Cats are better than dogs (to catch the coronavirus)
In the spring of 2020, as the new coronavirus infiltrated the Twin Cities, Hinh Ly couldn’t help but think of cats and dogs.
Dr Ly, a veterinary and biomedical researcher at the University of Minnesota, knew humans were the primary driver of the pandemic. But he also knew that many people enjoyed hugging and cuddling their pets, whether they were sick or healthy. He wondered: How transmissible is SARS-CoV-2 to mankind’s best friends?
In March 2020, Dr Ly learned that two dogs in Hong Kong had received positive PCR tests for the virus. But these tests require the virus to actively replicate and therefore only reveal active infections. Swabbing the snouts of many pets seemed to Dr. Ly too long a way to determine how easily animals could become infected.
So he suggested that his wife, Yuying Liang, a researcher from the same department who runs the lab with him, test cats and dogs for antibodies, which would reveal past infection with the virus. “I had the idea, but she’s the boss,” said Dr Ly.
The result of these antibody tests, published recently in the journal Virulencesuggest that domestic cats are more susceptible than dogs to SARS-CoV-2 infection.
Fortunately, infected cats seem to show mild symptoms at most. “I’m always a little surprised that cats are so easily infected and yet rarely show signs of disease,” said Dr Angela Bosco-Lauth, a biomedical researcher at the College of Veterinary Medicine and Biomedical Sciences at the University of State of Colorado, which was not involved in the research.
And there is still no evidence to suggest that infected cats or dogs pose a risk to humans, said Dr Jonathan Runstadler, a virologist at Tufts University’s Cummings School of Veterinary Medicine who has studied how the coronavirus affects animals but was not involved in the new work.
The new study supports recent research that it can be “quite common” in households where people who test positive for SARS-CoV-2 are also infected with cats and dogs, Dr Runstadler said.
To test for antibodies in pets, researchers in Minnesota needed serum from animals, the component of blood that contains antibodies. Dr Ly contacted Dr Daniel Heinrich, director of the clinical pathology laboratory at the university’s veterinary center. (Dr Henrich is also author of the new study.) Pets passed through the center daily, and their blood was tested for a myriad of reasons, including “annual checkups, unrelated illness, inappropriate peeing on the body. wall, ”said Dr. Ly.
These samples are usually discarded. But Dr Heinrich asked pet owners to allow anonymous use of the serum in the study, and the researchers got their first handful of samples in April.
The researchers first looked at around 100 samples and found that about 5% of cat serum contained anti-coronavirus antibodies, while almost no dog serum did. To be on the safe side, Dr Ly tested hundreds of other samples, from blood drawn in April, May and June, as Covid cases increased in the region.
Ultimately, scientists found that 8% of cats carried antibodies to the coronavirus, while less than 1% of dogs carried them, suggesting cats were more susceptible to infection.
Because pet owners gave their consent anonymously, researchers were unable to determine which humans could have transmitted the virus to different cats and dogs. It was also not clear whether the infected cats lived indoors or outdoors, or how transmissible the virus was from cat to cat, Dr Ly said.
Researchers don’t know why cats seem to be more sensitive than dogs. One possibility is ACE2, a protein on the surface of cells that is a receptor for the coronavirus. The genetic sequence of the human ACE2 protein is much more similar to the equivalent sequence in cats than in dogs.
But animal behavior could also be a factor. A recent study which presented similar results – that cats are more easily infected with the coronavirus than dogs – noted that cats are often more welcome to sleep on beds than dogs. “Maybe it’s because we hide cats more,” Dr. Ly speculated. “Maybe we kiss cats more.”
Dr Bosco-Lauth said she believes pets “are unlikely to contribute to the epidemiology of SARS-VOC-2 in the long term.” But there is still no way to know for sure.
For those who test positive for Covid-19, Dr Ly recommended staying away not only from humans, but also cats and dogs. “You can’t cuddle them,” he said.
Dr Ly and Dr Liang do not have cats or dogs in their own homes. They have a reservoir of guppies, which at the moment seem fairly immune to the coronavirus.