The National Veterinary School of Toulouse has world-renowned expertise in animal respiratory viruses. Pierre Bessière, teacher-researcher in infectiology, explains to us why cats and dogs, even infected with Covid, cannot contaminate us.
The National Veterinary School of Toulouse has world-renowned expertise in animal respiratory viruses. Pierre Bessière, teacher-researcher in infectiology, explains to us why cats and dogs, even infected with Covid, cannot contaminate us.
Why is the Toulouse Veterinary School working on the covid virus?
The Covid-19 pandemic has highlighted the importance of the One Health concept. Animal health and human health are closely linked, and both depend on the proper balance of ecosystems. While the majority of emerging diseases are of animal origin, veterinarians play a fundamental role in this concept. A veterinarian can have many hats: that of a practitioner, who participates in the surveillance of serious diseases, such as tuberculosis or rabies, that of a researcher, who helps to better understand the functioning of pathogenic agents, or even that of an inspector of veterinary public health, which coordinates in particular control and surveillance missions in the field of animal health. It is therefore quite natural that veterinarians and researchers from the National Veterinary School of Toulouse (ENVT) began to work on SARS-CoV-2. From the start of the pandemic, we set up collaborations with the Purpan University Hospital and with the National Agency for Food, Environmental and Occupational Health Safety. We have world-renowned expertise in animal respiratory viruses, such as avian influenza viruses, and have the necessary infrastructure to work on these viruses in complete safety.
How were traces of Covid identified in pets?
An infection with the in animals is diagnosed in exactly the same way as in humans: using PCR from swabs, or with serologies, i.e. the search for antibodies directed specifically against the virus, from a simple blood test. Surveillance programs were quickly put in place after the start of the pandemic, to determine the role that certain animals played in the spread of the disease. For example, it was at ENVT that we identified the virus for one of the very first times in cats in France.
“From the start, we studied the role that certain animals played in the spread of the disease.”
Why are cats infected and dogs not?
Cats can be infected just as well as dogs, contrary to popular belief. The protuberances that can be seen on the surface of many viruses observed microscopically are not decorative. They play the role of keys, able to open the locks of our cells to access them. Not all viruses have the same keys, and not all cells have the same locks. The keys present on the surface of SARS-CoV-2 manage to open many locks, allowing it to infect many animal species, including cats and dogs.
How does this manifest? Can the virus be deadly for them?
Fortunately, cats and dogs are not good hosts for the virus: according to work carried out in our laboratory, it multiplies much less well there than in us. Thus, infected animals excrete little virus, and for a short time. In almost all cases, the infection goes completely unnoticed. In animals with underlying diseases, such as heart disease, SARS-CoV-2 infection can cause clinical signs, but this is exceptional.
Can our pets infect us?
No, neither cats nor dogs can infect us. Hundreds of studies looking at COVID-19 in pets have been published, with one exception, that of a cat in Thailand that potentially transmitted the virus to its veterinarian, none have formally proven the opposite. As said before, the virus multiplies little in domestic carnivores, which therefore do not excrete significant amounts of virus.
Does the virus circulate a lot in animals and are there effective prevention measures?
Our work, and that of many other research teams, shows that cats and dogs play a negligible role in the epidemiology of the disease. Apart from applying barrier gestures with your animals when you are sick, there are no precautions to take. On the other hand, wild animals, such as mink or certain deer, are closely monitored because they are very good hosts for the virus. Studies from the United States, for example, have shown that SARS-CoV-2 circulates intensely in white-tailed deer, and has acquired mutations there so far not observed in humans. These elements also show how essential it is to involve veterinarians in zoonotic diseases, that is to say involving humans as well as animals.
