Cats can transmit SARS-CoV-2 to other cats. But they could be the future poster animals for developing a vaccine.

At least according to the findings of a new pilot study by researchers at Colorado State University, in which domestic cats and dogs were assessed for their susceptibility to SARS-CoV-2 infection. Specifically, the researchers wanted to know whether the novel coronavirus was able to reproduce inside the animals’ cells and then be released into the environment—a process known as “shedding.”

The researchers used viral plaque assays to measure the levels of infectious virus and confirmed those results with qRT-PCR tests.

In the admittedly small sample size (just seven cats and three dogs), they found that cats shed the infectious virus for up to five days and infected other cats via direct contact, while dogs don’t appear to shed the virus at all. Neither species developed clinical disease during the study.

NEWStat reached out to lead researcher Angela Bosco-Lauth, DMV, PhD, assistant professor of Biomedical Sciences at Colorado State’s College of Veterinary Medicine and Biomedical Sciences and lead author of the study, to find out more about how cats and dogs differ in their response to the virus.

According to Bosco-Lauth, cats are more likely than dogs to shed infectious virus, which means they’re capable of transmitting it to other cats. “The dogs in our study did not shed infectious virus, and other studies have found similar results, so we don’t believe dogs are capable of transmitting the virus.”

Bosco-Lauth said she doesn’t have a good answer as to why cats and not dogs seem able to transmit the virus, but she notes that susceptibility to SARS-CoV-2 has been closely linked to the ACE2 receptor. “My best guess is that something about the receptor in cats, as with humans, makes them more susceptible to infection than dogs.”

Although none of the animals in her study developed any clinical signs of disease, “reports from other sources suggest that some animals develop mild respiratory signs, not unlike humans with mild COVID disease,” said Bosco-Lauth. However, “the severity of disease and symptoms in humans does not seem to be replicable in cats or dogs.”

Interestingly, when the cats were challenged to reinfection with SARS-CoV-2, they had an effective antibody response that prevented reinfection.

Meaning they may be key to future vaccine trials—both for humans and other animals.

And for pet owners who remain concerned about zoonotic transmission, Bosco-Lauth says, “We strongly believe that pet exposure is almost certainly via SARS-CoV-2 infected humans, and not the other way around.”

“There’s no evidence to date of humans contracting the virus from cats,” she added.

But perhaps they could help save us both from it!

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