Disclaimer #1 is my standard “COVID-19 is almost exclusively a human disease. Information about this virus in animals is important to investigate and consider, but don’t over-react.”

Disclaimer #2 is that this post is about another paper that’s available as a pre-print, meaning it hasn’t yet undergone peer review. However, it provides some useful new information that’s worth mentioning at this stage.

The study (Zhang et al. 2020) investigated the prevalence of antibodies  to SARS-CoV-2 in cats in Wuhan, China where the COVID-19 outbreak began.  One of the things we want to know is how often animals (cats, in this case) may get infected when they’re exposed to infected people.  Antibodies in the bloodstream indicate the immune system has responded to the pathogen, which generally means the animal was infected at some point.  Whether an infected animal can pass on the virus to someone else is a related, but separate question. This study didn’t look at the implications of infection of cats (e.g. clinical signs or transmission), just how often it occurred.

Blood samples were collected from 102 cats in animal shelters and veterinary clinics in Wuhan from January to March 2020 (i.e. during the COVID-19 outbreak). A set of 39 samples from cats that was collected from March to May 2019 (prior to the outbreak) was also studied.

  • Antibodies against SARS-CoV-2 were found using an ELISA test in 15 (14.7%) of samples. Eleven of those were also positive on a second type of antibody test (virus neutralization test).
  • Three of the positive cats belonged to owners known to have had COVID-19, and they had the highest antibody levels. Six were stray cats, and 6 were sampled at veterinary clinics but had no known contact with an infected owner.
  • None of the cats had positive PCR results, meaning there was no evidence that the virus was still present.
  • The limited knowledge of the cats’ contact with infected people limits interpretation of the results, but that’s a pretty high rate of seropositivity, especially among a group of cats that didn’t mainly consist of animals known to have been exposed to infected people.

All 39 blood samples taken from cats before the outbreak were negative. This is important to show that there’s no cross-reaction or non-specific reaction with other antibodies that may be present in the cats that would lead to a false positive result.

Overall, it’s not too surprising to see seropositive cats from infected households. If an infected person is present and cats are susceptible to infection (which we’ve already seen), it makes complete sense that seropositive animals would be found.

It was more surprising to see that high a number of positives from households without confirmed COVID-19 patients. Certainly, it’s possible that there were undiagnosed people in the households of some of them.

The strays are another interesting group. Were they pet cats that were caught as strays? Abandoned pets? In those situations, they may have been exposed to an infected owner. If they were truly feral cats, where did they get infected?  Contact with people who were feeding them? Indirect contact with infected people? Other animals? It’s hard to say.  We need to do more work rather than just keep speculating.

The take home messages remain the same:

  • If you’re sick, stay away from animals.
  • Keep your animals away from other people or animals.  Social distancing applies to the whole household, not just the human members.
  • Your own pet poses virtually no risk to you. If my cat is infected, he got it from me (in which case I’m already infected) or my family (who pose a much greater risk of transmission to me than the cat). If we keep pets with us but socially distanced from others, we don’t need to worry about them as sources of infection outside of the household.

I think most people agree that the best thing we can do with pets of people with COVID-19 is to keep them in the home with the owner. However, what do we do with someone’s pet if they have to be admitted to the hospital and they live alone?  Someone needs to take care of the pet.  But who, and how? That’s a contentious topic.

The risk posed by that pet to someone outside the household isn’t clear. The risks are presumably greatest with ferrets and cats, and risks from dogs are probably pretty limited and short-term. But, since we can’t say the risk is zero, we want to keep things contained as much as is practical.  Hong Kong’s approach of isolating and testing exposed pets isn’t going to be common, so we need another plan.

The main goal is to reduce contact of the animal with new people and new environments. Additionally, we want to make sure the animal stays away from people that are high risk for serious disease (e.g elderly, people with underlying respiratory disease or compromised immune systems, diabetics, smokers). That’s not always possible, but here is my take on some options, based on what we know to date.

Continued care in the pet’s household by someone who has recovered from COVID-19 (e.g. recovered family member goes to the house every day to care for the pet)

This may be the best scenario, since it appears that once you get over COVID-19, odds of a new infection (at least in the short term) are very low. If someone who has recovered can come into the house as needed to care for the pet, that keeps it contained and away from susceptible people.

Care by someone who has recovered from COVID-19 in the caretaker’s household

This is a good option too, assuming no one else in the caretaker’s household is susceptible (i.e. any other household members have also already recovered from COVID-19). It’s more convenient and the risk posed by moving the animal into a new house with non-susceptible people is probably inconsequential.  Preferably the household doesn’t include any other pets either, or there’s a way to make sure the animals are kept in separate areas from each other.

Care by someone who has also been exposed (e.g. family member that doesn’t live in the household but had close contact with the sick person)

As the pandemic progresses, we’ll have more people who have recovered. However, not everyone will have a recovered person available to help. If a close friend or family member of the pet’s owner has already been exposed, bringing the pet into their household adds some risk (since the person hopefully hasn’t been infected) but less than bringing it into a household with no previous exposure (where the people are even less likely to be infected). From a pet containment standpoint, it would be ideal if the pet stayed in its own household and the exposed person went there to take care of it; however, the exposed person should be self-isolating and therefore not leaving their own house for 14 days. An exception might be if it was an immediate neighbour, where going next door poses no risk of exposing anyone else, but that would ideally be figured out with public health authorities.

In any situation, I would not want an exposed pet to be brought into a household where there were high risk people.

Care by someone who’s not recovered or exposed

This is less desirable since you’re bringing an unexposed person (or at least one that’s not known to have been exposed) into the situation. If that person is low risk for serious disease and doesn’t have high risk people at home, that helps. This situation increases the risks, though. The best approach would be short term, controlled visits to the pet’s household, just for basic animal care, and ideally wearing some form of personal protective equipment (especially for the first couple days – after that, at least there wouldn’t be any significant concerns with contamination of the pet’s haircoat). By keeping the duration of contact short, controlling the type of contact, and using good hygiene practices (especially hand hygiene), exposure risks can be limited.

Taking the animal into the new caretaker’s household increases the risk because the pet and the person will likely have increased duration and closeness of contact, and there’s less ability to use barriers and hygiene around any contacts. If the animal can be kept in a cage or crate all or most of the time, or at least for the first few days to negate coat contamination concerns (not ideal for the pet but reasonable in the short term), that would help.

Other options

If the “friends, family and benevolent neighbour” approach isn’t an option, then it gets trickier. Temporarily transferring the pet to a shelter would be a consideration, if the shelter is able and willing to handle potentially contaminated or infected pets, but that varies.  There’s been a lot of planning by shelters for this contingency.

Vet clinics are another option. However, it’s not ideal given the limited isolation capacity in most clinics, as well as limited staffing and operations in some. Clinics that have the facilities, personnel and comfort with handling infectious cases would be an option. (We are set up to handle potentially infectious cases like this, but even our facility can only handle a limited number of animals.)

If exposed animals have to be moved from a household where there was a person with COVID-19, a bath or disinfectant wipe of the haircoat is reasonable to try to reduce any risk from contamination of the haircoat. We have no idea if this is a real risk, but the virus would presumably survive for some time on a hair coat if deposited there by the owner. How long? We don’t know. Probably minutes to hours, but that’s unclear. That’s why bathing and some additional short term precautions (e.g. cage/crate) might help. After a couple of days, we just need to worry about whether the animal is truly infected. We still don’t understand how common that is, or whether an infected animal can infect a person. Hopefully we’ll sort that out more soon. I’m set up to do surveillance on exposed animals but it’s been very difficult getting into households to get samples, for obvious reasons. As we learn more about how commonly or rarely exposed animals are infected, we can refine our recommendations. For now, it’s a tough balancing act between being prudent and practical.

We’ll soon reach the time when I won’t bother reporting on every new instance of SARS-CoV-2 infection in an animal in contact with an infected person, but at this stage a little more discussion is probably still warranted. As part of Hong Kong’s One Health approach to COVID-19 (one that is sadly very rare), they are investigating human-to-animal transmission of this virus by testing pets of COVID-19 patients that have had to be put in quarantine when their owners were too sick to look after them. In addition to two positive dogs that were previously reported, the Hong Kong Agriculture, Fisheries and Conservation Department has now identified a cat that tested positive for SARS-CoV-2. The cat’s owner has COVID-19 and samples from the cat’s mouth, nose and rectum were positive for the virus by PCR.

This is not a surprise at all at this point.

The cat hasn’t shown any sign of illness. That’s an important thing to keep watching, as it’s unknown how commonly (if ever) cats may get sick when they are infected, but has obvious implications for cat health, as well as potential control measures and our overall understanding of the virus.

The messages remain the same:

  • If you’re sick, stay away from people AND animals (as much as possible).
  • If your pet has been exposed to someone with COVID-19, keep it away from other people. The best thing to do is simply keep the animal in the affected household if it’s been exposed. That way, if it does get infected, it can’t spread it outside the household.
  • If an exposed pet has to leave the house (e.g. to go to a veterinarian for urgent medical care), a plan should be in place to limit the risks to anyone handling the cat in transit and on arrival at the destination.

Hot on the heels of the experimental study of SARS-CoV-2 in ferrets that I discussed a couple days ago is another new study, available in pre-print, that looked at susceptibility to SARS-CoV-2 in a slightly wider range of animals, including ferrets, cats, dogs, pigs and poultry (Shi et al. 2020).  Bear in mind that the study is only a pre-print (made available by bioRxiv), meaning it is only a preliminary report and hasn’t yet been peer-reviewed.

The overall take-home was that, as previously reported, SARS-CoV-2 replicates well in ferrets, which isn’t surprising. The authors also reported that cats seem to be quite susceptible to infection. That’s not  surprising either based on cats’ susceptibility to the original SARS virus, but it raises the stakes a bit in our need to investigate natural infection in this species (i.e. in people’s pets). The good news is they didn’t find any evidence of infection in pigs or poultry. Read on for more details.

Ferrets

In this experiment, ferrets were infected through intranasal administration of virus, and live virus was detected from nasal washes days 2-8 after infection.  Testing for the virus is often done using PCR, a method that detects viral RNA, but can’t differentiate between “live” (infectious) virus or dead virus. Virus isolation (usually done in cell culture) is more difficult, but lets us know if live virus is present. Here, there were positive results with both techniques.

Lower levels of virus were detected in feces by PCR but live virus wasn’t recovered. The virus seems to replicate mainly in the upper respiratory tract. Unlike the previous study, disease wasn’t as consistent, with only some of the ferrets developing fever and loss of appetite. Antibodies were detected in all ferrets, consistent with infection.

Cats

Subadult (8 month old) cats were inoculated intranasally, as for the ferrets, but the reserachers didn’t collect routine nasal samples from the cats because they were too aggressive to risk handling them that often (the risk of human exposure through a bite probably played a role here). Virus was detected in feces of some cats on day 3 and all cats on day 5. Two cats were euthanized 6 days after infection and live virus was detected from the upper respiratory tract of one. In the other, viral RNA was detected by PCR in the small intestine, but live virus wasn’t detected.

To look at transmission, they also placed 3 uninfected cats in adjacent cages. Virus was detected by PCR in 1 of 3 cats and all three developed antibodies against the virus. It was concluded that the virus was transmitted to all three cats, presumably as a result of respiratory droplets moving over a short distance from one cage to the other (just like in people).

Testing was then repeated with younger cats (70 to 100-days-old). The results in the preliminary report are sparse, but they said younger cats were more permissive to infection, with  “massive lesions in the nasal and tracheal mucosa epitheliums, and lungs of both cats”.  No obvious illness was mentioned, though.

Dogs

Five three-month-old beagles were inoculated with virus and housed with 2 uninfected beagles. Viral RNA was detected using PCR in feces in 2/5 inoculated dogs on day 2 and in one on day 4. Live virus wasn’t isolated. The dog was that positive on day 2 was euthanized and virus wasn’t detected in any tissues. However, 2 of the 4 remaining dogs developed antibodies against the virus, indicating they had been infected and their immune systems had responded. There was no apparent transmission to the two dogs co-housed with the inoculated dogs. These data suggest that dogs are susceptible to infection but that susceptibility is low and there is less risk of transmission from an infected dog to another dog (or person) compared to ferrets or cats.

Other species

The researchers did similar studies with pigs, chickens and ducks. None became infected. Pigs are the noteworthy species here since there was some concern about their susceptibility based on genetic analysis of the virus’ receptors. It’s a small study that needs to be replicated but that aspect was encouraging.

Take home

Overall, the ferret results are not surprising. Ferrets are clearly susceptible to this virus. Cats also appear to be susceptible but are less likely to get sick. No shock there either, though the fact that cats could transmit the virus without direct contact raises some concerns. It was a very small transmission study so we need to see more data from other studies. The dog results are encouraging and support a low risk of infection of, and from, dogs.

Ferrets and cats remain our main focus, both in terms of keeping infected people away from them (so the animals don’t get infected) and keeping exposed animals away from unexposed people. In a household with a person with COVID-19, the risk to others in the household is still mainly from that person. However, we want to make sure pets don’t track it out of the household if people don’t recognize the potential for animal infection. The size of the overall impact of this is completely unknown, but it makes sense to take simple steps to reduce exposure of pets and keep exposed pets away from others.

A couple of new guideline documents have been released.

First up, a Canadian COVID-19 FAQ for veterinarians, created by a working group of Canadian public health and animal health experts (French translation to come).

Also, there’s a revised version of animal shelter guidelines from the US: “Interim recommendations for intake of companion animals from households where humans with COVID-19 are present”, a collaboration of the American Veterinary Medical Association, University of Wisconsin-Madison Shelter Medicine Program, the Association of Shelter Veterinarians, University of California-Davis Koret Shelter Medicine Program, University of Florida Maddie’s Shelter Medicine Program, and the CDC COVID-19 One Health Team.

Based on what we knew from the original SARS virus and the similarity with SARS-CoV-2 (the cause of COVID-19), we expected ferrets to be one of the species that could be susceptible to infection with the latter. When ferrets were infected with the SARS virus, they got sick (unlike cats that just shed the virus). Various experimental studies are underway internationally to look at susceptible species, both to understand the virus but also in large part to develop an experimental model (for things like vaccine research).

So, it’s not surprising to see that ferrets are susceptible to SARS-CoV-2 infection, as described in a pre-proof manuscript from the journal Cell Host & Microbe (Kim et al. 2020). It’s a small but important study.

The short version:

  • Ferrets were experimentally infected and developed fever, lethargy and cough.
  • Ferrets in direct contact with infected ferrets got sick too.
  • Ferrets in adjacent cages got infected (i.e. virus was passed to them) but they didn’t get sick, showing that the virus was spread by indirect contact, but that the amount of virus spread this was was probably low and not enough to cause disease.

The longer version:

  • They inoculated 2 ferrets intranasally with the virus. Two days later, they put some uninfected ferrets in the same cages and put some other uninfected ferrets in adjacent cages.
  • This was repeated three times (6 infected and 12 exposed in total, plus 6 uninfected ferrets as controls).
  • Blood, nasal washes, saliva, urine and feces were tested for the presence of the virus every other day for 12 days.
  • After inoculation, ferrets developed a fever, decreased activity and occasional coughs. None died. Virus was detectable by day 2 after infection and viral levels were highest in nasal secretions. (That’s not surprising.)
  • Peak viral levels were on day 4 and persisted to day 8. All were negative at day 10. In addition to nasal shedding, lower levels of virus were found in saliva, feces and urine on days 2-8. Low levels were found in blood for a shorter period of time.
  • In addition to detection of viral nucleic acids (i.e. not necessarily live virus) by PCR, live virus was also isolated.
    • That’s not surprising since infected ferrets were able to pass the virus on to other ferrets, but is an important finding nonetheless. Studies that involve PCR always end up raising questions about whether live or dead virus was detected. Virus was also found in tissue samples from another group of infected ferrets. Overall, there’s no doubt these ferrets were truly infected.
  • All 6 ferrets that had direct contact with the infected ferrets developed fevers and decreased activity. These ferrets were all infected, as virus was detected in nasal samples by day 4 after they were put into contact with the experimentally infected ferrets. Virus was also found in saliva and feces.
  • None of the indirect contact ferrets (those in adjacent cages) showed any signs of illness. However, they were infected.  This raises a few interesting points:
    • One is the potential for aerosol transmission (the authors say “airborne’” but I assume that’s unlikely and I’ll bet  there will be some debate over their use of that term).
    • The other is that the lower level of exposure from indirect contact possibly accounted for the lack of disease (although we can’t get too carried away with conclusions based on what happened to 6 healthy adult ferrets).
  • By 12 days after infection, all ferrets were back to normal.

This study was focused on seeing if ferrets would be a good experimental model (and it looks like they would be, getting consistently sick but not seriously ill).

What does this mean for pet ferrets and their owners?

Not much beyond what we’ve already said.

  • If you’re sick, stay away from your ferret.
  • If a ferret is exposed to an infected person, keep it away from other people (and other pets).
  • Veterinarians should continue to ask owners about household COVID-19 exposure to help protect themselves from the owners, but also to consider potential issues when caring for their pets.

I’ve written several posts in the last two weeks about social distancing and small animal veterinary clinics. They’ve mostly focused on social distancing between veterinary personnel and pet owners. However, veterinary clinics almost always have multiple people working in the clinic itself, and sometimes close contact between staff is unavoidable. I’m getting lots of questions about how to socially distance while working in a clinic.

Here are some ideas:

  • Whenever possible, stay at least 2 metres / 6 feet apart. We can’t always do it but we need to make it the goal.
  • If a procedure will necessitate close-contact between people (e.g. blood collection, catheter placement, pretty much anything that involves restraint), take a moment to step back and think about whether the procedure is really needed or if there are alternative ways of accomplishing the same thing that don’t require multiple people.
  • When people have to be close together, be efficient.  Get everything set up in advance so that whatever needs to be done can be done quickly.
  • Try to keep “contact groups” together. If people have to work in close proximity at times, it helps to keep the number of different combinations of people in close contact to a minimum.
  • Look at clinic layout and operations to see if people who normally sit near each other can be separated. For example, just have one person at reception. If more than one person is usually present, think about what can be done to avoid this (especially since most clinics aren’t currently allowing people to come into the reception area).  It might mean moving someone to an office or lounge, or transitioning some activities to someone who can work at home.
  • Look at lounge, lunchroom or office spaces and try to move people around or schedule things such that only one person is hanging out in a small room at a time.
  • Make sure all staff are paying attention to their health and staying home if they are sick.
  • Encourage staff to be responsible outside of work. They need to be responsible with social distancing at all times to protect coworkers.
  • Practice good routine infection control measures like hand hygiene, and cleaning and disinfection of high-contact surfaces.
The question about masks always comes up. 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.

A cat in Belgium, owned by a person with COVID-19, has tested positive for the virus. The cat developed diarrhea, vomiting and respiratory difficulty about 1 week after the owner got sick, and SARS-CoV-2 was found in the cat’s feces. It’s not clear whether the test used was PCR (which can detected live or dead virus) or virus isolation (which only detects live virus), or if other samples were also tested. It’s also not clear whether the cat was sick because of the infection with SARS-CoV-2 or whether it had some other co-incidental problem (or whether the cat is still alive or not).  They were clear that this is another suspected case of human-to-animal transmission, and not the other way around.

Is this surprising?

Is this concerning?

  • I don’t have any more concern today than I did before this report, since it was likely that this was going to happen, and animals (still) presumably pose very limited risk. An infected cat isn’t a big concern in the household since the person who exposed the cat in the first place is the main risk. This virus is being transmitted very effectively person-person, so animals likely play little role, if any in the grand scheme of things.  But we still want to take basic steps to keep the risk as low as possible.

So, what do we do?

  • The same thing we’ve been saying all along. If you’re sick, stay away from animals just like you would other people. If you have COVID-19 and have been around your pets, keep your pets inside and away from other people. While the risk of transmission to or from a pet is low, we don’t want an exposed pet tracking this virus out of the household (just like we don’t want an infected person doing that).

This is completely unsurprising. It doesn’t mean things are changing or that we have more risk today than yesterday. It just emphasizes again the importance of paying attention to basic infection control measures.

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.