Q&A: Can My Pet Catch or Transmit the COVID-19 Virus?

Here are answers to some common questions that shelters might be facing from their volunteers, staff and the public right now. Feel free to copy and paste if you wish. The situation is changing rapidly and this information will be updated as needed. Thank you to Dr. Scott Weese for regular updates and counsel through the Worms and Germs blog. [CASCMA blog started March 17, 2020; last updated June 15. As the general landscape of pets and COVID-19 hasn’t changed for a while, this blog has been closed and any new information will be presented in subsequent blogs.]

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TAKE-HOME MESSAGE FROM DR. SCOTT WEESE, ONTARIO VETERINARY COLLEGE:

• “If you’re infected, limit contact with people and pets.
• If your pet is exposed, keep it in the house with you.
• If your pet is exposed and is sick, talk to your veterinarian to see if it actually needs to be seen at a clinic.
• If the pet of someone with COVID-19 has to leave the house (e.g. to go to a veterinary clinic for medical care), precautions need to be taken to reduce the risk of exposing other people or animals.
• If you socially distance your pet(s) in the same way you should be socially distancing yourself from other people, there is basically no chance they will bring this virus into the household.”

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There is still no firm evidence that pets are involved in the spread of this virus to people and no reports of pets in the community spreading the infection to other pets. Two mink-to-human cases were strongly suspected to have occurred on a mink farm in the Netherlands.

Confirmed COVID-19 infections in domestic species*

Species	Confirmed natural infections (PCR-positive)	Able to be infected experimentally	Transmitted infection to same species experimentally
People	> 8,100,000	N/A	N/A
Cat	10	Yes	Yes
Dog	3	Yes	No
Ferret	0	Yes	Yes
Hamster	0	Yes	Yes
Mink	?	N/A	N/A
Pig	0	No	N/A
Chicken	0	No	N/A
Duck	0	No	N/A

1. Can my pet catch COVID-19?

This is getting a little more complicated as more information emerges… One thing to remember, as more studies are published, is that experimental infections use high doses of virus and are unlikely to reflect what will happen out in the real world. The dose of virus influences how an infection behaves.

• What do we know about dogs?

Two asymptomatic dogs in Hong Kong, exposed to COVID-19-infected owners, have tested positive so far. It’s not known how many pets were tested there. One of the positive dogs was geriatric and died two days after release from quarantine; the death was not thought to be COVID-19 related. A dog from a positive home in the US was mildly affected and was positive on clinical testing, which was done as part of a research study . This test was later reported to be inconclusive (so it’s been removed from the table above.) Subsequently another dog was diagnosed with COVID-19 in New York State and the other dog in the household tested negative but had antibodies, showing it had been infected at some point.

Beagle puppies were experimentally infected. Two had virus detected in the stool and 2/4 others had antibodies, showing they had been infected at some level and their immune system had responded. They did not get sick or spread infection to other dogs. Another study found that none of 3 dogs shed virus or got sick, but they developed an antibody response.

A new study from Ottawa speculated that the SARS-CoV-2 virus may have jumped to humans through dogs. The immediate reaction (here and here – note the cheeky photo of the dog’s rear end) has been skepticism. There isn’t much evidence to support the hypothesis, and no new epidemiological data to suggest that dogs are involved (other than supporting their people through quarantine and giving us a reason to walk off that chocolate).

• How about cats?

Natural infections in domestic cats

An exposed cat in Belgium tested positive . The cat had respiratory signs, vomiting and diarrhea, all consistent with symptomatic infection. Another exposed cat tested positive in Hong Kong but showed no signs of illness. Two cats in New York have tested positive and are reported to have had clinical signs. One cat had a confirmed positive owner. The other is suspected to have been infected by a mildly affected or asymptomatic person but the source of infection is not known for sure. The cats were mildly affected and another cat in one of the households was not affected at all. Two positive, symptomatic cats have been identified in France, here and here. Both were presumed to have been infected by symptomatic people in the household. A cat in Spain tested positive – this cat may have had severe clinical signs but they could also have been caused by its underlying heart condition. Most recently, a cat in Minnesota, from an infected household, tested positive. The cat had fever and mild upper respiratory signs.

Remember, when these cases are reported, that we usually don’t have a denominator – i.e. how many pets have been tested that tested negative? That’s a really important number, but unfortunately less newsworthy.

We do have some data, though. Thousands of dog and cat samples tested by IDEXX laboratories tested negative. These samples came from the US and South Korea, in February and March. (Great job, IDEXX, for generating and reporting this data so quickly.) They have since extended testing into Europe and Canada. So far all results have been negative.

The animal diagnostic laboratory in Washington State U has so far reported results from 34 pets (9 dogs, 21 cats, 2 ferrets and 2 tamanduas). All these results were negative. Watch their website for new results.

Twelve dogs and 9 cats, living with French veterinary students with COVID-19 infection, did not test positive for virus and did not have antibodies to it, showing that they did not become infected. These animals were in close contact with the students, who did not observe social distancing with their pets. “This suggests that the rate of SARS-CoV-2 transmission between humans and pets in natural conditions is probably extremely low .”

Seven of 24 cats on a mink farm had SARS CoV-2 antibodies and 1 of these tested PCR-positive. It’s not known if the cats were infected through contact with feces of infected mink or by direct contact with each other. But this does most likely represent animal-to-animal infection, which does break the pattern and, while predictable, is cause for some concern.

Experimental infections in cats

Young (6-9 month-old) cats were experimentally infected. Virus was detected in the stool in all of them. They did not get sick. They were able to infect other cats to the extent that virus was detected in 1/3 and antibodies in 3/3. Experimentally infected kittens 10-14 weeks old had marked changes in the trachea and lungs on necropsy. It’s hard to know from the publication if the kittens got sick as they don’t comment on this.

A second study used 3 pairs of 15 week-old kittens. Three kittens were experimentally infected and transmitted infection to in-contact kittens after an incubation period of 2-5 days. (There’s room for speculation about whether the in-contact kittens were infected from the original inoculum as opposed to infection established in the inoculated cats, because they were co-housed after 24 hours instead of the more standard 48 hours. But the findings are nonetheless consistent with previous work. The question really is around contagiousness and incubation period.) None of the kittens were obviously ill; there were no positive results from stool samples; and the nasal shedding time was very short – 4-6 days.

A third group were able to infect cats, who infected cats in direct contact; none of the cats were sick. Viral sheddding lasted 5-7 days, which is good news as it means these cats were only contagious for a short period.

About 15% of 102 cats tested in Wuhan, China, had antibodies to the SARS-CoV-2 virus that causes COVID-19. This means they were exposed to the virus and presumably infected at some point. It wasn’t clear in all cases how they were exposed but it’s still most likely that this was from infected people.

Summary regarding cats and COVID-19:

• The positive cases are not surprising, given predictions (notably by Dr. Weese) that cats would probably be able to be infected;
• There is some suspicion that mink-to-human infection occurred in the Netherlands but this is difficult to prove;
• There is still no evidence that cats are in involved in community spread of the virus;
• Experimental infections don’t necessarily predict how natural infections will behave;
• The most important risk, by a massive margin, remains human-to-human transmission.

• And that tiger?

The report of a tiger testing positive at a New York zoo, and several other tigers and lions there showing symptoms of COVID-19, attracted a lot of attention – and concerns for, and about, pet cats. Quite a few diseases can occur in both domestic cats and big cats, so it’s not too surprising that these animals are susceptible. It doesn’t change anything as regards pet cats. The story has developed since the initial report but we won’t be adding much here because the blog focuses on pets. For more about lions and tigers at the Bronx zoo, see this update from Worms & Germs.

• Ferrets

During the SARS outbreak, ferrets were experimentally infected and became sick with that virus. Two studies (here, and the other is here) found that they are also able to be infected with COVID-19. There is now a third study showing the same thing. The infection made the ferrets sick and they were able to transmit it to other ferrets. The experimental illness in ferrets is milder than it was with experimental SARS infections, and some of the ferrets did not get sick. Dr. Weese’s recommendations:

• COVID-infected people should stay away from ferrets
• Ferrets that have clinical signs (fever, decreased activity +/- cough) should be isolated from people and other ferrets; contact your veterinarian and Public Health agency

• And now hamsters

Another experimental study has demonstrated the ability to infect young hamsters. All the infected hamsters developed clinical signs, and infected hamsters were able to pass on infection to in-contact hamsters. There were no fatal infections. Pathology studies showed changes in the respiratory tract that were similar to those in people. No confirmed or suspected natural infections have been reported in hamsters so far.

• Other domestic animals

The mink outbreak in the Netherlands has grown, with infected and symptomatic animals identified on twelve commercial farms. The numbers of infected animals are unclear. Mortality rates varied from farm to farm, from almost none to about 10%. The initial infection was presumed to be from contact with infected workers and cats on the premises were also implicated. In two cases, infection was strongly suspected to have been transmitted by mink to people. This is significant as it represents the first reported animal-to-human transmission.

After the initial introduction from people, infection appears to have been indirectly transmitted between animals. Routes of transmission may have been fomites on feed or bedding, aerosol droplets or fecal contamination of dust from bedding.

The fact that mink can be infected is not surprising as they are closely related to ferrets. Compared with pets in homes, there are higher levels of risk when large numbers of animals are housed in crowded, unnatural conditions. Animal shelters should take note and avoid overcrowding and stress, especially for cats, kittens and ferrets.

Researchers were unable to infect pigs, chickens and ducks experimentally, with a second study also unable to infect pigs and chickens. This is very good news.

2. I’m confused that authorities are saying pets don’t spread the infection. This virus CAME from an animal. Can’t it just go back and forth from animals to people?

This IS confusing, on the surface. The SARS-CoV-2 virus that causes the disease called COVID-19 is closely related to a bat coronavirus and has made the jump to humans through mutation. It’s quite unusual for these viruses to jump species and it takes special circumstances, such as occurred in the wet food market in Wuhan.

Coronaviruses that have jumped from one species to another in the past have typically mutated to the point that they can’t infect the original species. So the COVID-19 virus is now a human virus. The studies mentioned above have led to some precautions being put in place, but there is as yet no epidemiological evidence that pets are involved in disease spread outside of laboratories.

3. What about other coronaviruses that affect pets?

Coronaviruses are quite a large family of viruses and each one is different. Cats have their own coronavirus that can cause diarrhea and, less commonly, FIP. Dogs have their own enteric coronavirus and a respiratory coronavirus. These viruses are  different in terms of the species they infect and the diseases they cause.

4. Could the virus be transmitted to people from pet animals’ coats?

There’s good news on this front! Early suggestions were to “decontaminate” animals’ hair coats if they had been exposed to an infected person and then moved elsewhere. The Centers for Disease Control and American Veterinary Medical Association released recommendations March 31 stating that bathing or any other kind of decontamination is NOT needed. This is because there is no evidence that the virus can spread from hair coats.

Spread from hard plastic or metal surfaces (cell phones, computer keyboards, light switches, door handles) is a definite concern, so focus decontamination efforts on those.

5. How should shelters manage known exposed animals?

• Keep pets with their people and support the owners as much as possible. Return animals to their homes as soon as possible. Infected people should minimize contact with pets and un-infected people should minimize contact with exposed pets.
• Do NOT bathe or wipe down exposed animals, this is no longer considered necessary.
• “Out of an abundance of caution”, the CDC and AVMA are recommending separation of exposed animals from the rest of the shelter population for 14 days, before fostering or adopting. It remains to be seen if this is really necessary.
• See the University of Wisconsin sample protocol for how shelters should collect and handle exposed animals.

6. Testing shelter animals

IDEXX laboratories announced April 20 that they are making a COVID-19 PCR test available to veterinarians. Testing will be restricted and will need to meet specific conditions. Veterinarians must first consult with a public health authority before ordering a test. In addition, three specific criteria must be met:

• Pet is living in a household with a human who has COVID-19 or has tested positive for the virus;
• Pet has already been tested for more common infections, that a veterinarian has ruled out;
• Pet (especially cats and ferrets) is showing clinical signs consistent with COVID-19.

7. Keep things in perspective

Close to 4 million people have been diagnosed with COVID-19 so far. We know that the risk to people, by a very, very, very long margin, is other people. Keep this in mind and in your messaging, when facing media queries about pets and infection.

Blog post by Dr. Linda Jacobson BVSc MMedVet PhD

Sources:

1. COVID-19 Infection in Animals: Living Systematic Review, https://promedmail.org/promed-post/?id=20200407.7196506 https://promedmail.org/promed-post/?id=20200407.7196506   
2. Questions and Answers on the 2019 Coronavirus Disease (COVID-19), OIE World Organisation for Animal Health, https://www.oie.int/en/scientific-expertise/specific-information-and-recommendations/questions-and-answers-on-2019novel-coronavirus/
3. The New Coronavirus and Companion Animals – Advice for WSAVA Members (updated March 7), World Small Animal Veterinary Association, https://wsava.org/wp-content/uploads/2020/03/COVID-19_WSAVA-Advisory-Document-Mar-9-2020.pdf
4. Leading Veterinary Diagnostic Company Sees No COVID-19 Cases in Pets, IDEXX Laboratories March 13, 2020, https://www.idexx.com/en/about-idexx/news/no-covid-19-cases-pets/
5. Q&A on coronaviruses (COVID-19), World Health Organization, https://www.who.int/news-room/q-a-detail/q-a-coronaviruses
6. Coronavirus Disease 2019: How it Spreads, https://www.cdc.gov/coronavirus/2019-ncov/prepare/transmission.html
7. Animals and Coronavirus Disease 2019 (COVID-19), Centers for Disease Control, https://www.cdc.gov/coronavirus/2019-ncov/prepare/animals.html
8. COVID-19 and potential animal hosts, Worms & Germs. https://www.wormsandgermsblog.com/2020/02/articles/animals/cats/covid-2-and-potential-animal-hosts/
9. SARS virus infection of cats and ferrets. https://www.nature.com/articles/425915a
10. Can pets contract coronavirus from humans or vice versa? https://www.vetmed.ucdavis.edu/news/can-pets-contract-coronavirus-humans-or-vice-versa
11. Coronaviruses at the human-animal interface https://www.cahss.ca/media/uploads/CEZD/documents/20-02-18_16-24/Infosheet_-_Coronaviruses_at_the_Human-Animal_Interface.pdf
12. COVID-19 virus in a cat: Belgium https://www.wormsandgermsblog.com/2020/03/articles/animals/cats/covid-19-in-a-cat-belgium/
13. Experimental infections in dogs, cats and ferrets https://science.sciencemag.org/content/early/2020/04/07/science.abb7015?rss=1