Worms & Germs Blog

Holiday bites

Posted in Dogs, Rabies, Vaccination

No, we haven’t changed to a cooking blog, I’m talking about bites of the canine variety. I can’t think of any specific data that would show it, but I wonder whether bites are more common around the holidays, with disrupted schedules and more visitors (and a potential midnight intruder in a red suit).

The rabies-related response to a bite is nothing new, but it still causes a lot of confusion so I’ll re-hash it here. Rules vary a bit (no pun intended) by jurisdiction so relevant personnel (e.g. public health, animal health) should be contacted,  but here’s the general response when a dog bites a person.

What’s the concern?

  • Rabies exposure from dog bites in areas where canine rabies is widespread (e.g. Africa, India, China) is a major concern. In other areas (e.g. Canada, the US), rabies is very rare in dogs. However, since rabies is almost invariably fatal in people, we don’t mess around. The immediate concern is to figure out whether the dog might have been shedding rabies virus in saliva at the time of the bite.
  • Rabies isn’t the only problem, as trauma from the bite and various other infections diseases are also of concern, but we’ll focus on rabies here.

What happens to the dog?

  • A 10 day observation period is pretty much universal. This can be a strict quarantine or less formal confinement, with the key being to keep the dog under control and make sure it’s normal 10 days after the bite.

What is the purpose of the observation/quarantine period?

  • Shedding of rabies occurs quite late in course of infection. The virus has to travel  through the body from where the dog was bitten, via nerves, to the brain, and then through nerves down to the salivary glands, at which point the dog becomes infectious to others. Therefore, by the time rabies virus can be shed in saliva, it’s already been in the brain for a little while. When it reaches the brain, signs of rabies develop pretty soon thereafter due to damage caused by the infection. So, if a dog is still neurologically normal 10 days after the bite, it would not have had rabies virus in its  saliva when the bite occurred.

What if the dog is vaccinated against rabies?

  • It doesn’t really matter. The vaccination status does not generally impact the response to a dog that bites someone (it does change the response if a dog is bitten by something else (e.g. fight with a raccoon) and is potentially exposed to rabies).
  • Rabies vaccination is very effective but given the severity of rabies, we can’t assume that it’s impossible for a vaccinated dog to have rabies.

What happens if the dog is not available for observation/quarantine?

  • If the dog can’t be identified and quarantined, you can’t rule out rabies. Therefore, it ends up being a discussion of the likelihood of rabies and whether post-exposure prophylaxis is indicated. Usually, the default is to treat it as exposure even if it’s very unlikely, since post-exposure prophylaxis is very effective and rabies is very bad.

What if the dog can’t be observed/quarantined?

  • If there’s a health or safety reason that quarantine can’t be done, euthanasia is indicated. This allows for testing of the animal’s brain, which is the only definitive way to determine if the dog had rabies at the time of the bite. Quarantine is preferred from a dog welfare standpoint, obviously, and it’s also best for the person in most situations. If the dog is alive and clinically normal in 10 days, rabies is not an issue. If the dog is euthanized, there is always the low (but possible) chance of an equivocal test, or, as I wrote about last year, a brain that gets lost in transit.

What else?

  • The big thing that often gets overlooked is consideration of why the bite happened in the first place. This is important to help prevent it from happening again.  It involves thinking about potential health or behavioural problems in the dog, poor supervision or poor handling on the part of the people involved. Bites shouldn’t be dismissed as an unavoidable consequence of dog contact.

Update: Canine influenza, Ontario (December 3)

Posted in Dogs, Other diseases

I’m once again prepared to call Ontario (and Canada) canine influenza-free… for now, at least. The latest cluster, associated with another importation of the virus from China, seems to have been contained.

The last new positive case was identified October 30, with the likely date of exposure being October 23. We are now beyond the 28-day shedding window that we use for H3N2 canine flu, plus some extra time tacked on to give us time to identify new cases that might have been exposed near the end of the last dog’s shedding period.

The apparent abrupt halt in new positive cases, within two weeks of the first case, once again shows how this highly contagious virus can be contained with quick identification (astute primary care vets), quick response (testing, contact tracing and communication) and responsible ownership (complying with requests to keep infected dogs away from other dogs).

Will canine flu come back?

  • Probably. It’s widespread in Asia and parts of the US. We import a lot of dogs from those areas.

Can we reduce the risk?

  • Yes. Quarantine and testing of new dogs after they have been imported from high risk areas is a fairly straightforward measure that is used too uncommonly.

What else about imported dogs?

  • We need to figure out more about the risks associated with importing dogs and how we can contain those risks. While I’d like to see importations decrease, I’m not naive enough to think that’s going to happen anytime soon, and at this point, I’d rather work with importers to reduce the risk. More on that soon.

Feline TB warning: Possible food link

Posted in Cats

A recent article from the Veterinary Information Network (VIN) News Service describes a strange cluster of feline tuberculosis (TB) cases in the UK, with a possible link to food. In cats, TB is rare and usually caused by Mycobacterium bovis, a bacterium most often associated with cattle and bovine TB. M. bovis is present in the UK and circulates in some wildlife species. TB can be a nasty disease, and without treatment, it’s fatal (in humans and animals). While potentially treatable, the prognosis is still guarded and months of antibiotics are required. There is also some (but poorly understood) risk to owners of infected animals, since M. bovis can infect people too. Cat-human infections are rare (or rarely identified) but it’s still a concern.

The cluster of cases in the UK is unusual for a few reasons:

  • One is that it occurred at all, since TB is cats is rare.
  • Another is that it affected young cats with no history of outdoor access. Typically, cats get infected outside from bites and scratches that occur when hunting.
  • All cats were fed the same brand of a commercial frozen raw diet.
  • Some of the cases were in cats living in low risk areas of the UK.

In cats, M. bovis usually causes skin and soft tissue infections, a testament to the typical route of exposure in this species (i.e. bites). However, the cases in this report had intestinal disease, characterized by signs such as weight loss, abdominal masses and diarrhea, consistent with exposure through ingestion of contaminated food.

Dr. Danielle Gunn-Moore of the University of Edinburgh is leading the investigation and emphasizes a few points:

  • Veterinarians in the UK should be aware of TB in cats, as infected animals may show non-specific signs of infection.
  • If TB is a possible reason for a cat’s illness, diagnostic testing should be performed ASAP.
  • Food history should be questioned in potential cases, with particular attention to raw diets.
  • Veterinarians in the UK that suspect they have a case of feline TB should contact Dr. Gunn-Moore.

Update: Canine influenza, Ontario (November 17)

Posted in Dogs

I’ve been behind on posts so here’s a quick update: things seem to be going well in the latest Canadian H3N2 canine influenza outbreak. Here’s the rundown:

  • After eradicating the last outbreak in the spring, cases were identified again in mid-October, associated with more importation of dogs from Asia.
  • The last new positive dog was identified October 30th.
  • All infected dogs that have been identified in the latest cluster have  close ties to the index site and have been from one area. One of these dogs left the region but has (hopefully) been kept quarantined for 28 days (as have the rest of the infected dogs).
  • Most of the infected dogs that we have been able to follow serially (i.e. test multiple times) are no longer shedding the virus.

We can’t call this over yet, since our last new case was October 30. Dogs can shed the virus for a few weeks after infection (even if they look healthy). Currently, we use 28 days as the potential shedding period. So, we’re looking at ~November 26 as the end of the window for the last known case. I tack on a week or so to give us time to find any cases that might have been infected at end of that period. Odds are quite low at this point that there will be more transmission from this outbreak, but we need a bit more time and testing to be sure. By early December, we can hopefully declare this over.

This is hopefully another example of our ability to eradicate this highly infectious virus with astute primary care veterinarians, quick testing, good communication and responsible owners who will quarantine infected animals. I’m always wary of speaking to soon (or jinxing it), but it’s important to know this approach can be successful. It’s not often done (explaining why flu continues to spread in some regions) but with some effort, diseases like this can be contained.

At the same time, the effort required and the potential for such a virus to spread beyond our control can’t be ignored. That’s why we need to be careful when importing dogs from areas where canine influenza is widespread.

Update: Canine influenza, Ontario (October 30)

Posted in Dogs

Things have been quiet over the past few days. That’s good news (but always makes me a bit antsy, because I want to be sure it’s because there are no new cases vs we’re just not finding them). Documented infections have been confined to one region, with the exception of a dog that travelled out of the area, and which is (hopefully) being kept under quarantine for 28 days at its new location. We’re still testing and getting negative results, and veterinarians in the area are still looking out for potentially infected dogs, so hopefully the situation is being contained. The next week or so will tell us more, as we continue to test and as initially infected dogs start to eliminate the virus.

At a minimum, we want to go 35 days or so after the last new infection before we say we might be in the clear again. Since some dogs can shed the virus for over 3 weeks, I use 28 days as the upper end of the shedding period. I then tack on an additional week, since it takes some time for a newly exposed dog to get sick and be tested. So, if our last known dog was infected Oct 23 (to pick a random but reasonable date), it could shed until Nov 20. Add on a week, and we get to Nov 27. If there are no new cases by then and we still have excellent surveillance by vets and dog owners, we would suspect that the virus has again been contained. If we find any new cases, the clock restarts each time. (I hesitate to write about containment at this point because it sounds like I’m inviting bad luck, but I get a lot of questions about this).

To contain the current cluster of canine influenza we need:

  • Continued diligence by veterinarians and dog owners
  • Continued testing of exposed dogs and any other suspected cases
  • Compliance with quarantine recommendations so infected dogs don’t pass on the flu to other dogs

So far, so good, but time will tell.

Raw pet food and human salmonellosis

Posted in Cats, Dogs, Salmonella

We’ve known for some time that there are human health risks from feeding pets raw meat-based diets. Most of the evidence of this has been anecdotal, as published reports have been sparse. A few better documented reports have started to appear, including the fatal E. coli O157 infection I wrote about recently.

A few days ago, the CDC released a report about an outbreak of Salmonella Infantis infections in the US. It involved 92 people from 29 US starts and was linked to raw chicken products. Raw chicken-based pet food was among the raw chicken products from which the outbreak strain was isolated, and one person got sick after their pets ate chicken-based raw food.

This isn’t particularly surprising since Salmonella contamination is an inherent risk with raw poultry. Human disease can occur when people ingest Salmonella from undercooked meat or from contamination of their hands or environmental surfaces (e.g. in the kitchen). When it comes to raw pet food, people can be exposed from handling the food, cross contamination of food or surfaces, contamination of the food bowl or exposure to Salmonella in in feces of the pet.

CDC’s recommendation is pretty straightforward: “CDC does not recommend feeding raw diets to pets. Germs like Salmonella in raw pet food can make your pets sick. Your family also can get sick by handling the raw food or by taking care of your pet”.

I have the same recommendation, but am realistic enough to know that it’s still going to be done by some people. It definitely shouldn’t be done in households with very young, very old, pregnant or immunocompromised people or animals.

If you are going to feed raw diets to your pet, do it wisely. More information about this is available on the Worms & Germs Resources – Pets page.

Update: Canine influenza, Ontario (October 25)

Posted in Dogs

As expected, a few more cases have been identified in the most recent cluster of canine influenza virus (CIV) identified in Ontario. So far, there are about 20 confirmed or suspected cases. To date, we’re still only finding cases that have a link to another infected dog or facility. That’s good news. If we start getting cases of unknown origin and/or cases outside the currently affected area, I’ll be more concerned (specifically about the prospects of containing the cluster). A couple of dogs that were potentially exposed and left the area already are being tracked.

Continued diligence by pet owners and veterinarians will help contain this virus. The key is finding all the potentially infected (and infectious) dogs, testing them and keeping them quarantined until they’re no longer a risk to others.

A 28 day quarantine is recommended because of the potentially long shedding period of this virus. In the previous outbreak (as in this one), we sampled positive dogs repeatedly, and some shed the virus for over 3 weeks. So, even a 28 day quarantine doesn’t leave a lot of cushion, but the longer the quarantine period, the greater the risk of non-compliance. Getting people to keep their dogs away from other dogs for 28 days often isn’t easy to do. We like to complain about the weather in Canada, but it will probably help in this situation. It’s forecast to be few degrees above freezing with mixed precipitation over the next few days, something that may help keep dogs from congregating outdoors, buying more time to sort out the problem.

More details to follow.

CDC didn’t actually say “don’t dress up your chickens for Halloween”…but don’t do it anyway

Posted in Other animals, Salmonella

Lots of media reports have been saying that the US Centers for Disease Control and Prevention have warned people not to dress up their chickens for Halloween.

  • Yes, chickens.

I wouldn’t have thought that policing chicken fashion would be high on the CDC’s to-do list, but the concern is obviously related to the perpetual outbreaks of salmonellosis linked to chicks and pet poultry.

Did CDC actually say it?

  • No.

Does that mean they disagree?

One concern is the risk to chicken owners. A bigger concern is the likelihood that a fashionably dressed chicken out for Halloween would be encountered and handled by many other people, particularly young kids (a high risk group for infection with Salmonella).

If you want to dress up your chicken for Halloween, go for it, I guess. Just wash your hands and keep others away, or at least make sure they also wash their hands after touching the chicken.

Basically, handle bespoke chickens like raw chicken – you don’t need to run screaming from the room, but do take some basic precautions to reduce the risk of contamination (of yourself and other surfaces or objects) and wash hands (or use a hand sanitizer) to get rid of any harmful bacteria that are transferred.

Image from: https://www.dailymail.co.uk/health/article-6307585/CDC-warns-against-dressing-pet-chickens-Halloween-costumes-salmonella-fears.html

Raw pet food and human illness

Posted in Cats, Dogs

Human health risks from raw pet food (either from exposure to pathogens in the food or in the feces of pets eating the food) are known to exist but they’re not well characterized. We know that dogs fed raw meat-based diets clearly have increased risk of shedding various pathogens, particularly Salmonella and multidrug resistant E. coli. We know this results in some degree of disease risk in animals and in humans, but the scope of the problem is poorly understood. A recent report from Public Health England provides some more information about the risks associated with feeding raw pet food.

The report is about four people who were infected with E coli O157, a particularly nasty strain of E. coli that can cause serious disease in people.

  • One person developed hemolytic uremic syndrome (HUS), a particularly severe consequence of infection, and died.
  • The four cases involved the same strain of E. coli O157. Three individuals had been exposed to dogs fed a raw meat diet. Tripe was the specific ingredient that was implicated.
  • Samples of raw pet food were collected for testing. All samples from one raw pet food producer were positive for STEC (shiga toxigenic E. coli, the group to which E. coli O157 belongs). A positive test was also obtained from the freezer of one of the affected individuals, and from one sample of raw tripe. It strain isolated from the tripe was a different from the outbreak strain but supported the notion that tripe might have been the cause. It’s not surprising that they couldn’t isolate the outbreak strain from the food, given the lag from the time of exposure of people to the time of sampling of pet food. Contamination is probably sporadic, with different strains contaminating different batches.

Feeding raw meat-based diets is popular, but associated with risks to pets and people (have we said that enough times yet?). My preference is for it not to be done, but I’m realistic enough to know that people are going to do it anyway. So, I focus on two things:

  1. Who should definitely NOT feed raw meat to their pets?
    • Households where pets or people are at increased risk of severe disease, including those where young, old, pregnant or immunocompromised individuals (human or animal) are present.
  2. If raw meat is to be fed, how can the risk be reduced?