This mainly refers to botulism, which causes adult horses to get sick after eating feed contaminated with botulinum toxin. Poorly fermented feed or feed that has (accidentally) incorporated the remains of an animal that died of botulism can be the source. Botulism outbreaks are usually fairly characteristic clinically since animals with botulism have pretty consistent and remarkable clinical signs of illness. Presumably, it's low on the list here as I haven't seen it mentioned in any reports.
- Toxins: A toxic cause is pretty high on the list, and can be hard to trace. Potential culprits include toxic plants or inadvertent access to toxic chemicals (I remember an outbreak of dead horses I was involved with a few years ago in which the horses died of pesticide exposure... on an organic beef farm!). Malicious poisoning always has to be considered as well.
- New diseases: New diseases don't come along very often, but they can. Similarly, diseases that have been rare can sometimes peak out of nowhere, but something like this is much less likely than the categories above.
- Miscellaneous: For example, if all the horses died inside, electric shock would have to be considered. I assume that's not the case here.
Diagnosis of the cause in an outbreak like this requires a lot of effort, including careful consideration of any signs of illness that were identified before death, good post mortem examinations (necropsies) of dead animals, thorough investigation of the farm looking for toxic plants and other toxic substances, investigation of other farms in the area to see if there are any unexplained horse deaths, investigation of any unexplained deaths of other animals in the area (e.g. looking for abnormal numbers of dead birds on the farm or in the area), testing of samples from horses for various toxins and testing tissues for possible infectious causes. Not easy or cheap, but hopefully effective, and hopefully will ultimately help save other horses from the same fate.
Dealing with dog bites
A recent article in the Toronto Sun described one physician's approach to dealing with dig bites in kids. It contains some useful information, but also a couple of areas that probably require some clarification.
In the article, the physician lays out a few points regarding management of dog bites in kids:
The first thing a parent should do after such a bite is to stop the bleeding by applying pressure. Then, clean the area with warm water and soap. Dogs, like humans, have dirty mouths, so you want to wash and rinse well and even flush out the wound if it's deep.
- "The solution to pollution is dilution" is a old adage. Thorough cleaning is a critical step.
If the bite wound is small, it's usually not sutured, as this might increase the risk of infection. On the other hand, facial wounds and larger bites have to be well cleansed and irrigated, and may require stitches. The sooner this can be done the better.
For a child with a dog bite that has broken the skin, most pediatricians would recommend a seven-day course of an antibiotic, typically Augmentin (unless the child is allergic to penicillin).
- I'm not sure "most" doctors would start a child on antibiotics after any bite that has broken the skin - at least I hope not. Typical recommendations for bites include that antibiotics should be considered with moderate to severe injuries, puncture wounds, people with compromised immune systems and bites over specific areas like joints or the face. Antibiotics for minor soft tissue injuries in otherwise healthy individuals are not typically recommended, although there is some controversy.
Rabies is usually not a risk in dogs that are family pets and live in homes. If the dog is not known or their rabies status is unclear and you can't locate the pet, check with your pediatrician about rabies prophylaxis.
- True. Rabies from pet dogs is very rare in North America. However, if you get it, you almost certainly die, so we take precautions even in low risk situations. So, a little more discussion of this point is important.
- Every dog bite must be approached as a potential rabies exposure. Key points for this are identifying the dog and ensuring it's quarantined for 10 days. After 10 days, if it's healthy, it couldn't have transmitted rabies with the bite. Related to this, any dog bite should be reported to local Public Health personnel. They will ensure that quarantine is imposed if the dog is known, and facilitate rabies post-exposure prophylaxis in the rare situations that it is needed. In Ontario, physicians are bound by law to report bites to Public Health.
Dog bites are unfortunately very common. Usually they are minor and heal without much trouble, but serious or fatal injuries can occur and infections are a potential problem. Knowing what to do in response to a dog bite is important to reduce the risk of a range of complications.
Equine Quarantine Recommendations
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Quarantine is an important, effective and underused practice on horse farms. Quarantine can reduce the risk of introducing new infectious agents to animals on the farm or limit the spread of something that’s already starting to circulate through the herd.
A recent article from TheHorse.com gives a good overview of why and how to implement quarantine. Importantly, it emphasizes that quarantine is not just for large, high-risk farms, and that any farm can and should have a quarantine plan. Not everyone can implement a quarantine protocol easily. We know and accept that, but the inability to implement a textbook quarantine program can't be used as an excuse to do nothing. Even a cursory quarantine program, with some basic practices to reduce direct and indirect contact of quarantined horses with other horses, can be very useful.
Most of the time, quarantine goes uneventfully and no problems are encountered. That sometimes leads to complacency, but it's the few cases where quarantine contains a problem that makes it all worthwhile. The implications of a single horse getting past quarantine can be huge, both for the individual farm and more broadly (e.g. Australian influenza outbreak). The article has some sound, practical advice that all horse owners should consider.
US Rabies update, 2010
The CDC's annual animal rabies surveillance report has been published in a recent edition of the Journal of the American Veterinary Medical Association (Blanton et al 2011). It's the regular synopsis of the state of rabies in domestic animals and wildlife in the country. It contains some interesting information but few surprises. Among the highlights:
- Rabies was identified in 6154 animals in 48 US states, plus Puerto Rico. The true number of animals that died of rabies in the year would have been much higher, since not all animals (particularly wildlife) that die of rabies get tested.
- 92% of positive animals were wildlife, including raccoons (37% of cases), skunks (24%), bats (23%) and foxes (7%).
- Cats were the most commonly affected domestic animal, accounting for 4.9% of cases (303 cats), followed by cattle (1.1%), dogs (1.1%) and horses (0.6%).
- Different rabies virus variants predominated in different regions. For example, raccoon rabies virus was most common on the east coast. Different skunk rabies variants predominated in the south-central and north-central regions, along with California and Nevada. A couple of pockets of fox rabies were present in the southwest, along with one in Alaska. Mongoose variant was present in Puerto Rico. Bat variants were spread out across the country.
- Most rabid cats were from states where raccoon rabies is endemic. About 1/3 of infected cats were from Pennsylvania and New York. Texas was the leader in dog rabies, followed by Puerto Rico and Virginia.
- Two cases of rabies in humans were identified, compared to 4 in 2009. One was a migrant worker infected by a vampire bite while in Mexico. The other was a man from Wisconsin who was infected with a bat rabies strain. Both died.
Canadian and Mexican data are also reported:
- 123 cases of rabies were identified in Canada, 93% of which were wildlife. 7 (5.7%) were dogs or cats. No rabid raccoons were identified, continuing a trend that has been observed since 2009. Bats and skunks were the wildlife leaders. No people were infected.
- 357 cases were reported in Mexico. 83% were cattle, 20 were dogs. Four human cases were identified.
While rabies does not exert anywhere near the impact on people in North America compared to many other regions (where tens of thousands of people die from the disease every year), it continues to take its toll on wildlife and, to a lesser degree, domestic animals. It's also a preventable disease that can be controlled with vaccination, and human cases can effectively be eliminate by proper post-exposure treatment. Continued efforts are needed to reduce rabies in wild and domestic animal populations, for both the protection of those populations and protection of the people who may come in contact with them.
