What the story with SARS-CoV-2 in horses?

This one’s easy to answer: we have no clue.

There’s been almost no investigation or research regarding this virus in horses. Horses often get left out in situations like this because they’re livestock, but not (typically) food animals, and investigation of livestock tends to focus on food animal species. Horses are often more akin to companion animals, but a smaller number of people own or have contact with horses compared to household pets. Experimental studies aren’t commonly undertaken because trials in horses are generally very expensive due to their size and upkeep.

So, what do we actually know about SARS-CoV-2 and horses?

Not much.  As I’ve mentioned in several other posts, there are studies that have looked at the composition of the ace2 receptor in different animal species. Ace2 is the part of the SARS-CoV-2 virus that it uses to attach to (and ultimately invade) the body’s cells. If the virus can’t attach to cells, it can’t infect them. The structure of this receptor varies between species, and that accounts (in part) for differences in species susceptibility. Not all studies have included horse, but one ace2 receptor study suggested that horses might be susceptible to SARS-CoV-2 – possibly even more susceptible than a few species we already know are quite susceptible, such as cats and ferrets. Another study based on ace2 receptor analysis ranked the likely susceptibility of horses to SARS-CoV-2 to be equivalent to cats (specifically domestic cats and lions, both of which we know can be infected) and camels (which we also know nothing about, beyond their being a host for another zoonotic coronavirus, Middle Eastern Respiratory Syndrome Coronavirus (MERS-CoV)).

We have to take such predictive studies with a (big) grain of salt, because the real world situation hasn’t always mirrored what was predicted.  Those studies basically tell us we should pay more attention to horses and see if there’s a problem, not that a problem is necessarily likely.

Have any horses been tested for SARS-CoV-2?

Maybe.  I haven’t tested any, and I haven’t heard of anyone who has, but it’s possible someone’s looked but not found the virus, or antibodies against it, in horses. If there was a positive, I assume it would have been reported somehow somewhere. I suspect few, if any, horses have been tested.

What should be done with horses?

Some surveillance would be good. Testing horses that have been exposed to infected people would be interesting, and tell us more about interspecies spread of the virus. There have been outbreaks of COVID-19 in grooms in racing stables, a human population that’s probably very high risk for infection, and for working while sick. They usually have close and frequent contact with horses, so testing horses from stables with outbreaks in the grooms or other staff would be a good start.

However, as for all animal species, the most important thing to do is stay away from them if you have COVID-19 or if you’ve had high-risk exposure to someone with COVID-19. It’s better to prevent a problem than have to figure out how to deal with it after it happens. If we reduce the number of infected people who have contact with horses, we reduce any potential problems.

Image source: https://dailymemphian.com/article/15734/germantown-horse-mask-ordinance

I’ve spent a lot more talking about mink in the past few months than I ever thought I would. In regard to SARS-CoV-2 (the virus that causes COVID-19 in people), mink and ferrets (their close relatives) are a fascinating story, but I’ll try to be brief about it. Mink have become important because of the widespread outbreaks of SARS-CoV-2 on mink farms in some countries, and ferrets are important because they’re household pets and appear to be equally susceptible to the virus.  What we know about these two species within the mustelid family is quite different. We have good experimental data for ferrets and very little field data. For mink, it’s the opposite.

What’s the story with mink and SARS-CoV-2?

I think it’s fair to say this caught us off guard. At the start of the COVID-19 pandemic, no one was talking about risks to/from mink farms. Yet, mink are highly susceptible to the SARS-CoV-2 virus. There have been widespread outbreaks on mink farms in some countries, first in the Netherlands but now in several countries in Europe, as well as in the US. In the vast majority of cases, it is suspected that the mink were initially infected by a person, and then the virus spread further from animal-to-animal.  Some affected farms have had few health issues while others have reported considerable illness and increased mortality in their animals, which has led to widespread culling of mink in some countries to try to contain the spread of the virus.

There are a few additional concerns with these outbreaks beyond the health of the animals themselves. One is zoonotic transmission back to people, as apparent mink-to-human transmission has been reported in one Dutch study. Infection of feral cats on mink farms has also been identified, which raises concern about the cats (or escaped mink) potentially infecting wildlife in the surrounding area.  Work on this issue is ongoing.

So, mink can be infected, the virus is effectively spread between mink, mink can potentially infect people in contact them, and mink may be a source of exposure for other animals. All of those are concerning.

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

Whether ferrets are “as susceptible” as mink is hard to say; however, they are clearly susceptible to infection, can get sick, and can shed enough virus to infect other ferrets, as has been demonstrated in multiple experimental studies. Notably, ferrets can be infected with fairly low doses of SARS-CoV-2.

One thing that raised some concern and confusion was a report that ferrets could spread the virus “via the air.” While the study showed that ferrets were able to transmit the virus to other ferrets in cages 10 cm away, the results weren’r actually indicative of true airborne spread (a bit of a loaded term). Rather, it was likely droplet spread over a short distance. A more recent study raised a bit more concern, as it  reported transmission of the virus between ferrets over more than 1 metre. In this study, airflow was high and was directed from the infected to uninfected ferrets, so while the virus traveled at least 1 metre under those conditions, we have to be careful when assessing what that means. I think it supports the fact that this virus can move in the air for short distances, but a lot of factors influence how far it goes and the risks associated with aerosol transmission. We’re learning more and more than ventilation and environmental conditions are important for human-to-human transmission as well.

How sick can ferrets get from SARS-CoV-2?

At the start, I was expecting ferrets to be susceptible to severe disease because ferrets can also get quite sick, and sometimes die, after infection with the original SARS virus. The SARS-CoV-2 doesn’t seem quite as hard on them, but experimental data are variable. Some studies have reported infections with limited or no obvious signs of disease (Shi et al.Schlottau et al., Kim et al.)  However, at least one study reported more serious disease from SARS-CoV-2 in ferrets, sometimes requiring euthanasia. The difference in results might be related to the dose of virus, with higher doses used in the experimental study where more serious disease was observed.

If ferrets are susceptible to SARS-CoV-2, why aren’t there reports of infected pet ferrets?

Good question. That probably relates to limited testing. In our Canadian SARS-CoV-2 surveillance study, we’ve only been able to test one ferret. I haven’t seen much other surveillance data in this species. There’s one pre-print study looking at human-to-ferret transmission in a household where there were two infected people and 29 ferrets, but they didn’t find any evidence of transmission to ferrets. However, it’s hard to conclude much from a study of one household. Testing of the ferrets started 16 days after the onset of the first person’s illness and 13 days after the onset of the second person’s illness. It’s a challenge getting samples from the animals early in the disease of the people, so we probably under-estimate transmission with studies like this (ours included). The same study looked for antibodies in the ferrets too, but it was antibodies from oral swabs that were submitted for virus testing, and I’m not sure anyone knows how sensitive that technique is. So, there was no evidence of human-to-ferret transmission, but it was only one household and the testing had some significant limitations. Study of more ferrets in more households is needed. The lack of reports of infected ferrets may also be a function of there being fewer pet ferrets compared to dogs/cats, and correspondingly less testing for that reason as well.  Ferrets seem to be more susceptible than dogs and cats in experimental studies.

Can ferrets infect people with SARS-CoV-2?

We don’t know.  Given their susceptibility to the virus, the experimental study data and evidence of potential transmission of SARS-CoV-2 from mink to people, I think we have to assume that an infected ferret might pose some degree of risk to people as well. However, if a ferret is infected, it almost certainly got it from a human household contact, and that person poses much more risk to others in the household than the ferret does. The main risk is if the ferret leaves the household (e.g. to see a veterinarian) during the period when people in the household are infected, as it may take the virus along for the ride and could then potentially spread it to others.

What should be done with mink and ferrets?

  • Anyone with COVID-19 should absolutely not go near a mink farm (or anyone who works on a mink farm). That’s the big one.

The same general approach that we recommend for dogs and cats applies to ferrets:

  • 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 or animals.
  • If your ferret has been exposed to someone with COVID-19 and is sick, let your vet know.  Discuss what to do over the phone, at least initially, rather than showing up to the veterinary clinic with your ferret.

Next up for animal reviews: Horses

Image source: https://www.cbc.ca/news/canada/newfoundland-labrador/covid-outbreaks-mink-farms-canadian-breeders-prepare-1.5769815

Moving on from cats and dogs, let’s talk about one of our major livestock species, pigs.

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

  • Kind of, but not really. There are conflicting experimental data that show no or very little susceptibility to the virus.

Why did we talk a lot about pigs and SARS-CoV-2 initially?

At the start of the pandemic, we were worried about the potential for this virus to infect pigs because of their ace2 receptor, which is used by SARS-CoV-2 to invade pigs’ cells. If the virus can’t enter an animal’s cells, it can’t infect them. Different animals have slightly different ace2 receptors on their cells. The pig ace2 receptor is quite similar to the one people have,  suggesting there could be similar susceptibility to SARS-CoV-2. Looking at ace2 receptors has been interesting, but we’ve also seen the limitations of this method, with some purportedly low-risk species being susceptible and some purportedly high-risk species being resistant. Ace2 is only a part of the picture, so while it’s worth considering, it really doesn’t answer the question of whether there’s a concern with pigs.

Trying to grow the virus in a laboratory in cell lines from a particular animal species can provide some additional information on potential susceptibility. In one study, SARS-CoV-2 was grown in 2 of 3 pig cell types, but did not damage the cells. In another study, the virus was grown in pig cell lines and caused some cell damage.  These all raised concerns about the virus’ ability to infect pigs, but there are limitations to what in vitro studies can tell us. To get the real story, we need to look at real pigs.

So, forget about pig cells – are actual pigs susceptible to SARS-CoV-2?

In three separate studies (Shi et al.,  Schlottau et al., Meekins et al.), pigs were experimentally inoculated with SARS-CoV-2 and mixed with naive pigs. Nothing remarkable happened. None of the pigs got sick and all samples collected were negative for the virus. Antibodies against the virus weren’t found in any animal. All of these results indicated that the pigs were not infected, and there was a collective sigh of relief as it appeared that concerns about pigs were unnecessary.

In another study, pigs were exposed to the virus via the nose, trachea and injection. All the pigs stayed healthy and the virus wasn’t detected in any samples, but antibodies against the virus were found after pigs were injected with the virus. Exposure by injection doesn’t tell us much about natural infection, and the other results are consistent with no natural susceptibility.

However, leave it to Canadians to be disruptive – an experimental study conducted by the CFIA found slightly different results in pigs.  It didn’t raise major concerns, but it suggested things are not not quite as clearcut. In that study, 16 pigs were exposed to a higher dose of the virus than in previous studies.  Once again, nothing remarkable happened. Some developed mild discharge from the eyes for a few days. One had a slight cough and was mildly depressed for a few days. However, low levels of virus were detected from respiratory samples by PCR from two of the sixteen pigs, although live virus could not be isolated. The virus was also isolated from a lymph node of one pig, and antibodies were detected in the blood of two pigs, supporting some level of true infection. Two pigs were added to the exposed pigs 10 days after inoculation, and they did not get infected. Overall, 5 of the 16 pigs (~30%) had some evidence of mild infection. So, this study showed some degree of susceptibility, but with infrequent mild disease and no evidence that pigs are infected to the degree that they would be able to pass on the virus to other animals or people.

Have any pigs outside of the lab been infected with SARS-CoV-2?

There are no reports of infected pigs to date, but I’m also not aware of any testing of pigs on farms. Field data are always useful because experimental studies don’t tell the full story of what happens in the “real world.” Some data about pigs exposed to infected farmers would be useful to have, to round out the story, but it would probably be low yield research since it’s quite unlikely anything would be found.

What should be done with pigs?

The same general recommendations apply as for other animal species. While the risks are low, we can’t say they are zero. If we keep infected people away from animals, we don’t need to worry about human-to-animal transmission, and any subsequent animal health or animal-to-human transmission issues. While the odds of someone infecting a pig are very low, it’s best to avoid exposing pigs to infected people whenever possible. That may not be an option on small farms run by one person or a family, but the more we can keep infected people away from animals, the better.  In short, better to be safe than sorry.

Next up for animal reviews: probably mustelids (mink and ferrets).

Image source: https://theconversation.com/could-chinas-strategic-pork-reserve-be-a-model-for-the-us-139949

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.


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

I’ve let the blog slip over the past week so it’s catch-up time. (I’ve been busier on Twitter – @weese_scott if anyone wants to follow that).

I want to get back to some COVID-19 discussion, and rather than a multi-species update, I figured I’d back up and focus on an overview of one species at a time. We’ll start with cats (so this will be longer than a typical blog post).

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

Yes, cats are clearly susceptible. This has been shown in multiple experimental studies and infected cats have been found in the “real world,” infected by their owners.

How often do cats get infected?

That’s a good question, but we don’t have a good answer because surveillance has been limited. One of the earliest studies from Wuhan, China, raised concern about this because they found anti-SARS-CoV-2 antibodies in 14.7% of cats from that city, even though they did not target cats with known exposure to infected people. Finding antibodies indicates that the cats were previously infected. In contrast, another study of cats in Wuhan didn’t find any cats with antibodies.

The most relevant studies are those looking at cats living in households with people who had COVID-19, in which the rates of infection appear to be pretty high. A study from Hong Kong identified SARS-CoV-2 by PCR in 12% of cats from COVID-19-positive households.

Studies looking for the virus by PCR will under-estimate the number of infected cats, because there appears to be only a short window of time that cats will shed the virus. This is illustrated in the figure below from a small experimental study, which shows the shedding time for experimentally infected cats and cats infected by those cats.

The logistics of sampling cats right around the time their owners are infected are challenging, so looking for antibodies against the virus can tell us more, because antibodies stick around for longer after infection.

Our (small, so far) study found antibodies in ~50% of cats living in households with infected people. A pre-print of a study from France had somewhat similar results, finding antibodies in 24-59% of cats from positive households (depending on how the tests were interpreted).

So, my assumption is that cats living with people with COVID-19 are quite commonly infected. Whether it’s 5%, 15% or 50% we don’t know yet, but I think human-to-cat transmission in households is likely pretty common.

Figure from Halfmann et al. N Engl J Med 2020 (https://www.nejm.org/doi/full/10.1056/nejmc2013400).

Do cats get sick from SARS-CoV-2?

They can, but most often if appears they don’t. Experimentally, clinical signs in cats have been pretty unremarkable. Most infected cats have been reported to be healthy, but it’s not always the case. There are reports of sick cats, including a pre-print describing what appeared to be a fatal infection with SARS-CoV-2 in a cat from the UK. More work needs to be done in this area. I get lots of anecdotal reports about sick cats that have been exposed to the virus, and I suspect many of them really are due to to SARS-CoV-2. When an otherwise healthy adult indoor cat with no contact with other cats develops signs of upper respiratory tract infection around the time its owner had COVID-19, it’s pretty suggestive since there aren’t many other probable causes for the cat’s illness.

Similar to people, most exposed cats probably don’t get sick or get mild disease. A subset get more serious disease, and a smaller subset may even die from the infection. The relative size of those different groups is completely unknown.

Can cats infect other animals with SARS-CoV-2?

Yes. Experimentally, cats have been shown to infect other cats. That’s also been seen outside the lab, with the outbreak in lions and tigers in the Bronx Zoo (where cat-to-cat transmission was more likely than all the big cats being infected by people). How often this occurs in households will be hard to figure out, because if multiple pets are infected in a household, it’s pretty much impossible to say whether the pets spread it between each other or whether people infected them all.

Can cats infect people with SARS-CoV-2? (Yes, people are animals too, but I assume you know what I mean.)

We don’t know. Since cats can infect other cats, we have to assume there’s some risk of them infecting people. However, sorting out how much of a risk is a challenge.

Why haven’t we figured out cat-to-human transmission yet?

If a pet cat gets infected with SARS-CoV-2, it almost certainly got it from its owner(s). Your average pet cat mainly or only has contact with its owners, especially when an owner has COVID-19 and visitors hopefully are not around. If I get COVID-19 and infect my cat, and then the rest of my family gets sick, did I infect them or did the cat? Most likely, it was me, and it would be essentially impossible to differentiate.

For a cat to spread SARS-CoV-2 to someone outside the household, it would have to leave the household during the short window when it’s actually shedding the virus. That can happen (e.g. veterinary visit, indoor-outdoor cat), but fewer veterinary visits would occur when the owner is sick due to the human-to-human transmission concerns. Even then, if the cat infected someone at the vet clinic, a link to the cat would be hard to find, especially if the cat was not showing any signs of illness. If the cat was sick, it might be considered as a potential source, but with rampant human-to-human transmission, that’s not enough proof. What we’d need is for the cat and person to both be tested and have whole genome sequencing performed on the virus from both, to show it’s the exact same virus (even then we can’t be 100% certain, since cat and person could have been infected by the same source (e.g. another person), but with identical virus in both, it would be a pretty solid conclusion). Since there’s limited testing of cats and little likelihood that samples from both owner and cat would be sequenced, the odds of identifying a cat as the source of a human infection are low.

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

Probably not. Cats are pretty susceptible but they don’t shed the virus for long. To maintain the virus in circulation in the cat population, an infected cat would have to interact with another susceptible cat within a few days (and on and on…). Most cats don’t do that. In community cat colonies, I could see it spreading through the group, but it would likely burn out quickly as most of the cats became infected and recovered, assuming there’s some degree of immunity to re-infection. In order to maintain a virus in a population when it’s only carried for a short period of time, you need a lot of animals and a lot of animal-to-animal contact. That’s more of a concern with some wildlife species (but that’s a story for another day).

So, should we worry about SARS-CoV-2 in cats?

  • Worry, no.  But we should pay attention to it.
  • There’s a cat health risk, and we want to avoid that by reducing contact of infected people with cats. It’s probably most important with older cats and cats with underlying diseases that may make them more susceptible to severe disease.
  • The risk of cats spreading the virus in a household is limited, but can’t be ignored. When you have someone isolating from the rest of the household (e.g. living in the basement), we want to make sure pets like cats are considered, so they’re not tracking the virus from the infected person to the rest of the family. It’s easy to see how someone might do a great job staying away from other people, but not think about the cat that runs back and forth between them and the rest of the family.
  • We also don’t want cats tracking the virus out of the household and exposing other cats or wildlife. The odds of this causing a big problem or creating a wildlife reservoir are very low, but not zero. A little prudence makes sense.

What should be done with cats?

  • Cats are people too, when it comes to SARS-CoV-2.
  • If you are infected, try to stay away from animals – all animals, human and otherwise.
  • If your cat has been exposed to SARS-CoV-2, keep it inside and away from others.

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

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.

The UCLA Fielding School of Public Health, Department of Epidemiology, is seeking volunteers to participate in their Veterinary and Zoonotic Surveillance for SARS-CoV-2 (COVID-19) and Other Coronaviruses Study.  Their goals are to assess potential exposures to SARS-CoV-2 and other zoonotic pathogens among veterinary and animal healthcare workers, as well as clinical symptoms, mental health, and attitudes and practices associated with the pandemic response. To be eligible to participate, you must work with or around animals, for example: in a veterinary clinic/hospital, with a mobile veterinary clinic, at an animal shelter, animal rehabilitation facility, animal control facility, zoo or aquarium, in an animal research lab, or animal husbandry operation.

Click here for more information and to enroll in the study.

As things continue to gradually open up (more gradually in some areas than others), myriad questions of “can we do…” or “how do we do…” come up. One that I’m getting increasingly is about pet visitation or pet therapy programs. These programs can be very valuable to patients in hospitals and residents in long-term care homes and other settings; however, they always come with some degree of risk from interaction with the animal, and the handler.

Currently, most places have these kinds of visits on hold, which is reasonable in this phase of the COVID-19 pandemic. Fewer people coming in means fewer potential sources of infection. However, some programs are restarting, so thought needs to go into doing this safely.

What are the risks?

While we often try to get people to think about the various pathogens that pets (particular dogs in this case) can leave behind or pick up in these settings, right now the main risk with pet visitation programs is SARS-CoV-2 from the human handlers. This virus likes people a lot better than dogs – the COVID-19 pandemic is being propagated almost exclusively through human-to-human transmission. While there is some potential for dogs to be infected or for them to act as fomites (i.e. tracking virus around on their haircoats), the far greater susceptibility of people means that dogs are probably the lower-risk component of visitation teams.

Routine prevention measures:

  • Standard pet therapy program measures, as outlined in the 2015 SHEA guidelines on animals in healthcare facilities, are still key, with particular emphasis on making sure:
  • Handlers self-screen and are healthy before entering a facility.
  • Everyone involved pays close attention to hand hygiene. Patients should use hand sanitizer before and after animal contact. Handlers should use hand sanitizer before and after every visitation, regardless of whether they touched the person or any part of the person’s environment.

Added COVID-19 measures:

  • Ensure the patient has no signs of COVID-19 and is not being isolated. (Yes, that sounds like common sense, but you’d be amazed how often things like that get missed.)
  • Ensure the handler and animal have not had exposure to an infected person in the past 14 days.
  • Have everyone involved (that is to say the people, not the dogs) wear a mask.
  • Remember the 3 C’s to avoid: closed spaces, crowded spaces, close contact. (I also talk about a fourth C, “continuous,” with regard to time.)
  • Limit person-to-person contact. Handlers should stay as far back from patients as possible.
  • Have the visit outside in an open space, when possible.
  • Keep the visits relatively short – 15 minutes is typically used as the time when risk goes up.
  • Have handlers use a tracking app, like Canada’s COVID Alert app. Anyone involved with pet therapy in a region with an app like this should use it. It might help pick up exposure in a facility, but more importantly, it helps identify other community exposures, so exposed people know when they’ve been exposed and can suspend their visitation activities.
  • Stick to one facility. Some visitation teams typically visit multiple facilities. That’s probably best avoided, especially now. Teams should focus on one facility, to reduce the risk of cross-transmission.
  • Consider limiting visits to one person per team per day, especially as programs restart and while there’s less risk tolerance. Limiting a visit to a single patient each time reduces the risk of encountering or spreading the virus between patients.

How to respond to an outbreak or exposure

  • The key here is being able to identify exposed individuals quickly and easily. One recommendation we’ve had since our very first guidelines on pet therapy is keeping track of who gets visited when, and by whom. This has been very hard to get implemented, but it’s especially critical now. Tracking can be as simple as having handlers write down the date and the rooms/patients they visited, and leave the log with the facility as they depart.
  • An additional component of this tracking should be recording the duration of the visit, since the time spent with the infected person plays a role in determining whether exposure was likely.  With basic practices like hand hygiene, mask use, and distancing, it’s unlikely a handler would be considered exposed if they visited an infected patient for a short time. However, some visits could end up stretching beyond that typical 15 minute limit, and some could end up involving direct contact between the handler and patient. If the handler fits the criteria for exposure, the response would depend on the local public health directives for exposed people (e.g. self-monitoring vs isolation). However, given the severe implications of COVID-19 in most populations where pet therapy is used, handlers with any plausible degree of exposure should suspend visitation for 14 days. If a dog had direct contact with an infected person, then I’d isolate the dog for 14 days as well, to be safe.
  • Handlers also need to have an established means of communication with the facility and must be able to report illness. If a handler develops COVID-19 (probably acquired in the community, not during visitation), the person needs to be able to contact the facility as soon as possible, so they can then determine if any of the patients/residents might have been exposed, based on the timing of illness and visitation.

None of this is rocket science, or expensive. It’s use of basic infection control practices and good communication. Unfortunately, those are often lacking.

The risk from a well-run pet visitation program following these precautions is low, but not zero. There’s never going to be risk-free pet visitation. The key is limiting the risk as much as possible, while maximizing the benefits. The implications of tracking SARS-CoV-2 to, within or between facilities (especially long-term care homes) can be huge, so serious thought needs to go into when and how to restart these programs.

As things change, both in the epidemiology of COVID-19 and our approach to containment, re-assessment of how we practice veterinary medicine and COVID-19 protection is important. The latest iteration of our guidance document has been released: COVID-19: A Guide to Reopening Veterinary Medicine in Ontario, Stage 3. As for the previous versions, this is a guide, not a standard – meaning it’s a document of recommendations and considerations, not a “standard of care.”

The guidance is designed for Ontario veterinary clinics, but much of it applies more broadly as well. Balancing the need to reduce SARS-CoV-2 transmission risk and the need to deliver practical, effective and efficient veterinary care is a challenge (I assume, as always, that I will get an earful of complaints from both sides of the spectrum).  A lot of factors need to be considered when deciding what to do in a particular clinic, including the epidemiology of COVID-19 in the region, clinic layout, clinic size, presence of high-risk individuals in the clinic, and risk aversion just to name a few. This document outlines the issues and some of the possible approaches, and hopefully will help clinics tailor their practices to find the right balance for them.

Previous versions of the guidance and other related documents can be found on the Worms & Germs COVID-19 Veterinary Resources page.

I’ve been away and need to catch up on some posts.  I was planning a nice non-COVID post, until a few seconds ago when I saw the CNN headline “Chinese officials say chicken wings imported from Brazil tested positive for COVID-19.”

My response… oh crap.

Not because I fear a wave of foodborne COVID-19. Rather, I fear a wave a paranoia about foodborne COVID-19 (and an overstuffed email inbox today).

According to the report, testing identified SARS-CoV-2 in a sample of chicken wings from Brazil. We have to realize that it’s most likely the testing was done by PCR, which is a very sensitive method that detects the nucleic acid building blocks of the virus (the RNA). That means it can detect live OR dead virus.  This virus does not live long outside its host, so it’s almost certain the virus (or more specifically pieces of virus) detected in the chicken wings wasn’t infectious.

How did the virus get there?

  • Likely from people handling the food. While research is still limited, this virus has not been identified in poultry, so a human origin is almost certain. That would fit with other recent reports from China of detection of SARS-CoV-2 on packaging of imported food. Infected people contaminate surfaces they touch.

Is there any risk?

  • Presumably no. Small amounts of this virus are probably common of surfaces in areas where the virus is circulating. The more infected people, the more contamination is likely. Yet, transmission risk still seems to be mainly from droplets and direct contact. The presence of viral “bits” on surfaces does not mean the presence of risk.
  • The risk from handling chicken wings is mainly from our run-of-the-mill foodborne bugs like Salmonella.

What should people do?

  • Pay attention to measures that we use to reduce the risk from our run-of-the-mill foodborne bugs like Salmonella, such as handwashing after handling raw meat, and cooking meat properly, and avoiding cross-contamination of food and surfaces in the kitchen. (If you want an extra level of protection, avoid sticking raw chicken wings up your nose.)”

There are a lot of things regarding SARS-CoV-2 to be concerned about. This isn’t one of them.