As the weather cools down and wildlife of various kinds become less active (as do many pets and people!), we tend to see a decline in the number of rabies cases detected in the province.  It doesn’t mean the risk is no longer there, it just means we’re less likely to encounter the animals that most commonly carry the virus (i.e. skunks, raccoons, foxes, and especially bats).  So far in 2022, bat-variant rabies has been confirmed in 27 bats across the province (very typical number at this point in the year).  Raccoon-variant rabies has been confirmed in 15 skunks and 5 raccoons, remarkably all in one very small area in and around St. Catharines.  There was also one case of bat-variant rabies in a skunk in Waterloo region, which again emphasizes that we always need to be vigilant for this disease, even in areas where it hasn’t been recently detected in non-bat wildlife.  The only domestic animal diagnosed with rabies so far in 2022 was a dog that had been imported from Iran that was carrying canine-variant rabies.

The Ontario Ministry of Natural Resources and Forestry (MNRF) has just launched a new interactive map to help provide more information about where active (within the last two years) and expired (more than 2 years ago) rabies cases have been detected in Ontario, and where wildlife testing has been done.  The map lets you select the year (or multiple years) of testing, and can be zoomed in to your own municipality (but still protects the confidentiality of where specific animals were found).  You can also click on individual case dots for more information.  The image below is a screen shot of the map showing the cases that were detected in St. Catharines in 2022.  The map does NOT show cases of bat-variant rabies, because the risk from bats is present across the province, and is not higher or lower in a given area based on whether there have been recent detections.

Remember: It’s still important to keep your pets up-to-date on their rabies vaccination every 1-3 years (depending on the vaccine product) – and it’s legally required for ALL dogs, cats and ferrets over 3 months of age in Ontario – even if they never go outside (because bats can and do get inside!).  More information about rabies and rabies response in Ontario can be found on and on the OMAFRA rabies webpage.

With any new, changing or inadequately investigated infectious disease, we need to first understand the scope of the problem, including the range of species that can be infected. The ongoing human monkeypox outbreak has raised concern about spillback of monkeypox virus into animals from humans since, we don’t know much about susceptible animal species.

A recent paper in Eurosurveillance (Shepherd et al. 2022) describes investigation of monkeypox in animals from UK households with one or more persons infected infected with monkeypox.  Affected pet owners were asked if their animals were sick, and if so, that prompted discussion about whether it might be due to monkeypox or another cause, and whether testing for monkeypox was indicated. That’s an easy way to investigate something like this, but it has a few weaknesses:

  • Mild disease might be missed by pet owners. While raging pox-like skin lesions would hopefully be noticed, subtle skin lesions, enlarged lymph nodes or some other potential signs of monkeypox wouldn’t likely be detected by the average pet owner.
  • Owners might be fearful of the implications of infection in their animal (e.g. quarantine) and therefore not want to disclose potential issues.

Nonetheless, it’s useful to see the results of this study.

154 animals from households with a person with monkeypox were investigated. That included 42 dogs (including one household with 13 dogs), 26 cats (from 14 households), as well as 5 “rabbits or guinea pigs,” one group of 7 unspecified “mammalian livestock,” one group of 64 poultry, and a smattering of tropical frogs, a snake and one “unspecified” animal. We can largely disregard the poultry, reptile and amphibian data, since there’s not much reason to think those species are of any concern with regard to monkeypox infection.  That leaves us with 80 mammals of different species, none of which showed any evidence of overt disease due to suspected monkeypox infection, despite household exposure to the virus. Good news.

The other big thing that is missed using this methodology is assessment of subclinical infections, i.e. where the animal is infected (and maybe infectious) but is not showing any signs of illness. That’s a particular concern for potential reservoir species.

What can we take home from this study?

The big thing this study suggests is that serious infection with monkeypox virus in pets is unlikely. It doesn’t prove it can’t happen, since the numbers are relatively small, but it shows that transmission to pets and subsequent serious disease is probably uncommon, if it occurs at all.  That’s useful information.

It’s still just one step on our path to understanding more about the potential for human-to-animal (and human-to-animal-back-to-human) transmission, as well the range of species that are susceptible to monkeypox.

While there are limitations to this study that are easy to pick apart, the results are still important and useful, and help us think about next steps. To figure out more, we need more intensive studies with veterinary examination and testing of exposed animals, including larger numbers of animals and diverse species. Getting animals examined and tested isn’t a cheap, easy or fast process (we’ve had a really hard time recruiting for our own monkeypox surveillance efforts), so quick basic studies like this can help fill in some preliminary gaps.

Things have been pretty quite regarding monkeypox in domestic animals lately. Whether that’s because human-to-animal infection is truly rare, and human case numbers are dropping, or whether it’s because there’s not enough surveillance in domestic animals that have been exposed to the virus isn’t clear. I suspect it’s a combination of the two. Our surveillance has been really slow since it’s been hard to recruit participants, but I doubt that human-pet transmission of monkeypox is very common.

However, uncommon doesn’t mean irrelevant.

For veterinarians, it brings up a new round of questions about potential occupational risks for veterinary staff and the potential for veterinary clinics to become hubs where the virus could spread. Those concerns aren’t without foundation, since pet-to-veterinarian transmission of monkeypox was identified in the 2003 prairie dog-associated outbreak in the US.

When we don’t have much data, it can be a challenge to provide clear guidance on how to prevent virus spread, but realistically we still have a good idea of what control measures are likely important based on basic our understanding of monkeypox virus and principles of infection control.

Like we did for SARS-CoV-2, we’ve teamed up to release some interim guidance for veterinarians about handling animals that may have been exposed to monkeypox, this time in conjunction with the Canadian Veterinary Medical Association. It’s also available in pdf format.

As always, guidance might change as we get more information on what is (and is not) a significant risk). Changing guidance is actually a good thing – it shows we’re learning and improving. However, while we’re gathering more data, this is a good starting point to reduce the risk of monkeypox transmission to and from veterinary patients.

As H5N1 avian flu ramps up again across Canada with the fall wild bird migration, we’re likely going to see more situations where more unique populations of captive birds are affected, beyond the usual large or small poultry flocks. The CFIA’s standard response to highly pathogenic avian flu (like the current H5N1 strain) is “All infected flocks are humanely destroyed, and carcasses are disposed of in an environmentally acceptable fashion.

As would be expected, this response is based primarily on commercial poultry, where if one bird in a flock is infected, you can be pretty sure the virus is widespread in the group. However, other kinds of birds that can still be infected may be housed very differently, and management and infection control measures may affect their risk if an infected bird is found on the property.  Other factors to consider are the ability to contain the risk from potentially exposed birds (which may include financial costs), and the importance of some birds in terms of conservation or genetics.

The standard approach is understandable with poultry that are highly susceptible to the virus and housed in a manner that transmission can be rampant.

However, given how widespread this virus now is in the wild bird population in North America, and the wide variety of captive birds that can be affected, could a one-size-fits-all approach perhaps cause more harm than good in some situations?

  • Maybe.

The main issue relates to non-commercial birds (those not raised primarily for food), particularly pet birds and birds in rehab facilities.

Sometimes, exposure of the entire group is likely and a whole-group response (euthanasia) might be indicated.

  • Risk assessment should play a role in this.
  • If a rehab facility has waterfowl and raptors (and maybe some pet birds in the house), and those groups are kept separate, does it make sense to depopulate all the birds on the property? Maybe not, at least all the time.
  • It comes down to the risk of exposure. Often, there can be pretty good  physical and procedural separation.

We shouldn’t realistically aim for “is there absolutely, positively, no chance that the birds were exposed?”. We can never hit that bar. Rather, we should aim for “are these birds at any greater risk than any other birds in the area, when we know that H5N1 flu is circulating in wild birds?”. That changes things a bit and recognizes that there might be some degree of risk, but it might not be any more than is inherently present with a virus that’s currently fairly widely distributed in nature.

Another major concern I have with any strict policy is driving things underground. If bird owners know a positive test means all their birds will be killed, they’re more likely to try to ride out a problem and not get testing done. That means we lose valuable information, don’t get a chance to respond to help contain the issue, and we can miss the ability to manage disease properly if it’s something other than flu. I can absolutely see non-commercial bird owners avoiding testing if stories of mandatory depopulation of birds like theirs increase. We need to know the extent of the spread of this virus so we can take other steps to control it, and driving things underground doesn’t help.

I fully admit it’s a tough situation. It requires people to change standard approaches, make decisions on the fly and do risk assessments without much information (at a time where CFIA is certainly not overflowing with resources).

We want to contain this virus for both human and animal health reasons. But, we have to realize this is an unprecedented avian flu situation in North America. We’ve never had this degree of sustained and widespread infection of wild birds.

I’m certainly not saying we should surrender and say ‘it’s endemic, we’re done, good luck.” but a more risk-based approach than has previously been considered is warranted, based on the risks to people and animals in the broader context. That’s a challenge, and we absolutely have to prioritize protecting human health.  As we enter human flu season (which is shaping up poorly), we don’t want mixing of avian and human flu viruses. We also need to minimize the risks to commercial poultry operations, which can affect thousands of birds at a time and can have ripple effects on the entire agri-food supply chain.

However, does a one-size-fits-all approach that requires euthanasia in every situation make sense? I don’t think it does.

What are the challenges to a risk based approach?

  • Lack of data to guide risk assessments in more unique situations.
  • Overloaded regulatory personnel (most veterinarians can relate to this right now too).  Case-by-case assessments and tailored responses typically take more time and resources than using the one-size-fits-all approach.
  • Often unclear or unreliable information on premises about what’s done and what the risks might be.
  • Perceived risk and risk aversion (e.g. the safest thing for regulators to do from a risk standpoint is euthanize any potentially exposed birds. Doing something different, even for good reasons, can increase risk to people or other animals, and then regulators may get blamed if things go wrong).

I think it’s time to try to implement some risk assessment-based approaches to control of this virus in some unique collections of captive birds. Often, euthanasia will still be the result if transmission between birds cannot be controlled, and that makes sense. However, there may be some situations where it can be argued that not all groups on a property are at the same risk for exposure.

What about hold and test?

  • That’s a consideration but it brings in some challenges.
  • Some tests are better than others, but no test is 100%.  It’s not as straightforward as it may first appear. However, with serial tests in a group, I think we can be pretty confident whether flu is or isn’t in a group of birds. That’s what we’re really looking to say. We want to say “are one or more birds in this specific group infected” vs “is this individual bird infected’. We can design logical testing strategies to do that.
  • Testing takes time, and also involves cost and that would be on the facility/owner. Cost concerns might certainly prevent this approach from being viable in some situations, and risks need to be carefully controlled while testing is undertaken.
  • Human exposure risks also need to be considered. If we’re collecting samples from birds, we’re potentially getting exposed to this flu virus. We can do things to reduce the risk, and any testing approach would require people that are properly trained and willing to accept the risk (like we, as veterinarians, do regularly). Fortunately, the current H5N1 seems very low risk for causing disease in people, but flu viruses are notorious for changing and low risk doesn’t mean no risk. We also want to make sure potentially infected birds don’t get exposed to human flu, another reason for careful handling during sampling.

Although the safest (and easiest) way to eliminate an “animal problem” is to eliminate the animal, euthanasia of any captive birds that might possibly be exposed to this virus when a positive is detected may not be the “best” approach in all cases.  It will be interesting to see if and how the CFIA adjusts their approach as they continue to deal with this unprecedented outbreak of avian flu.

Since rabbit hemorrhagic disease virus type II (RHDV2) made its first incursion into Canada, and again more recently with the first detection of this virus in Ontario, there’s been a lot of interest in vaccination of rabbits (rabbits and hares are the only species known to be affected). Effective vaccines are available for this highly transmissible and fatal rabbit virus, but they are not licensed in Canada. To access the vaccine, Canadian veterinarians therefore have had to apply to the Canadian Centre for Veterinary Biologics (CCVB) for an import permit (which takes some time) and then source a vaccine from Europe (which takes time and money). It’s doable, but it makes it hard to get vaccine quickly, which can hamper response in a potential outbreak.

Better access to RHDV vaccine is on the horizon, though, as one of the European vaccines, Filavac VHD C+V, now has market authorization in Canada through Ceva Animal Health. It’s currently available to veterinarians from some of the key purchasing groups, and should be available through others very soon. So, veterinarians should now have relatively easy access to this vaccine through their normal purchasing channels, should they have a need for it.

PS: I don’t usually write about specific products or companies, but this is an important issue and not a matter of one product vs another – it’s something that’s now available that wasn’t before. At Worms&Germs, we try hard to be independent and not have any external influences, perceived or otherwise. We don’t have advertising on the blog, we don’t have any sponsors, we control all our content, and the few thousand dollars a year that it takes to pay for the site come from the University of Guelph’s Centre for Public Health and Zoonoses.

If you follow zoonotic diseases, you might look at the title of this post and think “What is he rehashing now? We already know Salmonella is common in reptiles, and contact with reptiles is a major risk factor for salmonellosis in people.

In large part, you’d be right. Not a lot has changed on the Salmonella-in-reptiles front, but since it’s an important issue (and there are still those who haven’t gotten the message), it doesn’t hurt to provide some updates.

A recent study in the journal Biology (Merkevičiene et al. 2022) fits in the “unsurprising but worth a mention” category.

Researchers collected samples from 75 captive reptiles in Lithuania, from private homes and a zoo. All of the reptiles were healthy and none had been treated with antibiotics in the past 6 months. They also collected samples from 22 wild reptiles at three locations in Lithuania. Samples were cultured for Salmonella.

  • Overall, Salmonella was isolated from 50 (52%) reptiles; 46 (61%) pets and 4 (18%) wild reptiles.
  • 25 different reptile species were tested. One or more positive samples were detected from 68% of species.
  • A wide range of different serovars (strains) were detected.
  • Antimicrobial resistance was variable, but 24 (48%) of isolates tested were resistant to 1 or more of the antibiotics on the testing panel.
  • 10 (20%) isolates were multidrug-resistant (i.e. resistant to 3 or more antimicrobial classes). This includes three wild reptiles that harboured Salmonella resistant to 5 or more of the tested antibiotics (including cefoxitin, tetracycline, chloramphenicol, ampicillin, streptomycin, ciprofloxacin, pradofloxacin, ofloxacin and potentiated sulfonamides). Yikes!

Does this change anything? No, but it highlights (yet again) a few important messages:

  • Reptiles commonly harbour Salmonella. These results showed over 61% of pet reptiles were carrying Salmonella based on testing just a single sample. If serial sampling was performed, I suspect the number would be even higher.
  • Reptiles should be handled with the assumption they are carrying Salmonella, with careful attention to basic infection control practices such as hand hygiene and preventing cross contamination of objects, surfaces, clothing, etc..
  • People at higher risk of serious disease (e.g. very young, elderly, pregnant, immunocompromised) should not have contact with reptiles, and should not live in the same house as a reptile, whether or not they are allowed to have direct contact with them.
  • Antimicrobial resistance rates highlight ecological complexities inherent in this silent pandemic of resistance.

I’m not saying to get rid of all captive reptiles. However, it’s important that only lower-risk people are exposed to reptiles and that we do a good job of using basic infection control practices to reduce the risks of transmitting Salmonella to people.

We already have an update on the Michigan dog disease outbreak that I wrote about yesterday which has attracted a lot of attention.

An update (August 24) from the Michigan State Veterinarian indicates this appears to be an outbreak of parvovirus. I’m not overly surprised. As I wrote yesterday:

An outbreak of our typical canine parvovirus?

  • This is probably the most likely explanation, or at least the one to rule out first. That will require confirmation that parvovirus is actually the cause in most cases, and investigation of the vaccination status of those dogs.

Further investigation identified canine parvovirus in affected dogs. Initial point-of-care (i.e. in-clinic) tests for parvovirus were negative and while we rely on these tests a lot (and they’re generally quite good), we know they are not 100% sensitive. The report says those tests were consistently negative, which suggests a reasonable number were performed. That’s interesting since with severe disease and a lot of tests, I’d expect a positive. However, knowing that the tests aren’t perfect and that parvovirus is very common, we still shouldn’t jump to ruling it out too quickly, even with negative screening tests in multiple dogs.  More sensitive tests performed at the Michigan State University Veterinary Diagnostic Laboratory were used to confirm the dogs were indeed infected with parvovirus.

The other key factor here was vaccination history. Affected dogs were incompletely vaccinated. This likely means the dogs were young and not fully vaccinated yet, or hadn’t been properly vaccinated when they were puppies.  I covered parvovirus vaccination issues in yesterday’s post as well.

So, from a population standpoint this is encouraging, because it means the cause of the outbreak is not likely something new, and our current preventive measures should be effective… they just need to be used.

I’ve been holding off writing about this, hoping for more details, but my inbox has been flooded with questions about it so I figured I’d get the ball rolling. There’s been a bit of a media frenzy about an apparent outbreak of severe disease in dogs in northern Michigan.

What do we know?

  • Not much.  There have been various social media and news reports about an unknown disease or a “new parvovirus” outbreak in dogs in the area. Reports mention “dozens” of dogs affected, most less than 2 years of age, mainly with vomiting and diarrhea.
  • Concerns about a new strain of canine parvovirus are circulating on social media, but some reports have indicated that while parvo is suspected, test results have been negative. I suspect that’s incorrect, or that there are some nuances to the situation that haven’t been conveyed.

On Monday, Michigan’s state veterinarian’s office issued an update:

“We are still in the early stages of this investigation, but some of the first samples submitted to the Michigan State University Veterinary Diagnostic Laboratory were positive for canine parvovirus. However, there are more results pending and more to be learned,” State Veterinarian Nora Wineland, DVM. “When MDARD first learned of these cases in northern Michigan, we immediately reached out to the veterinarians and animal shelters involved and began our response efforts. Protecting animal and public health is one of the department’s key pillars, but it is a team effort. Dog owners need to ensure their pet is up to date on routine vaccinations as it’s the first step in keeping your pet healthy.”

While light on details, the statement highlights that parvovirus is a leading candidate for the cause at this time. The number of dogs that were positive and the number that were tested area important to put those results into context. Social media reports talk about large numbers of dogs, but that’s not really reliable since cases can quickly be blown out of proportion.  Dogs with any random / routine illness can lumped into case counts without a good case definition and proper data collection, so it’s hard to know the scope of the issue at this time.

What could this be?

A new virus?

  • Probably not. Most outbreaks are caused by the usual suspects. I never discount the possibility of something new, but we start by looking for common things.

An outbreak caused by a new strain of parvovirus?

  • The big concern is about a new strain of parvo that current vaccines don’t protect against. I’d say this is unlikely. Outbreaks caused by “new” strains of parvovirus get talked about frequently but ultimately, they’re usually caused by well-established strains.
  • The “new strain” fears often come up when disease occurs in vaccinated dogs, but most parvo cases in vaccinated dogs aren’t caused by a new strain. Vaccines may not always work in young dogs because antibodies from their mother are still present and can interfere with the vaccine. That’s why we (should) vaccinate dogs at frequently intervals until they’re 16-20 weeks of age. We start early in the hope that they will respond to an early vaccine, then keep vaccinating until an age that we’re confident they will respond.
  • Disease in younger vaccinated dogs can also occur because the vaccine didn’t get a chance to work. We also see issues that are likely due to use of dodgy vaccines or vaccine handling, like when dogs are vaccinated by owners or breeders that get their vaccines from questionable sources, or when cold chain might not have been properly maintained.
  • Disease in vaccinated dogs doesn’t necessarily mean this is a new virus, or a new strain of a common virus, but it’s a consideration, for sure. Disease in older, properly vaccinated dogs would cause me more concern.

An outbreak of our typical canine parvovirus?

  • This is probably the most likely explanation, or at least the one to rule out first. That will require confirmation that parvovirus is actually the cause in most cases, and investigation of the vaccination status of those dogs.
  • Sequencing of parvovirus from affected dogs would ideally be done to see if it’s a different strain.

A social media frenzy?

  • We always have to step back and figure out what we know versus what people are talking about.
  • Not uncommonly, I get questions about an outbreak of X disease and ultimately nothing unique is happening.  Sometimes, a few routine cases get blown out of proportion online.  Sometimes, we hear more about cases that occur routinely in the background, just because people start talking about them.
  • Reports of a large number of sick dogs could truly be an abnormally large number of sick dogs, or it could be the typical number of dogs that are sick but that no one usually talks about. This could also be a situation where there is a small outbreak of parvo in dogs in one area, but lots of dogs with unrelated GI disease are getting lumped in with them, which confuses the issue.

How can dog owners protect their dogs? Especially if they live in or are traveling to Michigan.

It’s mainly common-sense measures and the same things I’d recommend for any area at any time:

  • Make sure your dog is probably vaccinated against parvovirus (and other vaccine-preventable diseases)
  • Keep your dog away from dogs that might be sick
  • Limit contact with other dogs, especially large numbers of dogs and transient populations of dogs that are unfamiliar to you and of unknown disease / vaccination status.

As I mentioned, we typically recommend vaccinating puppies for parvovirus every 4 weeks until 16-20 weeks of age. In shelters, the recommendation is often every 2 weeks because of the increased risk. We have confidence that a vaccine given at 16+ weeks of age will be effective in the vast majority of dogs. At that point, it’s a bit case-by-case. Dogs might get one more dose 2-4 weeks later, especially if they are at higher risk of exposure (e.g. lots of parvo in the area, lots of contact with other dogs and dogs of unknown health status) or we might stop the initial series at that point.  Dogs then get a booster 1 year later, then go on an every-3-year schedule.  The key is getting things started off right.  Proper vaccination of puppies is key to preventing this potentially devastating disease.

As an Associate Editor for Emerging Infectious Diseases and as a frequent peer reviewer for other journals, I see lots of paper that report finding a “new” virus. These can be a challenge to interpret, because advances in technology now let us find things we’ve never been able to find before. The problem is, we can find things a lot more easily and quickly than we can understand them, and it’s easy to jump to questionable conclusions.

Let’s say we look at individuals with a certain disease and we find a specific virus in many of them that we haven’t seen before. That’s interesting, but in terms of proving that virus could be a cause of disease, it’s only step one of many.

Maybe we then test a few other animals with the same disease and find the same virus.  Convincing, right?

  • Not necessarily.  We live in a microbial world, and lots of microbes live on or in us all the time. We have a “commensal microbiota” of bacteria, viruses, fungi and parasites with which we co-exist. Some help us.  Some can hurt us at times. Mostly we live blissfully unaware of their presence.

So, finding X virus in people or animals with Y disease could mean that it’s a cause, or that it’s a normal inhabitant of the microbiota that we finally just noticed. Or, it could be something that’s relevant but only when some other microbe is present as well.

I see lots of papers that stop at this step. They find a virus (or often just genetic bits of a virus, not the whole virus or even evidence of a live virus) and link it with a disease. Sometimes they’re right (or lucky). Sometimes they’re wrong, and that sends people down some unnecessary paths.

The next step in the process is looking at similar but healthy individuals to see if the implicated microbe is found in them too, or only in the sick individuals. If so, that’s still not a guarantee it’s the cause of disease, but it provides much more solid evidence.

That was a long preamble to the actual topic of this post:

“Staggering disease” is a unique and interesting neurological disease found in cats in some parts of Europe. Clinically, it usually causes hind limb ataxia resulting in a staggering gait. Various other neurological signs can be present, but hind limb ataxia is the most consistent, obviously giving rise to the disease’s name. First described in the 1970s, the cause has been elusive, but a virus has long been suspected. Borna disease virus 1 (BoDV-1) was previously a leading candidate, but has fallen out of favour lately.

A recent preprint (Matiasek et al. 2022) may have answered the question of what causes staggering disease in cats. They started off looking for Borna disease virus in 29 affected cats from Sweden, Austria and Germany. They went 0/29, using both PCR and immunohistochemistry. That might put to rest suspicions that Borna disease virus is involved in the disease.

Then, they used a metagenomic approach to identify genetic material from any virus that might be present in the cats. Unlike PCR, where you must have a target, metagenomics lets you find snippets of virus genetic material that you can then try to stitch together into larger fragments, and compare them with known viral genomes to identify what’s there.

Using this approach, they found sequences that matched Rustrela virus (RusV) in 14/15 samples tested. They then developed a new PCR test for RusV and got positive results from 15/15 cats from Sweden, 8/9 from Austria and 3/5 from Germany. They followed that up with some other tests of brain tissue (in situ hybridization, immunohistochemistry) to confirm the presence of the virus. Overall, 28/29 cats tested positive for RusV with at least one of the tests. Importantly, samples from 21 cats without encephalitis and 8 cats with encephalitis of other causes were all negative.

Rustrela virus is a close relative of rubella virus (which causes rubella in people). That doesn’t mean there’s any link with people or rubella virus, but it helps us understand more about the virus. Rustrela virus has also previously been found in the brains of a few different mammals with neurological disease in a zoo in northern Germany.

Even if Rustrela virus is the cause of staggering disease, lots of questions remain. A big one is waht is the virus reservoir? Does it circulate only in cats, or spillover from other species (e.g. wildlife)? That will take a lot more work to figure out, but they started looking into it by testing brains of 116 rodents from Sweden that were caught between 1995-2019 for other studies. Using PCR, they got positive results from 8/106 (7.5%) wood mice. None of the infected mice had changes in their brain, which fits with a reservoir species that can carry (and spread) the virus, potentially for a long time, because it doesn’t cause disease in the host. If the virus lives in the brain of the mice, cats could be exposed through hunting, but a lot more work needs to be done to look at virus shedding and transmission routes.

I assume we’ll be hearing a lot more about this virus in coming years as more work gets done. It’s not a slam-dunk, but this seems pretty convincing, and definitely enough to launch more studies since lots of important questions remain.

Now that human-dog transmission of monkeypox has been identified, there’s a lot more interest in what to do about animals that have been exposed to infected people. As more people get monkeypox, more animals will be exposed. We want to reduce the risk of animals getting infected (and possibly then infecting more people), while at the same time not causing undue stress on the animals or their owners.

This is a big déjà vu moment, as this is pretty much the exact same topic I had to write about for SARS-CoV-2-exposed animals at the start of the pandemic.  Similarly, specific guidance in this situation is tough to develop because of knowledge gaps, emerging new information, and differences between households, lifestyles, risk tolerance and other factors. Nonetheless, we can break down some general guidance into three main approaches:

1) Remove the pet from the infected household ASAP

  • This one gets mentioned as an ideal option, but I think it’s actually probably the worst one unless it’s certain that the animal has not yet been exposed to the infected person, or anything potentially contaminated by the virus.
  • Prompt removal of the pet would reduce the risk of a pet getting infected, but it also increases the risk of a pet spreading monkeypox. If the animal was already exposed to the infected person, it could already be infected and incubating the virus. Moving the animal therefore creates a risk of moving monkeypox to another household or facility and exposing others.  (The animal could also potentially have virus on its fur that it picked up from the contaminated home environment, even if it’s not infected.)
  • Considering how little we know about the risks, I’m more concerned about the implications of an animal spreading monkeypox outside the household than I am about the pet getting monkeypox in a household where the virus is already present but being contained, and where the animal has probably already had a lot of exposure.

2) Keep the pet in the house and use isolation measures to prevent transmission to (or from) the animal

  • This is the ideal response, in my mind. It’s not easy, though, in part because we don’t really understand the likelihood of human-to-dog or dog-to-human transmission risks in households.
  • Pet contact with skin lesions of infected people probably poses the biggest risk of transmission to the pet, but other types of contact also have to be considered. The degree of risk from aerosol transmission is still controversial.

Here are some basic isolation precautions that would help prevent transmission to pets (and they also help prevent transmission between people):

  • If there are uninfected (or not known to be infected) people in the household, they should be the animal’s primary caregiver(s).
  • Keep the pet away from monkeypox skin lesions.
  • Keep monkeypox skin lesions covered, whenever possible.
  • Limit contact between people and the pet as much as possible.
  • Keep the pet in a separate room or area of the house as much as possible (being practical and considering the pet’s welfare).
  • Keep the pet away from bandages, clothing or other materials that have come into contact with the infected person’s skin, especially skin lesions.
  • Keep the pet off furniture used by people (e.g. couch, bed).
  • Limit the amount of time the pet is in the same airspace (especially small, enclosed areas).
  • Don’t let the pet sleep in the same bedroom as people.
  • Pay close attention to hand hygiene, especially before any direct contact with the animal, or with things like food and water bowls.
  • Maximize ventilation in the house.  If possible, have a HEPA filter running in areas where the infected person tends to spend time (especially if the pet is in the same area).

To mask or not to mask?  That is the question.

  • Mask use will reduce the risk of aerosol transmission. It would make sense for an infected person to wear an N95/KN95 respirator or equivalent when in close proximity to the pet. That’s tough to maintain over time, but at least doing it when close contact is required can be practical.

3) Keep the pet in the house and carry on

  • This approach is based on an assumption that the pet is already exposed and/or that isolation measures will not be able to be done effectively. I understand those points and there’s some validity to them. However, it’s hard to support a “do nothing” approach. I’d rather see “do as much as you can from the list above” versus simply surrendering and saying “what happens, happens.”

In my (limited) experience to date, a combination of approach #2 and #3 has been most common. By the time people are diagnosed and think about potential risks to pets, there’s already been lots of exposure of the pet. They then try to take some precautions like limiting contact, keeping the pet away from their skin lesions and keeping the pet out of the bedroom. It’s hard to strictly isolate in the household when you have to care for the animal, and motivation decreases over time (especially when people think that they’re not able to strictly isolate from their pet anyway). So, in the end, measures taken tend to be limited. That’s not a criticism, it’s a reality. Pets can be peoples’ support systems when they are going through a tough time. All things considered, while owners don’t want to infect their pet, they often drift from “strict isolation” to “let’s do what we can do.” That’s still useful, though.

What if the owner cannot care for the animal and/or the animal has to be moved?

In some situations, the pet might have to be temporarily removed from the household.  These situations could include if the infected person cannot care for the pet, if the pet can’t be safely managed by the person (e.g. they have to go in an elevator and through busy common areas to go outside multiple times a day), or if the owner ends up hospitalized and no one else is present in the household. There are a few possible approaches for handling this:

  • If the owner cannot care for the pet but the pet can stay in the home, someone else can come and care for the pet a couple of times a day (this is easier with cats and caged pets). This avoids having to move the pet to another household or facility, and makes it easier to minimize exposure to the pet and to facilitate use of personal protective equipment, as needed.
  • If the pet has to be moved, it should be moved to a household or facility where it can be easily contained and managed, with as few people as possible, no high-risk individuals including kids or immunocompromised persons, and no other animals. The pet’s caretaker would have to understand and accept the unknown degree of risk of transmission of mokeypox from the pet (as it’s pretty much completely unknown).

These approaches are far from impossible, but require some work and still come with a good degree of uncertainty.

Regardless of the option chosen, there needs to be an effort to reduce exposure of the animal to other animals and people:

  • Veterinary care: Only if essential and it can’t be postponed for a few weeks.
  • Grooming: Big no.
  • Time in the yard: Short, supervised periods are okay. We want to prevent exposure of wildlife or through-the-fence transmission to neighbouring people or animals. (I’ve seen fence line transmission of both canine flu and canine parainfluenza; different bugs, but it shows there’s some degree of viral transmission risk with this kind of contact.)
  • Walking: This comes down to context and need. If the animal can be walked but still kept away from others, the risk is negligible. That might be very easy or next-to-impossible depending on the situation, so it would need to be assessed on a case-by-case basis, and the dog walker needs to be diligent about avoiding close contact between the dog and others.

How long do these measures need to be kept in place?

That’s a tough question too. Measures to reduce the risk of transmission from the owner should be maintained until the owner has been told they are no longer infections. Often, that’s considered to be 21 days after onset of infection.

But (there’s always a but)…

We have to think about the other part of our pet concerns: whether an exposed pet could infect someone else. If we say the person was infectious until day 21, then the pet could have been exposed up until day 21. So, if we use a similar 21 day isolation period for exposed animals (which is a huge assumption in itself), that would start at the end of the owner’s isolation period. That’s hard to enforce since it’s not what’s done for human contacts, but since we know nothing about whether dogs, cats and other species can be subclinically infected (i.e. infected without obvious signs of illness) and the risk of transmission from animals if the are infected, some degree of prudence is warranted. At a minimum, I’d want to keep an exposed dog from situations like groomers, kennels and off-leash dog parks for a while after the owner is considered no longer infectious themselves.

As always, these are initial thoughts and subject to change as we learn more. But infection control isn’t rocket science. It’s a lot of basic measures that apply to a wide range of situations, so I think the approaches outlined above are a good starting point.