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Cats can be coronavirus carriers—for other cats

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Cats with SARS-CoV-2 can give it to other cats.

That’s according to researchers at the University of Wisconsin, who infected cats experimentally with SARS-CoV-2 as part of a study to see what would happen when those cats were exposed to other, uninfected cats.

The researchers reported their findings in the New England Journal of Medicine.

In the study, researchers administered SARS-CoV-2 isolated from a human patient to three cats. The following day, the researchers swabbed the nasal passages of the cats and were able to detect the virus in two of the animals. Within three days, all the cats had tested positive for the virus.

The day after the researchers administered the virus to the first three cats, they placed another cat in each of their cages. Researchers did not administer SARS-CoV-2 virus to these cats.

Each day, the team took nasal and rectal swabs from all six cats to check for the presence of the virus. Within two days, one of the previously uninfected cats was shedding the virus, which researchers detected in the nasal swab. Within six days, all of the cats were shedding the virus.

At no point in the study did any of the rectal swabs show signs of the virus.

Each cat continued to shed SARS-CoV-2 from their nasal passages for up to six days. The virus was not lethal and none of the cats showed signs of illness. All of the cats ultimately cleared the virus, and none ever showed signs of illness.

The researchers say the findings suggest that cats may be capable of becoming infected with the virus when exposed to people or other cats positive for SARS-CoV-2, which backs up the findings in another recent study by scientists at the Chinese Academy of Agricultural Sciences that also showed cats (and ferrets) could become infected with and potentially transmit SARS-CoV-2. The virus is known to be transmitted in humans through contact with respiratory droplets and saliva.

Both teams of researchers advise that people with symptoms of COVID-19 avoid contact with cats. They also advise cat owners to keep their pets indoors to limit the contact their cats have with other people and animals.

NEWStat reached out to Peter Halfmann, PhD, who co-led the study, to find out more.

Halfmann, an associate scientist in the Department of Pathobiological Sciences at the University of Wisconsin’s School of Veterinary Medicine, says he was surprised at the lack of symptoms: “Our healthy cat subjects never showed any noticeable symptoms of infection—a high temperature, coughing, or sneezing—but had high amounts of virus in the nose, and the virus transmitted easily to naïve cats.”

What advice does Halfmann have for veterinarians inundated with questions from concerned pet owners who worry that their cats might catch COVID-19?

First, Halfmann concedes that there’s cause for concern: “If a sick cat is from a household where a human has or had SARS-CoV-2, then there is a chance the cat could be infected.” But, Halfmann adds, unless the cat has underlying illnesses or conditions, “the cat will most likely be fine. Just like humans, cats with underlying illnesses should be monitored more closely.” For clients who ask about treating cats with SARS-CoV-2, there’s not much they can do—Halfmann notes that there are currently no recommendations on treatment.

Halfmann says to tell worried cat owners to do what they’d do in cases of human-to-human transmission: “Take extra steps to prevent transmission to your cat. Don’t interact closely with your cat and disinfect household surfaces [regularly].”

As for concerns that cat owners might catch the virus from their cat, Halfmann is more reassuring.

“You’re more likely to get infected by another human,” he said. Humans remain the biggest risk to other humans for virus transmission. There is no evidence that cats readily transmit the virus to humans, nor are there documented cases in which humans have become ill with COVID-19 because of contact with cats.

Again, the real risk here is people giving the virus to their cats: There are confirmed instances of cats becoming infected because of close contact with infected humans, and several large cats at the Bronx Zoo have also tested positive for the virus. Two cats in two private homes in New York state also tested positive for COVID-19. One had been in a home with a person with a confirmed case of the viral disease. The cats showed mild signs of respiratory illness and were expected to make a full recovery.

Given those cases, however rare they might be, Halfmann says clients should definitely be aware of the possibility of passing it on to a household cat that sleeps with them or shares close quarters.

Photo credit: © iStock/Larysa Lyundovska