It seems highly likely that the new coronavirus, catchily named COVID-19, originated in animals. The current consensus seems to be that it is primarily a bat virus, although some genetic input from related coronaviruses circulating in snakes or pangolins has also been suggested. As a result, wondering if it could be transmitted to – or even by – other animal species is a reasonable question to ask. Can dogs carry coronavirus? Can cats carry coronavirus? In fact, can any pet carry coronavirus? In this blog, we’re going to look at the evidence, and discuss realistic ways forward for animal owners and veterinary organisations.
Is this virus related to canine coronavirus, feline coronavirus, or feline infectious peritonitis?
Not closely, no. Canine coronavirus usually causes mild, self-limiting diarrhoea; feline coronavirus the same symptoms, although it can (rarely) cause Feline Infectious Peritonitis. However, these viruses are both alpha-coronaviruses; COVID-19 is caused by a beta-coronavirus. These are genetically only very distantly related, and an alpha-coronavirus cannot mutate to form a beta-coronavirus.
Is there any evidence that COVID-19 can infect domestic pets?
This is a really tough question. There are now several reported cases – despite many thousands of cats and dogs being tested. This would suggest that if infection is possible, it is very, very rare.
However, there are so far no reports of any dogs developing the disease, and it is unlikely that they are capable of sustaining long-term replication infection with the virus. There is one report of a cat in Belgium who tested positive for the virus and had respiratory and gastrointestinal symptoms. However, whether the virus caused the symptoms, or whether the cat had something else and was simply contaminated by their (infected) owner is not yet clear. There are also reports of tigers becoming infected and showing symptoms – but the tiger genome is quite different from that of domestic cats, and so they may be more susceptible.
There has also been a study demonstrating that cats and ferrets (who are, apparently, regularly used as models for human lung disease) are capable of being clinically infected with the virus. However, this study used huge amounts of infective viral particles in a small, confined space, so may not be representative of the real world.
It’s important to remember that there is a huge difference between an animal (or person, for that matter) carrying a few viral particles on them, and being actively infected and shedding the virus. A simple “passive” carrier (of any species, and also inanimate objects) may carry virus particles on their skin, or in their nose and mouth, for a short while. However, the number of viral particles will fairly rapidly decline over minutes or hours as they die off. This sort of carrier is sometimes called a “fomite”.
Active infection – where the virus replicates inside the animal – is a different situation.
If full-blown infection occurs, we see the levels of virus not stable or decreasing, but increasing as the virus hijacks the host animal’s cells and replicates itself. This is what we usually mean when we talk about an animal or object being infected, rather than contaminated.
However, there is also a middle ground – where the virus infecting a few cells, replicates to a small degree, but is unable to spread throughout the body or be shed in to the environment in significant quantities.
What about the news from Hong Kong about a dog that tested positive?
On 28th February, it was reported that a dog in Hong Kong tested “weakly positive” for the virus. However, despite massive scare stories in the media, we need to be cautious in how we interpret this test result.
The current COVID-19 tests work by detecting the presence of live virus in a sample. Now, this has some advantages – for example, there’s no possibility that people who have recovered from the disease would be detected as infected unless they had live virus in their samples. However, it also has some major disadvantages. In particular, the amount of viral genetic material (in the form of RNA, for this particular virus) is very, very small, even in a heavily infected patient. As a result, the test process involves “amplifying” the genetic material present many, many times.
Now, while it is entirely possible that the virus was able to replicate a few times in a few respiratory cells (which recent reports are suggesting), that doesn’t mean that the dog was actively shedding viral particles. The “weak positive” suggests that only very, very small amounts of the virus were present. This probably means that, as the virus is not adapted to dog cells, it cannot replicate efficiently within them, or spread efficiently even from cell to cell, let alone from dog to other potential hosts. This would also explain why no other tested dogs have come up positive, or why no dogs have developed symptoms – the virus may be able to infect a few cells, but cannot spread within the canine patient in the same way that it does in a human (or, presumably, the bats it originally lived in).
As a result, at the moment, the evidence would suggest that as dar as dogs are concerned, COVID-19 is an “anthroponosis” not a “zoonosis” – an infection that spreads from humans to animals, but not to any significant degree from animals to humans.
So it definitely was infected?
Unfortunately, we can’t say that yet. The dog (a Pomeranian) is now in quarantine while researchers from Hong Kong and the World Health Organisation carry out additional tests to see if this is indeed a self-limiting infection or if it could be more serious.
At the moment, though, it seems very unlikely that any large-scale virus multiplication is taking place in domestic pets. The World Health Organisation (WHO), the World Organisation for Animal Health (OIE), and the World Small Animal Veterinary Association (WSAVA) are all agreed that actual transmission from domestic animals is both unproven and unlikely.
What about the Belgian cat?
This is a much newer situation, and is still under investigation. It has been reported that a cat owned by an infected human developed respiratory signs and diarrhoea, and the owner collected a sample, which was tested. This test came up positive for the new Covid-19 coronavirus. However, there are a lot of questions still. In the first place, if it is true that the owner collected the samples, there is a huge possibility for accidental contamination. Secondly, the results of further tests to confirm active viral replication have not yet been released. And given that Idexx and other laboratory companies have been testing many thousands of samples from dogs and cats and have not recovered virus from any of them, infections seem very rare.
The threat from cats to humans, even if they can develop symptoms (which is still unproven!) is still deemed negligible (see the report, English summary on p4) compared to the threat that humans pose to each other!
Can pets be vaccinated against coronaviruses?
There are vaccines available for cats and dogs in some countries against canine and feline coronaviruses. However, as these viruses are quite distinct from COVID-19, it is very unlikely that they would provide any protection.
How should I protect myself and my pets from the virus?
Although pets aren’t at all likely to contract the disease, this coronavirus has jumped species at least once before, so some precautions are wise. As the virus is primarily transmitted from human to human, avoiding contact between any people with confirmed or suspected infection and your pet (or you!) is a sensible precaution.
In humans, the advice is well publicised and straightforward. The virus is mainly transmitted in droplets, so the current advice is to:
- cover your mouth and nose with a tissue or your sleeve (not your hands) when you cough or sneeze;
- put used tissues in the bin immediately;
- wash your hands with soap and water often – use hand sanitiser gel if soap and water are not available;
- try to avoid close contact with people who are unwell; and
- do not touch your eyes, nose or mouth if your hands are not clean.
See the NHS Website for more details.
What should I do if I think my pet is infected?
It is very unlikely, unless you or a member of your household has the virus. Ensure that you are safe first by calling the NHS 111 Coronavirus helpline (dial 111 or visit https://111.nhs.uk/covid-19).
If you are concerned about your pet’s health, call your vet and ask for advice. If you are on self-isolation or under quarantine, do not venture out to take your pet to a vet – instead, phone them and ask for advice. All vets in the UK must have 24/7 provision, and they will be willing to talk to you about your pet and decide if a visit is needed, and if so, how to do so safely.
What should I do with my pet if I have to self-isolate or be quarantined?
There is a chance that your pet may temporarily carry a few viral particles on their coat or in their nose and Public Health England recommend keeping away from pets during home isolation. If that is unavoidable you should wash hands before and after contact. At the moment, all the evidence suggests that pets from an infected home pose very little risk to anyone else. That said, it would be reasonable for whoever is going to look after them to avoid kisses (sorry!) and wash their hands thoroughly with soap and water after handling them. The usual rules apply of course about not touching nose, mouth or eyes until after they’ve washed their hands thoroughly or applied an alcohol-based hand sanitiser. The WSAVA also recommend wearing a facemask while caring for a pet belonging to someone diagnosed with the virus as an additional safety margin. That said, as far as we know, the virus cannot survive on or in dogs or cats for more than a few days at the very most.
Obviously this is a rapidly changing situation so we will update this post as soon as we have more information! Cats and ferrets may be more susceptible to it than dogs, but the bottom line is that it seems unlikely that dogs or cats can actively transmit the virus to humans. However, the virus may be able to survive on them for a short period so basic hygiene precautions when dealing with any pets from a potentially infected household seem to be a wise precaution.
Want to know more?
- The current status update from the World Small Animal Veterinary Association can be found on their website here.
- Guidance from the World Organisation for Animal Health (the OIE) is available here on their website.
- A good article about the testing technology is Coronavirus and the race to distribute reliable diagnostics, from Nature Biotechnology