A recent paper in the Journal of Clinical Pharmacy and Therapeutics entitled “A doggy tale: Risk of zoonotic infection with Bordetella bronchiseptica for cystic fibrosis (CF) patients from live licensed bacterial veterinary vaccines for dogs and cats” (Moore et al. 2021) discusses (as the title suggests) human health risks from commonly-used B. bronchiseptica vaccines for pets.

Bordetella bronchiseptica is just one of a few different bugs that causes “kennel cough” in dogs (more accurately called canine infectious respiratory disease complex (CIDRC)). A variety of vaccines against B. bronchiseptica are available, including both oral and intranasal formulations that contain “modified live” bacteria, and injectable formulations that contain killed bacteria. Modified live vaccines (MLVs) contain attenuated (weakened) forms of the bacterium or virus in question that are not supposed to be able to cause disease, but induce a more natural immune response. So MLVs aren’t completely innocuous, and therefore generally aren’t used in immunocompromised individuals, because of the chance that even a modified/weakened bug could cause disease in such a person.

Bordetella bronchiseptica causes disease in a number of different animal species, but seems to be a rare cause of disease in people (unlike it’s cousin, Bordetella pertussis which causes whooping cough). However, infection with B. brochiseptica can occur in people, and those with diseases like cystic fibrosis (CF) are presumably at higher risk.

The authors of the paper state that patients with CF “should avoid exposure to live veterinary bacterial vaccines and seek animal vaccination utilising non- live vaccines.

  • I agree with point #1. High-risk individuals should avoid direct exposure to live vaccines, which can occur during vaccination of the animal, as the vaccine is squirted into the dog’s mouth or nose (and sometimes splattered elsewhere). Ideally, high-risk owners should not be in the room when such a vaccine is given. That’s a very practical, very easy and probably the most effective preventive measure.
  • I’d argue against point #2. Injectable killed vaccines for B. brochiseptica are inferior to MLVs, and that has relevance to the exposure and health of a high-risk owner too.

Here is my thought process when is comes to this situation:

  • No vaccination or less effective vaccination increases the risk of disease in the pet.
  • Bordetella bronchiseptica can cause disease in high-risk people, so we don’t want the pet to be infected.
  • Disease probably also increases the risk of exposure of people to this bacterium and others (from coughing/sneezing pets).
  • Disease also increases the risk that the pet may need to be treated with antibiotics, leading to an increased risk of antibiotic resistance in other bacteria carried by the pet, and some of those bugs can also be transmitted to people.

Millions of doses of these MLVs have been given to dogs with little to no clear evidence of risk to people. The main reference to which the authors point is a report about a mild infection in a boy who was squirted directly in the eye with a vaccine. That’s a lot different in terms of exposure than having contact with a recently vaccinated dog.

The issue of residual modified live bacteria from the vaccine being present in the dog’s nose or mouth for a while after vaccination is usually raised. That’s fair, to some extent, but it ignores the big picture. Yes, there is a very minimally risk that the modified live bug might be present in the dog’s nose/mouth, but there are lots of other (and more dangerous) bacteria in the nose/mouth of every dog. The risk is basically no different from a dog that was recently vaccinated and one that has not been vaccinated, because it’s the more common bacteria found in both dogs that I’m most worried about.

The statement that vaccination “requir[es] a period of CF patient exclusion from the shedding dog,” is not supported by anything I’ve ever seen and doesn’t make sense to me given the above thought process.

Like most things, we need to consider the cost-benefit in each situation.

What’s the human health risk of using MLVs for B. brochiseptica in dogs?

  • Exceptionally low.

What’s the benefit of using MLVs for B. brochiseptica in dogs?

  • Improved animal health, and I could argue reduced human health risks from decreased exposure to sick animals (because we have to think beyond just the risk from the vaccine).

There’s also a statement in the paper that “CF pharmacists, hospital pharmacists and community pharmacists are important custodians of vaccine-related advice to people with CF, who are frequently consulted for such advice. “

  • Very true. However, I’d add the need for a One Health approach. Veterinary input is needed for a proper risk assessment, and to put the issues into context for the individual pet/pet owner. It would be nice to see papers like this written in collaboration with veterinary experts, and for pharmacists and veterinarians to engage more with each other in situations like this. Connections between pharmacists (and many other human healthcare professionals) and veterinarians tend to be pretty poor.

“Kennel cough” (now more conventionally termed “canine infectious respiratory disease complex’)  is a fairly common problem in dogs that can be caused by an array of bacteria and viruses. We commonly see it in outbreaks, often linked to kennels, but sometimes we see higher levels of disease in the broader community. What we’re more concerned about is new problems , new patterns or more severe disease.

We may be seeing an increase in respiratory disease activity in dogs in a few parts on Ontario at the moment. It’s always hard to say for sure because it’s based on information from different sources, and whether it’s a true increase, an increase in reporting of the normal amount of disease, or just a misperception is hard to say.

We don’t want to over-react, but we also don’t want to miss the start of something important, so we’re paying attention to the information that’s coming in and trying to make sense of it.

An important limitation to the available data is the amount of diagnostic testing that gets done. Only a small percentage of dogs with “kennel cough” get tested to try to determine which viruses and bacteria are actually involved.

Should all dogs with “kennel cough” be tested?

  • No.  Since a lot of pathogens can cause the clinical signs we see with this syndrome and we can’t test for them all, the test results rarely impacts how we treat an individual dog. It’s nice information to have but it’s usually hard to justify the cost for an average household pet. This recommendation is also part of the 2017 ISCAID  treatment guidelines for respiratory disease in dogs and cats.

When is testing more rewarding?

  • Testing is more useful when something is unusual about the scenario or the patient. From the patient standpoint, testing can be more useful when it involves a kennel or shelter, since the result could affect the infection control response. It also can help differentiate “vaccine breakthrough” from the presence of a bug we can’t vaccinate against.
  • By “unusual scenario” I mean something different in the incidence, distribution or severity of disease. If we think we’re seeing more disease, testing is useful to see if disease is mainly caused by one bug, whether we have a mix of causes, or whether the cause can’t be identified (suggesting something different/new might be present).

When do I really want to test dogs with respiratory disease?

  • When I’m concerned about a foreign disease like canine flu, I definitely want to get testing done. Figuring out when to worry about that comes down to two big factors: high attack rates and links to imported dogs, especially from Asia. When most dogs in a group get sick, I worry about something new like flu and want to test them, so that we find out as early as possible if flu is present and we can take measures to contain it, like we successfully did last year. A high attack rate was what led to identification of the biggest flu cluster we had when canine flu hit Ontario in 2018.

So, what about now in Ontario?

  • I’d like more information but don’t have any money for testing, so I’m relying on information that comes in from various sources. It’s always a fine balance between raising awareness and causing paranoia, so it’s important to put things in perspective. We’re on the lookout for respiratory disease in dogs and want to learn more, but we’re far from panicking about the situation.
  • The average dog owner doesn’t need to do anything more than good routine care and using common sense. However, we’d like to figure out if something new or interesting is going on.

More to come (hopefully).

Kennel cough, also (and more properly) referred to as canine infectious respiratory disease complex (CIRDC), has been in the news lately. This condition is a syndrome, not a specific disease, being potentially caused by a range of bacteria, viruses and Mycoplasma, including canine parainfluenza virus, canine influenza virus, canine respiratory herpesvirus, canine adenovirus, distemper virus, Bordetella bronchiseptica and Streptococcus zooepidemicus. Regardless of the cause, it’s still a highly infectious disease characterized by a hacking cough. Serious illness, including deaths, can occur but is uncommon.

Here are a couple of kennel cough issues have hit the press lately:

  • Mandatory kennel cough vaccination is now required for dogs competing in the Iditarod Trail Sled Dog Race. It’s easy to see how this disease is a concern in these sled dogs, given the stress and rigours of competing and the mixing of many dogs from different areas. Kennel cough vaccination doesn’t prevent all cases, since it only protects against Bordetella bronchiseptica +/- parainfluenza virus, but it’s a useful infection control tool in high risk populations. The requirement has been implemented in part due to cases of kennel cough that were encountered in the 2011 race, along with the publicity that was generated (including the attention of PETA).
  • In Rocklin, California, a dog park was closed for two days because of a kennel cough outbreak. It seems the closure was in response to the diagnosis of kennel cough in two dogs, and it’s an unusual move given the apparently low number of cases. The issue isn’t the park environment itself being biohazardous – rather, the park provides an opportunity for dog-dog transmission. Given that, it’s a questionable control measures since it’s unlikely that people will keep their dogs at home. Rather, they’ll probably just go to another park, where the same risks will be present. It’s a bit like the debate around school closures with pandemic influenza. On the surface, it seems like a good idea, since kids won’t pass around flu at school. However, in reality, what happens is kids congregate at the mall and other places if schools are closed, so it just moves the site of transmission somewhere else and probably doesn’t have any net benefit. Here, a better response would probably be an educational campaign to get people to keep sick dogs at home, have people keep their dog away from other dogs at the park and encourage vaccination of high risk dogs (which would include those that go to a park and interact with other dogs).
  • A kennel cough outbreak was reported in Bozeman, Montana, with veterinarians asking owners to be on the lookout for disease. Local veterinarians reported a spike in the number of cases, with one clinic reporting  around 20 cases in the past month, which is a pretty remarkable number for your average vet clinic.
  • And locally… nothing specific, but I keep getting reports of clusters of respiratory disease in dogs. We often don’t get a chance to investigate small clusters to figure out the cause, since information often gets to me after the fact, but it’s a recurrent problem in Ontario. Most of the reports are rather poorly defined clusters of sick dogs, with occasional severe outbreaks involving fatalities (including one I’m dealing with at the moment).

An article from NBCMontana.com describes a kennel cough outbreak in dogs in Bozeman, Montana. It’s a pretty basic article that outlines a rather typical presentation of kennel cough (now largely referred to as canine infectious respiratory disease complex – a respiratory infection that can be caused by a range of viruses, bacteria and Mycoplasma).

As part of the story, they state that if you have a sick dog, the "best course of action is to call your local veterinarian and get medication." I realize it’s a quick statement, perhaps tossed in without much consideration, but there are some important issues to consider.

Should someone call a veterinarian and get medication, or should a veterinarian actually see the dog?

  • Sometimes dogs just need to be given time and rest. Viruses are often the cause of this condition, and it just takes time for the infection to resolve (just like person with a cold virus). If that’s the case, a little over-the-phone veterinary advice might be fine. If drugs are needed, then the dog needs to go to a veterinarian. Affected dogs might need something to control cough, which need to be given by prescription, and occasionally antibiotics are needed, but in either case a veterinarian needs to see the dog first. If the dog is sick enough that it needs additional treatment above and beyond this, then of course it needs to be seen by a veterinarian.

Are there any problems with a dog like this going to the veterinarian?

  • Here’s where the ball often gets dropped. The last thing we want to see is someone walking through the from door with a hacking, biohazardous dog who goes nose-to-nose with other dogs in the waiting room, breathes on half of the surfaces in the room, sits there for ten minutes while waiting for the appointment, and gets handled by every staff member before they realize the dog might be infectious. A situation like that can turn a veterinary clinic into a source of infection for many other dogs, and help an outbreak spread.

A very basic but well coordinated approach can greatly reduce the risk of dogs infecting other dogs in the clinic. These would include:

  • Not taking a biohazardous dog into the waiting room. The owner can call from the car upon arrival or come in without the dog to let the clinic know they’re there.
  • The dog can be admitted directly into isolation or an exam room, thereby avoiding contact with other animals in the waiting room or elsewhere in the clinic.
  • Veterinarians and techs that are going to work with the dog can know in advance and come in prepared, wearing appropriate protective outerwear (e.g. gloves and a labcoat or gown that they use for only that appointment) to prevent contamination of their clothing or body.

Very easy to do. Probably very effective too, but often not done.

It’s very common for kennels to require dogs be vaccinated against "kennel cough" before they are allowed in. There are two main reasons for this:

  1. Reducing the risk that a dog will bring kennel cough into the facility and spread it to other dogs.
  2. Reducing the likelihood that a dog will acquire kennel cough if someone else brought it in.

Overall, it’s a sound policy, but it’s far from 100% effective and it needs to be part of an overall kennel infection control program to work. Relying solely on vaccination to prevent kennel cough is a weak approach that can ultimately fail, particularly if other infection control practices are poor or if vaccination protocols are illogical.

Why isn’t it 100% effective?

1) Kennel cough is a syndrome, not a specific disease. It can be caused by many different viruses and bacteria, often in combination. Kennel cough vaccines are typically targeted against Bordetella bronchiseptica +/- canine parainfluenza, two important causes of kennel cough, but not the only causes.

2) No vaccine is 100% effective. Vaccines help reduce the risk of illness, but they don’t completely eliminate it. Some vaccines are better than others, and some animals respond better to vaccines than others.

3) Timing is another issue. One of the weak points of many kennel protocols is the requirement that the dog be vaccinated "before entry," or within a certain number of weeks or months. The problem with this is vaccines are not immediately effective. What often happens is people decide to board their animal at the last minute or realize the night before that they need their dog vaccinated, so the vaccine gets given a day (or less) before kenneling. The intranasal kennel cough vaccine (squirted up the nose) takes a few (3-5) days to be effective, and the injectable vaccine takes even longer (a week or more). Vaccination very soon before boarding, particularly for a dog that has never been vaccinated against kennel cough before, is unlikely to result in protection from infection by the time of boarding.

Requiring vaccination before boarding makes sense, but it’s important to remember that:

  • It’s not 100% effective.
  • It doesn’t negate the need for a good infection control program.
  • It needs to be given at an appropriate time to be effective.

I had a call from a colleague in Ottawa (Ontario) the other day, asking if I’d seen an increase in kennel cough in dogs lately. Kennel cough is a respiratory infection of dogs that can be caused by a variety of different viruses and bacteria, or combinations thereof, but is often associated with the bacterium Bordetella bronchiseptica. Apparently, this colleague’s clinic has seen a large number of cases compared to normal, and he was wondering if the trend was more widespread and/or if there’s something new out there to be concerned about.

Informal reports like this are often the key to identifying new problems. There are only a few reportable diseases of companion animals (such as rabies), and existing federal and provincial public health and animal health agencies tend to have little mandate regarding non-reportable infectious diseases of companion animals. That means that there is no centralized reporting or investigation for all these other diseases (in other words: we’re on our own).

Most often, reports of higher disease rates or suspected outbreaks don’t end up leading to anything. Things tend to revert back to baseline fairly quickly without any explanation of what happened. Sometimes, however, reports like this are the first in a series that can flag the emergence of a new disease or a change in existing disease patterns.

Is anything actually going on with kennel cough in Ottawa? It’s hard to say. A report like this could be due to:

  • A focal outbreak caused by exposure at a single kennel, park or event.
  • A local outbreak of "run-of-the-mill" kennel cough that is being spread from multiple sources, but which involves the normal kennel cough bacteria and viruses.
  • Increased reporting of the normal baseline rate of disease, with increased awareness leading to the appearance of an outbreak.
  • A new disease (either a brand new disease or, more likely, the first instance of an existing disease in the area).

Whenever I hear reports like this in Ontario, I think about canine influenza. This virus is present in dogs in many regions of North America, but we have yet to identify it in Ontario (at least from the last data I have. We also couldn’t find any evidence of canine influenza virus in a surveillance study we did a while ago). It is certainly possible that this virus could make it to Ontario, and I would not be surprised at all if canine flu caused a readily detectable cluster of respiratory disease cases when it arrived.

Should dog owners in Ottawa be worried? No.

Should dog owners and veterinarians in Ottawa pay attention? Sure. It’s always good to be aware of things that are happening locally. Dog owners need to be aware of the risk of exposure to a variety of infectious diseases. Veterinarians should consider testing for canine influenza (and dog owners need to be willing to pay for the testing) if they see changes in respiratory disease patterns in their area.

How can dog owners reduce the risk of exposure of their dogs to respiratory diseases? Common sense. The more dogs that a dog meets, the closer they get to them and the less vaccination in the population, the greater the risk. Kenneling and other situations where many dogs get together increase the risk, and preemptive kennel cough vaccination should be considered in such cases. This vaccine doesn’t protect against all causes of respiratory infection, but it can protect against some of the most likely causes. People should keep their dogs away from other dogs that look sick (especially dogs that are coughing), and if they have a sick dog, they should keep their dog away from other dogs for a few weeks.

(click image for source)

A large whooping cough (pertussis) outbreak has been ongoing in people California in 2010. This bacterial infection, caused by Bordetella pertussis, is a highly transmissible disease that can result in serious problems (including death) in young infants. At last report, there were over 6000 cases of whooping cough, making this the largest outbreak in 60 years. Over 200 infants have been hospitalized, and there have been at least 10 deaths. Nine of the 10 deaths were in infants less than two months of age.  Infants in this age group have little to no immunity to the disease because they haven’t been vaccinated, and they are more prone to severe complications.

Bordetella pertussis is a human bacterium. It does not infect animals and animals are not direct sources of infection. (Actually, experimental infection of neonatal puppies with large doses of B. pertussis can result in shedding of the bacterium by a small percentage of dogs, but that’s not particularly relevant to the normal household situation). Therefore, people don’t need to worry about infecting their pets and pets passing the infection on to other people. However, it’s not impossible that pets could play an indirect role in transmission. A pet’s haircoat could possibly become contaminated with the pertussis bacterium from someone coughing around it, or touching it with contaminated hands. The bacterium could survive on the haircoat for a while (probably days), and someone could potentially get the bacterium on their hands by petting it, and subsequently become infected.

What are the odds of this happening? Who knows. It’s not something that anyone has investigated, as far as I know.

Could dogs and cats be important sources of pertussis in households? Probably not. I assume that if there is a person with whooping cough in a household, that person is more likely to be the source of infection for other people than a pet. 

Could pets spread pertussis outside the home? That might be a more realistic concern. People with pertussis might keep themselves away from others and stay at home, but if they contaminate their dog’s coat and the dog meets people on a walk or at the park (or at a veterinary clinic, or anywhere else), I have to wonder whether there could be the potential for spread of the disease.

What should we do about this? Common sense should prevail, and itt’s important for pertussis as well as other diseases. If someone in the household has an infectious disease that is transmissible and for which a pet could potentially be a vector, some basic precautions should be taken. Good attention to hygiene might help reduce contamination of the pet’s haircoat. This includes regular handwashing (especially after coughing and before petting an animal), avoiding coughing close to the pet and not letting the pet sleep close to the person’s head. Keeping the pet away from people outside the house, or at least limiting it’s contact with high-risk people might also be useful. In particular, keeping pets that might have been contaminated away from infants would be wise.

Overall, the risks are very low. We don’t need to fear dogs and cats as potential pertussis vectors. However, in the absence of proof that there’s no risk, and with a highly transmissible and potentially serious disease, use of some simple infection control measures makes sense. https://youtube.com/watch?v=KZV4IAHbC48%3Ffs%3D1%26hl%3Den_US

Kennel cough is a highly infectious respiratory disease in dogs. The disease got its name because infection and outbreaks often occur in kennels, where many dogs from various backgrounds are mixed together.  Some of the dogs in kennels may be carrying infectious diseases, and other dogs may be very susceptible these diseases – putting them all together in what can be a stressful environment for any dog creates a recipe for infection.

Kennel cough itself is more of a syndrome than a specific disease. It can be caused by a few different bacteria and viruses (and combinations thereof) that produce the same type of clinical signs. These pathogens include Bordetella bronchiseptica, Mycoplasma, canine parainfluenza virus, canine adenovirus-2, canine distemper virus and canine herpesvirus. Of these, only Bordetella bronchiseptica is a potential concern in terms of transmission to humans.  Bordetella bronchiseptica can cause respiratory infections in people, but this is probalby quite rare and largely confined to high-risk individuals, like those with a weakened immune system, who have had their spleen removed, who already have underlying respiratory disease of another kind, and pregnant women. The evidence of transmission of B. bronchiseptica from pets to people is relatively weak and circumstantial – it is not clear whether the human Bordetella infections in these cases were truly due to contact with a pet.

In households with individuals with a weakened immune system (e.g. HIV/AIDS, transplant or cancer patients), some measures that can be taken to help reduce the risk of transmission of Bordetella from pets include:

  • Avoid boarding dogs at kennels or veterinary clinics. If boarding cannot be avoided, ensure that dogs have been properly vaccinated against Bordetella bronchiseptica, and that the kennel or clinic requires all other dogs boarding there to be vaccinated as well.
  • Avoid obtaining a dog directly from from an animal shelter.
  • Wash your hands regularly after handling any dog, particularly if you’ve touched the dog’s  nose or mouth.
  • Don’t allow dogs to lick your face or hands.

The Bordetella vaccine for dogs is a modified live vaccine, meaning that a live but less virulent (pathogenic) form of the bacterium is administered to "prime" the immune system against regular Bordetella. Concern has been raised by some people that exposure to the vaccine strain could actually cause disease in high-risk individuals, whose immune systems might be unable to fight off even this "weaker" version of the bacteria.  It is unclear whether exposure to the vaccine strain actually poses any risk.  Nonetheless, it is reasonable to pay extra attention to avoiding contact with the dog’s face for a day or two after vaccination. Also, it is probably wise for immunocompromised owners to not hold the dog when it is being vaccinated, in order to reduce the risk of exposure to the vaccine. 

Back in October/November 2020, I wrote a series of posts about what we know about SARS-CoV-2 and different animal species. It’s a dynamic field, so it’s about time I got around to updating them. We’ll start back at the beginning with one of the most susceptible domestic species: cats.  A lot of research about SARS-CoV-2 in cats in the last year has largely supported our initial observations and have helped refined what we know.

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

Yes, cats are clearly susceptible. No change here. We’ve known that for a while and more research has just solidified that. More on that below.

How often do cats get infected?

There are a lot of papers now about SARS-CoV-2 in cats. Some are very good. Some are interesting but low-impact single case reports, and some are rushed studies (“I want to be first, not the best”) that use small sample sizes, indistinct populations or cherry-pick interesting results from what should have been more comprehensive, bigger studies.

Overall, it’s apparent that human-to-cat transmission is common in households where people have COVID-19. A small number of studies have looked at active infection using PCR testing +/- virus isolation, which is tough to do logistically. It’s a lot of work to identify infected people, arrange to sample their pets and (typically) go to the household to do that. A study from Texas (Hamers et al. 2021) identified the virus in 3/17 (18%) of cats in infected households. The results of our Canadian study (which have been presented but not yet published) were fairly similar.

Testing for virus only tells us part of the story, because of difficulty with sampling infected cats soon enough to catch them during their short-term active shedding period. We assume that we often miss infections because we get into the household to sample too late. That’s why more studies are based on looking for antibodies in the blood of house cats as an indicator of previous infection. It’s less definitive than detecting the virus, since the performance of antibody tests can be variable, but with good tests it can really help our understanding of the situation.

When we look at antibodies to SARS-CoV-2 in cats in infected households, the apparent infection rates go up. The Texas study reported a seroprevalence (the percentage of cats with antibodies) of 44% (7/16), and the seroprevalence in our preliminary data from Canada was even higher at 67%.  Other studies have had variable results (for example,  a study from Peru found a seroprevalence of 17-30% among cats from infected households, depending on how the testing was interpreted), but the take-home message is that human-to-cat transmission of SARS-CoV-2 is pretty common.

There are also many studies that have looked at antibodies against SARS-CoV-2 in the general cat population, usually without any information about whether the cats were exposed to an infected person. These studies are fairly easy to do (for example, by testing leftover blood from samples collected for other purposes, or collecting convenience samples from cats presented to veterinary clinics or shelters), but their value is variable. Typically, these studies report low seroprevalence among cats. One study reported close to 10% prevalence, but <2% is more common (e.g. Dileepan 2021, Klaus 2021, Smith 2021, Stranieri 2021, Udom 2021, van der Leij 2021). Positives could be cats that actually had infected owners, but the information wasn’t known or collected, or false positives, due to an imperfect test. In our surveillance study of cats from shelters or spay/neuter clinics, we found there was often very limited history about the cats (e.g. cats recently acquired off Kijiji), so we can’t use the history to put the results into context.

There’s always a lag between disease occurrence and publication of reports, so it would be expected that rates of infection in cats would increase over time as the human pandemic continues and more cats become exposed.

Risk factors for infection in cats haven’t been carefully investigated yet, often because of fairly small study sizes. A Brazilian study reported that cats that slept in the bed were at higher risk of being seropositive (Calvet 2021), something we also found in our Canadian study. That’s not too surprising as things that increase close contact (direct or shared airspace) presumably increase the risk of human-to-cat transmission.

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 paper describing a fatal infection in a cat in the UK.

In our surveillance, cats that had antibodies against the virus were more likely to have been reported as being sick at the same time as the COVID-19-infected owner, but most of the time any illness in the cats was mild (e.g. coughing, sneezing, quieter than normal). 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, there aren’t many other probable causes for the cat’s illness. However, at the same time, since infection of cats seems to be quite common, we’d expect to find incidental infection of cats that get sick or die from various other unrelated things. A small study by the US CDC (yet to be published) explored this, and the take-home message was that some cases of severe disease seemed to occur but much of the time, cats that died while infected didn’t die from the effects of SARS-CoV-2.

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, such as the high-profile outbreak in lions and tigers in the Bronx Zoo, where cat-to-cat transmission was more likely than all the big cats being individually infected by people. We also investigated one large group of infected cats, and it’s most likely there was cat-to-cat spread there too, rather than all human-to-cat infections.

Can cats infect people with SARS-CoV-2?

We still don’t know for sure if cat-to-human infection occurs. Since cats can infect other cats, we have to assume there’s some risk of them infecting people, but sorting out how much of a risk there is is a challenge. If someone got infected by a cat, it would be very difficult to determine that they got it from a cat vs a human contact, because the virus is still circulating widely in people, and contact with the infected cat would probably coincide with contact with that infected cat’s (probably infected) owner.

I think we have to assume that cat-to-human transmission is biologically possible and has probably happened. However, in the real world, it’s probably very rare given the dynamics of cat-to-human contact. If my cat gets infected, he got the virus from me, my wife or my kids. In that event, transmission from the cat to other people in the household is possible, but transmission between people is far more likely. Most cats don’t encounter a lot of different people, especially when their owners are sick. The biggest risk is likely when a cat leaves the house, such as to go to a veterinary clinic, or is surrendered to a shelter. We’ve detected infected cats in shelters, so it’s a plausible scenario, and it’s why we recommend asking about owner infection status prior to bringing animals into clinics, shelters or other places outside the home.

Do we have a SARS-CoV-2 vaccine for cats, and should we consider vaccinating cats?

My current answers are “kind of” and “no.”  There’s a SARS-CoV-2 vaccine (of unknown safety and effectiveness) licensed for use in cats in Russia.  In North America, there’s an experimental vaccine that has been used in mink and some zoo animals, and it would be the best option if we needed a vaccine. However, I don’t see a need at this point given the apparent rarity of severe disease. There’s more information on the possible utility (or not) of SARS-CoV-2 vaccines in pets in an earlier post. 

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

Probably not. Cats are pretty susceptible to the virus, but they don’t shed it 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 (which seems to be the case) . 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).

Could cats be a source of new SARS-CoV-2 variants?

Probably not. Variants occur because of random mutations. These occur when the virus replicates. So, the risk of variant emergence is directly proportional to how much transmission (and therefore virus replication) is going on. Since we don’t expect sustained transmission in the cat population, there’s limited risk of variants emerging in there.

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.  Keep cats indoors if they’re in contact with any infected people.

What should be done with cats?

This hasn’t changed from the first post….

  • 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.

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

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

Increased disease caused by the usual suspects

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

Increased disease caused by a new pathogen

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

Increased reporting of disease

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

What about SARS-CoV-2?

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

What about canine influenza?

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

What can people who are worried about their dogs do?

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

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