Animals tested "positive" but
If we have been saying loud and clear since the start of the covid-19 epidemic that dogs and cats do not spread the coronavirus, several publications in the media still cast doubt in our minds. pet owners.
On March 27, one of them reported the discovery of a “confirmed” case of covid-19 in a cat that presented unexplained respiratory symptoms in Belgium. Tests have found traces of the SARS-coV-2 virus, the coronavirus responsible for the COVID-19 epidemic, in the animal's excretions.However, should we conclude that the new virus is transmissible to cats?
It's not that obvious because several gray areas persist in this case. The first uncertainty is based on the very quality of the samples. These were collected by the cat's owner - herself infected with the coronavirus - at her home. There is therefore no indication that the samples were not involuntarily contaminated by the owner herself or by the environment in which the cat was evolving. And, even if the samples were taken according to the rules of the art, the presence of the virus in the stool of the animal does not in any way mean that the animal suffers from the same disease as its owner. On this subject, Professor Etienne Thiry, professor at the veterinary faculty of Liège and member of the scientific committee of Afsca, declared in La Libre Belgique that “We currently have no proof that the symptoms of this cat are linked with SARS-CoV-2”.
A virus present does not mean that it is infective
What's more, the analyzes that were carried out on the samples of the Belgian cat used the PCR method. This technique uses the “Polymerase Chain Reaction” or, in French in the text, Polymerase Chain Amplification. It makes it possible to obtain large quantities of a specific DNA fragment from a small sample containing this same DNA. In other words, this method only makes it possible to detect the genetic material of the virus but in no way provides information on its activity or its infective potential.
From this analysis alone, we therefore have no way of knowing whether the virus is able to replicate in the cells of the cat, whether it is the cause of symptoms in the latter or yet if it can shed the virus, the only conditions that would allow scientists to say with certainty that a cat can catch and then transmit COVID-19.
As for the Belgian cat, like dogs tested positive for Covid-19 in Hong Kong and whose homes all included a sick person, the most likely hypothesis is therefore that their "positivity" results simple environmental contamination or contamination from humans to animals.
Doubts alleviated by several studies
A preliminary study report conducted in partnership with the Institut Pasteur, the Alfort Veterinary School and INSERM further weakens the few doubts that still remain about the idea that our animals can be affected by COVID-19 or spread the disease to humans. Published on April 9, 2020 on bioRxiv, this report presents the results of tests carried out for 1 month on 9 cats and 12 dogs who lived in close proximity with their veterinary student masters on the campus of the veterinary school, in rooms from 9 to 13 m². Eleven students among the 18 participants in the study had contracted Covid-19 or presented clinical signs compatible with the infection while the others were asymptomatic.All the PCR tests carried out on oral and anal samples as well as all the serologies carried out on their animals thus came back negative.
This new preliminary field study, the results of which must still be reviewed and validated before its official publication, corroborates the results of a large-scale test campaign carried out by the Idexx laboratory on dogs, cats and horses that have been in prolonged contact with humans infected with Covid-19 in Wuhan (China) and the United States. Out of thousands of PCR tests performed, no positive animal was detected.
A few Chinese studies report a specific immune reaction to infection in a dog and several cats and a receptivity of cats and ferrets to the virus, but the results of these controversial studies however, remain to be confirmed and are obviously to be put into perspective with the few "positive" and symptomatic cases in pets compared to the millions of infected humans.
Be that as it may, the He alth Authorities agree that it is not possible, to date, to formally conclude that there is a productive infection in the animal and a transmission of the animal-to-human disease. In other words, to date there is still no formal and indisputable proof that pets can spread SARS-coV-2 and infect humans. According to the WHO, the current covid-19 pandemic is therefore solely the result of human-to-human transmission.
Are pets passive carriers of the virus?
In a press release, the French Veterinary Academy, on the other hand, raises the possibility that pets could be moving "passive carriers" of the virus on which an infected person could deposit viral particles. Another person who would handle this virus-carrying animal on its coat in a short period of time could then be contaminated in turn.
But here again, the risk of contamination is infinitesimal and drops to practically zero when you respect the rules of social distancing during walks and basic hygiene gestures such as washing your hands after each contact with an animal.