There’s not as much to update about SARS-CoV-2 in dogs as there was in cats. We have more numbers than we did before, but the overall issues in dogs and our understanding of them haven’t really changed.

Spoiler alert: dogs and owners can both relax, as the risks are very limited.

Are dogs susceptible to the SARS-CoV-2 virus?

Yes, but… not very… maybe.  It depends on what you mean by “susceptible.”

Nice and clear, eh?

There’s a difference between getting infected and getting sick. Yes, dogs can clearly be infected. However, they don’t seem to be as susceptible as cats, and it’s debatable whether they get sick from the infection… I’m still a bit on the fence about that (more below).

How often do dogs get infected?

This is where we’ve gotten the most information recently.  Studies that have looked at dogs living with COVID-19-infected people have generally identified impressive rates of human-to-dog transmission. In these studies, researchers either look for evidence of the virus itself in the dogs (usually using a PCR test) or they look for antibodies against the virus in dogs’ blood. The problem with PCR testing is that there’s a very narrow window of virus shedding in this species, so it’s easy to miss the window (in which case the test comes back negative even though the dog was infected) based on sampling logistics and timing. With good antibody tests, we can get a good idea of whether dogs were infected in the past (although there are potential issues there too) because the antibodies hang around for a lot longer.

Early in the pandemic, the virus was identified by PCR in dogs from infected households, setting the scene for further studies. The best initial effort was from Hong Kong, where they identified the SARS-CoV-2 virus in nasal, oral and rectal swabs from 2/15 dogs that were quarantined because their owner was infected. Neither dog had signs of infection, both developed antibodies to the virus, and gene sequencing showed that the viruses in the dogs were the same as the viruses in their respective owners. Subsequent work has found similarly, fairly low rates of PCR-positivity among dogs with household exposure to infected people (e.g. Hamer 2021).

Serological studies looking for antibodies against SARS-CoV-2 in dogs have shown that transmission is actually much more common than this, with rates of up to 46% in dogs from infected households (e.g. Stevanovic 2021Hamer 2021). The results from our (hopefully soon to be submitted) Canadian study were similar, with about 43% of dogs with household exposure testing positive for antibodies to the virus.

Some studies have tested blood from undefined populations of dogs, for example by testing leftover samples of blood submitted by veterinarians to diagnostic labs. These studies tell us very little, because there’s no accompanying info about the dogs, particularly whether dogs were exposed to anyone with COVID-19. Not surprisingly, low rates of antibody detection (0.2-3.4%) have been found in these stuies (e.g. Ito et al. 2021,  Patterson 2020, Smith 2021). Whether these positives represent infected dogs from households with infected people vs false positive results isn’t clear.

Do dogs get sick when they are infected?

That’s still unclear. In small experimental studies, dogs could be infected but didn’t show any signs of disease (e.g. Shi et al. 2020, Bosco-Lauth et al. 2020). Field studies are harder to evaluate because there’s nothing specific about the clinical signs we’d expect to see from SARS-CoV-2 infection in a dog (e.g. lethargy, coughing, sneezing, decreased appetite and other flu-like signs). These non-specific signs can be caused by lots of diseases in dogs, so if we find a dog that has evidence of previous SARS-CoV-2infection (i.e. antibodies) and it was reported to have been sick, it’s hard to say whether it was sick because of SARS-CoV-2 or whether it was sick because of something else and had an incidental SARS-CoV-2 infection. Larger and better designed studies are needed to figure that out.

In our preliminary work, we found an association between antibodies in dogs and the owner reporting that the dog was acting sick around the same time the owner was infected. That is to say, this finding was significantly more common in dogs that had antibodies than in those that didn’t, suggesting infection with SARS-CoV-2 could have caused (or contributed)  to illness in (at least some of) the dogs. However, the signs that were reported were very mild and often vague (e.g. “the dog was a little quieter”), so while it might suggest that dogs can get sick, it would seem any illness is generally really mild.

Serious disease from SARS-CoV-2 has been identified in cats, and there has been some chatter about a very small number of dogs getting really sick or dying. However, when you consider the massive number of people that have been infected and the apparent high rate of transmission to dogs, if there was a true serious disease issue, I think we’d see more evidence of it by now. Also, we’re going to find incidental infection in some dogs with serious diseases or that die for other reasons, just because of the large number of infected dogs.

My take-home message on this at this point – with the variants that are currently circulating – is that SARS-CoV-2 poses very little health risk to dogs. More work on that is underway, though.

Can dogs infect other animals or people with SARS-CoV-2?

Probably not. Dogs are probably much lower risk than cats, and the even the risk from cats is still unclear. The fact that the virus has been isolated from dogs (e.g. Hamer 2021) is a concern, because if there was live virus in the dog’s nose, you have to assume there was some risk of exposure to individuals in-contact with that dog. Whether there was enough virus being shed to actually infect someone is completely unknown, and it’s probably exceptionally rare for a dog to be shedding enough virus to pose a risk. Experimentally, dog-to-dog transmission has not been seen. That’s not a guarantee that it can’t happen, since these experimental studies were conducted in an artificial environment with very small numbers of animals, but it provides more support of limited risk.

Overall, I’d say the risk of SARS-CoV-2 infection from dogs is very low. I don’t think we can say it’s zero (we can’t guarantee much with this virus), but I think it’s very unlikely that a dog would pose a realistic risk to a person or another animal.

That said, why chance it? If a dog is infected or at risk of being infected (e.g. living in a household with an infected person), it should be kept away from other people and dogs. Dogs interact nose-to-nose and nose-to-bum a lot, and have a lot of contact with their faces, so keeping exposed dogs under control and away from others is a reasonable precaution. We’ve also seen transmission of other respiratory viruses between neighbouring dogs through fence-line contact, so this should be avoided as well, just in case.

Could dogs be an important reservoir of the SARS-CoV-2 virus once it’s controlled in people?

No, dogs are not susceptible enough to the virus to serve as a reservoir. To be a reservoir, the virus would have to be able to keep spreading dog-to-dog. That’s not going to happen because of the low susceptibility and short shedding time in this species. You’d need a very large number of dogs in regular close contact to even begin to have a risk, and then only IF dogs were able to effectively transmit the virus.

What about variants of concern (VOCs) in dogs?

Variants of SARS-CoV-2 such as alpha have been reported in dogs (e.g. Barroso-Arevalo 2021 and Hamer 2021). That’s expected as different variants become dominant in people, because people are the source of infection in dogs. Unless a human variant has more or less affinity for dogs than the original strains (possible, but not very likely), we expect the strains infecting dogs to be a reflection of the strains infecting in humans. I assume that large numbers of dogs have been infected with the delta variant as it now dominates in people as well.

Could new variants of concern emerge in dogs?

Almost certainly not. Variants develop by chance during viral replication. The more transmission, the more replication, the greater the risk of a variant emerging through random mutation. Since dogs are not going to be involved in sustained transmission of the virus, there’s pretty much no chance we’d see a new variant emerge in dogs and spread back to people. Yes, it just takes one replication error and transmission event for a variant to emerge, but the odds of it happening from a human-to-dog transmission AND the dog then infecting a person are pretty much zero.

Could dogs be a bridge to infecting wildlife with SARS-CoV-2?

Probably not, or at least much less likely than cats. Their low susceptibility, short period of infection, limited (if any) infectivity to others, and limited direct contact with susceptible wildlife mean the odds of dogs being infected by their owners and then infecting wildlife are very low.

So, we shouldn’t worry about SARS-CoV-2 in dogs?

Worry, no.  But we still need to pay attention to it.

What should be done with dogs?

Do the same as for cats:

  • If you are infected, try to stay away from animals… all animals, human and otherwise.
  • If your dog has been exposed to a person with COVID-19, keep it inside and away from others.

The risks to and from dogs are exceptionally low, but precautions are common sense and easy… a few short term mild hassles for some peace of mind.

Ultimately, dogs are part of the family – so if your family is isolating, the dog should be included in that too.

I’ve written about COVID-19 scent-detection dogs before, and I’ve done a variety of interviews on the subject, but it keeps coming up.

Can scent-detection dogs help with COVID-19 control?  The answer is (as with many things about the SARS-CoV-2 virus) less than clear.  My current answer is… maybe… in some situations… potentially.

Let’s break it down.

Can dogs detect SARS-CoV-2 using their sense of smell?  Presumably not. The virus should have no smell.

Can dogs detect SARS-CoV-2 infection using their sense of smell?  It appears that some dogs, in some situations, can actually do this.  There are a few preliminary studies of varying strengths (from laughable to pretty good) indicating that dogs can detect infected people. They aren’t smelling the virus though, they’re smelling something that an infected person’s body produces in response to virus.

What are the the dogs detecting in infected people?  We don’t know exactly what the dogs are smelling, which makes it harder to train and assess them. If we had “eau de COVID-19″ it would make training and assessment much easier.  As of yet, we don’t know the best sample for dog’s to smell (saliva vs nasopharyngeal swabs vs skin wipes vs sweat vs…?) or the best kind of patient (really sick person vs moderately sick person vs asymptomatic person…?) from which to get the samples for training.

Can a dog detect someone with COVID-19 walking by?  We don’t know. The best work has been done with samples taken directly from a person, such as sweat wipes. I haven’t seen any data about dogs detecting infected people from just sniffing around them (despite the Miami Heat trying to use dog walk-bys to screen fans for COVID-19).

Can dogs be used to tell if someone doesn’t have COVID-19, so they can be allowed to do something or go somewhere (e.g. use public transit, or attend an event like a basketball game)?

  • Maybe, but it depends on the scenario.  At best, dogs are going to be a reasonably good screening tool for COVID-19. They won’t be 100% accurate, so we can’t rely on them in critical situations.  But they could be an adjunct screening tool that’s far from perfect but still useful.

Where might scent-detection dogs be used to help with COVID-19 control?

I do NOT see scent detection dogs as a tool to say either:

  • Yes, this person is infected. They need to go home.
  • No, this person is good. Off they go.

If dogs are actually good at detecting people from a distance, then they could be used like rapid antigen tests to say either:

  • Yes, you’re good to go. But still wear your mask and do everything else because I’m not perfect.
  • Hang on a minute… something might be up. You need to go for a PCR test to find out for sure.

Even if dogs aren’t that good for rapid individual screening, they could still be useful. I think the greatest potential is identifying high risk environments. For example, they could be taken into a homeless shelter, workplace, migrant worker housing or other high risk environment, and if they detect a whiff of COVID-19, that would be the trigger to bring in targeted testing (rather than the dog trying to figure out which individual are positive).

Rapid, cheap, person-side antigen testing will probably be more useful than dog screening, but scent-detection dogs could be useful in some situations if rapid testing isn’t universally available.

First ee need to know that COVID-19 scent-detection dogs work, how well they work, and their limitations. As with a lot of things, this is an area where some people have jumped from “idea” to “application,” without all the necessary steps in between.

What we can’t do is try to use these dogs as untested tools that give people false confidence to engage in higher risk behaviours (like having them at the door of a sporting event).  They’re a potentially useful add-on, but not an excuse to do something that wouldn’t be done without them. So, if an event is going on and rules at set, sure, add dogs as an additional measure. If the dogs are being used as the argument to allow people in, allow more people in or allow them to reduce infection control measures, that’s possibly counterproductive.

Round two of my COVID-19 in animals summaries: Dogs

Are dogs susceptible to the SARS-CoV-2 virus?

Yes, but not very… maybe.  It depends what you mean by “susceptible.”

Nice and clear, eh?

There’s a difference between being infected and getting sick. Dogs can be infected by the SARS-CoV-2 virus (which is the virus that causes COVID-19 in people), but they don’t seem to be as susceptible as cats, and it’s debatable whether dogs get sick (more on that below).

Infection in dogs has been shown in a few different experimental studies, and through identification of infected pet dogs that were exposed to people with COVID-19.  In one small study, SARS-CoV-2 was detected by PCR in experimentally infected dogs, but the researchers could not isolate any “live” virus from the animals, suggesting the virus was present at a low level and the dogs were probably not infectious. The dogs remained healthy, but some developed antibodies against SARS-CoV-2, supporting the idea that they were truly infected and their immune systems responded accordingly. They did not pass to virus to other dogs with which they were co-housed. In the end, some or all of the exposed dogs got infected, but none got sick and they didn’t infect any other dogs.

Another experimental study yielded similar results, in that dogs were infected and mounted an antibody response, but didn’t get sick and were probably not infectious.

How often do dogs get infected with SARS-CoV-2?

We don’t know. Surveillance has been limited, so the scope of human-to-dog transmission isn’t clear. In Hong Kong, early in the pandemic, they quarantined pets of COVID-19 patients who could not care for them (e.g. owner lived alone and had to be hospitalized), and the pets were all tested at the quarantine facility. Hong Kong authorities identified SARS-CoV-2 in nasal, oral and/or rectal swabs from  2/15 dogs that were quarantined following exposure to their infected owners. Neither of the positive dogs had signs of infection, both developed antibodies to the virus, and gene sequencing of showed that the virus from the dogs was the same as that of their respective owners. Of particular note was they were able to isolate live virus from one of the dogs, which suggests the dog could have been infectious to others, at least briefly.

Additional data has been limited, in large part because it’s a logistical challenge to sample dogs in households with infected people during their isolation period. One small study in Spain didn’t detect SARS-CoV-2 in any of the 12 exposed dogs tested.  An investigation of pets from a cluster of infected and exposed veterinary students in France also failed to identify the virus in 12 other dogs, although it wasn’t clear how many of the dogs were actually exposed to an infected person.  A study from Italy reported no detection of the virus in 64 dogs from households with previous human COVID-19 infections, including 3 dogs that had respiratory disease.

Our Canadian study didn’t initially find the SARS-CoV-2 virus in any of 18 dogs (more to come on the expanded version).

There are still numerous reports of individual infected dogs from different countries. In the US, approximately 23 dogs have tested positive for the virus so far. That’s not a lot in the context of the dog population, but remember that not many dogs have been tested. Furthermore, testing has focused on looking for the virus by PCR. That will underestimate infections, because based on what we’ve seen so far there’s only a short window of time when you can get a positive PCR result from an infected dog. Dogs seem to only shed the virus for a few days after infection, so sampling dogs in infected households (after the people are no longer infectious and it’s safe to do so) runs the risk of a lot of false negatives simply based on the timing of sampling.

Studies looking at antibodies in dogs (and other animals) will be more informative, if the tests are accurate.  Antibodies are an indicator of past infection, and they tend to hang around significantly longer than the virus itself.  So unlike PCR-based surveillance, we don’t have to get into the household right away during the time of human illness – we can test dogs later to see if they were infected.

Not a lot has been reported yet on antibody testing (also called serology) in dogs. A study in Italy found antibodies to SARS-CoV-2 in 3.4% of dogs; 6/47 (14%) dogs from known-positive households, 1/7 (14%) dogs from households of suspected cases, and 2/133 (1.5%) dogs from other households. Whether the 1.5% prevalence in other dogs is from dogs that were infected by owners that were never diagnosed, or it represents the false positive rate of the test isn’t clear. A French study found antibodies in 2/13 (15%) exposed dogs and 0/22 dogs from households with no known cases of COVID-19.  Those results are similar to our preliminary 20% (2/10) prevalence in dogs from positive households in Canada so far. Obviously, we need to test a lot more dogs to get better estimates, and the study is ongoing.

Do dogs get sick from SARS-CoV-2?

That’s still unclear. I’d say that evidence is still far from convincing. There are a few poorly documented reports of sick dogs, but the question largely unanswered in those cases is “were they sick from infection with SARS-CoV-2, or were they sick with something else and coindicdentally happened to have been infected by this virus at the same time?” My guess is that disease is rare in dogs, but not impossible, especially in animals that may have other comorbidities that make them more prone to severe disease from many other pathogens as well.

Can dogs infect other animals or people with SARS-CoV-2?

Probably not, but that’s unclear too. Dogs are likely much lower risk that cats in terms of transmission. The fact that live virus was isolated from a dog at one point raises concern, because if there was live virus in the dog’s nose, you have to assume there was some risk of exposure to in-contact individuals. Whether the dog was shedding enough virus to actually infect someone is completely unknown. Lack of transmission in experimental studies isn’t a guarantee (because of the artificial environment and very small animal numbers) but provides more support of limited risk.

Overall, I’d say the risk of transmission of SARS-CoV-2 from dogs is very low. I don’t think we can say it’s zero, but I think it’s unlikely that a dog would pose a realistic risk.  That said, why chance it? If a dog is infected or at risk of being infected (i.e. living in a household with an infected person), it should be kept away from other people and pets. Dogs interact nose-to-nose and nose-to-bum a lot, and we have a lot of contact with their faces. We’ve seen transmission of other respiratory viruses between neighbouring dogs through fence-line contact, so keeping exposed dogs under control and away from others is reasonable and practical.

Could dogs be an important reservoir of SARS-CoV-2 once it’s controlled in people?

No. Dogs are not susceptible enough to the virus. For dogs to be a reservoir, they’d have to be able to keep spreading it dog-to-dog. That’s not going to happen because of the low susceptibility and short shedding time. You’d need a very large number of dogs in regular close contact to even begin to get a risk.

Could dogs be a bridge to transmit SARS-CoV-2 to wildlife?

Probably not, or at least they’re much less likely to be a bridge than cats. Their low susceptibility, short period of infection, limited (if any) infectivity and limited direct contact with wildlife mean the odds of them being infected by their owners and then infecting wildlife are pretty negligible.

So, we shouldn’t worry about COVID in dogs?

Worry, no. But, we should pay attention.

What should be done with dogs?

Do the same things recommended for cats:

  • If you are infected, try to stay away from animals – all animals, human and otherwise.
  • If your dog has been exposed, keep it inside and away from others.

Ultimately, dogs are part of the family – so if your family is being isolated, the cat needs to be a part of that.

and

Relax. This is almost exclusively a human virus. With a modicum of common sense, the risk posed from pets approaches zero.

I’ve written before about COVID-19 scent-detection dogs. I get lots of questions about them, and there are now several groups working in this area. There’s been a mix of information to date, ranging from encouraging to some pretty bad preliminary studies released on pre-print websites and other places. A dog’s nose is a wonderful thing (except when my dog sticks his in places I don’t want it to go), and dogs have been shown to be able to detect a wide range of different scents with great sensitivity.

The first question is: Will dogs be able to detect people with COVID-19?

If the answer is yes, then the bigger question is, will it be a practical way to detect people with COVID-19?

We may get more answers now that dogs are being used in a Finnish airport to sniff out COVID-19.  Ten dogs have been trained to detect people with COVID-19 based on smelling wipes collected from individuals. News reports include claims of close to 100% accuracy… I’d love to see good data on that, as I suspect it’s not 100% effective in the field. However, even if the dogs are moderately effective, they could be a useful tool when combined with other measures (e.g. rapid confirmatory testing of people that dogs flag as potentially infected).

My big questions at this point is, how effective is it really?

  • We need to consider both sensitivity (how good dogs are at detecting infected people) and specificity (how good they are at only detecting infected people).
  • For a screening test, we want a test that is highly sensitive, meaning it detects most infected people, even if it has some false positives (i.e. people who are mistakenly identified as positive but aren’t actually infected). That works if the false positive rate isn’t massive and if there is a convenient way to follow up to confirm who’s really positive. If we have a quick follow up test of another kind, the initial false positives are a bit of a hassle but not a big deal and easy enough to weed out, so we could tolerate some loss of specificity.
  • False negatives on the other hand (i.e. people who are infected but go undetected by the test) are a bigger concern.
  • So, knowing the sensitivity and specificity of these COVID019 detection dogs in a field situation (where there are lots of people of different types, with different stages of infection and with different smells) is key. Hopefully that’s being studied well.

Another question I have is, what’s the management plan for dogs that stick their noses in wipes from people with COVID-19?

  • Dogs have limited susceptibility to SARS-CoV-2, but limited and zero aren’t the same.
  • Will the dogs be screened in case they get infected in the process?
  • And (an oddball question perhaps) if a dog gets infected, does it lose the ability to detect infection in people? would the dog then smell the scent associated with the virus all the time?

There will be more to come, I assume.

A colleague asked me about scent detection dogs the other day. My response was that I hadn’t heard much after all the initial buzz, which might suggest things weren’t going well. However, as opposed to the horrible pre-print about COVID-19-sniffing dogs I wrote about previously, a paper in BMC Infectious Diseases (Jendry et al. 2020) provides some more robust and interesting information. It’s a pilot study, so it’s small, preliminary and underpowered, but it shows potential. Whether that’s “potential for dogs to be able to detect SARS-CoV-2 under certain circumstances” or “potential for dogs to be an effective detection tool” isn’t clear, but that’s the big question.

Here’s a breakdown of the study and some commentary:

The researchers collected saliva samples and respiratory secretions from hospitalized COVID-19 patients, and healthy people who were PCR-negative for the SARS-CoV-2 virus.

  • This may not be ideal, depending on the goal. My vision is using these dogs in the community to rapidly detect infectious people in high risk situations (e.g entrance to transit stations, public buildings, schools). In that case, people who are hospitalized with severe COVID-19 are likely not the best test population. A dog isn’t going to replace a PCR machine in the hospital.  It’s simply not practical in most cases to collect a sample from a patient, take it to a dog as a quick screening test, and then submit the sample for definitive testing.  We want dogs that can detect a mild case in the community, long before the patient needs to be hospitalized.
  • They didn’t test samples for other human coronaviruses, like those that cause the common cold. It’s a potential limitation, but I don’t think it’s a big deal in this case.
  • They also don’t explain where they got their negative samples. A clear description of the study populations is critical and it’s somewhat lacking here.  We want to be sure the dogs were detecting SARS-CoV-2 and not something else unique to the positive sample population, like a smell associated with being from a hospital.

Because of the potential susceptibility of dogs to the SARS-CoV-2 virus, samples were inactivated prior to exposing them to the dog.

  • That’s a reasonable step, but raises more issues of practicality and how the dogs could ultimately be used (e.g. can the dogs only be used to screen specimens collected from high risk patients, or can they be used to detect infection in someone walking by).

Eight dogs were trained using standard methods. They had a 2-week habituation process for the training system, then had 5 days of training until their rate of detection was greater than what would be expected by chance alone. They then started the study

  • The sample size was small, but reasonable for a proof-of-principle study.

The ability of dogs to detect positive samples increased over time. There was some variation between dogs, but all of them were pretty good. The overall sensitivity (percentage of positive samples that the dogs correctly identified as positive) was 83%, ranging from 70-95%. The specificity (percentage of negative samples that the dogs correctly identified as negative) was 96%, ranging from 92-99%.

  • For a screening test, we’d actually want the reverse, that is to say higher sensitivity at the expense of specificity. That would mean the dogs would catch most of the positives. Lower specificity is okay initially if the screening test (i.e. the dog sniffing) can be followed up with a more specific test, and if the implications of an initial false positive aren’t high. If a dog calling a person positive results in that person being sent home to self-isolate for 14 days, then a high false positive rate is a problem. If it just results in the person being pulled aside to have a swab collected for a lab test, that’s not as big of a deal (perhaps a bit of a hassle but maybe not a deal breaker).
  • A low sensitivity and high specificity means you run into fewer hassles with false positives, but the test will miss more positive people. The fact that 17% of prime samples from people hospitalized with active COVID-19 were called negative is a concern in terms of the dogs being able to detect the virus in less severely affected people and from less voluminous and close samples (e.g. detection directly in someone walking by).

I’d file this in the “interesting but preliminary” folder. Anything that can help identify infectious people is useful. If dogs can do it, that’s great, but they also have to be able to do it from a distance, because a handler and a dog getting very close to large numbers of people might cause more problems than they fix.

In my perfect world:

  • A SARS-CoV-2-sniffing dog would be parked at the entrance of schools, office buildings, transit stations, etc.
  • The dog would be able to detect infected people from a short distance away (i.e. without direct contact).
  • The dog would signal its handler when it detected a positive person.
  • That person would then (discretely) be pulled aside for testing, which would (in my perfect world) be done quickly, right there (there is lots of work being done to develop a more rapid test like this that can be done on the spot, but we don’t have one yet).
  • If positive, the person would be told right away and sent home to self-isolate. If negative, the person would be good to go (though maybe wondering why they smell like a coronavirus).

As I’ve said, it’s an interesting and useful preliminary study that shows potential. The key is to follow up preliminary studies with more detailed, rigorous work, which unfortunately often doesn’t get done. Nonetheless, I suspect media headline writers will jump on this and over-interpret the results. It’s also another example of the remarkable things a dog’s nose can do, but the potential practical applications (if any) are still very much up in the air.  I’ll be a bit surprised if this ever becomes a common/useful tool, but I’d love to be wrong about that.

I’ve had countless questions about the potential for scent detection dogs to be useful for COVID-19 surveillance. It’s an interesting idea, but it’s dependent on COVID-19-infected people producing some volatile compound detectable by the dogs than uninfected people do not.  (The virus itself is not likely to have a detectable odour.)

A recent pre-print paper on bioRxiv provides a rambling description of a pilot study about the potential for dogs to sniff out COVID-19 in people based on their armpit sweat.  This one can probably be filed under the “not likely to ever be published in a journal, but an interesting story” category.  (It may also be another paper in the “let’s get something online first, who cares about the depth and editing” category. Sixty-one authors is a bit extreme too, but I digress.) As I’ve said before, pre-prints can be useful, but there has to be at least a modicum of effort…

Anyway, they collected armpit sweat samples from people with COVID-19 and patients without signs of COVID.

They used 18 dogs that had been trained for explosive detection, search and rescue and colon cancer detection, but their table also lists an arson detection dog.  Further, they say that “We did not decide to work with drug detection dogs as there is always a possibility that COVID-19 positive or negative people use prohibited substances that would let catabolites be excreted by the axillary sweat.” And yet, their table lists a drug detection dog.

After training, the dogs were tested to see if they could differentiate sweat samples from COVID-19 patients in scent boxes, from the samples from the non-infected patients.

  • Three of the 18 dogs flunked out of COVID-19 detection school as they were “unable to adapt to an olfactive search on a line of sample”.
  • Eight others were removed because they were “late in their testing period due to this necessary basic “retraining”. I’m not really sure what that means. I guess they weren’t completely kicked out of school but had to repeat the year, and no one wanted to wait to rush out the pre-print.

The authors say that left 8 dogs whose results they used for the analysis; however, my math says that 18-3-8=7, not 8.

Numbers aside, results were interesting, as the remaining dogs seemed to have fairly high detection rates (84-100%).

It’s hard to say what this means and whether it’s relevant. I guess it means that there’s potential for some dogs, but you have to find the right dogs, and train them.  The authors make a fair point that they were looking at effective dogs, not whether it worked in the whole dog population.

Is this of any use?

It’s hard to say. They tested samples from people with overt COVID-19 disease, and that’s likely not very relevant. If someone has signs of COVID-19, we want to treat them like they have COVID-19 at least until they are definitely tested, regardless of what the dog thinks. Where this would be more useful is for detecting asymptomatically infected people, in which case the dog might provide an early warning of infection. The downside is that it requires a dog and a person to be in close proximity to the patient being screened. Dogs are low (but not no) risk for picking up SARS-CoV-2, but there’s also reasonable concern about handlers. The practical nature of this is also questionable. The study mentions that armpit sweat is “easy and safe to collect”, but if the “test” relies on people taking samples of their own armpit sweat, it’s no longer a quick, easy detection method. It’s more appealing if the dog can, for example, be used to screen people coming into a building or workplace.

The authors have a few excuses for some of the false negative results, which seem to be a bit of a stretch, or indicate potential issues applying this to a real world situation (e.g. distraction by a “too zealous television team”). Some other discussion points are a bit hard to follow. They attributed false positives to two male dogs and a young woman that “had been sampled during her fertile period”… they’d better sort that problem out since that’s a reasonably common subset of the population.  The paper’s discussion devolves considerably from there: “In Shakespeare’s day, a woman in her fertile period used to hold a peeled apple under her arm until the fruit became saturated with her armpit scent ; then she presented this “love apple” to her lover to inhale in order to provoke his sexual excitation. Pheromones are defined as substances produced by on animal which conveys information to other individuals by olfactory means. And in such a situation androsterone and molecules like benzoate derivates, excreted in axillary sweat, enhance sexual attraction by men toward women near the end of follicular phase of the menstrual cycle when fertility is at highest.”

Overall, it’s an interesting pilot study that shows more study might be warranted. In particular, it’s important to figure out whether dogs can be good detectors of COVID-19 infected people in situations like busy, high risk places in the community.  Criticisms aside, it would be really cool to have a dog hanging out at the entrance of busy places, picking out infected people, to help curb further spread of SARS-CoV-2 in the community.

Updated document: April 28, 2020

Below are some timely comments, headed up by OVC veterinary parasitologist Dr. Andrew Peregrine, about heartworm testing and heartworm preventive administration during this period of “urgent care only” veterinary services.  You can also click here for a pdf version of the comments Please note that this was created for the Ontario context, considering the provincial directives for urgent care and the epidemiology of heartworm in this province.  It may not apply equally to areas that are approaching social distancing differently or where heartworm risks are greater. 

COVID-19 Recommendations for Heartworm Testing and Prescribing Heartworm Preventives for Dogs in Ontario

In the OVMA guidelines entitled “VETERINARY MEDICINE DURING A TIME OF RESTRICTION OF

ELECTIVE SERVICES AND SOCIAL DISTANCING (REVISED)’ dated April 17, 2020 (OVMA 2020), the recommendations for “Heartworm prophylaxis” are as follows:

“If pets have been on prophylaxis in previous years, dispensing without a heartworm test is reasonable. Maintain social distancing (see below), arrange delivery or use eCommerce. If there are concerns about owner compliance or if prophylaxis history is unclear (or absent), risks should be discussed with the owner but preventives can be dispensed without testing, with owner consent. Postpone visits to clinics for heartworm testing.”

As such, heartworm testing is considered an elective procedure and should only be carried out if there is a high likelihood of infection, e.g. a dog that has been imported in to Canada from a high-risk area with an unknown prevention history. For dogs that reside permanently in a low risk area (i.e. almost all of Canada) and have previously received a heartworm preventive with reasonable to good compliance, testing is not required prior to prescribing a heartworm preventive. For Canadian dogs with an unknown heartworm prophylaxis history or a history of poor compliance with the use of heartworm preventives, a test should only be carried out if there are clinical signs consistent with heartworm. For dogs >6 months of age for which a baseline heartworm antigen test has not been obtained, the test should be delayed until COVID-19 testing recommendations no longer apply; until that time, a heartworm preventive should be used that is safe to give to a heartworm-positive dog.

It should be recognized that:

  • Some heartworm preventives are approved for use in Canada with label text that states “may be safely administered to heartworm infected dogs” (e.g. Revolution®, Advantage Multi®). However, safety data are available for other products and should be discussed with the respective company.
  • All heartworm preventives are approved with a requirement to carry out an annual heartworm antigen test, prior to prescribing the product. As a result, not carrying out the test means the product is being used off label; historically, pharmaceutical companies have typically not covered heartworm adulticide costs if their product is used off label. As of April 22, 2020, no pharmaceutical company in Canada has indicated whether they will cover heartworm adulticide costs for dogs where testing was delayed because of COVID-19. However, such cases are uncommon.
  • These recommendations differ from those provided by the American Heartworm Society (AHS 2020) and reflect the lower risk of heartworm in Ontario compared to the USA.
  • Since there is a legal requirement for rabies vaccination of dogs in Ontario, yet rabies vaccination has not been classified as an urgent procedure, it is hard to position heartworm testing above this.
  • Guidelines for heartworm adulticide treatment during the COVID-19 era are provided by the American Heartworm Society (AHS 2020).

Please note: These guidelines are a compromise between the risk of heartworm causing problems in Canadian dogs and the risk of COVID-19 infecting people. At the end of the day, a veterinarian always has the right to test a dog for heartworm if they believe the test is warranted. The COVID-19 recommendation is to only test if there is a high risk of infection.

References:

AHS (2020) ahs-covid-19-recommendations-20200406.pdf

OVMA (2020) OVMA COVID-guidelines-essential-elective_social-distancing_April-17.pdf

Andrew Peregrine & Scott Weese, Ontario Veterinary College, April 28, 2020

Mink are not a species most people think about. When they do, they typically think of mink coats or fur farming protests. While the mink industry has been on the decline in most regions for many years, there is still a massive number of mink being farmed for fur internationally. Some of these farms are very large, which makes for lots of animals in close contact with each other, and in contact with their human caretakers, which leads to the risk of pathogens such as SARS-CoV-2 passing back and forth between them all.

Mink aren’t the only critters in the mustelid family that are a concern when it comes to SARS-CoV-2. Any species from the mustelid family probably has similar susceptibility to the virus.  The domestic pet relative of mink is the ferret. Ferrets are “niche” pets but they’re far from rare, and many ferrets have very close contact with their owners.

So, we have widely different issues in how we manage and interact with different mustelids, whether on a farm, in the home or in the wild. Regardless, the net result is situations where there’s a good chance for respiratory virus transmission.

What’s the story with mink and SARS2CoV-2?

There’s been a lot of attention paid to mink during the COVID-19 pandemic, even since the original review I posted last October.  I think it’s fair to say this caught us off guard. No one was talking about mink or risks to/from mink farms at the start of the outbreak, even among those of us who were thinking about risks from other species (lots of people tried to ignore animal risks altogether from what was clearly an animal-origin virus, but that’s a rant for another day).

While we may not have initially paid attention to mink, SARS-CoV-2 did. Mink are highly susceptible to this virus, and there have been widespread outbreaks on mink farms, first identified in the Netherlands but subsequently in multiple countries as well (including Canada and the US).

What happens when SARS-CoV-2 makes its way (from people) onto a mink farm varies, and there are still lots of knowledge gaps. Some affected farms have had few health issues, while others have reported widespread illness and deaths amongst mink, especially older or pregnant mink. The virus seems to have persisted on some farms, at least for a while, with little apparent disease, while on others it seemed to burn through the population and then disappear like a more classic respiratory outbreak. Why? We’re not sure. This virus clearly can cause disease in mink, but it doesn’t always. There may be a predilection for severe disease in mink of a certain age, or in pregnant mink (as with people), but there are still lots of things we don’t understand.

Can mink infect people with SARS-CoV-2?

For most species, I say “we don’t know if they can infect people and it would be hard to figure out”, we know that SARS-CoV-2 can definitely be transmitted from mink back to people, because of the nature of spread and sampling that has been done on mink farms and the people who work on them. If mink and people on a farm all had positive tests, you couldn’t necessarily determine whether some of the people were infected by mink or whether the people all infected each other. However, viral sequencing and the timing of infections on some mink farms has provided more information than we can usually get. Tiny, mainly innocuous changes in the virus commonly occur during replication, and those changes create a kind of “signature” that can help us track the virus better. Using sequencing, you can track how the virus evolves on a farm, where the initial infections are a strain that’s present in people in the community (since that’s where the virus usually comes from), and then the strain changes a bit as it’s transmitted over and over between mink. If that slightly modified strain then pops up in people on the farm, it’s strongly suggestive that the virus was spread from mink back into people.

Are mink farms a reservoir for the SARS-CoV-2 virus?

That’s an important question and a big concern. “Reservoir” can be considered a few different ways. The main concern is whether the virus can spread on a farm for prolonged periods of time, creating an ongoing source of exposure to people (and possibly wildlife) on the farm, including new variants of the virus.

Can the virus spread from mink farms to the community?

  • Yes. That’s been shown. It’s rare in the grand scheme of human COVID-19, but it has happened.

Can the virus spread from farmed mink to wildlife or other animals?

  • When SARS-CoV-2 is present on a farm, there could be exposure of a range of wildlife that may come and go from the property through contact with mink feces (which fall through the animals’ cages and accumulate under them) or from aerosol exposure (e.g. virus in dust particles within the animal sheds). There’s also the potential for exposure of farm animals (farm dogs, barn cats). Transmission to farm dogs and cats has been identified.
  • Infected “feral” mink were found around an infected farm in the US; these were presumably mink that had escaped at some point from a nearby farm, but it shows another way the virus can make its way off the farm.  This has also been seen in Spain, where infected feral American mink were found (and at some distance from the closest mink farm…). Since American mink are not native to Europe, it’s safe to say those mink (or their ancestors) were escapees at some point. Where the virus could go from there is a good question. It might just burn out in the wildlife population (since wild mink are primarily solitary creatures), but if it’s able to continue to find susceptible hosts (e.g. wild mink, certain mouse species, white tailed deer), it’s possible mink farms could be a source of broader spread, bridging human SARS-CoV-2 with wildlife.

Can the SARS-CoV-2 virus be sustained on a mink farm long term?

  • A big factor that might influence the risk from mink farms is whether there is long term, sustained transmission of the virus within the farmed animal population. If the virus enters a farm, burns through the population quickly, and is eliminated (either naturally or through culling of infected animals), then there’s lots of transmission but over a very short period of time. If SARS-CoV-2 enters a farm and continues to spread over months (or even) years by continuing to find new susceptible mink in the population to infect (or re-infect), the risk probably increases substantially. We don’t know how much of a risk it is, but we know there’s some risk because the virus already seems to have maintained itself on certain farms for a long period of time (months). We still have limited information about the long term outcomes, because many infected farms were depopulated, and on those that weren’t long term testing wasn’t necessarily done (or reported).

Are mink a source of new variants of SARS-CoV-2?

In the first 3 parts of this review update that I posted last month, I dismissed the potential for dogs, cats and pigs to be significant sources of new SARS-CoV-2 variants because of reasons like poor susceptibility (pigs), minimal virus shedding (pigs, dogs) or lack of enough animals in close contact for sustained transmission within the animal population (dogs, cats).

Unfortunately, mink create the perfect storm for new variant emergence. They are a highly susceptible species that can effectively transmit the virus mink-to-mink and mink-to-human, and they are raised in large enough groups that there can be widespread and sustained transmission. Since variants emerge due to random mutations, and the likelihood of that is dependent on lots of virus replication, and more transmission leads to more replication, variant emergence is definitely a concern on large mink farms.

“Mink strains” of SARS-CoV-2 have been identified. Whether that’s because the virus adapted to be better able to infect mink or the changes were purely random (i.e. conferring no specific advantage to the new strain in terms of infecting more mink) isn’t clear. However, the new strains provide a way to help track virus transmission in some situations. In early outbreaks, there was concern about a mink variant that was identified in the Netherlands. There was also concern that mink strains with a common mutation (Y453F) that spread from mink farms into the general human population in Denmark might be less responsive to antibody-based treatments used in people  (these are important therapies for high-risk people with early infection). However, there was no evidence that these mink strains would compromise vaccine efficacy, and fortunately they didn’t end up being a significant problem as they weren’t any worse than “regular” strains in people in terms of disease. In fact, there’s some (albeit pretty weak) evidence that mink-derived variants might be less virulent in people. I think we have to assume both things could happen: mink could be the source of new variants of concern that pose more risk to people, as well as new variants that would pose less risk to people. We can’t really predict what will happen, or when.

Realistically, the biggest risk of variant emergence still lies in the human population, since we still have rampant human-to-human transmission of SARS-CoV-2 internationally. But mink are a potential source, and all it takes is one event with the right (or wrong) mutation to cause a problem. Further, as we (eventually) control this virus in the human population, animal reservoirs will become more important, as the relative risk from them will increase if true reservoirs are being created through infection of different wild and domestic animal populations.

How about ferrets? Are they as susceptible as mink to SARS-CoV-2?

Whether ferrets are “as susceptible” to the virus is hard to say, since they haven’t been directly compared. However, ferrets are clearly susceptible and are able to effectively transmit the virus to other ferrets. We’ve seen this in multiple experimental studies where ferrets were infected, got sick and were able to transmit the virus ferret-to-ferret.

I was a bit surprised that we didn’t see reports of naturally infected pet ferrets early in the pandemic. That was likely because of limited numbers of ferrets and limited testing. In our surveillance, we only got to test a handful of ferrets.  Despite the small number of reports, there have been documented infections in pet ferrets (e.g. Giner et al. 2021, Gortazar et al. 2021, Racnik et al. 2021) As with dogs and cats, infection in ferrets is likely under-diagnosed, and may actually be a common event that occurs under the radar in households where people have COVID-19. I assume the odds are 50:50 or greater than a ferret from a household with active COVID-19 in a person is, was or will become infected, if it has close and/or regular contact with infected people.

The health impact of SARS-CoV-2 infection on pet ferrets hasn’t been well described. Some get sick, but it’s mainly been mild disease, which fits with the findings of experimental studies as well. Some report infections with limited or no obvious signs of disease (e.g. Shi et al. 2020,  Schlottau et al. 2020Kim et al. 2020). However, more serious disease, sometimes requiring euthanasia, has been reported. That might be related to the dose of virus, as high doses were used in the experimental study where more serious disease was encountered. The overall health risk to pet ferrets is probably low, but we can’t rule out the potential for severe disease, particularly in older or pregnant ferrets, or ferrets with pre-existing health problems.

Can ferrets infect people with SARS-CoV-2?

We don’t know, but they probably could. Since ferrets are susceptible and can infect other ferrets, and we know that mink can infect people, it makes sense that ferrets could also infect people. However, the true risk to ferret owners needs to be considered.  Being able to infect a person is one thing. Actually being an important source of infection is another. To pose a risk, ferrets have to first be exposed to a person with SARS-CoV-2 infection. This would almost always be their owner. In that situation, the owner poses greater risk to other people in the household than the ferret does. The main risk to others is if the ferret leaves the household (e.g. if it needs to be taken to a veterinary clinic for an exam) during the period when the household members are infected.

What are the recommendations when it comes to mink, ferrets and SARS-CoV-2?

Anyone with COVID-19 should absolutely not go anywhere near a mink farm. Period.  That’s the big one. If we’re going to continue to farm mink for fur, there needs to be a strong focus on biosecurity and surveillance for this virus. Surveillance is an issue because of cost (i.e. who pays?) and the general lack of desire among many parties involved to really know what’s going on (especially if the mink don’t look sick).

In terms of ferrets, the same general approach that we recommend for dogs and cats applies:

  • If you have COVID-19, try to limit or avoid contact with your ferret.
  • If your ferret has been exposed to someone with COVID-19, keep it away from other people and animals.
  • If your ferret has been exposed to someone with COVID-19 and is sick, let your veterinarian know, to help determine whether it might be infected with SARS-CoV-2 (do that by phone, at least initially, rather than showing up to the veterinary clinic directly with your ferret).

Next up for a review update… horses.

For the past year or more, we’ve been trying to track infectious upper respiratory tract disease (officially known as “canine infectious respiratory disease complex (CIRDC)” but more commonly called “kennel cough”). It’s a tough thing to do since testing is limited, the disease is always present to some degree in the dog population, and there’s no formal reporting system. Enquiries about CIRDC in different areas seem to fill my inbox in waves, but that’s probably more related to reporting (especially social media rumours) vs actual frequency of illness. This week’s been busy so far  with a dozen or so emails asking about things like “new” respiratory diseases, or specific things like canine influenza (and it’s only Monday…).

We’re still not sure what’s going on. It does seem like there’s increased CIRDC activity over a lot of North America right now, and it’s been going on to some degree for quite a while. When we think about increases in respiratory disease reports, there are a few  potential causes (as I have mentioned many times before):

Increased disease caused by the usual suspects

  • This is my main guess at this point for what’s currently going on. Common things occur commonly, and that’s particularly true for the variety of bacteria and viruses that cause CIRDC in dogs.
  • A few potential reasons for the increased disease from these pathogens can be postulated. One is there’s more dogs mixing with each other now as people start to increase activity and get together post-lockdowns, and as people prioritize safer outdoor activities (often with their dogs). Combine that with a surge in new dogs and potentially decreased vaccination (due in part to overloaded veterinary clinics and access difficulties from earlier restrictions), and it’s easy to see how we might have more disease.
  • Another potential dynamic is increased use of oral “kennel cough” vaccines, as they are easier to administer to some dogs compared to intranasal vaccines. The problem is oral vaccines only protect against one cause of CIRDC (Bordetella bronchiseptica) while intranasal vaccines protect against Bordetella and canine parainfluenza virus (CPIV). That’s important because CPIV is the most commonly diagnosed cause of CIRDC in many areas.

Increased disease caused by a new pathogen

  • We’re always on the lookout for something new, but nothing is apparent yet. With a new virus, we’d be more likely to see widespread transmission in exposed groups, since no dogs would have any immunity. We’re not really seeing that. The cases being reported are more sporadic, as we’d expect with our typical causes of CIRDC. However, we can’t rule out a new pathogen completely, and there are undoubtedly various causes of CIRDC (mainly viral) that we simply haven’t identified yet.  I don’t think it’s the explanation for the current situation, though.

Increased reporting of disease

  • This is probably part of what we’re seeing. There’s more social media use these days so word spreads quickly. One voice can be amplified disproportionately and unsubstantiated claims can be disseminated easily. Further, it feeds on itself. When there’s more buzz about sick dogs, more people that otherwise wouldn’t have said anything chime in. So, we probably hear about a greater percentage of sick dogs simply because people are talking about them when they otherwise wouldn’t have.
  • Also, as more people are at home with their dogs, we probably hear more about the typical mild cases of CIRDC, because owners pay more attention when the dog is coughing beside them all day.

What about SARS-CoV-2?

  • SARS-CoV-2 is very unlikely to be playing a role. We can never say never, since the COVID-19 pandemic is a dynamic situation and we don’t know much about recent variants in animals. However, what we know so far is that infection of dogs and cats with SARS-CoV-2 is quite common, but disease is uncommon in cats and rare in dogs.

What about canine influenza?

  • Canine flu certainly can cause large outbreaks of respiratory disease in dogs. It spreads quickly because of limited immunity in the dog population. There has been some canine flu activity in a couple places in the US in the past few months, but these seem to have burned out (or at least burned down) relatively quickly.
  • There have been social media reports of canine flu outbreaks in Ontario. As far as I know, that’s false. Canine flu is reportable in Ontario, and no such reports have been received from any lab. We haven’t seen canine flu in Ontario since we eradicated it in 2018. I’m always on the lookout for it, but I’m most concerned about flu when there’s an outbreak that has a very high attack rate, including dogs that have had intranasal kennel cough vaccine. We’re still looking but I doubt canine flu is playing a role currently.

What can people who are worried about their dogs do?

  • Reduce contacts with large numbers of unknown dogs. Just like with other respiratory pathogens, the more contacts, the greater the risk of encountering someone that’s infectious.
  • Reduce contact with sick dogs. This can be harder but it’s common sense: if a dog looks sick (e.g. coughing, runny nose, runny eyes), keep your dog away from it.
  • Keep sick dogs at home. (Duh… but you’d be surprised.)
  • Avoid things like communal water bowls in parks that are shared by multiple dogs.
  • Get your dog vaccinated (ideally intranasally) against kennel cough if it tends to encounter other dogs regularly. My dog doesn’t get this routinely since we live in the country and he has a very limited number of other dogs with which he interacts. If I was in town and/or going to dog parks or other places where he’d mix with lots of dogs of unknown status, I’d vaccinate him (especially as he’s getting older now).
  • Consider testing your dog if your dog gets sick. Testing is useful to help figure out what’s going on and maybe to help control things. However, it rarely tells us something that influences care for the individual dog (since we don’t have specific treatments). So, the cost of testing is (understandably) hard to justify for some.

We’re also still tracking cases so people with sick dogs can provide information by filling out our quick survey here:
https://uoguelph.eu.qualtrics.com/jfe/form/SV_eP6E6AzIiJfnDlY

I get asked about this topic a lot. Early in the pandemic, I wrote a post about options for caring for pets of people with COVID-19.  Some things have changed a bit now that we know more know about SARS-CoV-2 in animals and the associated zoonotic risks, and we have a vaccine for people.

One example of a commonly encountered scenario is: A dog owner is being hospitalized because of COVID-19 and a friend or family member has been asked to take care of the pet.

What are the risks to the caretaker of the dog?

  • We don’t know. I’d consider it very low but I can’t say it’s zero.
  • Person-to-dog transmission of SARS-CoV-2 is fairly common in households where the owner has COVID-19, based on our and other groups’ surveillance efforts. However, dogs are not really a great host for this virus and infections are probably fairly low grade and transient, and therefore low risk for further transmission.
  • Dog-to-dog transmission of SARS-CoV-2 hasn’t been seen experimentally, but the studies to date have been fairly small so we can’t read too much into that.  Nonetheless, it’s clear that dogs are lower risk than cats for passing the virus on to other individuals. Yet, live virus has been grown from canine respiratory secretions, suggesting there is at least some plausible risk.

What can or should be done in this situation?  There are two key considerations:

1. Should the person in question agree to look after the animal at all?

  • This requires consideration of the risk status of everyone in the household (e.g.  is anyone at high risk of serious disease if they get infected?), vaccination status of everyone in the household, whether other pets are present, how well the dog can be contained in the household, and whether the household members are willing to accept a small degree of risk.
  • The best case scenario is to send the dog to a pet-free household where everyone is vaccinated and where they can keep the dog away from other people or animals (e.g. they have a fenced yard). Asking someone else to look after a pet like this was harder earlier in the pandemic, but now that we have highly effective vaccines, it’s easier.  Asking if someone from a fully vaccinated household will take the job is reasonable.

2. How should the dog be managed?

  • That also depends on the risk status of the household. In a vaccinated household, I’d say it can be “business as usual” in the house, but restricted outside. By that, I mean I’d do nothing different with the human-dog interactions in the household, but when the dog goes outside it should be under control (e.g. on a leash, or in a fenced yard) so the dog doesn’t interact with other people or dogs from outside the household.
  • If there are unvaccinated people in the household, it’s tougher. I still consider the risk of transmission from a dog to be very low, but I can’t say it’s zero. So, it would be prudent to keep the dog away from unvaccinated individuals as much as possible for the first 14 days (7 days is probably reasonable if it’s a major issue, but 14 days is ideal).  That doesn’t mean locking the dog in the bathroom and never going near it, but rather avoiding contact with respiratory secretions, not having the dog in the same small airspace for prolonged periods of time (e.g. not sleeping in the bedroom), and focusing on good hand hygiene.

The main issue is we just don’t know the risk. It’s definitely very low and could be zero, but I don’t think we can say it’s zero at this point. Vaccines are a game changer for these scenarios.

Okay, but what if the pet in question is a cat instead of a dog?

That changes the risk a bit, but not really the overall approach. Cats are more susceptible to SARS-CoV-2 and cat-to-cat transmission can occur, so there’s also more concern about the potential for cat-to-human transmission.  That means the issues above all apply to cats as well, but are probably heightened.

My focus here would be on finding a vaccinated household to look after the cat, if possible.  If not, it’s a matter of restricting contact with anyone who isn’t vaccinated. The good thing about cats is they are (for the most part) easier to contain than dogs.  They can be kept in a large cage or kennel if necessary, or they can be confined more easily to certain areas of the house, and cats don’t need to go outside. So, if someone who’s unvaccinated has to take in a cat, it’s easier to limit contact. The concepts above still apply, with a goal of minimizing the closeness and duration of contact during the first 7-14 days after the cat is removed from the person who was infected with COVID-19.