An employee takes the temperature of a cat in a cat cafe in Bangkok.
LILLIAN SUWANRUMPHA / AFP via Getty Images
By David Grimm
Science‘s report on COVID-19 is supported by the Pulitzer Center and the Heising-Simons Foundation.
Last month, the first American dog to test positive for COVID-19 in New York City died. The rooster – a German shepherd named Buddy – probably had lymphoma, but the case served as a reminder that pets are also a risk.
COVID-19 cases are now growing in some areas of the United States, including in places that escaped the virus for the most part in the spring, and some countries around the world are struggling with renewed outbreaks. People also question them and worry about their pets.
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Scientists are that too. It remains unclear, for example, how often cats and dogs are infected with the virus, what their symptoms are, and how likely they are to pass it on to other animals, including us. However, veterans are hard at work on the matter, and a handful of studies are beginning to provide some answers. Experts have some concrete advice based on what we know so far.
We are a much greater risk to our pets than they are to us.
Federal health agencies and veterinary experts have said since the beginning of the pandemic that pets are not likely to pose a significant risk to humans. Hard evidence from controlled studies for this claim was not – and still is – but everything scientists have seen so far suggests that cats and dogs do not transmit SARS-CoV-2 to humans. “There’s a much greater risk of going shopping than hanging out with your own animal,” says Scott Weese, a veteran of the University of Guelph’s Ontario Veterinary College who specializes in emerging infectious diseases and those almost every study on COVID has dissected -19 and pets on his blog.
In fact, pets are much more likely to get the virus from humans than vice versa. “Almost all pets that have tested positive have been in contact with infected people,” says Jane Sykes, chief veterinary medical officer at the University of California, Davis, and a founder of the International Society for Companion Animal Infectious Diseases, who The COVID provides -19 information to both pet owners and veterans. A genetic study of the viral sequences in the first two dogs known to COVID-19 indicated that they caught it from their owners. Even tigers and lions became infected at the Bronx Zoo in New York in April, appearing to be infected by humans.
But some researchers caution that this finding may be due in part to limited testing: Most of the pets that were evaluated received the tests because they lived with people who already tested positive. “It’s a stacked deck,” says Shelley Rankin, a microbiologist at the University of Pennsylvania School of Veterinary Medicine, whose lab is part of the U.S. Food and Drug Administration’s Veterinary Laboratory Investigation and Response Network.
However, most researchers think that pets pose a small risk to humans – and to other pets as well. A few studies have shown that cats can transmit SARS-CoV-2 to other cats, but all were performed in an artificial laboratory. And, like many COVID-19 studies in humans, most research are preprints that have yet to be published in peer-reviewed journals. What’s more, Sykes notes that there have been multiple reports of households where one pet tested positive and others did not. “Everything we’ve learned so far suggests that pets are unlikely to be a major source of transmission,” she says.
COVID-19 symptoms in pets are likely to be mild to non-existent.
Because petting remains rare, it is unclear how many cats and dogs are infected with SARS-CoV-2. A serological survey published last month indicated that 3% to 4% of cats and dogs in Italy were exposed to the virus at the height of the pandemic there – comparable to the rate among humans.
A girl and her dog don mask in Regensburg, Germany.
Isa Foltin / Getty Images
But even if the numbers are really that high, there has not been a simultaneous uptick in symptoms. The Seattle-based Trupanion, which provides health insurance for more than half a million dogs and cats in North America and Australia, says it has not seen an increase in respiratory claims – like any other type of health claim – since the pandemic began. “No big trends are springing up,” said Mary Rothlisberger, vice president of analytics, even when she looked at pandemic hotspots. Two recent studies have also shown that cats are at least unlikely to exhibit symptoms. ‘My gut feeling is that [the disease is] much less than we see in humans, ”says Sykes.
This may mean that pets are silent transmitters of the virus, as some scientists have suggested, but so far there is no direct evidence of this.
It probably makes no sense to test your pet.
Various pet tests are available, but they are not widely used because the priority has been on human testing. Agencies such as the U.S. Department of Agriculture have warned against routine testing of cats and dogs.
Even if your pet tests positive, Weese says, “What are you going to do with the results?” If your dog or cat has COVID-19, it’s probably because you do too, he says. “It does not change anything for the pet or the family.” And because there is no cure for the disease, he says, “We would not prescribe anything” for the pet.
Pet precautions have not changed.
Whether it’s taking your dog to a dog park or petting an outdoor cat, the standard advice still holds true: wear a mask, wash your hands and social distance. “If you do not take precautionary measures … you are putting yourself and your animal in danger,” Rankin says. But, she says, “If you’re a responsible pet owner, then it’s probably safe to say your pet’s risk [of infection] is lower than that. ”
Wees agree that people should be more concerned about other people than about pets. “The risk of people attending dog parks or animal clinics is much higher than the risk of dogs at those locations,” he says.
Scientists have even more questions than answers.
Researchers have just begun to understand how companion animals play the pandemic. The pet studies so far “are all part of a puzzle we are still trying to collect,” says Sykes.
And they are prepared. “Almost every preprint I’ve seen is somehow flawed,” says Rankin, who cites small sample sizes, incomplete data and a lack of rigorous testing. That does not necessarily invalidate the results, but she and others want to see more robust studies.
Sykes and Weese, for example, want to do more research in-house. This would give scientists a better sense of how likely pets are to transmit the virus to other pets, how long pets remain contagious, and what – if any – clinical signs of COVID-19 appear.
Rankin is part of a project to do what she calls “full-on epidemiology” of the full medical backgrounds, including all COVID-19 cases, of 2,000 pets seen for various reasons at their veterans school, or simply for routine checks. The hope is that such an approach will give some of the parties to previous studies – such as those looking only at pets in COVID-19 – positive homes – and get a better sense of the true risk factors for the disease.
Sykes and Weese are involved in similar endeavors. Weese also hopes to investigate whether pets, especially feral and outdoor cats, are at risk for wildlife. “If we want to get rid of this virus,” he says, “we need to know everywhere what it could be.”
Other researchers are investigating whether drugs that treat other coronaviruses in cats can also fight COVID-19 in both pets and humans. “Answering these questions is not only important for accompanying animal health,” says Sykes. “It could help us, too.”
