We have a lot of different concerns about SARS-CoV-2 on mink farms. Mink are really susceptible to this virus, and human-to-mink transmission isn’t uncommon, so if we continue to farm mink, we will continue to expose mink to SARS-CoV-2 as long as the virus is still circulating in people.

Two of the biggest concerns relate to the potential for infection of mink to make things worse in the “big picture:”

  1. Development of mutations of the virus in mink that lead to new variants of concern (VOCs) that spread back to people
  2. Spread of the virus to other animal species

For this post, I’ll focus on concern #2.

We want to keep COVID-19 a human-only disease as much as possible. If it gets established in animal populations, especially wildlife, that changes the game in terms of disease control. I doubt we’re going to eradicate this virus entirely regardless, but if it establishes animal reservoirs, there’s no chance whatsoever.

Furthermore, if SARS-CoV-2 gets established in animals (of any species), we may have to deal with greater risk of VOCs. VOCs are already worsening and dragging out this pandemic, and with more transmission (in animals or people), there will be more VOCs. Mutations are a normal event when viruses replicate. The more a virus spreads, the more mutations occur, and the greater the chance that a mutation that impacts transmissibility, virulence or vaccine evasion emerges.

For a virus to establish an animal reservoir that poses a risk to people, a few things need to happen:

  • Animals have to be exposed, directly or indirectly, to infected people.
  • The animal species has to be susceptible to the virus, and able to transmit it between individuals.
  • The species must live in large enough groups for sustained transmission within the population.
  • There has to be a mechanism to spread the virus back to people from the animals

That might seem like a tough list to fulfill, but it’s not impossible (and it’s what has happened with some other zoonotic viruses).

Therefore, we want to keep this virus away from animals, particularly wildlife.  This is where we come back to mink.

A recent paper in Transboundary and Emerging Diseases (van Aart et al. 2021) reports on surveillance for SARS-CoV-2 in dogs and cats on mink farms in the Netherlands, where SARS-CoV-2 was identified in over half of the mink farms in the country.

  • 13 farm dogs and 101 (mostly feral) cats (69 adults and 32 kittens) on 10 farms were tested.
  • SARS-CoV-2 was detected by PCR in 3 (4.4%) adult cats and 1 (7.7%) dog.
  • Since PCR testing just tells you a single point-in-time result, antibody testing was used to identify prior infection. Antibodies to the virus were found in 18% of adult cats, 0% of kittens and 2 (15%) dogs.
  • When PCR and serological test results are combined, 19.4% of adult cats and 15% of dogs had evidence of infection with SARS-CoV-2.

That’s pretty impressive.  There’s no guarantee that all the dogs and cats were exposed to the virus by mink vs an infected farm worker, but mink-to-cat transmission seems reasonable since these were mostly feral cats that would not have interacted closely with people. The source of infection of in the dogs is harder to tease out since they presumably had closer contact with farm personnel.

Interestingly, none of the nine domestic cats that were tested were positive, despite having infected owners. Infection was only found in the feral cats. Whether all the cats were infected by the mink or there was some subsequent cat-to-cat transmission (a likely scenario) is also impossible to discern.

Mink-to-cat infection would have been through indirect exposure, because the cats generally wouldn’t have direct contact with the mink in their cages.  This raises concerns that other species could have been similarly infected through indirect contact with the mink, including small mammals like mice, or from direct/indirect contact with an infected cat (e.g. mouse surviving an encounter with an infected cat).

These concerns are why there is wildlife surveillance conducted around many infected mink farms. That type of work has also found SARS-CoV-2 in “wild” (or more likely “previously escaped” free-ranging) mink.

What’s the relevance of all this?  It’s hard to say.

However, it supports plausible concerns about animal-to-animal transmission of SARS-CoV-2 and the need to reduce exposure to animals.  Vaccination of mink is a consideration, and I’ve written about that recently. Ultimately, the best way to reduce the risks associated with the virus in animals is to control this disease in people.

Overall, this shows the importance of the “One Health” approach and a need to be proactive to identify and hopefully prevent problems, rather than our typical reactionary approach whereby we wait for definitive proof of an animal-related issue before putting any real effort into addressing the risk.

As we start seeing a light at the end of the (long) tunnel, we have to think about how and when to restart various activities. One particular activity that I get a lot of emails about is pet therapy/visitation programs. These are great programs, where animals (usually, and ideally, dogs) are taken into facilities to interact with residents or patients. They’re not for everyone, but have been shown to have physical and mental health benefits.  Not surprisingly, they were largely stopped during COVID-19 pandemic, but many are now gearing up again.

What’s the risk of animal visitation programs?


The main issue isn’t the animals (at least when it comes to dogs), it’s the human component. Human visitors pose much more risk than most pets, since people are more likely to be infected with the SARS-CoV-2 virus and an infected person poses a greater risk of spreading the virus than an infected pet. That’s particularly true with dogs, who are not uncommonly infected by their owners but who are low (or maybe almost no) risk for transmitting it back to people.  Also, if the animal happens to be infected, it’s quite possible the owner is too.

So, there is some risk from these programs, but the main (if not exclusive) risk is from an infected handler.

When can these programs restart?

The focus should really be on deciding:

  • when COVID-19 is controlled enough in humans the area
  • when resident/patient vaccination rates are high enough
  • when animal handler vaccination rates are high enough
  • what basic practices to identify high risk handlers (e.g. those with respiratory disease) need to be in place.

Should vaccination be mandatory for pet therapy program participants?

(Bracing for the next wave of anti-vaxxer “love” letters as I say this…)

In my opinion, yes, vaccination should be mandatory for the people (not the animals).  A reasonable exemption for people that TRULY CANNOT be vaccinated is reasonable, but the bar has to be high so that “cannot” and “don’t wanna” are differentiated.

Mandating vaccination of handlers would be a logical measure for a voluntary activity that involves close contact with a disproportionate percentage of high-risk participants.  Also, there’s a need to make sure handlers received both doses of vaccine, as concerns about the delta variant increase.

The other approach could be to have a phased re-introduction, e.g. fully (2-dose) vaccinated people can start first, with follow up assessment of when people who are not vaccinated can start as well. That way the policy isn’t saying unvaccinated people can’t participate, it just says they can’t yet. That’s not an unusual approach now as people start to think about re-opening in other areas and how vaccination comes into play for that.

How to we reduce the risk in the event an infected person (or animal) ends up visiting?

Good ol’ infection control and common sense. There are very good guidelines for healthcare visitation programs that apply to most animal visitation settings, and those are the core of risk reduction.  A little basic hygiene and common sense go a long way.

I’ve written before about animal vaccines against SARS-CoV-2 with regard to mink, but with Russia having recently licensed its Carnivac-Cov vaccine for use in several species (namely dogs, cats, foxes and mink) and Zoetis developing a vaccine in the US for mink, there’s continued interest in the subject, so I’ll revisit it.

I’m glad companies are working on SARS-CoV-2 vaccines for animals. It’s good to be prepared and have the work done in case it’s needed in a particular situation. Whether there’s much use for these vaccines in most animals at this time is hard to say.

When I think about SARS-CoV-2 vaccines for animals, there are three main reasons we would use them:

1. Prevention of severe disease

This is the main goal of most vaccines. However, dogs and cats don’t seem to get very sick, very often, from this virus.

  • I’m still on the fence as to whether this virus really causes significant disease in dogs at all. We have some data that suggests infection is associated with risk of very mild disease but overall, it’s still not entirely clear. However, it is clear that they rarely, if ever, get seriously ill.
  • Cats are commonly infected with SARS-CoV-2, but even cats rarely develop severe illness. There’s evidence that they can, so we can’t dismiss it. However, our research and others suggests that a large percentage of cats from households where people have COVID-19 get infected. So, we have probably had millions of infected cats worldwide since the start of the pandemic. If this was causing severe disease in a reasonable percentage of cats, I think we’d have clear signs of that by now. Since serious illness can occur in a small minority of cases, vaccination could help, but in the grand scheme of things, given the low risk of severe disease, it’s hard to say that the potential benefits justify the cost and potential adverse events.  (We don’t know about any specific adverse effects of vaccination in animals to date. I’m not talking about VITT or the misinformation about mRNA vaccine adverse events in humans. I’m talking about the typical adverse events that we can see in animals with any vaccine.) I’d rather focus on better rabies vaccine coverage and other good preventive medicine things than trying to get cats vaccinated against SARS-CoV-2. I’m not opposed to it. I just think the value is probably limited.
  • Mink are different. They are clearly susceptible to infection and it can cause serious illness and even death. The two points below probably are more important when considering vaccination of mink, but there could be mink health benefits from vaccination.

I’d be most interested in vaccination of endangered species with suspected high susceptibility that have human contact, particularly wild felids (e.g. lions, tigers) and non-human primates (e.g. great apes). Vaccination of captive animals (zoos), animals in rehab facilities and animals in areas where there’s close contact with human populations (mainly applicable to primates) might be worthwhile because of the potential implications of infection in endangered populations.

2. Prevention of transmission from animals to people

Dogs pose little risk to people, if any, in terms of transmission of SARS-CoV-2. Dog-to-dog transmission has not been seen experimentally, and infected dogs seem to have pretty low viral loads, so I doubt there’s much risk. Cats pose more risk to people. Cat-to-cat transmission does happen, so we have to assume cat-to-human transmission can occur too.  But human-to-cat transmission is still far more common. Because most infected cats probably catch the virus from their owners in the first place, they are probably “dead-end” hosts in households and rarely play a role in transmission. Cats get infected from family members, who have also infected each other, and everyone burns off the virus together. I think the greatest risk of cat-to-human transmission is when infected cats leave the house, particularly to go to a veterinary clinic or shelter. However, the risk associated with that can be significantly reduced using basic infection control practices..

The risk of animal-to-human transmission is probably highest with mink, as mink-to-human transmission clearly occurs. Vaccination of mink could be an important way to control mink-to-human transmission (but preventing human-to-mink transmission is most important).

3. Prevention of viral mutation

This is an important aspect for species that might serve as reservoirs and source of new variants. Virus variants emerge because of random mutations in the viral genome, and mutations happen when the virus replicates. So, the more the virus replicates and the more individuals are infected, the greater chance of a “bad” mutation occurring. For dogs and cats, this isn’t really a big concern. We don’t have massive numbers of dogs or cats together where widespread sustained transmission  is of great concern. Yes, a mutation could happen within a single infected dog or cat, but it’s really unlikely (and even then, it’s only relevant if that dog/cat then can pass it on to a person.)

The greatest risk of significant viral mutation in any animal species to date appears to be in mink.  We know that the virus can mutate in mink populations AND spread back to people. When you house thousands of a highly susceptible animals close together and introduce the virus from an infected person, that’s the recipe for widespread transmission and massive viral replication that’s needed for “bad”mutations to result in the emergence of a significant variant. Vaccination of mink farm workers helps reduce the risk of mink getting infected and from passing the virus back to people, but there’s still some degree of risk.


Overall, I can’t see a need at this point for vaccination of dogs and cats against SARS-CoV-2. The cost-benefit comparison of vaccination of those species doesn’t seem convincing.  Vaccination of high-risk (e.g. endangered) susceptible animals like large cats and non-human primates might make more sense, such as in zoos, rehab facilities and other places where there’s some degree of human contact with these species.

Mink are a different story. If we’re going to continue to farm mink, vaccination is a reasonable consideration.

The final disclaimer here is that all this is based on what we know about current virus variants. New variants always have the potential to reset our knowledge to some degree.  Variants that can infect a wider range of animal species, cause more serious disease in animals or be more transmissible from animals to humans might impact the current risks and make vaccination of other species more beneficial.  That’s why I’m glad we have some information about vaccines for animals now. I don’t think we need them currently for most species, but it’s good to be prepared should things change.

I seriously considered this as my email auto-reply today:

  • Thanks for your email. Yes, I’m aware of that new canine/human coronavirus paper that was released today. I’m in a symposium all day and have only skimmed the paper. I’ll read it later tonight and presumably blog about it.
  • PS: This isn’t the next COVID-19. Relax.

I actually got a chance to carefully read the paper, published in Clinical Infectious Diseases (Vlasova et al. 2021), and here are some of my thoughts, as promised…

The paper describes an interesting preliminary study that found a new coronavirus in a small number of hospitalized patients with pneumonia in Malaysia.  Analysis of the viral genetics was consistent with it having originated from a canine coronavirus.

To back it up a bit, there are lots of coronaviruses out there in lots of different species that we deal with all the time. Animals are likely the origin of most or all of our coronaviruses, ranging from SARS-CoV-2 to the coronaviruses that cause the common cold. Some of these jumped to people very recently. Some probably hundreds of years ago.

A few different coronaviruses are known to infect dogs. The one I pay the most attention to clinically is canine respiratory coronavirus, a betacoronavirus that’s increasingly recognized as an important cause of respiratory disease in dogs.  That’s NOT the virus they’re talking about in this study.  The dog virus the authors discuss in this study is an alphacoronavirus called canine coronavirus (CCoV), of which there are a couple types.

Back to the study:

  • In swabs from 301 people hospitalized with pneumonia, they found PCR evidence of CCoV in 8 patients.  A live coronavirus was cultured from one of those samples.
  • When they looked at the genetic makeup of the virus, it was most closely related to CCoV and therefore named CCoV-HuPn-2018 (canine coronavirus-human pneumonia-isolated in 2018).
  • It’s a new strain within the Alphacoronavirus 1 species. It is suspected to have evolved as a result of multiple different recombination events (viruses swapping RNA) between different Alphacoronavirus 1 strains.
  • Some genetic changes might have increased its affinity for people compared to regular CCoV. How well it can infect people and whether people can transmit it (to other people or dogs) isn’t clear.

Is this surprising?

Yes and no. A new recombinant virus is always noteworthy, but this is what viruses do, and why we always have to pay attention to zoonotic disease risks.

Is it concerning?

Not really. It’s not clear that the virus actually caused disease. Other respiratory viruses were found in 7 of the 8 positive patients, including the person from whom the virus was cultured. That person also had influenza. So, it’s hard to say if the virus was just there doing nothing, if it’s a rare cause of disease, if it’s an established but previously undetected cause of human infections, or something else.

Also, there was no evidence of human-to-human transmission. It’s impossible to say whether that was occurring –  presumably it was (versus repeated spillover events into multiple individuals from animals harbouring this virus) but who knows. The key is there wasn’t a concerning disease pattern.

One more thing: the study was based on samples from 2017-2018. Clearly nothing big has happened in the interim.(Well, you know what I mean. Nothing big with this virus.)

Take home message

New coronaviruses are a concern. We will see more viruses emerging that can jump from animals to people, some with pandemic potential. There are so many coronaviruses, and our interactions with nature (and the stress we’re putting Mother Nature under) mean the risk of inter-species transmission events will only increase. The more coronaviruses that we’re exposed to, the greater chance we encounter one that we’re susceptible to.  The more coronaviruses that can infect us,  the greater the chance they can recombine further to become more infectious to people.

However, this isn’t one I’m worried about. It’s worth studying more to make sure it’s not an issue and better understand the situation, but I won’t lose sleep over it.

This is best taken as another reminder that zoonotic threats are always lurking. We need to be prepared, be vigilant, have good surveillance systems and ensure we communicate – and treat our planet and its inhabitants with a little more respect.

I’ve written a lot about raw pet food in the past. Initially, the concerns were about Salmonella, since raw-fed dogs and cats have high rates of shedding Salmonella, and both pets and owners can get sick from it (owners can be infected directly by the pet or from handling or cross-contamination from the pet food… it’s always hard to sort that out).

More recently, I’ve been concerned about multidrug-resistant E. coli and related bacteria in raw pet diets. I think this may now be a much bigger but insidious risk. Eating a raw diet has been shown in a few studies to be a major risk factor for fecal shedding of highly antibiotic-resistant bacteria in pets, particularly extended spectrum beta-lactamase (ESBL) producing bugs.

There are other facets to this problem as well. A recent paper in the journal Epidemiology and Infection (Kaindama et al, 2021) describes a cluster of human E. coli O157 infections in the UK that were linked to raw pet food. This strain of E. coli can cause serious illness in people, including hemolytic uremic syndrome, which can be fatal. The bacterium can be found in the intestines of food animals (mainly cattle) and can therefore sometimes contaminate meat, or vegetables fertilized with manure.

In this cluster, 4 people infected by a similar strain of E. coli O157 were identified.

  • All 4 patients got sick within a one-month period in 2017.
  • I’m guessing three were 6-year-old children, based on the median and age range provided in the paper. The burden of zoonotic diseases often falls disproportionately on kids.
  • Three of the patients were hospitalized, and one died.

During the investigation, no typical sources of E. coli O157 exposure were identified. The only commonalities between cases were all had contact with dogs, and a history of consuming raw carrots. Three of the patients had been exposed to dogs fed a raw meat diet, two of which had received tripe from the same supplier. The other person’s dog was not fed a raw meat diet but had contact with another dog that was fed raw meat.

E. coli O157 was subsequently found in raw pet food samples from the affected households, but they were different strains. That’s not too surprising, since contamination of the pet food would be variable, and testing would have occurred well after the food that likely caused the infection was fed. One batch might be contaminated, the next not and the next contaminated with a different strain. Finding different strains doesn’t round out the story as nicely, but it highlights other concerns. This wasn’t a one-time point exposure cause by some unusual event. Contamination of raw pet food with this concerning bacterium might be more common than has been previously recognized.

Whether these are rare cases or a small subset of actual cases is unclear. This cluster was identified because:

  • The infections occurred close together in time (within 1 month)
  • Public Health England does detailed whole genome sequence testing of E. coli O157 isolates
  • They have detailed case questionnaires
  • They looked for and found a link

Large outbreaks of disease in people involving the same E. coli O157 strain wouldn’t be expected from exposure to dogs fed diets where there’s probably a lot of small batches of the pet food produced and batch-to-batch variation with regard to contamination. Patterns need to be apparent to flag a potential problem, and sporadic cases aren’t as amenable to that. So, we don’t know if this was an exceptional event (i.e. infections are rare) or whether this was a matter of the right circumstances allowing for rare diagnosis of a more common problem.

My personal opinion here is based on seeing enough sick pets and sick people from raw diets. For that reason, I don’t like to see these diets fed. That’s particularly true in households with people or animals that are at higher risk of severe disease (i.e. young, old, pregnant, immunocompromised). If someone is going to feed a raw diet anyway, there are ways to reduce the risk to people and animals, both in terms of products that are purchased (e.g. high pressure pasteurization likely reduces the risk a lot, even though it doesn’t eliminate it) and how raw diets are handled in the home. More information about feeding raw diets and reducing the risk is available on the Worms & Germs Resources – Pets page.

The Canadian Food Inspection Agency (CFIA) has released new rules for importation of dogs less than 8 months of age for commercial purposes into Canada. The issues around canine importation have been increasingly prominent in recent years, and came to the forefront following an importation debacle in June 2020 that led to the deaths of dozens of dogs imported as part of a shipment from Ukraine last year.

The new rules are a good step. They don’t fix all the issues, they don’t address all imported dogs, and don’t seem to beef up penalties, but they should result in some improvements and hopefully a greater ability to get data about at least some of the dogs being brought into Canada every year.  The rules (for now) only apply to dogs under 8 months of age being imported for “commercial” purposes, including breeding, showing and most importantly sale/adoption. Although this is just a subset of all imported dogs, it’s a big one, as it includes commercially imported puppies like the shipment from the Ukraine last year.

Here is a summary of the main changes (you can also check out the “then and now” table from the CFIA for a side-by-side comparison with the old rules):

No more unlimited “multiple entry” import permits.

  • Previously, you could get a permit for multiple batches of dogs of undetermined sizes over a period of time. Now, you can only get single entry permits for a specific number of dogs.

Stricter rabies vaccination requirements.

  • Dogs must be vaccinated at least 28 days before shipping (previously there was no waiting period between vaccinating and importing a dog).
  • Since rabies vaccine can’t be given until 12 weeks of age according to label instructions, dogs will now have to be at least 4 months old before being shipped (although it doesn’t solve the problem of importers lying about the age of the dogs in a shipment…)

Mandatory treatment for internal and external parasites before departure.

  • That’s a good general practice for a number of reasons, so it’s great that it is now a requirement. Among other things, it helps reduce the risk of importing parasites along with the dogs, including foreign ticks or tickborne diseases. I haven’t seen the specific details yet, but the drugs used and timing of treatment relative to shipping will impact how useful this is.

Provisions for quarantine when needed.

  • We don’t have federal quarantine facilities and there was no provision for this before. Now, importers have to have an arrangement with a facility to quarantine imported dogs, if needed.
  • When quarantine will be required isn’t clearly defined, but if an issue is identified at arrival, it provides a mechanism to get the dogs quarantined and treated if necessary (at the importer’s expense) while the issues are assessed and resolved.
  • Notably, this only applies to dogs imported by air.

More organization required prior to arrival of the dogs.

  • Rather than just showing up at the border unannounced, shipments must be scheduled in advance to ensure adequate staff are available for inspecting the dogs on arrival.

Clearer rules around the kennel of origin.

  • The kennel where the dogs came from must be certified by an official vet of that country, indicating the kennel meets certain criteria specified by the CFIA.
  • This new rule still has a lot of potential loopholes and potential for corruption (e.g. if the dogs are transferred to a temporary facility before shipment, does that then become the kennel of origin?).  At least it’s an improvement on the previous rule and a step in the right direction.

Overall, I’d say the new rules are a good start, but let’s hope they don’t stop there. These changes won’t fix all the problems, but they should help.

The biggest issue that remains: Canadian consumers.

There would be no mass importation of poorly raised puppy mill dogs if people weren’t willing to put on blinders, avoid asking questions and pay thousands of dollars for a dog from a questionable source.

Ivermectin is a commonly used anti-parasitic in animals, and it’s also used in people to treat some parasitic diseases. Additionally, it’s still widely discussed in some internet circles for treatment or prevention of COVID-19. That’s based on mainly anecdotes, some in vitro study, and very poor quality “clinical trials”.

It’s led to stories of people using or even hoarding veterinary ivermectin products. I’ve had lots of questions from the general public and veterinarians as a result (including stories of people buying more heartworm meds for their dog  than they’d ever need).

Bad idea. Here are some reasons why:

  1. There no evidence that it works. An in vitro study showed ivermectin inhibited SARS-CoV-2, but only at massive doses, well beyond what would be safe for use in people.
  2. Anecdotes aren’t data.
    • I don’t dismiss clinical observation, as it is the starting point of many important discoveries. However, a lot of things I have thought I observed or initially appeared to “work” didn’t pan out to be true over time.
    • Observations should lead us to take specific steps to figure out if something is real.  They help raise questions, not answer them.
  3. Other factors may be involved that make the drug appear effective in some siutations, but those factors don’t apply broadly.
    • One potential reason ivermectin may seem to work in some areas is because it’s an anti-parasitic. Strongyloides stercoralis is a human respiratory parasite that is common in some countries. People get infected and the parasite can lay dormant in the body, but when they are immunosuppressed, it can be re-activated.
    • Dexamethasone is a common and effective treatment in people with moderate to severe signs of COVID-19.  It reduces inflammation, but also impacts the function of the immune system (since that’s what triggers inflammation).
    • If someone is infected with dormant Strongyloides stercoralis, dexamethasone treatment for COVID-19 might lead to re-activation of the parasite, and that would complicate respiratory disease.
    • I don’t dismiss that potential, but it would mean that ivermectin might be effective in people with dormant Strongyloides stercoralis infection that are also receiving dexamethasone.
    • That’s a lot different than “ivermectin works against SARS-CoV-2 and everyone, everywhere, who is infected should be on it.”  They should not.
  4. Ivermectin isn’t a very commonly used drug in people, but it is important for treatment of certain parasitic infections.
    • Diversion of the relatively small amount of human ivermectin products towards unnecessary use compromises the care of people that really need it. (I realize that isn’t associated with “don’t steal Fido’s stash” but it’s still an important point.)
  5. Your dog’s heartworm preventative is a low dose treatment.
    • To get the levels used in the aforementioned in vitro study, a person would require a dose of  about 3500 ug/kg. Heartworm prevention in dogs is dosed at about 6 ug/kg.
    • So, my dog Merlin gets one 272 ug chewable a month. To get 3500 ug/kg, I’d need 965 tablets per dose. If I had a small dog, I’d need even more of his supply.
    • If I wanted to self-treat for Strongyloides stercoralis (not sure why I would, but let’s pretend), I’d need 52 of my dog’s chewables – per day.
  6. Ivermectin also comes in more concentrated oral, injectable (don’t even think about it) and pour-on (topical) forms. While I have good confidence in mainstream veterinary pharmaceutical companies, I still don’t want people taking a product that is only intended for (studied in and approved for) use in animals.

Ivermectin is one of many so-called “miracle cures” that we’ve seen pushed on the internet. Like most others, there’s limited substance to the stories behind it. There’s no magic bullet for COVID-19. I’d love it if ivermectin was one, as it’s a drug we know how to use and how to produce. Production could be ramped up and it’s relatively cheap. While conspiracy theories abound, no one has come up with any plausible explanation why an effective drug would be suppressed. Dexamethasone is cheap, widely used and widely produced, and it’s standard of care for some patients. That’s because it works. Ivermectin fits all of those except the “works for COVID-19” which is the most important one.

I’ve had a blog writing dry spell lately (too much other stuff to catch up on), so I’ll jump back with a quick summary of some recent papers on SARS-CoV-2 in animals. There isn’t really anything surprising here, but it’s a continuation of what we’ve been learning and saying for a while.

SARS-CoV-2 infection in cats and dogs on affected mink farms, the Netherlands

We have various concerns related to SARS-CoV-2 outbreaks on mink farms. One is the potential for spread to other animal species, with further risk of transmission, the potential evolution of virus mutants, and possible establishment of a virus reservoir, especially among wildlife.

This study tested a few different groups of companion animals, including 44 stray cats on infected mink farms. Ten of the cats had SARS-CoV-2 antibodies (seropositive), indicating previous infection. The single dog that was tested was also seropositive. This is consistent with other data that the virus can spread beyond mink on infected farms. The risk that poses for further transmission back to people or to other animals is unclear, but it’s a reminder of why we really need to keep this virus out of large susceptible animal populations like mink.

They also tested 500 feline and 500 canine serum samples that were submitted to their diagnostic lab for routine testing.  Two cats (0.4%) and 1 dog (0.2%) were positive for antibodies. Since we don’t know anything about whether those pets were exposed to anyone with COVID-19, it’s hard to put those results into perspective.

SARS-CoV-2 in pets from COVID-19+ households in Utah and Wisconsin

This pre-print describes a study involving 37 dogs and 19 cats from 41 households where a person had COVID-19.

  • No active infections were identified in the pets by PCR.
  • Four cats and 4 dogs had antibodies to SARS-CoV-2, indicating they had been infected. That’s consistent with our ongoing surveillance, in that it’s easy to miss the active infection based on timing of sampling but previous infection can be detect retrospectively based on antibodies.
  • They also reported that of 14 pets that had limited contact with infected people after the person’s diagnosis, none of them became seropositive, compared to 4 of 19 (21%) pets that had ongoing contact with an infected person. That’s not surprising, and supports our messaging to limit contact with animals as much as possible when COVID-19 is suspected in a person.

Role of SARS-CoV-2 infection in pets with severe disease

It has been a challenge in a small number of cases to figure out if an animal got very sick or died from SARS-CoV-2 infection, or whether infection was just incidental.  A pre-print from the US CDC describes an investigation of 5 cats and 5 dogs that died while they were infected with the virus.

  • In one cat with severe respiratory disease, examination of the cat’s tissues and lack of other potential causes of illness suggested that SARS-CoV-2 was the primary cause of disease and ultimately euthanasia.
  • In one dog, it was suspected that SARS-CoV-2 infection exacerbated the animal’s underlying severe and chronic respiratory disease and likely contributed to its illness.

So, in those two cases, SARS-CoV-2 likely caused or contributed to the animal’s death.

  • In the other 8, infection was deemed incidental (although in a couple of the cases, I think an argument could be made that infection may have worsened an underlying problem – it’s hard to say).

This information is consistent with what we’ve already been saying: Infection of cats and dogs isn’t rare, but severe disease is. It’s possible, but not a common outcome.

More on infection and heart disease in cats

I wrote earlier about how we need to be careful interpreting a pre-print suggesting the B.1.1.7 SARS-CoV-2 variant was linked to myocarditis in cats.  This new pre-print describes a single case report of hypertrophic cardiomyopathy (HCM) in an infected cat.  Note that HCM is not uncommon in cats.

  • A person in the household was diagnosed with COVID-19 about a week before the cat got sick.
  • The cat was euthanized and testing identified a thickened heart muscle, consistent with HCM.
  • SARS-CoV-2 virus was detected in various tissue samples, including the heart.  That supports that the cat was truly infected at the time of death.
  • There were clear signs of respiratory infection, which isn’t surprising since SARS-CoV-2 is a respiratory virus. Whether that means it caused heart disease or exacerbated it is the bigger question.
  • There was evidence of inflammation in the heart tissue, which raises concern that the virus was at least contributing to the heart disease.

Overall, it’s quite possible that SARS-CoV-2 infection exacerbated this cat’s underlying heart disease to the point that it required euthanasia. That would be consistent with the pre-print described above about rare cases of severe disease in already-compromised dogs and cats. It’s relevant because it shows that while most of the time infection is mild or inapparent, severe disease can happen, and it’s probably more likely to occur in dogs and cats with pre-existing heart or lung disease. People shouldn’t get too worried because we’ve probably had hundreds of thousands of infected pets (or more, since we’ve had millions of infected people) and only very rare reports of severe outcomes.

We’ve once again updated the Guide to Mitigating the Risk of Infection in Veterinary Practices During the COVID-19 Pandemic (14-Apr-2021)It can also be accessed through the Ontario Veterinary Medical Association Coronavirus FAQ webpage (member login required).

I’ll be happy when we can stop updating these guidelines. Progress is good and adding new information is useful. I just long for the day when we don’t need them.

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

I’ve taken a look back at some posts from the start of the COVID-19 pandemic, to see how my thoughts have evolved, what I got right and what I screwed up. We have a lot of COVID-19 posts (starting from when we called it “novel coronavirus” or “Wuhan coronavirus” before the SARS-CoV-2 terminology existed). Here are some highlights and “grading” of my comments from a selection of posts

January 20, 2020 “New coronavirus: Companion animal concerns?”: Very early on I said While this virus still seems to be less transmissible and less virulent than its relative, the SARS coronavirus, it’s pretty early to have a lot of confidence in that.

  • Grade B: It turns out SARS-CoV-2 is not less transmissible than the first SARS virus, but I guess I covered myself by saying it was early to have much confidence.

For containment measures for SARS, this new coronavirus or any other new disease, we need to assume that multiple species can be affected until proven otherwise, and we need to act accordingly. That doesn’t necessarily need to be complex. It might just be making sure animal contact questions are asked along with human contact questions, that quarantine protocols consider what to do with exposed animals, and that quarantined individuals are kept away from animals. 

  • Grade A: This turned out to be a fairly accurate statement, but fortunately risks from animals seem to be pretty limited (let’s hope this statement holds up). This is also around the time I sent some (essentially ignored) emails to try to get some consideration of animal aspects in any human exposure response planning here in Ontario.

January 23, 2020 “Novel coronavirus in China… Hold off on blaming snakes”:  In a post talking about how snakes might be the source of SARS-CoV-2, I wasn’t convinced and said I’m sure we’ll see much more genetic analysis of this virus by many different groups, but I suspect it will keep coming back to bats as the source. 

  • Grade A:  A final answer is still needed but this seems correct.

February 5, 2020 “Novel coronavirus and animals”: In talking about whether there’s actually a problem with companion animals, I said we need to focus on ensuring exposed animals are quarantined, using good old fashioned infection control like hand washing, keeping fear at bay and applying logic to the problem.

  • Grade B+: I’ll dock myself some marks on this one since it was focused on dogs. To be fair, the post was about concerns regarding over-reaction and euthanasia or abandonment of dogs, but it didn’t get into the bigger risks we now know are present with other species.

February 14, 2020 “More on COVID-19 (novel coronavirus) in animals”: I said We still have no evidence that this virus affects domestic animals, but since we also still have no real evidence that it doesn’t, it’s best to continue to take reasonable precautions to reduce the risk of exposure of animals to infected people, and to properly manage pets of people who are infected. “

  • Grade A+: Especially since it was at the same time groups like the US CDC were actively pushing back against there being any risk to/from animals.

February 18, 2020 “COVID-19 and potential animal hosts”: This post talked about a study that predicts species susceptibility based on ACE2 receptors. The potential susceptibility of cats is obviously a concern given their commonness as pets and the close interaction many people have with their cats. Pigs could be an even worse issue. If pigs could be infected and shed the virus, and it got into the commercial pig population, it would potentially be an even worse issue.  As with SARS, mice and rats are likely resistant to infection – that’s good from the standpoint of them not being reservoirs in the wild, but it also means they can’t be used for experimental study (as these are the most common lab animal species).

  • Grade C+: I think I over-estimated how useful these studies would be. They were interesting, but some species predicted to be high risk (e.g. pigs) aren’t, and some that were predicted to be lower risk (e.g. cat) most certainly as susceptible to SARS-CoV-2.  I also missed a couple of points. It seems like infection of pigs isn’t a concern but I think I missed some of the main potential concerns, as I wasn’t thinking about them as sources of virus mutants or wildlife exposure.

February 28, 2020 “COVID-19 in a dog”: A post about the first SARS-CoV-2 positive dog: Overall, my concerns are still more about cats. Dogs will probably get investigated more because there are more pet dogs than cats in most regions, and people tend to seek healthcare for the dogs (or alternative caretakers if the owner is indisposed due to illness) quicker than for their cats. 

  • Grade A: That turned out to be true.

March 27, 2020 “Human-to-cat COVID-19 transmission: Belgium”: I said If you’re worried about getting COVID-19, worry about your human contacts, not your pets. Keep pets away from high risk people, but otherwise, your risk is from exposure to people, not your pet

  • Grade A: I haven’t really changed that line in the past year.

March 29, 2020 “Social distancing WITHIN veterinary clinics”: I said Masks can reduce the risk of transmission if someone is unknowingly shedding the virus . Masks aren’t perfect but there can be some benefit. Whether it’s a good use of masks is questionable. Putting on masks for occasional close contact procedures (and ideally reusing that mask for the whole shift) isn’t unreasonable, but whether it’s really worth the mask use is hard to say.

  • Grade D: My line on masking was influenced by influenza data and concerns about mask availability, and I underestimated the usefulness of routine masking. I also focused on it being needed for known close contact situations, not more broadly. Those were the standard recommendations at that time but I still get a “D” for this one.

March 30, 2020 “COVID-19 and ferrets”: Here, I discussed concerns about ferrets.

  • Grade C:  We haven’t seen much SARS-CoV-2 activity in ferrets. Maybe that’s just because they aren’t common pets and don’t get taken to a veterinarian as often. Where I missed the boat was thinking about related species. Mink were not on my radar at all… (see below.)

April 24, 2020 “Pets and COVID-19 fears”: A commentary sent in partnership with the Ontario Veterinary Medical Association to veterinarians to balance awareness and paranoia when talking to pet owners about SARS-CoV-2.

  • Grade A: I’m not sure I’d change anything a year later.

April 26, 2020 “COVID-19 in mink: The Netherlands”: I said We’ll put this in the “interesting but not really surprising” file.

  • Grade C-: Fair statement, but while I talked about the concerns, I don’t think I really appreciated how susceptible mink would be and the issues that would develop from that.

April 28, 2020 “COVID-19 modelling and the impact of releasing cats”: This was a commentary about a crap-tastic paper about releasing infected cats and the potential impact on virus tranmission. Little did I realize this was one of many future “studies” based on little substance, little common sense and a complete abandonment of any principles of peer review. Academic opportunism has abounded in the past year and a bit, with some people putting out utterly useless papers, reviews and commentaries, and sometimes causing harm.

  • No grade… just a rant.

May 28, 2020 “Veterinary clinic staff cohorting”: I said One concept that we’ve recommended for COVID-19 control in veterinary clinics is staff cohorting.

  • Grade D: This turned out to be too impractical in most situations. It might have been useful if this was a short lived problem, but obviously that hasn’t been the case. I dropped this idea pretty quickly.

In the same post Routine cloth mask use whenever a 6-foot gap can’t be maintained between people is emerging as a key infection control tool. Cloth masks are far from perfect, but they can do a good job containing most infectious droplets, which are probably the main source of exposure.

  • Grade C: We now know the focus on the 6-foot distancing as a risk/no risk cutoff isn’t valid. Emphasizing mask use was good, but focusing on known close contact situations wasn’t.

I’d give a higher grade for the rest of the post. Most of it was actually pretty good, but these are some glaring issues.

I’ll pause here to avoid this post getting even longer. Overall, I think we had some pretty good thoughts about animals from the start. I missed the ball on a couple of key things:

  • Importance of masking: I mentioned masking above, but I didn’t realize how much of a core lifestyle component this would be.
  • Duration of the pandemic: I was expecting the pandemic to hit hard in the spring of 2020 based on modelling, so I wasn’t surprised at what we encountered then. However, I didn’t expect the pandemic to drag on this long. I was truly thinking we just needed to hit it hard in the spring of 2020 to return to normalcy in the fall or winter.