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 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.

I get a lot of emails about vet clinic access from a wide spectrum of individuals. This includes:

  • Owners who are upset they aren’t allowed in the clinic with their pet
  • Owners who are worried that their vet clinic isn’t doing enough to prevent transmission of COVID-19
  • Vets who want to know how to increase owner access to clinics safely
  • Vets who want to keep people out of the clinic as much as possible for safety
  • (And still some that just yell at me regardless what I say)

There’s no “one-size-fits-all” approach to veterinary medicine in the COVID-19 era. I‘ve written about different approaches before but since I get so many questions, here are some more thoughts.

Why can’t someone just say “here’s what all vet clinics should do”?

There’s too much variation between clinics. This includes things like the degree of COVID-19 activity in the region, local rules, staff and management risk tolerance, clinic size, waiting room and overall clinic layout, exam room numbers and size, and ventilation, among others.

What are the basic concepts of COVID-19 prevention in a clinic?

  1. Restrict access as much as possible
  2. Choreograph movements in the clinic
  3. Restrict close contact situations, especially in small rooms
  4. Use appropriate PPE

1. Restrict access

I’ve said to keep owners out “as much as possible” in the past. This has led to issues since “as much as possible” is very subjective, but I can’t really say more. There’s a cost-benefit consideration. Every time someone new comes into a clinic, there’s some risk. The more that happens, the more the risk. The better our other control measures are, the lower the risk (i.e. we can get away with more people in the clinic by doing everything else right).

We can limit access but still allow some people into clinics, with some preventive measures. There may be logistical reasons to let people in (e.g. owner walks to the clinic and would have to wait outside in -20C weather) or patient care reasons (e.g. something needs to be shown to the owner that can’t be done well remotely, euthanasia, patient for which curbside transfer might be risky) that are worth the limited increase in risk. There are many other situations where it’s not worth the risk. We can still do a lot with telemedicine, curbside drop offs and hybrid appointments (e.g. telemedicine appointment followed by a drop off for a quick in-clinic procedure like vaccination or blood sampling) where the owner doesn’t need to be present.

2. Choreograph movements

I was in a clinic the other day looking at traffic flow, and it’s a good exercise to try. It’s not usually too hard to come up with a logical flow system that creates one way traffic and avoids mixing of people… if numbers are limited. Minimizing the number of people who come into the clinic helps us optimize other preventive measures in the clinic. In combination with some floor markings, furniture re-arranging, designated direction of movement and designated entry/exit points, we can significantly limit contacts and decrease the risk of virus transmission.

3. Restrict close contact situations

Close contact. Closed spaces with poor ventilation. Droplet generating procedures like talking. Those are the high-risk situations for COVID-19 transmission, and they also happen to describe a vet clinic exam room. Time plays a big role in the amount of risk. Fifteen minutes isn’t a magical number, but it’s the one typically used to indicate the time that risk goes up. The smaller the space and the worse the ventilation, the higher the risk and the less time you should spend in it.

All those factors together show how the normal exam room visit needs to be rethought. To me, exam rooms are now “owner waiting spaces.” If the owner needs to accompany the animal into the clinic, they check in and are admitted directly to an exam room (again, the number of people in the clinic needs to be limited to some degree for this to work). Vet personnel come in and retrieve the animal, keeping chatting to a minimum, distance to a maximum, and everyone’s masked. A little conversation is fine and is good for patient care and the vet/owner relationship, but it should be distanced and short. The pet is then taken to a treatment area for examination and whatever needs to be done. Vet personnel can pop into the exam room or connect electronically to ask more questions or talk about things. The owner and pet are re-united in the exam room, and a short conversation can be had to explain or demonstrate things. If a demo is needed that requires restraint of the animal, someone from the clinic joins in so the owner does not have to help out, and can maintain distance from staff. (That’s still a potential issue because of the reflexive nature of owners jumping in to help hold, but that just needs some communication to head it off.)

4. Use appropriate PPE

As much as they are annoying, masks are critical. Masks need to be worn for any close contact situation, by owners and clinic personnel alike.

 

Lots of questions remain, I know. I’ll touch on a couple of them here but I’m sure there will be more to follow.

What do we do with the exam room after the owner leaves?

The room is ideally minimally stocked with easy to disinfect surfaces. Routine disinfection, focusing on owner contact surfaces (vs our previous focus on things like the examination table) is straightforward. A sign on the door indicating the room has been disinfected is useful and is good for clients to see.

What about the airspace in the exam room? Can the next person go right in?

That’s a tough one. We focus on droplet transmission and direct contact when it comes to SARS-CoV-2, but there is likely some risk from accumulated aerosols in closed spaces with poor ventilation (like an exam room). It’s probably limited in time and degree of risk, but we just don’t know. Most aerosols settle quickly out of the air so they’ll be taken care of with surface disinfection. However, should we leave 1 minute, 2 minutes, 5 minutes, or more between owners? Who knows. There are no recommendations for this kind of precaution in similar human healthcare situations, and I haven’t seen any real evidence of risk. A few minutes between occupancies, with disinfection performed after this brief waiting period, is probably reasonable, based on what we know (especially with good mask compliance, as masks reduce aerosol release).

How important is ventilation in the exam room?

More is better. Looking at how much airflow can be achieved in the clinic is useful, as better ventilation disperses and dilutes any aerosols that may be present. Ventilation rates of less than 3 L/s per person have been suggested as being high risk, and 8-10 L/s per person as being low risk. If you don’t know what your ventilation rate is and can’t figure it out, go with the “more is better'” approach.

Just some quick thoughts that I’m sure I’ll add to soon (and get more questions about).

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 been slow posting in the past few days, so here are a few quick recaps from the animal/COVID-19 world.

Higher quality debunking of crappy dog-SARS-CoV-2 paper

Back in April, a paper (Xia 2020) was released that suggested dogs could be the source of SARS-CoV-2.  Most of us considered it crap at the time (read more about it in our previous post), and most people moved on pretty quickly, but it still left some fear and poor messaging in its wake. Now, a proper dismissal of this paper (in the same journal) has been published.  I won’t get into the details, but it basically says “Everything that was written in that paper… yeah, not so much.”

More formally, here’s what they concluded: “In summary, the proposition of Xia (2020) that dogs are a likely pre-human host for SARS-CoV-2 is not justified by available evidence. Xia (2020) did not demonstrate that the low CpG frequency in the SARS- CoV-2 genome was driven by a unique selective environment in dog digestive tracts. The SARS-CoV-2 is also less virulent than other human betacoronaviruses (SARS-CoV-1 and MERS-CoV), contradicting his assertion that CpG-deficient viruses are more virulent. Furthermore, closely related betacoronaviruses from bats and pangolins have CpG-deficiencies similar to SARS-CoV-2. Dogs are not more plausible than most other potential host species, and based on current data, far less plausible than bats or pangolins. Still, we are missing ~20-70 years of the recent evolutionary history of the lineage leading to SARS-CoV-2, and we must broadly survey a wide range of wild and domestic species to uncover the origin of SARS-like coronaviruses.

More SARS-CoV-2 in mink

Mink are really susceptible to this virus, and human-to-mink transmission seems to occur quite easy.  In the Netherlands, SARS-CoV-2 has infected mink on at least 24 farms, with widespread disease in mink and even some plausible mink-to-human transmission. There was a plan to end the mink industry in the Netherlands by 2024, and this crisis appears to be speeding things up as mink on affected farms are culled.

In Denmark, multiple farms have also been affected. They’re taking a different approach there, now choosing not to cull affected mink farms, but putting strict measures in place to control any outbreaks and monitoring closely for more.

In Canada, so far, so good. Since infection with SARS-CoV-2 in mink was first reported, there’s been an emphasis on biosecurity measures to avoid infecting mink, and relatively low disease rates in people in Canada (at the moment) mean the risk is currently fairly low. However, it’s still a concern. An additional worry is mink farms becoming a source the virus that could spread to wildlife. Feral cats have been infected on at least one affected mink farm in the Netherlands. Spread to wild mink (which are present throughout Canada and the US) is an even bigger concern given how susceptible this species is. We don’t want to create a wildlife reservoir of SARS-CoV-2, either through spread from farms to wild animals or from escape of farmed mink.

Human-to-pets transmission is still a thing

Reports of cases of human-to-pet transmission of SARS-CoV-2 continue to trickle in, and probably represent a small fraction of cases that actually occur. I’m sticking to my promise not to report each new case if there’s not really anything new about it. Infections in pets are still uncommonly reported, but a lot of cases are likely not detected because there’s limited testing. The animal and public health risks of these cases are probably very limited regardless, especially in places where there’s rampant human-to-human transmission. But, we’d still like to contain exposed animals to prevent them from playing any relevant role.

Still no signs of infection in livestock

So far, so good on the livestock front. Fortunately, major livestock species do not seem to be overly (or at all) susceptible to SARS-CoV-2. We still need to pay attention to this though, and I think the message “If you might be infected, stay away from animals” remains important, regardless of the species. However, the risk of significant issues from livestock seems pretty limited right now.

Still looking for the animal origin of SARS-CoV-2

This is still a huge question. It seems a little late, but the World Health Organization has sent a team to China to further investigate the animal origin of the virus. Kind of.  They’ve sent two people there to discuss a larger investigation.  It might be a challenge to find the animal source but we still have to try. We need to know if this virus is still lurking somewhere in the wild, and where. We also need to understand how and why this outbreak happened, to help prevent it from happening again (with this virus or one of many other potentially nasty bugs that are no doubt also lurking in the wild).