The question of the transmission of Covid-19 to domestic animals has worried animal lovers since the start of the epidemic.
If, until now, few studies had been able to be carried out, that of the University of Minnesota is rich in lessons and in astonishing conclusions.
She bases her research on the finding that it is "quite common" for cats and dogs to be also infected in homes where people test positive for SARS-CoV-2.
A fact already noticed by other scientists like Dr. Jonathan Runstadler, virologist at the Cummings School of Veterinary Medicine at Tufts University, who has studied how the coronavirus affects animals.
This is the starting point for research carried out by a couple of scientists. Dr Ly, a veterinary and biomedical researcher at the University of Minnesota, has always known humans are the primary driver of the pandemic. This time, he asked himself the following question: to what extent is the Covid transmissible to man's best friends? As the New York Times reports, in March 2020, Dr Ly learned that two dogs in Hong Kong had tested positive for the virus. However, swabbing the muzzle of many pets seemed far too tedious to be able to determine the propensity of animals to be infected, the object of his study.
He therefore suggested to his wife, Yuying Liang, a researcher from the same department who runs the lab with him, to test cats and dogs for the presence of antibodies, which would reveal a past infection with the virus.
Their body of research consists of urine and blood samples from 239 Minnesota cats and 510 companion dogs, “clients” of a veterinary clinic, during the early phase of the Covid-19 pandemic, the mid-April to early June 2020, to detect signs of exposure to SARS-CoV-2.
8% of cats carried antibodies against the coronavirus, less than 1% of dogs
The researchers first looked at around 100 samples and found that about 5% of cats' "serum" contained antibodies to the coronavirus, while dog serum hardly did. To be on the safe side, Dr Ly tested hundreds of additional samples, drawn from blood and urine taken in April, May and June, as Covid cases were on the rise in this region of the northern United States.
In the end, scientists found that 8% of cats carried antibodies against the coronavirus, while less than 1% of dogs were, suggesting that cats are much more susceptible to infection.
"Our results show that SARS-CoV-2 seropositivity rates are higher in companion cats than in companion dogs at the start of the pandemic," the researchers specified in their study.
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As pet owners gave their consent anonymously, researchers were unable to determine which humans may have transmitted the virus to different cats and dogs.
"It is also not known whether infected pet cats lived indoors or outdoors, or to what extent the virus was transmitted from cat to cat," Dr. Ly told the NY Times. .
"We cuddle cats more"
The study also leaves room for some questions. So researchers don't know why cats seem to be more susceptible to the virus than dogs. One of the possibilities is related to "ACE2, a protein on the surface of cells which is a receptor for the coronavirus". The genetic sequence of the human ACE2 protein is indeed much closer to the equivalent sequence in cats than in dogs, said the North American scientific team.
Another possible explanation: our special relationship to the "sphynx", which haunts our living rooms and squats our beds and sofas.
A recent study that showed similar results - namely that cats are more easily infected with the coronavirus than dogs - noted that felines are often more inclined to sleep on beds than canines.
“Maybe it's because we hug cats more,” laughs Dr. Ly.
As a result of his study, Dr. Ly therefore recommends that you distance yourself not only from humans, but also from cats and dogs if you have ever tested positive.
“You can't hug them,” he says.
Pets are unlikely to contribute to the outbreak in the long term.
But there is still no way to be scientifically sure.