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An employee takes a cats temperature at a cat caf in Bangkok.

By David GrimmAug. 14, 2020 , 4:00 PM

Sciences COVID-19 reporting is supported by the Pulitzer Center and the Heising-Simons Foundation.

Last month, the first U.S. dog to definitively test positive for COVID-19 died in New York City. The caninea German shepherd named Buddylikely had lymphoma, but the case served as a reminder that pets, too, are at risk.

Now, COVID-19 cases are surging in some areas of the United States, including in places that had largely escaped the virus in the spring, and some countries around the world are grappling with renewed outbreaks. People are also wondering and worrying about their pets.

Scientists are, too. It remains unclear, for example, how often cats and dogs become infected with the virus, what their symptoms are, and how likely they are to pass it along to other animals, including us. Yet veterinarians are hard on the case, and a handful of studies are starting to provide some answers. Experts have some concrete advice based on what we know so far.

Federal health agencies and veterinary experts have said since the beginning of the pandemic that pets are unlikely to pose a significant risk to people. Hard evidence from controlled studies for this assertion was lackingand still isbut everything scientists have seen so far suggests cats and dogs are highly unlikely to pass SARS-CoV-2 to humans. Theres a lot greater risk of going to the grocery store than hanging out with your own animal, says Scott Weese, a veterinarian at the University of Guelphs Ontario Veterinary College who specializes in emerging infectious diseases and who has dissected nearly every study on COVID-19 and pets on his blog.

Indeed, pets are much more likely to get the virus from humans than the other way around. Almost all pets that have tested positive have been in contact with infected humans, 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, which is providing COVID-19 information to both pet owners and veterinarians. A genetic study of the viral sequences in the first two dogs known to have COVID-19 indicates they caught it from their owners. Even tigers and lions infected at New York Citys Bronx Zoo in April appear to have contracted the virus from humans.

But some researchers caution that this finding may be due in part to limited testing: Most of the pets that have been evaluated got the tests because they lived with humans who had already tested positive. Its 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 Administrations Veterinary Laboratory Investigation and Response Network.

Still, most researchers think pets pose little risk to peopleand to other pets as well. A few studies have shown that cats can transmit SARS-CoV-2 to other cats, but all were conducted in an artificial laboratory setting. And, like many COVID-19 studies in humans, most studies are preprints that have yet to be published in peer-reviewed journals. Whats more, Sykes notes there have been multiple reports of households where one pet tested positive and others didnt. Everything weve learned so far suggests that its unlikely that pets are a significant source of transmission, she says.

Because pet testing remains rare, its unclear how many cats and dogs have been infected with SARS-CoV-2. A serological preprint published last month indicated that 3% to 4% of cats and dogs in Italy had been exposed to the virus at the height of the pandemic therecomparable to the rate among people.

A girl and her dog don masks in Regensburg, Germany.

But even if the numbers are really that high, there hasnt been a concomitant 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 claimsor any other type of health claimsince the pandemic began. No big trends are jumping out, says Mary Rothlisberger, the companys vice president of analytics, even when she looked at pandemic hot spots. Two recent studies have also shown that cats, at least, areunlikely toexhibit symptoms. My gut sense is that [the disease is] much more minor than were seeing in people, Sykes says.

That could meanpets are silent transmitters of the virus, as some scientists have suggested, but so far theres no direct evidence for this.

Several pet tests are available, but they arent widely used because the priority has been on human testing. Agencies like the United States Department of Agriculture havecautioned against routine testingof cats and dogs.

Even if your pet does test positive, Weese says, What are you going to do with the results? If your dog or cat has COVID-19, its probably because you do too, he says. It doesnt change anything for the pet or the family. And because there arent any drugs for the disease, he says, We wouldnt prescribe anything for the pet.

Whether it comes to taking your dog to a dog park or petting an outdoor cat, thestandard advice still holds: Wear a mask, wash your hands, and social distance. If you are not taking precautions you are putting both yourself and your animal at risk, Rankin says. But, she says, If you are a responsible pet owner, then it is probably safe to say that your animals risk [of infection] is lower than yours.

Weese agrees that people should be more concerned about other humans than about pets. The risk from people present at dog parks or vet clinics is much higher than the risk from dogs at those locations, he says.

Researchers are just beginning to understand how companion animals play into the pandemic. The pet studies so far are all part of a puzzle were still trying to put together, Sykes says.

And theyre preliminary. Almost every preprint I have seen is flawed in some way, says Rankin, who dings small sample sizes, incomplete data, and a lack of vigorous testing. That doesnt necessarily invalidate the results, but she and others would like to see more robust studies.

Sykes and Weese, for example, want more research done in the home. That could give scientists a better sense of how likely pets are to transmit the virus to other pets, how long pets remain contagious, and whatif anyclinical signs of COVID-19 show up.

Rankin is part of a project to do what she calls full-on epidemiology of the complete medical backgrounds, including any COVID-19 cases, of 2000 pets that have been seen at her vet school for various reasons, or just for routine checkups. The hope is that such an approach will weed out some of the biases of previous studiessuch as those that only looked at pets in COVID-19positive homesand 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, pose a risk to wildlife. If we want to eradicate this virus, he says, we need to know everywhere it might be.

Other researchers are exploring whether drugs that treat other coronaviruses in catscould also combat COVID-19in both pets and people. Answering these questions isnt just important for companion animal health, Sykes says. It could help us, too.

Read the original:
What does the COVID-19 summer surge mean for your cats and dogs? - Science Magazine

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