Search results for: dog respiratory

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There’s still not really a lot to report with the current canine infectious respiratory disease situation in North America, which is probably good news. As ever, we’re largely flying blind because we have no coordinated surveillance for canine infectious respiratory disease, so we’re try to figure out as much as we can through a variety of sources.

Current status:

The hype is dying down. We’re seeing a far fewer reports of disease in dogs, and I’m getting fewer calls from veterinarians. The question is whether that’s because there’s less disease, or because people have gotten bored with reporting or have simply adapted to the current situation. The news cycle is pretty short, as are attention spans, so in the absence of fairly dramatic changes, social media and traditional media usually move on fairly quickly. My somewhat educated guess is that we still have an elevated baseline level of canine infectious respiratory disease complex (CIRDC)(which has been gradually increasing over the last couple of years), and some local outbreaks (as we always have), and decreasing rates of CIRDC in places that reported higher numbers this past fall. Those are all things we expect with the normal waxing and waning of endemic disease.

Where is this disease present?

CIRDC is everywhere, as always.

I get a bit annoyed seeing reports about “the disease” being present or absent in a particular area or those that try to give it a new name like “atypical CIRDC.” Canine infectious respiratory disease has been around as long as dogs have been around. Various respiratory viruses and bacteria are circulating in the dog population all the time, everywhere. When people ask “is it here?!” they’re really referring to an increase in CIRDC (or an increase in awareness of it), not introduction of some specific pathogen. Maps showing where the disease “is” cause confusion, and they’re purely made up.

Increased rates of disease absolutely occur in different areas at different time. When that happens, sometimes it’s missed, sometimes it’s high profile. Almost invariably, rates come down again after a few weeks, as things revert to normal.

Is there a new “mystery virus” causing disease in dogs?

Many good laboratories are doing deep sequencing to look for any new pathogens. The longer we go without anyone reporting something potentially relevant, the less likely it is that something new is involved. It’s possible that (but would be really disappointing if) a laboratory has found something they’re not reporting, but given the number of laboratories that are working on this, if there was a widespread new virus, I’m pretty sure we’d know by now.

My theory is still that the increase in CIRDC is being caused by our regular respiratory pathogens (e.g. canine parainfluenza virus, Bordetella bronchiseptica, canine respiratory coronavirus, canine pneumovirus, Mycoplasma) doing their regular things, just at higher levels in some areas.

What about that weird Mycoplasma-like bug from the laboratory in New Hampshire?

Not much new has been reported on this finding either. It’s good that they’re still working on it, but we’re not hearing similar reports from other laboratories, so it’s probably not a key player. If this bug is a cause of disease in dogs, I’d guess it’s something that’s been a cause of disease all along, but we just didn’t know about it, versus it being a new organism that’s emerged and is spreading in the dog population.

Do our “kennel cough” vaccines still work?

Yes (and no). We have good mucosal (i.e. intranasal, oral) vaccines for some respiratory pathogens in dogs that work quite well. The problem is that they don’t work against all causes of canine infectious respiratory disease. We have vaccines that will cover one or more of Bordetella, canine parainfluenza virus and adenovirus; while they don’t protect against other pathogens, protection against those three is important (especially the first two).

We also have a vaccine against canine H3N2 influenza virus. It’s been in short supply because of production issues over the past couple of years. Canine flu is a sporadic (but locally dramatic) cause of disease in dogs in the US. Like any flu vaccine, the canine flu vaccines are moderately effective and best for prevention of severe disease (versus prevention of infection), and are lower on my priority list for the average dog.

What do we do now?

  • Dog owners should relax. Think about your dog’s exposure risk and susceptibility to severe disease, and make some modifications to their routine if indicated. Talk to your veterinarian about respiratory disease vaccines. And did I mention relax?
  • As for me – Wait. Watch. Continue to collect as much data as we can. Continue to try to walk the fine line between increasing peoples’ awareness of CIRDC and avoiding paranoia/panic.

Why don’t we have a good canine disease surveillance system?

Money, specifically lack thereof. That’s not the whole issue but it’s a lot of it. The broader issues include:

  • Animal disease control and regulation has historically been developed for food animals. Animal health is usually under the purview of agriculture or food safety agencies. So, there is often little or no mandate to cover companion animals, and less expertise. There are often inadequate resources to cover core mandates with livestock species, let alone something peripheral like dogs. It’s not that these groups aren’t interested, it’s mainly that they don’t have the time, staffing or mandate to do much.
  • Limited veterinary infectious disease expertise. The veterinary infectious disease world is pretty small. There aren’t many of us and we have a finite degree of bandwidth.
  • Testing for CIRDC is scattered amongst various private, academic and government laboratories. Those system aren’t currently able to communicate effectively, and there are often various barriers to data sharing.  For effective surveillance, we need a coordinated, real-time system with integration of data across these sources. That’s probably a long way away.
  • There’s very little funding for companion animal infectious diseases, both for surveillance systems and targeted research. I think we get a lot of bang-for-buck with the limited money that flows to the area, but it’s really hard to get any money to investigate things like this. That means we don’t get the data we need and we don’t train more experts in the area.
  • Detailed study of disease situations like this requires collaboration with primary care veterinary clinics. That’s really tough because of the workload that they currently have – they’re swamped. Adding more work (usually unfunded) isn’t something for which most clinics are up, at least on a long-term basis. We can get little targeted studies done with some clinics, but it’s hard to do the broad work that’s needed with financial and IT support to make it viable over time.  

Am I optimistic or pessimistic for where we’ll be with CIRDC heading into 2024?

I’m fairly optimistic. I’ve felt this situation was overblown from the start, with some real disease issues over-amplified by media and social media. I’m not dismissing the real impacts in some areas and on some dogs, but I’ve never been convinced that we have a massive, broad outbreak. There have been real impacts, real concerns, as well as excessive fear, and there’s been a lot of good work done trying to sort this out. Increasing awareness about CIRDC in dogs and disease prevention is always good. As we head into 2024, hopefully we’ll see a continued die-down in reports of (and actual) disease, and improvements in infection prevention.

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Spoiler alert: there’s not a lot new to say about the ongoing situation with canine infectious respiratory disease in North America. Most of this I’ve said before. Talk seems to be dying down in a lot of areas, but whether that’s because there are fewer cases or people are just getting bored of talking about it is unclear. It’s probably a combination of both. Based on some data I posted last week and talking to people on the ground in different regions, it seems like most areas that have had a (real or perceived) increase in canine infectious respiratory disease complex (CIRDC) cases are returning back to baseline. Presumably, there are some other areas where disease is ramping up, as usual. However, there are still a few questions worth bearing in mind at this stage:

Is this really an outbreak?

I’d say it’s not so much an “outbreak” as a gradual increase in the incidence of CIRDC over the past couple of years, with typical periodic spikes of disease superimposed over top of it. We have fairly clear evidence of more cases in some areas, usually following the typical outbreak pattern where cases go up, then return back to baseline levels. We also have areas where there’s really nothing too different happening.

Is there a “mystery virus” causing the increase in cases?
This is commonly reported in news headlines, but there’s no evidence of that. There’s a lot of viromics work underway, where they sequence any and all viral bits present in a sample to look for anything new. Since nothing has been found (or at least reported) thus far, it’s becoming less and less likely that there’s a new virus causing any substantial number of cases. I’d also expect a bit of a different disease pattern with a new, highly transmissible virus. More time and more testing will provide more details but at this point, I don’t think we have a reasonable suspicion of a new pathogen.

What about that strange little bacterium reported by the lab in New Hampshire?

This bug needs to be investigated more, but it’s not looking like a leading candidate at this point. It hasn’t been found to be a potential important cause of respiratory disease elsewhere (although I’ve only heard of one place that’s said they’ve looked and failed to find it). We need to learn more about this bacterium, but I’d guess that it’s either just part of the normal bacterial microbiota in dogs or it’s a potential cause of disease that’s been around for a long time, we just didn’t know (and therefore didn’t test for it). I doubt it’s a new bug that’s just recently emerged and spread in dogs in North America.

Are the reported cases of CIRCD more severe?

I don’t think so. Concerns about severe disease in dogs are probably more of a media effect. With typical CIRDC, we expect a small percentage of dogs to get pneumonia, and an even smaller percentage to have serious disease and die. That’s always been the case. When the number of dogs with CIRDC goes up, the number of dogs with severe disease will go up proportionately. So, we’d expect to see more cases of severe disease when we have an more cases during outbreaks, not because the disease itself is more severe, but simply because there’s more overall illness. If we have 100 dogs with CIRDC, we’d expect maybe 1-2 severe cases. If we have 1000 dogs with CIRDC, our severe case numbers jump to 10-20, even if the disease itself is no different.

What about treating dogs with CIRDC with Paxlovid?

Ugh. Horrible headline writing has driven requests to use this drug in dogs with CIRDC.

Please don’t.

We have inadequate dosing data and little understanding of safety for Paxlovid in dogs, and no evidence that its use is necessary (or effective) in any of these cases

What about treating dogs with CIRDC with chloramphenicol?

UGH X2. Chloramphenicol is an antibiotic. It’s a great drug, but (as for all antimicrobials) should only be used when it’s really needed. This drug has fairly important animal and human health risks (even just handling the drug), so we should not be using it routinely; however, if I have a multidrug-resistant bacterial infection in an animal, and chloramphenicol appears to be the best option to treat it, I’ll use it. Standard treatments still apply for routine cases of CIRDC. If we start using Paxlovid and chloramphenicol routinely (be it out of fear, panic or just the desire to do “something”), I have little doubt that we’ll harm more dogs than we’ll help.

Is “kennel cough” vaccination in dogs worthwhile?

Yes. We have good vaccines against canine parainfluenza virus and Bordetella bronchiseptica, two important causes of respiratory disease in dogs. Protection is much better with “mucosal” vaccines that are given directly into the nose or mouth, so that’s the kind we want to use routinely for these pathogens. The vaccines won’t protect against all types of infectious respiratory disease, but reducing the risk of some major ones is still very helpful. Intranasal and oral vaccines are given once, then re-dosed annually. There’s currently nothing indicating we should re-vaccinate dogs more frequently than this.

Are some dogs at increased risk of infection with respiratory pathogens?

Risk of infection depends heavily on risk of (and amount of) exposure. Dogs that encounter a lot of other dogs, especially transient groups of dogs of unknown health status, are at increased risk of pathogen exposure. The more dogs encountered, the closer and more prolonged the contact, and the less certain the health status of the dogs involved, the greater the risk.

Reducing the overall number of dog contacts, particularly contacts with groups of dogs of unknown health status (e.g. random groups of dogs at an off-leash park, versus a small consistent group of known dogs at a day care or play group) is an important control measure.

Are some dogs at increased risk of severe respiratory disease?

Generally yes. We know there are some dogs that have a greater risk of severe respiratory disease or death if they get infected, so we want to be extra cautious with them, including avoiding exposure, vaccination and getting them to a veterinarian sooner if the dog gets sick. High-risk dogs include older dogs, very young puppies, dogs with pre-existing heart or lung disease, dogs with compromised immune systems, and brachycephalic breeds (i.e. flat-faced breeds like bulldogs).

Why might CIRDC rates be increasing?

It’s just a guess, but we could have a pandemic-associated confluence of factors that have led to more dogs with greater susceptibility to respiratory infection.

Changes in how we have interacted over the past few years, and how often dogs go to kennels or daycare (which is often the trigger for getting a kennel cough vaccine) could plausibly have reduced overall vaccination coverage in the dog population. Also, if fewer dogs were exposed to respiratory viruses over the past few years, there may be more dogs that are susceptible to them now. I try to stay away from the “immunity debt” discussion, since that’s more political than scientific, and it’s triggering for some people (my inbox is a testament to that). Nonetheless it’s quite logical that less immune protection from less vaccination and less infection over the past couple years could mean more susceptible dogs. It’s not “debt,” it’s just deferred exposure.

From a severe disease standpoint, changes in the popularity of different dog types could be playing a role too. The French bulldog, a higher risk breed, is now the most popular dog in the US. That’s plausibly going to increase the number of cases of severe disease just based on numbers.

What should the average dog owner do?

  • Breathe. This is not a doggie plague sweeping across the nation.
  • Consider your dog’s risk of exposure and whether you can do things to reduce it, while not being unnecessarily disruptive to life in general (e.g. if your dog needs to go to day care for you to work, send your dog to day care).
  • Consider your dog’s risk of severe disease when deciding whether to change your behaviours and how much to change.
  • Talk to your veterinarian about respiratory disease vaccines.

In situations like the ongoing concern with canine infectious respiratory disease complex (CIRDC) in the US, where we don’t have any semblance of a surveillance program, we can sometimes try to piece together the picture using different data sets and observations; insurance claims can be a valuable part of this. At our webinar on canine respiratory illness earlier this week, we were able to present some preliminary data based on pet insurance claims through Trupanion. The data are biased, since insured dogs are only a small subset of the whole dog population, but they can still be informative (especially when we don’t have much else on which to go).

The full video of the webinar, along with some other resources, is available on the Trupanion website, but I’ll give a snapshot of the of the data we presented. We’re working on more and hopefully will be able to piece together a more complete story with more data over time.

Here are few interesting slides from the webinar:

This graph shows respiratory disease claims from January 2021 to October 2023:

  • We’ve had a gradual but pretty impressive increase in respiratory disease claims over the past 2 years. Note that these data are adjusted for changes in insurance patterns, such as increasing numbers of dogs with insurance policies. This fits with my general observation from this time period that we’ve been seeing more disease, but not a sudden dramatic boom.
  • We see general ups and downs.
  • We’re at a high point now, consistent with recent concerns.

The map below is important. It shows states and provinces where there’s been an increase in respiratory disease claims year-over-year from August to October in 2022 vs 2023:

  • High rates of claims were/are present in some areas where there’s been a lot of buzz.
  • Some impressive increases have been seen in areas where we’ve had less buzz. I always get questions from Ontario veterinarians asking if we’re seeing more CIRDC cases, but I’d say it’s not much more lately than anytime over the past few years. Most often, I get asked “is that thing that’s going on in the US going to hit us here?” I think this map shows that we can’t just focus on media/social media reports to tell us what’s happening, because they can over-amplify issues and at the same time, some things might fly under the media radar.
  • Claim rates haven’t changed in most areas, though. We’re not seeing something sweeping North America, we’re seeing patchy disease. That fits with my current guess as to what’s really going on (see details below).

Oregon’s an interesting state to look at as an example. This graph shows canine respiratory-related claims in Oregon from 2021-2023, which demonstrates a typical epidemic curve with a nice increase followed by a corresponding decrease in 2023:

  • There was clearly something going on earlier this year. It didn’t seem to get much attention until it was already on the downswing, though. Talking to a few different people in Oregon, the perception seems to be that things have died down over the past month or two, and that’s consistent with the data from this graph.

This graph compares canine respiratory disease claims in California and Oregon for the last few years:

  • California has had an increase in respiratory disease claim rates too, but the pattern looks different. While Oregon had a big peak and then a return to the increasing baseline, California has had a gradual but sustained (and impressive) increase over time, eventually reaching about the same rate as Oregon overall.
  • Does California have more of a well-distributed higher rate of disease? Or, since California is a big state, have we had rotating outbreaks in different areas that end up looking like a steady increase? We’ll need to do a deeper dive on the data to figure that out. The graph shows that something’s going on in California too, but maybe in a different manner than in Oregon.

Let’s jump to some Canadian content. Here’s the graph of canine respiratory disease claims in Quebec from 2021-2023:

  • This one surprised me. I’ve been getting questions about CIRDC cases in Quebec but nothing that stood out as unusual. (Maybe there’s more in the French-language media than I’ve been seeing.)
  • The total number of claims is still relatively small, so we have to be careful not to overreact, but that’s a pretty big percentage increase.
  • The time frame is also different from the Oregon peak. There’s always a bit of a lag with insurance report data, so we can’t say whether this has hit its peak in Quebec yet, or if it’s still increasing or if it’s already on its way down.
  • Regardless, the pattern fits with something that’s been going on recently and is possibly ongoing. We’ll have to see how the numbers trend over the next few weeks.

When it comes to other factors that might increase insurance claims, we have to consider the influence of recent media attention. If a dog had mild respiratory disease (e.g. cough, runny eyes but eating well and otherwise pretty healthy), it might not normally be taken to a veterinarian. However, if the owner is freaked out because of all the news coverage about CIRDC, they’re more likely to take that dog to a veterinarian now versus in previous years. Those cases then end up in an insurance dataset like this (or in a testing dataset from a laboratory) because of owner factors, not dog or disease factors. One way to help tease this out is to look atmore expensive claims, or claims that involve things that would only be done on sicker dogs (eg. oxygen therapy). Our preliminary look at those data showed similar but more blunted trends in terms of increases in some areas, gradual increases over time overall, and no change in most regions. So, the increases we’re seeing in overall claims are probably pretty reflective of true changes, though likely with some fear-driven (vs disease-driven) increases.

Other things we need to consider are what types of dogs seem to be over-represented, beyond regional effects. Preliminarily, claims involving brachycephalics (squish-nosed breeds) seem to be significantly more common, which isn’t overly surprising as these dogs may have less tolerance of any form of respiratory disease. More to come on that.

What’s driving severe disease is also really important. Mild respiratory disease isn’t ideal, but we’re more worried about pneumonia and severe illness that can make dogs really sick, result in high veterinary bills, and kill a small percentage of dogs. Brachycephalics, senior dogs and dogs with pre-existing heart or lung disease are probably at higher risk for severe disease, but we need to look at the data more to confirm that.

Where does this take us?

As we get more data, look at disease patterns over time and locations, and talk to more people about what they are seeing, I’m increasingly convinced that this is a situation of the usual suspects (our normal CIRDC pathogens) doing their usual thing (mild disease in most dogs with a small subset that get pneumonia and a small subset that get really sick), but at a higher rate. I think the rate has been increasing for a while, which makes the normal ups that we see with waxing and waning disease more obvious. I think it’s clear that we’ve had true increases in disease in some areas, but not all, and that clusters are following the typical course of “what goes up, comes down.” Media attention is amplifying the concern, so that we’re hearing more about a lot of things we wouldn’t normally, but there’s a true disease underpinning to those reports.

Why? What is driving the increase in disease rates?

The “why” is unclear, since we still don’t really know the “what” well. When I think about what drives increased disease, I focus on dog factors and bug factors. We have various logical reasons why this increase could be driven largely by dog factors. For example, in the past few years, we’ve seen:

  • More dogs
  • Disrupted veterinary care (less vaccination)
  • Changes in human activities (e.g. more remote work, maybe leading to fewer dogs at day care and therefore less kennel cough vaccination)
  • Other changes in human activities that alter how dogs interact
  • Changes in the types of canine respiratory disease vaccines we use
  • Earlier pandemic restrictions reducing the normal level of exposure to kennel cough pathogens and vaccination

The net result would be an increase in dogs with less immunity from vaccination or previous infection.

For bug factors, I think about the possibility of:

  • A new pathogen
  • An existing pathogen that’s changed

We don’t currently have any clear evidence of either of these bug factors. The story about a previously unknown small bacterium that has been found by the New Hampshire veterinary diagnostic laboratory is still worth investigating, but at this point it’s not clear that it’s driving anything. If this bug turns out to be a pathogen in dogs, most likely it will be a “new to us pathogen” versus a “new pathogen” scenario. By that, I mean that it’s more likely that it’s a longstanding cause of disease that we’ve never diagnosed before, versus a new bug that’s recently emerged and is starting to spread. The current disease patterns don’t really fit with emergence of a new highly transmissible pathogen.

I’m open to new evidence and other opinions, but at this point, if I had to make a somewhat informed guess, I’d go with the assumption that we have patchy but significant increases in disease in some areas across parts of North America, but driven by our normal bacterial and viral causes.

We also have to avoid over-interpreting the insurance claim data, since it’s just one piece of the puzzle, albeit a potentially important one. Everyone always wants definitive answers “now,” but that’s not how outbreaks or outbreak investigations go (especially outbreaks in dogs where we have almost no funding for formal surveillance or analysis of any kind).

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There’s a lot of concern about respiratory disease in dogs at the moment, so it’s a opportunity time to revisit some routine preventive measures that we really should be using all the time (but unfortunately sometimes fall by the wayside). This post focuses on precautions for dog groomers, but really it applies to a broad range of places where dogs go.

Infection control is typically pretty straightforward and boring (which is why it often gets neglected). There’s nothing really fancy and it’s mostly pretty low tech – mainly a matter of using some good general practices and a solid dose of common sense.

With canine infectious respiratory disease complex (CIRDC), the main transmission concerns are from direct contact between dogs, contact with oral/nasal secretions (e.g. shared bowls, licking the same spot soon after another dog) and respiratory aerosols (from coughing, sneezing, heavy panting etc.). There is always a risk of disease transmission at dog grooming facilities, regardless of whether there’s an outbreak going on in the area or not. Various diseases are always circulating in the dog population, and sometimes we can’t tell when an animal is infectious to others, so we apply routine infection control practices in all situations, and increase those when we identify increased risk.

Some routine, every day infection control practices include:

  • Communication so owners know not to bring sick dogs to the groomer. If clients are being called or emailed with appointment reminders, add a statement about cancelling if the dog is sick. (Sound familiar? Lots of what we did for people during the pandemic can also be applied for control of disease transmission in dogs).
  • Business practices that don’t encourage owners to bring sick dogs (e.g. no charge if someone cancels at the last minute because their dog is sick. Yes, a policy like that can be abused, but we don’t want incentives for people to bring in a sick dog).
  • A housing setup that keeps dogs separated. At a minimum, we want no (or very limited) direct contact between dogs.
  • Good ventilation, such as having an in-room HEPA filter or two, especially in dog housing areas.
  • Routine use of personal protective equipment. Ideally, groomers should wear something over their street clothes that’s easy to change if it gets contaminated. If street clothing or scrubs are the only layer they’re wearing, it’s important to have a change of clothes handy. However, it’s easier and better to immediately take off a lab coat, smock or gown than it is to go go somewhere to change clothes completely.
  • Hand hygiene, such as washing hands or using a hand sanitizer between animals.
  • Cleaning and disinfection of areas and shared equipment between animals. Any routine disinfectant should work against typical canine respiratory pathogens, but I always like to use as good a disinfectant as possible. If you can get it, I’d use an accelerated hydrogen peroxide (AHP) product.

Routine stuff is, well, routine. It’s not rocket science (and pretty boring in the end) but it’s the core of good infection control. However, we also need to have a plan for higher risk situations. Ideally, this plan is written out and communicated to everyone in the facility before a situation happens, so it can be implemented by everyone without delay or confusion. Human factors are usually the biggest problem when we see infection control breakdowns.

How to respond to a dog with respiratory disease at a grooming facility

Even with good use of routine practices, it’s possible for a sick dog to get in once in a while. Sometimes people don’t realize or don’t care that their dog may be infectious, and it’s not always obvious as they walk in the door. There are generally two main scenarios:

1. Sick dog is identified as it arrives

 This one’s easy. Ask the owner to take the dog home right away. If there’s a need to discuss anything, ideally the dog should be removed from the facility and the discussion is done by phone. Otherwise, the discussion could take place outside, or inside after the owner puts the dog in a vehicle (if it’s safe to do so). While this is happening, attention should be paid to any other dogs in the vicinity, to keep them away from the sick dog.

There’s not a lot to do with the airspace by the time this happens. Aerosol transmission is the main concern here, and that’s only for a short period of time and over short distances. The risk of something wafting around the building in the air for a long time is low. The pandemic taught us the importance of good ventilation and air filtering, so it would be ideal if there was already a well-ventilated space and a HEPA filter running to further reduce the risk.

Any personnel that had direct contact with the dog before it was removed should change their outerwear and wash their hands.

The general environment is probably fairly low risk but it’s not zero, especially surfaces the dog may have licked, nosed or coughed/sneezed on. Disinfecting those surfaces ASAP would be wise. Having a spray bottle with disinfectant handy is good for many things, and would help speed up the process here too.

If the owner wants to reschedule, we don’t have a good handle on how long to wait, since we won’t likely have a diagnosis for the dog. Waiting a month would be ideal. It’s not a guarantee that the dog won’t still be shedding something, but we’re trying to balance protection and practicality. At a minimum, I’d want to wait two weeks before the dog comes back.

2. Sick dog is identified after being dropped off and the owner leaves

This creates challenges since “get the dog out ASAP” may not be an option. Owners should be contacted to pick up the dog as soon as possible. While waiting, the dog should be kept in an area away from other dogs. Ideally, every facility should have an area to isolate high risk dogs. It doesn’t need to be an isolation unit like in a veterinary clinic, but there needs to be a plan for housing dogs with respiratory disease, diarrhea or other things that get flagged as a concern after drop off. This could be a separate room, or even a well-ventilated storage room or closet, that can hold a crate. The idea is to get as much physical separation between the sick dog and other dogs as possible.

When we can’t physically isolate the dog, we try to contain it as much as possible and use procedures to reduce cross-contamination risks:

  • Keep the dog as far away from others as possible.
  • Position the dog such that there’s limited airflow toward other dogs (e.g. if there’s a window or fan blowing, make sure the high risk dog isn’t upwind).
  • If there are banks of cages, keep the sick dog on the bottom.
  • Put a blanket or something similar over the cage front to reduce aerosol spread.
  • Avoid handling the dog as much as possible. If you have to handle it, either put on single use (disposable or direct to laundry) outerwear like a gown and use gloves. Wash your hands after removing gloves when you’re done.
  • When the dog leaves, disinfect any items in the cage (e.g. bowls), launder any blankets/towels and disinfect the cage.

It’s all pretty basic, but basic is effective if done right.

I’ll write more about where we stand with the ongoing CIRDC situation, but it is a good reminder that we should be upping our routine infection control game.

As concerns about an outbreak of canine infectious respiratory disease in the US continue, we’re still at a point where media hype massively outweighs any true data. Not much new has been reported recently. If anything, I’d say we’re hearing more about things being stable in different areas, that investigations haven’t turned up anything beyond the usual suspects, and the typical messaging to use common sense but relax.

One thing that is getting some press is a suggestion that a rather bizarre little bacterium might be involved in some of the current canine illnesses. “Might” is the key word though. At the risk of having to eat my words later, I’d guess this bug is probably not going to pan out to be a driver of widespread disease – it’s possible, but there’s a long way to go before we can say that with any confidence. In the meantime, let’s recap what we know:

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In the spring of 2023, the New Hampshire Veterinary Diagnostic Lab reported they were investigating a potentially novel organism as a cause of respiratory disease in dogs. I remember reading about it in a taxi on my way to the airport in DC; I thought it was interesting, but in my experience, the vast majority of “new pathogens” end up being commensal organisms (i.e. also present in lots of healthy dogs) or otherwise not panning out to being relevant. But, I never totally discount the possibility, and was glad to see it investigated. The initial (and I think only) report involved a pretty small number of dogs. They found snippets of DNA that were similar to IOLA KY405 in 21/31 samples. Their latest update is here.

What on earth is IOLA KY405?

It’s hard to say. As far as I know, it’s only previously been reported in two papers from the same lab in Japan, where it was found in samples from humans with respiratory disease. It’s reported to be a bacterium with a very small and bizarre genome.

  • The first study (Fukuda et al. 2014) reported finding gene sequences from IOLA KY405 in a lung fluid sample from one person, then followed up by finding those DNA bits in samples from 6/386 samples from other patients with respiratory disease. Some unique aspects of this bacterium are a very small genome, similar to Mycoplasma  (just over 300K base pairs; for reference, staphylococci have about 2.8 million base pairs), and a very high AT content (about 80%).
  • In the second study (Fukuda et al. 2021), they presented the whole genome sequence of the organism. They also used PCR to look for it in samples from more people with respiratory disease, and got positive results in 2.7% of about 500 samples. Eight of the 11 positive patients had significant underlying disease, and five were being treated with corticosteroids or immunosuppressants. So, these individuals had lots of other excuses to have respiratory disease or to be infected with something that’s minimally pathogenic.

Someone with more background in genomics would need to assess the papers to know how confident we can be in the results. If they are real, then the researchers have found a small bacterium that’s similar to Mycoplasma, which maybe isn’t surprising since some Mycoplasma are able to infect lungs (but more often are present as normal respiratory tract inhabitants.)

What we’re still lacking is 1) actually growing the bug to confirm its existence, and most importantly, 2) context. Finding DNA from this bug in a small percentage of people with respiratory disease is interesting, but could it be just as common in healthy individuals and just part of our normal microbiota? I don’t think we can say either way at this point.

When something’s only reported by one group over a long period of time, it raises the question of why. Is one group just way ahead of the curve, or is this something that other people have tried to find but have been unable to replicate the results (or have looked at and dismissed as not being worth investigating)? Publication bias is a big problem in cases like this. If other groups have put in a good effort to investigate this and found nothing, odds are high we wouldn’t find out because there’s a tendency to not publish “negative” results, even though those data are really important. So, we have no idea if there are only two papers because only one group is looking for it, or whether lots of other people have tried and failed to find anything similar.

Genome-based pathogen discovery is an established and effective method. It looks at all the genetic bits we can find in a sample, then tries to assemble them into something interpretable, and then we try to figure out what it actually all means. It’s challenging because we have a vast population of viruses and bacteria that are normal inhabitants in our bodies and those of animals. Most are harmless. Many are beneficial. Some can cause disease. Sorting out into which category a new organism fits takes a lot of work, and is rarely straightforward.

We’ve been lead down the wrong path many times before by reports of a “new” organism found in sick animals (e.g. the panic about canine circovirus). People freak out, start testing more sick animals, find it, and freak out more. However, when the science catches up with the hype, we often realize that we can find the bug in the same percentage of healthy animals, and it’s just a normal inhabitant that we’ve recently discovered, versus something new that is causing disease. With modern molecular techniques, our ability to find something often surpasses our ability to understand it.

While it sounds like I’m downplaying the relevance of this finding, that’s not my intention. I suspect IOLA KY405 is a real organism, I just need a lot more convincing that it’s relevant to disease (in people or animals). In an ideal world, the New Hampshire lab and others would be investigating this robustly, including field studies in dogs, to deterimine what the real story is. Lack of funding for companion animal infectious disease research usually slows these to a crawl. The report from the New Hampshire lab adds good context:

  • “It is important to note that this is a preliminary finding, and under normal circumstances of a study we would not release these findings. The technology and methods used by the HCGS include cutting edge metagenomic sequencing, and multiple bioinformatic pipelines that are uncommonly utilized in veterinary medicine. Additionally this is an uncommonly studied group of bacteria. There are multiple experiments that need to be run in order to clarify correlation vs. causation, and this gives reason for pause in releasing the findings. However, the syndrome is ongoing and there may be an opportunity to benefit animal health as we continue to validate these initial findings. There is a chance that this preliminary data is disproven with further study, but at this point it does appear that the bacteria we have identified is a potential causative agent.”

Those disclaimers are key, but unfortunately are usually left out of the media reports.

This is an important but very preliminary finding that needs to be studied. However, we also have to realize that most findings like this don’t turn out to be anything big (or anything at all). We can’t dismiss the potential and it’s great to see the work being done, but we need to make sure that we don’t jump from a preliminary finding of some unusual DNA sequences to “here’s the answer!” which is what human nature wants us to do.

If we know one thing about influenza A, it’s that there will always be something new with this virus.

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A recent study out of China (Meng et al. 2023) describes what seems to be a new canine flu strain. Is it a concern? It’s hard to say at this point, but having more flu strains in a species with which we have close contact is never a good thing.

This was a surveillance study of dogs in an area of China where there’s a massive amount of pet dog breeding and trading. Our familiar H3N2 canine influenza is endemic there, and avian flu strains circulate in wild birds, creating the potential for spillover of avian flu viruses into dogs and/or emergence of new strains from virus reassortment.

Researchers tested dogs from November 2018 to April 2019, and identified influenza virus in 60 of 534 dogs (11%) by PCR. Follow up testing resulted in isolation of live influenza virus from 12 dogs. Isolation of live virus requires culture techniques. We expect to get less recovery with culture compared to PCR, since PCR will detect lower viral loads and does not require the virus to still be viable by the time of testing.

Five of the flu viruses that were isolated were H3N2.

  • That’s not surprising, since H3N2 is a well established canine flu strain in China.

Interestingly, seven of the viruses were H3N6.

  • Looking at the genetic makeup of the virus, it appears to be a mix of H3N2 canine flu and an H5N6 avian flu strain that was circulating in birds in China in 2017 and 2018.
  • It was hypothesized that this was a result of a dog being co-infected with H3N2 canine flu and H5N6 avian flu, resulting in creation of this new H5N6 strain.

Does this mean there’s a new canine flu strain circulating in China?

That’s unclear. Positive samples were from dogs in one shelter at one time point, which could happen for a few reasons:

They found the first dog with this strain, and picked up transmission in the shelter that burned out, making this a one-off event.

  • It’s very unlikely they would have gotten that lucky and captured the very first emergence of this virus. Some of the in vitro characteristics of this virus suggest it should be well adapted to mammals, so full containment is probably unlikely. There’s also some genetic variation in the H3N6 isolates, which we wouldn’t expect with a single point-source exposure.

This virus is rare in dogs and there was cluster in that shelter at that time.

  • Possible, but odds are low that researchers would pick up a rare event like that. As above, the genetic variation in strains suggests that this was more likely from multiple introductions of the virus into the shelter.

H3N6 is circulating in dogs and this study detected a strain that’s been present in the region for a while.

  • This seems most likely.

The lack of clear sampling information is a big limitation in terms of interpreting the study results (e.g. were the dogs sampled on admission to the shelter? Were the positive dogs housed together? Were they sick?).  That’s very basic information that needs to be in a paper like this, but that weak journals may let slip or don’t think to query.

The main things I take away from this report are:

  • We need more surveillance to see if this strain is still present and where it is distributed. H3N6 is probably a relevant new-kid-on-the-block. It’s probably established given it was found in an area like this with massive dog breeding.
  • Changes in importation rules will reduce the risk of this virus hitting North America, but there are enough loopholes that there is still a very reasonable likelihood that it will be introduced here at some point.
  • We need to continue to watch for influenza A infection in various animal species. That includes dogs, which often fall between the cracks because it’s usually VERY hard to get support for disease surveillance in companion animals (compared to food animal). Lots of agencies want to know the results, but rarely do they want to foot the bill. It’s a significant gap in One Health surveillance.

What will we see if H3N6 flu hits Canada (or another country)?

Assuming it causes disease similar to other flu strains, we’ll see large numbers of dogs with typical flu-like disease (which will be lumped together with routine occurrences of “kennel cough”). The number of cases will be the dramatic thing, not the severity; however, with lots of cases, we’ll see more severe cases just based on percentages.

Since dogs will presumably have no existing immunity to this strain, the main thing I’m looking out for is big outbreaks. We see “kennel cough” outbreaks all the time, caused by our usual suspects like canine parainfluenza virus, Bordetella bronchiseptica and canine respiratory coronavirus. However, if/when a new flu virus hits, it will likely be much more and obvious. Rather than an outbreak that affects a lot of dogs in a group (e.g. kennel, shelter), it will affect almost all of them. Rather than a single outbreak in a town, there will be many. I suspect it will be pretty obvious pretty quickly if this virus makes it here.

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This can be filed under “concerning but not surprising,” but H5N1 avian influenza has been identified in a dog in Ontario. 

It’s concerning because any spillover into mammals raises concerns about continued adaptation of this virus to spread outside birds, and because spillover infections in mammals can be severe. 

It’s not surprising because when you have millions of infected birds internationally, it’s inevitable that domestic and wild mammals will be exposed. Even if transmission is rare, when there’s a lot of exposure, transmission becomes more likely to occur and to be detected.

The case at hand is a dog from Oshawa, Ontario that died several days after being found scavenging a dead goose. Both the dog and goose were tested for H5N1 highly pathogenic avian influenza (HPAI) virus, and both were positive. Sequencing of the virus at the National Centre for Foreign Animal Diseases was performed and the virus from both the dog and goose were the same, and were consistent with the H5N1 strain that’s circulating in wild birds and domestic poultry. Further testing is being performed to confirm the cause of death in the dog. Given what we know about spillover infections into related species like foxes, it’s certainly possible that avian flu could have contributed to the dog’s death.

What should people in Ontario (or anywhere else avian flu is circulating) do?

  • Relax. That’s the first thing. This is concerning but not a doomsday scenario. We know that spillover into various mammals is happening and it will continue to happen. Also, this was a pretty high-exposure scenario where a dog had a lot of direct contact with a bird that had died of avian flu. It’s a reminder of why we’ve been emphasizing the need to try to better understand this virus since the outbreak was first identified, and to try to prevent more spillover infections from wild birds.

The next step is to just take (or continue to use) some basic common sense measures to reduce the risk of exposure.

What can be done?

  • The big thing is keeping dogs (and other domestic animals) away from wild birds.  It’s a good general rule to keep dogs away from wildlife anyway (alive or dead). That’s particularly true when there’s avian flu activity in an area.

Can dogs be vaccinated against this flu virus?

  • No, at least not at this point. Canine flu vaccines target different flu strains (canine H3N2 and H3N8) and there’s not likely any relevant cross protection. 

What’s the risk to people from infected dogs?

  • It’s probably very low but this is an unknown. Spillover infections into other species are often “dead end,” where the infected individual can’t/doesn’t infect anyone else. However, there have been some wild mammal outbreaks where limited mammal-to-mammal transmission has been a concern. When litters of wild canids have been infected, it’s hard to say if they were all exposed to the same infected birds or whether there was mammal-to-mammal spread.
  • So, it’s a big unknown. With that, it’s reasonable to take precautions to reduce contact with potentially infected mammals. However, the risk is probably quite low.

Should sick dogs be tested?

  • Testing would be considered in situations where there’s a plausible concern about H5N1 flu, based on likely exposure and the signs of illness in the dog. Lots of dogs have respiratory disease from various viral and bacterial causes and there’s no use testing every coughing dog (especially since a mildly ill coughing dog isn’t going to be a classical presentation for this viral infection). Testing for H5N1 influenza can be done through veterinarians, typically by PCR testing of oro-pharyngeal (throat), nasal and/or rectal swabs. 

What about cats?

  • Basically, replace everything above with “cat” instead of “dog.” The risks and preventive measures are pretty similar. Keeping cats indoors (when possible) to reduce their exposure to wild birds, is the main measure. That will help protect both them and their human contacts.

As a journal associate editor and reviewer, I’ve seen lots of papers about SARS-CoV-2 in animals. Some have been great, ground breaking papers. Many have been small, weak studies rushed out to be “first,” with inadequate depth and lacking critical assessment. Some have been a complete disaster. The latter two groups are a concern beyond just being bad science. Shortcuts can lead to bad conclusions when things aren’t studied properly.

A recent study (Hoppe et al, Infection 2023) highlights the need for proper study to avoid bad conclusions. It describes SARS-CoV-2 infection in a household where both people and a dog were identified as infected.

A human (the father) was the first identified case, and the rest of the family subsequently got COVID-19 as well. The source of the father’s infection was unclear, but he noted that his dog had been sick (i.e. coughing, lethargic) starting 11 days before the onset of his own illness. The dog had been taken to a veterinarian and tested negative for some routine respiratory pathogens, but false negatives are very common with these tests based on timing of sampling and our inability to test for all causes of respiratory disease.

After the owner was diagnosed with COVID-19, the dog was tested for SARS-CoV-2. Samples were taken 18 days after the onset of the dog’s respiratory disease, and all 3 samples from the dog were positive for SARS-CoV-2 at that time.

Timeframe figure of SARS-CoV-2 infection in a dog and 4 family members, with the dog’s infection preceding human infections.

It was suggested that the time frame was consistent with dog-to-human SARS-CoV-2 transmission. I’d say that’s a bit of a stretch based on what we know about infection of dogs, but it’s not impossible. Dogs seem to be commonly infected from their owners, but seem to be pretty resistant to clinical infection and don’t seem to be great hosts for the virus. Virus shedding in dogs tends to be low and of short duration. With a fairly short incubation period in people, the dog would have had to have been infectious for well over a week to be responsible for the father’s infection, and that’s unlikely. The dog also would have had to have been PCR-positive for 18 days after the onset of disease, which I’d consider really unlikely.

However, “unlikely” doesn’t mean “impossible,” so more study was needed. Presumably, at this point, they thought the dog was the source of the family’s infection and were waiting for sequencing results to confirm that.

(Un)surprisingly, the sequencing results didn’t implicate the dog.

There were enough differences in the viral sequences between the dog and owner that the viruses were classified as two different lineages (B.1.1.29 and B.1.1.163, respectively). They concluded the infections were independent, since the series of mutations that would have to happen between the dog and person were “so unlikely, that secondary zoonotic transmission can virtually be excluded.”

It’s pretty clear that the dog was infected. The dog was PCR-positive and antibodies to SARS-CoV-2 were later detected in the dog’s blood.

It’s also pretty clear that the dog wasn’t the source of human infection. The dog’s infection was actually unrelated.

Then how did the dog get infected?

That’s an interesting and unresolved question, since the pet had little outside contact given restrictions that were in place at the time.

  • Maybe he picked it up from unreported contact outside the household.
  • Maybe a person in the household had an undiagnosed (potentially asymptomatic infection) with the strain that infected the dog.
  • Maybe the dog picked up the virus while visiting the veterinary clinic.

It’s impossible to say. That highlights a challenge. Confirming interspecies transmission of a virus that’s widespread in humans is very difficult, and often a really unique set of circumstances need to be present (as was for the cat-human transmission of SARS-CoV-2 that occurred in a Thai veterinarian).

This is a good example of the need to investigate interspecies transmission but the need to do it right. 

Dog image from: http://www.quickmeme.com/meme/3oyz00

Figure from Hoppe et al, Infection 2023.

Dead raccoons have gotten a lot of attention in Toronto lately, for various reasons. Many urban areas have abundant raccoon populations, and whenever there are a lot of animals (especially of the same species) living in a relatively small area, there’s greater risk for disease outbreaks. A distemper outbreak is playing a role (maybe a big role) in the latest rash of dead raccoons being found across the Toronto area. That’s bad news for the raccoons, and unpleasant for the people who who find them, not to mention the overworked animal control agencies that get called to pick up the dead raccoons, while also trying to attend to sick and injured animals of all species.

Beyond the ick factor of finding these dead raccoons, there’s fear of infectious disease exposure, particularly for dogs, from raccoon carcasses and sick raccoons. (And let’s not forget about cats either… risks to cats usually get ignored in these situations).

What are the real disease risks from all these dead raccoons?

Overall, the risks are pretty limited.

Distemper in raccoons is caused by canine distemper virus (CDV), the virus that causes (unsurprisingly) distemper in dogs. Distemper can cause serious, including fatal, disease in dogs, just like it does in raccoons.

So are dogs at risk from sick and dead raccoons?

Yes, dogs can get distemper from raccoons, but the good news is that we have very effective vaccines against distemper in dogs. Distemper is included in the standard “core” vaccines that all dogs should get regularly. We typically start vaccinating puppies at 8 weeks of age and vaccinate them monthly until 16-20 weeks of age. At that point, we’re pretty confident they will be able to respond to the vaccine properly, so we normally then vaccinate a year later, then every 3 years. Distemper is extremely rare in properly vaccinated dogs. Even a dog that is overdue for vaccines is probably at very low risk of infection is they were properly vaccinated as a puppy.

How would a dog get distemper from a raccoon?

Most likely, it would occur when an unvaccinated (or under-vaccinated) dog has direct contact with an infected raccoon. Although the virus is excreted in respiratory secretions and feces which can contaminate the environemnt, most of the risk probably comes from direct contact with the animal. Survival of CDV in the envionment hasn’t been well studied in field situations, but it probably only survives for hours or at most a few days. If there’s sunlight, dry periods and temperature swings, that helps inactivate the virus faster. So while we can’t dismiss the risk from indirect contact, I’m mostly worried about a dog tangling directly with an infected raccoon, which happens commonly enough even when the raccoon isn’t sick or behaving abnormally.

What’s the risk from raccoon carcasses?

The risk of distemper exposure from raccoon carcasses is probably not much. While the carcasses are unsightly, any virus on the outside of the body would die fairly quickly. The longer the raccoon has been dead, the lower the risk, so delays removing dead raccoons create more ick than disease risk.

It’s still best to get dispose of carcasses (of any kind) as soon as is reasonable. Beyond distemper, there are other potential general infectious disease risks from carcasses, but overall the risk is low, and the risk of distemper transmission to dogs is very low.

That said, why tempt fate and have a dog potentially exposed to anything from a raccoon carcass? Regular readers will have seen various pictures of our new puppy, Ozzie. It’s looking like he’s (unfortunately) going to be one of those dogs that likes to roll in disgusting things. So, job #1 is keeping him from away from animal carcasses. If he did roll on a raccoon carcass, I’d be more concerned about the smell than a disease, but I’d still give him a bath (while trying not to contaminate myself in the process).

Raccoons with distemper can act strangely. Do we have to worry about rabies?

Yes and no. We’re always concerned about rabies. However, we don’t have raccoon variant rabies in Toronto (as far as we know). There’s pretty good surveillance in the region, and it seems not to have made its way to Toronto after its last incursion into Ontario in 2015, when raccoon rabies was focused a bit further west in the Hamilton area.  (In the last two years the only cases of raccoon rabies in Ontario were detected in skunks in the Niagara region.  Check out the interactive Ontario rabies case map for the latest surveillance and case info.)

At this point, the vast majority of abnormally-behaving raccoons in Toronto will have distemper. But, we can never completely dismiss the potential for rabies, either because raccoon rabies has sneaked into the city, or a raccoon was infected by another rabies virus strain (e.g. from a bat). Therefore, it’s important to keep people and animals away from raccoons – even those that look normal, but especially those that are acting strangely.

The take-home messages are pretty simple:

  • Keep pets under control and away from wildlife, being particularly strict with unvaccinated and under-vaccinated dogs.
  • Make sure dogs are vaccinated.

That’s about it. With some common sense and basic veterinary care, we can relax about the canine implications of distemper in raccoons.

A recent publication in the Journal of Veterinary Diagnostic Investigation (Haydock et al. 2022) describes an interesting but unfortunate case of tuberculosis in a dog. Published reports of rare cases like this are often of limited value, but sometimes they highlight important broader issues, and I think this one fits that category.

The patient was four-year-old mixed breed dog that was presented to the Ontario Veterinary College because she had some liver and lung masses, and fluid in her chest. She had a very extensive workup, including lots of bloodwork, radiographs, a CT scan, ultrasounds, bronchoalveolar lavage, and even exploratory surgery to get samples of the masses for testing. I was involved because an infectious cause seemed likely, but a specific cause wasn’t readily apparent despite a pretty vast array of infectious disease tests.

There’s another twist to this story based on the origin of the dog: she was living in Toronto, but had been adopted through a rescue 18-24 months earlier, originally having come from a remote community in northern Quebec. Whether it’s a dog from another country or from another region of Canada, we have to think about what different infectious diseases might be involved when we see dogs from other places. That can be a challenge since we often don’t have good data on disease risks in different areas. There were a few things we considered in this case, but nothing really fit.

As things progressed, it seemed there was a good chance the dog had a Mycobacterium species infection. Mycobacterium is a genus of bacteria that includes a lot of different species, including the causes of human (M. tuberculosis) and bovine (M. bovis) tuberculosis, along with a big group of environmental species that rarely cause disease. We divide Mycobacterium into two main groups, tuberculous mycobacteria (including M. tuberculosis and M. bovis) and non-tuberculous mycobacteria (NTM, which includes the important M. avium complex, or MAC).

At that point, I suspected the dog was infected with MAC, a fairly ubiquitous group of environmental mycobacteria that can sometimes cause severe disseminated infection.

  • I was partly correct, but that wasn’t much consolation when we got PCR results saying it indeed was mycobacterial – but it was M. tuberculosis, the cause of human TB.

I think the first thing I said in response to the result was “I suspect there’s an issue with the test. We’ve seen cross-reaction before in samples from that lab for that test. It’s probably a non-tuberculous Mycobacterium since that’s more common and the disease fits.”

  • But it turns out, that was not the case.

It was subsequently confirmed as M. tuberculosis by culture. Whole genome sequencing and MIRU-VNTU profiling showed it was a near exact match with a TB isolate from a person from Quebec, providing more support that the dog was infected before being moved to Ontario.

So, we had a diagnosis. Unfortunately, the dog deteriorated and was euthanized shortly before we got the TB result.

However, that led to a whole new issue: human exposure to TB from the dog. This dog had obviously had close contact with its owners for close to 2 years, and was cared for by numerous veterinary personnel at the referring veterinary clinic and at OVC, including some high-risk procedures (e.g. intubation for surgery, close contact in ICU). We don’t know a lot about dog-to-human transmission of TB, but there was certainly potential risk since the dog had lung lesions and could therefore have had viable M. tuberculosis in its respiratory secretions.

Public health units in both Guelph (where we are) and Toronto (where the dog lived) were informed, and coordinated contact tracing, using definitions for exposure we created for this situation (see table below). A lot of investigation and testing was required, but fortunately in the end there was no evidence anyone was infected by the dog.

TB has been reported in dogs before, but it originates from humans in these cases. Concern has been raised about importation of TB-infected dogs from areas where the disease is common in people, and this scenario both supports that risk and highlights how “importation” should really be thought of as “dog movement,” since there can be risks with dogs from other areas of the country, even if they haven’t crossed an international border.

Dogs don’t seem to be very good hosts for M. tuberculosis, but we don’t have great data about how often human-to-dog transmission occurs, in part because testing of dogs is a challenge. Typical human tests for TB (e.g. tuberculin skin test) do not work well in dogs, so there’s no quick and easy way to screen dogs who have been exposed to people with TB. Presumably, human-to-dog transmission occur sporadically but usually doesn’t result in severe disease in dogs. Transmission from dogs back to people is hard to evaluate, since most infected dogs come from infected households, so figuring out who infected who is a challenge. Scenarios like this, where an infected dog came into the household where there were no other known sources of exposure can help us figure these things out, but aren’t commonly encountered. The fact that no one got infected from this dog is encouraging, but it’s a pretty small sample size from which to draw conclusions.

This report doesn’t mean we need to think that every dog with strange disease has TB. This is a rare case. However, it should be taken as a reminder that strange things do happen, and that the origin of a dog needs to be considered when thinking about infectious diseases. We’re getting better at asking if dogs were imported. However, it’s not the act of changing countries that increases risk. It’s traveling between different risk areas, or between communities with different disease risks, even if they’re within Canada. We need to pay more attention to dog origin and dog movement (including people who take their dog on vacation), not just whether the dog was “imported.”

Image: Medical illustration of Mycobacterium tuberculosis (source: CDC Public Health Image Library 23254)