A cat in Belgium seems to have become infected with the coronavirus and may have had COVID-19, the disease that the virus causes. While the case — the first reported in cats — suggests that the animals can catch the virus, there is no evidence that felines play a role in spreading the coronavirus, and it’s still unclear how susceptible they are to the disease.
“This is an isolated case, so it is not the rule,” microbiologist Emmanuel André of KU Leuven said March 27 at a news conference held by Belgium’s public health institute.
The cat probably picked up the virus, called SARS-CoV-2, from its owner, who fell ill with COVID-19 after traveling to northern Italy. About a week later, the cat started to show signs of illness: respiratory issues, nausea and diarrhea. In lab tests, feces and vomit samples showed high levels of SARS-CoV-2’s genetic material.
But that positive result comes with caveats. The samples were collected and sent to the lab by the owner, and a veterinarian has yet to examine the cat. The cat recovered after nine days, and once it’s released from quarantine, researchers will run a blood test for SARS-CoV-2 antibodies, which would provide more concrete proof of an infection. Those results are expected in about a week.
Even if the cat tests positive for SARS-CoV-2 antibodies, it might be hard to definitively prove that the virus made the cat sick — lots of other pathogens cause respiratory and stomach issues in cats.
“What makes us actually believe that this cat was infected is that there was quite a lot of virus detected in the feces and vomit in multiple tests over several days,” says Jane Sykes, a veterinarian at the University of California, Davis.
It’s not that surprising that cats could pick up SARS-CoV-2. The virus zeroes in on a protein called angiotensin-converting enzyme II, or ACE2, to hack into cells. Cats and humans have versions of this protein that are nearly identical in spots where the virus binds. The virus that causes SARS targets cells using the same break-in method (SN: 2/3/20), and it has been shown to infect cats and ferrets in a lab setting, though cats did not develop signs of disease.
In a study in the March 2020 issue of Journal of Virology, researchers note that SARS-CoV-2 can probably recognize ACE2 in cats, ferrets, orangutans, monkeys and some bat species. Another study, published March 30 in Cell Host and Microbe, confirms SARS-CoV-2 can infect ferrets, too.
Earlier in March, the first dog tested positive for SARS-CoV-2 (SN: 3/5/20), followed by another pup on March 19. Neither dog had symptoms and both results were only weakly positive, but the first dog, a 17-year-old Pomeranian from Hong Kong, died of unknown causes shortly after its release from quarantine. ACE2 looks a little bit different in dogs, which might make it harder for the virus to recognize and could make dogs less susceptible to infection.
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As in people, more testing could provide a crisper snapshot of how the coronavirus affects pets. Hong Kong, for example, has continued to screen some animals in homes with people who have tested positive for COVID-19. Out of 17 dogs and eight cats, only those two dogs have returned positive results, as of March 25.
In the United States, a company called Idexx Laboratories has developed its own diagnostic test to detect genetic material from SARS-CoV-2 in animals. From February 14 to March 12, Idexx says that it tested over 4,000 dogs, cats and horses from the United States and South Korea. None has been positive for the virus. While the tests did include animals from hot spots like Seattle, it’s unknown if any of the animals lived in homes with people that had COVID-19. Idexx is continuing to test animals and has expanded its pool of subjects to Europe and Canada.
While all that testing could fill in some unknowns about how the virus affects cats and dogs, pet owners shouldn’t panic. Cases in pets have been extremely rare so far. Sykes points out that if COVID-19 were a serious problem for pets, we would know it by now. “Dogs and cats may be what we call dead-end hosts,” she says. “They get infected with the virus. They shed it, but they’re unlikely to shed it enough to spread it to people.”
The American Veterinary Medical Association recommends taking normal precautions when cleaning litter boxes and feeding animals. If owners test positive for COVID-19, they should consider having someone else in the household care for the pet while they’re sick or wear a mask around the pet and limit contact. The U.S. Centers for Disease Control and Prevention has similar recommendations.