Worms & Germs Blog

More Capnocytophaga Q and A

Posted in Dogs

Capnocytophaga questions keep coming in. I guess that’s good in some ways, because I usually get a lot of blank stares when I mention that bacterium. A recent article about the risks of Capnocytophaga and exposure to dog saliva includes some good information about the topic, but the statements below highlight some issues:

It’s important to see a physician if you’ve been bitten by a dog, especially if it hasn’t been vaccinated against rabies.

Not really. Rabies vaccination has very little to do with the response to a bite. Yes, if the dog was vaccinated it reduces the risk that it had rabies, but since it’s not a guarantee, one of two things generally still needs to happen: either the dog needs to be tested (which requires euthanasia) or the dog needs to be observed to make sure it’s still clinically normal 10 days later (meaning it couldn’t have been shedding rabies virus at the time of the bite).  Regardless of the rabies risk, there is always some risk of infection from bacteria in the dog’s mouth.  Antibiotic treatmemt decisions are based on the location of the bite and the health status of the person. Seeing a physician after a bite is important, from an antibiotic standpoint, in:

  • People who are immunocompromised (including pregnant women)
  • Bites over the hands, feet, joints, face, bone, surgical implants or the genitals

Severity of the bite is only part of the decision. A very minor bite in a high risk person or a small puncture wound over a joint may pose much more risk than a big flesh wound in an otherwise healthy individual.

Those with weakened immune systems who have difficulty fighting off infections are at greater risk of becoming ill (such as those with cancer, diabetes or an HIV infection).

This may be true, but that’s not the main issue. These groups are at increased risk for various infections in gerenal, but evidence of a major risk from Capnocytophaga specifically is limited. The main risk group for this bacterium, by far, is people who have lost their spleen.

The best way to find out if your dog or cat carries this bacteria is to have a veterinarian run a test. That said, “a negative result may not mean the animal will always be negative, and the same is true for a positive result,”

No/yes. No, testing doesn’t make any sense. Most dogs are carriers and testing isn’t simple. So, a negative result may be a false negative. The correct part of the statement above is that even a true negative result may not mean the animal will always be negative.

When it comes to Capnocytophaga, a few things needto be highlighted:

  • Assume all dogs are carrying it in their mouths, so every bite or contact of saliva with broken skin or mucous membranes is a risk for exposure.
  • People who are at high risk for Capno infections (most notably splenectomized individuals) need to know that they need antibiotics after any bite or exposure of saliva to broken skin. The risk from Capno is very low in the rest of the population.
  • People at high risk for Capno also need to make sure their healthcare provider knows they’re at increased risk if they have signs consistent with Capno infection, especially after a known saliva exposure.
  • Healthcare workers need to know this bug exists.
  • Healthcare workers need to ask about animal contact routinely and pay particular attention to it when presented with a high risk patient.
  • Testing of dogs makes no sense. I’ll do it for free right now:
    “your dog is carrying Capnocytophaga.”
  • Treating dogs for this bug won’t help. Trying to eliminate a bacterium that has evolved to live in a dog’s mouth is probably futile.
  • A little common sense goes a long way. Knowing your risk status, improving dog training and handling to reduce bites, proper bite first aid and some basic awareness by healthcare providers are easy and probably highly effective preventive measures that are often overlooked.

More information about Capnocytophaga and about bites is available on the Worms & Germs Resources – Pets page.

Eastern Equine Encephalitis: Ontario

Posted in Horses

It’s that time of year. Mosquitoes have been annoying me for months (I get bitten multiple times a day where I live, even with repellent), but now they’re becoming a bigger issue. While mosquitoes bite all season, some of the diseases they transmit are only a significant risk at certain times of year.

One high profile disease that is spread by mosquitoes is Eastern Equine Encephalitis (EEE). As you can guess by the name, the virus that causes EEE  affects horses, in which it causes severe and usually rapidly fatal neurological disease. EEE can also affect people (and rarely other species, like dogs). It’s a relatively rare disease even in horses, but when it occurs it’s devastating, so the risk should not be taken lightly.

Recently, two cases of EEE were confirmed in horses on separate farms in Haldimand County, Ontario. Both were euthanized. Three more potential (but untested) cases were also reported in the area. The two confirmed cases occurred at the end of July/beginning of August, which is pretty early in the season for EEE in Ontario.  Whether that’s simply yearly variation cases or a sign that things are more active this year is hard to say, but time will tell.

For horses:

EEE is a rare but nasty disease, and there are vaccines available to help prevent it. The cost-benefit of vaccination against very rare diseases can be debated, but given the severity of EEE, horse owners in areas where the virus is found should consider vaccinating.  But remember that horses need to be vaccinated before the virus starts circulating in the area in late summer and fall (so don’t wait until you hear about a case in your area, or you may be too late to protect your horse in the same season).

For people:

Horses cannot transmit the virus to people (or other animals). We get the virus the same way horses do, from the bite of an infected mosquito.  Surveillance in horse lets us know about viral activity in the area (i.e. the horses can act like disease sentinels for people). Regardless, the risk of EEE, West Nile virus and other mosquito-borne pathogens means we should all take basic precautions to reduce mosquito exposure, such as the use of DEET repelants, avoiding high risk areas at dusk and dawn (e.g. swampy areas) and removing standing water where mosquitoes breed whenever possible.

Hopefully there’s not more to come in terms of EEE in Ontario, but considering we usually only see a handful of cases a year, this year’s early August numbers are a concern.

Doxycycline use and resistant Lyme disease

Posted in Dogs

“Use it and lose it” is often said when it comes to antibiotic resistance concerns. Every time we use an antibiotic (in a person or animal), there’s some potential for resistance to emerge. The more we use antibiotics, and the worse we use them, the greater the risk, generally speaking.

Questions about the (rampant) use of doxycycline for treatment of Lyme disease and the potential for development of resistance come up periodically. For me, it’s mainly in the context of (over)treatment of dogs that come up positive on screening tests but are clinically normal. However, the same concept applies to people.

So, what’s the risk?

From a Lyme disease standpoint, it’s not much of an issue. That may not make sense at first glance, but when you think about it, it actually does.

Let’s look at some scenarios:

  • If a dog is not actually actively infected with Borrelia burgdorferi, the bacterium that causes Lyme disease, antibiotic use can’t result in resistance in that particular bug since it’s not there (but there are still all the other bacteria in and on the dog’s body to consider too… see below).
  • If a dog is infected with the bacterium and it is treated with doxy, odds are pretty good the bacterium will die, so still no resistance.
  • For the B. burgdorferi in an infected dog to become resistant, it has to do it fairly quickly in the face of treatment. It’s most likely to occur from acquisition of a resistance gene from some other bacterium, given what we know about the mechanisms of doxycycline resistance in other bugs. So the B. burgdorferi needs to encounter another bacterium harbouring a doxy resistance gene. If B. burgdorferi caused infections in the gut, respiratory tract or on the skin, that would be more likely. However, in blood, within tissue and in joints, there’s much less of a chance of encountering another bacterium, let alone one that’s doxycycline resistant.

Okay, so in the very unlikely scenario of a resistant bug meeting B. burgdorferi, and a resistance gene being swapped, what now?

  • Well, not much from a population standpoint. It could make Lyme disease harder to treat in that dog, but since dogs are dead end hosts (they aren’t a relevant source of infection of ticks), resistant B. burgdorferi would stay in that dog.

None of this is meant to say “sure, doxy for everyone!” Unnecessary doxycycline use is still a concern, but it’s a concern because of development of resistance in the myriad other bacteria that are present in the body, not B. burgdorferi. Creation of a wide range of other doxycycline resistant bacteria is the concern (and it’s almost certainly happening).

Resistant Lyme disease shouldn’t be an issue. If it occurs, it’s going to happen by the bacterium picking up tetracycline resistance genes in the wild, and there’s not much reason for a bacterium to go to the effort of picking up and maintaining an extra gene if there’s no benefit (because there should be little chance of being exposed to those antibiotics in the wild). It’s possible it could happen, since there are lots of resistance genes out in circulation, and there may be artificial/human influences (e.g. antibiotic use in livestock, resulting in exposure of wildlife to resistant bacteria), and because bacteria naturally develop some resistance genes to fight amongst themselves. However, odds of this creating a sustained, significant population of resistant B. burgdorferi have to be low.

Capnocytophaga in the news… again

Posted in Dogs, Uncategorized

Every couple of months there’s a news report about a person with infection caused by the dog-associated bacterium Capnocytophaga canimorsus. Most of these reports don’t get too much attention, but every once in a while they get picked up pretty widely, resulting in another round of questions about this strange bacterium. It’s a bit of an oddball bug that can be found in the mouths of most healthy dogs. It doesn’t often cause disease in people, but when it does, it’s usually severe and is often fatal. One reason we don’t see much disease, despite the commonness of the bacterium, is that it tends to only sicken certain types of people, particularly those who don’t have a spleen.

While it’s a rare cause of illness, it happens more often than the news reports.  I hear about additional cases from people who have been infected themselves or have affected family members. Some common themes tend to come up, which can be frustrating because they’re issues we’ve been talking about for a while.

Here are a few of the comments that are commonly heard:

I’ve never heard of this bug before.

That’s not really surprising since it is a rare cause of disease, and not one most people would be expected to have heard about.

My doctor didn’t seem to know anything about it. Neither did my vet.

Again, not too surprising. It’s not something most MDs or veterinarians see regularly (or ever) in practice. Medicine and veterinary curricula are already packed, so rare things like this don’t get much, or any, attention. I’ve talked to physicians and most say they haven’t heard of it. I talk to veterinarians about Capno regularly as part of zoonotic disease talks, and only occasionally does someone know about it.

I’m missing my spleen and I didn’t know this was a concern.

That’s a problem. People who lose their spleen (or have a spleen that doesn’t work) have lost one of their immune organs. That makes them more susceptible to certain infections, such as this one. They need to know that, and what it means to them (e.g. if you are bitten by a dog, you need antibiotics, regardless of the location or severity of the bite).

No one at the hospital knew I was missing my spleen.

Unless (until, hopefully) we have a universal medical record system that takes your health info with you, things like this get missed. Someone who’s undergoing chemotherapy and is immunocompromised is highly aware of their immunocompromised status, and is motivated to tell their healthcare providers and it might be more obvious to the healthcare team. Someone who lost their spleen years ago may have no outward signs and may not think about it (especially if they haven’t been adequately informed about the risks). Sometimes (often, perhaps) that big risk factor isn’t identified in Capno cases until very late in disease, after it’s diagnosed. (e.g. Dr: “This is a disease that occurs most often in people that have lost their spleen.” Response: “Oh, he lost his spleen in a car accident years ago.”)

No one asked about animal contact.

This is a major area of concern and one on which we’re not making a ton of progress. I get involved with lots of cases of various types of infections each year where the simple “do you have animals?” or “have you had contact with animals?” question would have likely lead to a quicker diagnosis. Sometimes, like with Capno, quicker might be the difference between eventual recovery vs lifelong consequences vs death. It’s an easy question but it’s not asked often enough.

I didn’t think to mention the bite (or other exposure, such as a lick over broken skin).

This is another weak link. If no one asks, people need to know to offer the information and to make sure someone’s paying attention to it. Too often, no one mentions it because it was a minor bite, and that can sometimes mean the difference between life and death.

Fortunately, infections from this bacterium are rare. Unfortunately, when they occur they are usually very bad. They’re also highly preventable with some basic understanding of who’s at increased risk and what to do. Like a lot of things, a little communication goes a long way.

More information about Capnocytophaga is available on the Worms & Germs Resources – Pets page.

‘Tis the season for travelling (ticks, that is)

Posted in Cats, Dogs, Parasites

A post from guest blogger Dr. Katie Clow, reproduced from our sister site www.petsandticks.com.

It’s summertime, and for most Canadians that means we’re taking some time off work to enjoy a little rest and relaxation. Maybe that’s a week at the cottage, or an adventure in another county. And if it’s a family trip, there’s a good chance your furry friend is coming along, too.

Not to put a damper on the situation, but in your trip planning, it’s a good idea to think about ticks and more broadly, disease risks to which your furry friend (and yourself) may be exposed when away from home.

Over the last few months, we’ve had several submissions of ticks from pets with international travel history. In June, we received two submissions from a dog that had been in Texas. One tick was a Gulf Coast tick (Amblyomma maculatum) and the other a brown dog tick (Rhipicephalus sanguineus). More recently, we had a submission from a dog that was in Myrtle Beach. Thanks to a nice photo that accompanied the submission, this tick could be identified as a Gulf Coast tick too.

Gulf coast ticks and brown dog ticks are rarely identified on dogs in Canada, and when they are, it is almost exclusively due to travel. In the case of the Gulf Coast tick, the risk posed is almost exclusively to the individual animal, as it is very unlikely for the tick to survive for a prolonged time in the environment. The brown dog tick on the other hand is a particularly nasty tick – it can survive and reproduce happily in a home or kennel and cause massive infestations even indoors!

With foreign species of ticks come different pathogen risks (and by pathogens, we mean bacteria, viruses and parasites). But it’s also important to remember that species of ticks that we commonly see here but have been picked up in a different county can transmit different pathogens. Take the example of the American dog tick, Dermacentor variabilis. We see this tick all the time in eastern Canada, but rarely do our resident American dog ticks carry pathogens (right now, anyways). The situation is completely different if you encounter this tick in the southern USA, where it transmits several pathogens, including Rickettsia rickettsii, the bacterium that causes Rocky Mountain Spotted Fever.

This story extends far beyond ticks and makes us think about other potential disease risks that our pets can encounter in different areas of the country, and the world.

So, what does this all mean if you want to travel with your furry friend? It’s as simple as being aware of the risks and taking the proper precautions (and in high-risk situations, leaving them at home).

It’s a smart idea to visit your veterinarian before traveling with your pet, whether this be local travel to the cottage or an international trip. That way you can make sure the preventative health care plan for your pet is appropriate. Parasite prevention and vaccinations are targeted towards the risks your pet may be exposed to on a regular basis, and adjustments can be made if your pet is going to be exposed to new health risks.

Happy travels.

KMC

Anti-vaccination and a fatal disease from horses

Posted in Horses, Other diseases, Vaccination

Being an equine vet in some parts of Australia (namely Queensland) is scary… to the point that people are leaving equine practice or refusing to treat certain cases. That’s because of Hendra virus, a bat-associated virus that infects horses and which can spill over into people. It hasn’t infected many people, but it is most often fatal, and it can be transmitted through regular kinds of occupational exposures when working with horses.

This disease is a good example of what can be done with vaccination. Even though it’s a small market, being a disease confined to one region of one country, a vaccine was developed and regulatory hurdles were lowered to get it to market as quickly as possible. That likely saved horses lives, and probably some human lives too in the process.

Yet, not everyone is as happy about the situation.  Despite a disease that is among the most deadly in terms of the percentage of infected people who die, there’s an anti-vax movement related to Hendra vaccine for horses. I’ll skip the synopsis, but click here to read the whole story about the situation on TheAtlantic.com. It’s worth a read, regardless of whether you’re in Queensland or have horses.

Image: Flying foxes are a type of large fruit bat found in Australia that can carry Henra virus and transmit it to horses.

Canine Leishmania map

Posted in Dogs

One of the first diseases that really hit home for me in terms of concerns about canine importation and travel was leishmaniasis. This nasty parasitic disease is something I certainly didn’t learn about in vet school, and it wasn’t on my radar at all until I started getting calls for help managing infected dogs.

As part of our new international disease mapping initiative, here’s our first Leishmania map. As with the other maps, it will presumably evolve over time as we get more information (including reports from readers). Soon, we’ll have the maps on a separate post or page for quick reference for all our mapped diseases, but for now, this map is below and you can click here for the interactive version.

Ontario hits 10 000 dRIT rabies tests since 2015

Posted in Other animals, Rabies

Today’s post comes from Rachel Gagnon, Rabies Science Transfer Specialist with the Ontario Ministry of Natural Resources and Forestry (MNRF), highlighting some of the amazing work being done in Ontario in the ongoing battle against wildlife rabies.

Ontario’s rabies control program is a world leader when it comes to controlling and eliminating rabies. The MNRF program was successful in eliminating the raccoon variant of rabies from Ontario in 2005 and has been highly effective in keeping the current rabies outbreak – which started in 2015 – contained to within about 50 km of the original case. The Ontario rabies program also reduced an epidemic of fox strain rabies from 46,000 cases (from 1957 – 1986) down to 0 by 2012 through the implementation of the large scale rabies program which began in the 1990s.

To control and eliminate rabies from Ontario, wildlife are vaccinated by two methods; trap- vaccinate-release, and by distributing oral rabies vaccine baits. Where these management techniques are used is informed through surveillance testing of dead or sick animals, enabling cost effectiveness response. The blend of these key elements is what has made the rabies program a success in the past and presently.

During the most recent Ontario outbreak, which began in December 2015, the MNRF implemented a new cost-effective test developed by the Centers for Disease Control (CDC) to assess large volumes of rabies samples in wildlife quickly and accurately. The method, called the direct Rapid Immunohistochemical Test or dRIT, has allowed for a new approach to assessing the most recent outbreak in Ontario. The MNRF has been using dRIT in conjunction with the Canadian Food Inspection Agency’s (CFIA) direct fluorescent antibody test (FAT), which has long been considered the ‘gold standard’ of rabies testing, but requires expensive fluorescence microscopy and specialized lab equipment. In contrast, dRIT uses a significantly more economical light microscope and can be done in relatively simple lab spaces. dRIT has allowed MNRF to test more animals and get results quickly and accurately to better assess the size and spread of the rabies outbreak and to make effective management and control decisions. [Image: MNRF staff test wildlife samples in the lab.]

This test has been a game changer in the global work of rabies control, and has played an important role in assessing where rabies is present and how it is moving across the landscape here in Ontario. As of May 2018, MNRF tested its 10,000th sample using dRIT, enabling Ontario to achieve unprecedented detail in the monitoring of the current rabies outbreak. During this most recent outbreak, 393 of the 405 (97%) rabies cases in Ontario have been discovered by the MNRF lab through the dRIT method.

When MNRF began implementing the dRIT test, knowing the accuracy of the test results was crucial. Beginning in 2016, research was conducted to validate Ontario dRIT test results against gold standard FAT results. In the study, agreement between rabies positive dRIT and FAT results was 98.8% and agreement between the tests for rabies negative samples was 100%. MNRF staff have since implemented two changes related to staff training and diagnostic determination, and have since been able to achieve 100% agreement of positive results between both tests.

Each week, the MNRF lab receives an average of 85 samples for testing from within the rabies surveillance area. Numbers will fluctuate depending on the time of year. The rabies surveillance zone is a buffer zone of 50 km around any rabies cases. Targeted mammal species found dead in the zone can be submitted to MNRF for rabies testing.

MNRF tests animals each week by creating a tissue impression of available brain tissue onto a microscopic slide. These slides are put through a series of chemical baths, and incubated with a rabies specific stainable antibody. Slides are viewed by light microscopy to determine the results. A negative test slide would show as all blue, if rose-red round masses are detected the sample is diagnosed as positive. Once MNRF has completed their testing, positive samples are shipped to the Canadian Food Inspection Agency for secondary FAT confirmation. [Image: left – positive dRIT result showing red specific staining; right – negative dRIT result.] When new cases of rabies are detected, MNRF notifies partners in the Ontario Ministry of Health and Long-Term Care, Ontario Ministry of Agriculture, Food and Rural Affairs and local public health units who will conduct follow-up investigations to ensure no members of the public had been exposed to the rabid animal. Rabies maps are also updated on the MNRF website weekly to reflect the number and locations of the new cases. [The maps are also reposted on the OMAFRA rabies website and on the OAHN website.]

Though human deaths from rabies in Ontario are rare, it is still a major global problem. The World Health Organization states that tens of thousands of people die each year from rabies, most often through canine exposure. dRIT was developed by the Centre for Disease Control and Prevention to provide a means to test animals for rabies in developing countries, where funding and infrastructure would prohibit the traditional standard and more expensive test. dRIT has proven to be such an important tool for the diagnosis of rabies cases all over the world that the test has very recently been approved as an official diagnostic test by the World Organization for Animal Health General Assembly.

For more information about rabies in Ontario, the rabies program, and to see updated maps visit the Ontario.ca rabies website.

Canine and feline antiparasitics

Posted in Cats, Dogs, Parasites

Negotiating the world of antiparasitics for dogs and cats can be daunting. With the wide range of products, similarly named products with different ingredients and differently named products with the same ingredients, it’s hard to keep up.

The Ontario Animal Health Network as put together some useful tables that outline antiparasitic products available in Canada and the parasites for which they have label claims.  There is a simplified version as well as a more detailed version specifically for veterinarians (Note: an OAHN login is required to access the more detailed version.  Veterinarians and veterinary technicians can sign up for free here.  OAHN membership also provides access to our quarterly network reports and the opportunity to contribute to surveillance efforts in companion animals through our quick, 5-minute quarterly online survey).

Label claims are the regulatory-approved claims of effectiveness that manufacturers are granted based on the evidence they submit. That doesn’t mean the product won’t work on other parasites or that all products with the same label claim work equally well, but products with label claims against a particular parasite have proven effectiveness.

The tables represent products and claims in Canada. While that’s pretty applicable internationally, some products may have different claims in different countries (not because their parasites are tougher or weaker, but mainly based on regulatory rules and what the company has asked for). As always, products and labels may change, and while we will attempt to keep up with those changes, the table should only be used as a guideline.  Owners should always consult their veterinarian and veterinarians should always check the label to ensure the product is right for the animal in question.