When the white-tailed deer interacts with humans, it doesn’t just cause the destruction of flora, an increase in road accidents and heated debates, as in Longueuil. Our deer can also be a “reservoir” of COVID-19.
Posted on March 2
For biologists, an animal species is a “reservoir” when it serves as a refuge for a pathogen, such as the COVID-19 virus, that can proliferate, mutate and reinfect humans.
But be careful ! Before jumping to conclusions, imposing the use of masks on deer and demanding compulsory vaccination, it is important to say that this field of research is embryonic and that there are many things that scientists do not know. . That said, a preliminary Canadian study shows signs of likely deer-to-human transmission for the first time. Scientists have identified a strain with a large number of mutations in southwestern Ontario. A very similar strain was also detected in a local hunter who had been in close contact with deer.
what do we know
“We know that the virus infects animals. And once established in animals, it is transmitted between animals. So why wouldn’t it go back in humans? “, says Hélène Carabin, professor of epidemiology of infectious diseases at the University of Montreal (UdeM).
Several animal species are indeed carriers of SARS-CoV-2. Possible cases of human-to-animal transmission followed by animal-to-human transmission were also observed. In particular in Denmark and the Netherlands, where millions of mink were culled in autumn 2020 following the discovery of a mutation of the coronavirus that is transmissible to humans and likely to be resistant to vaccines.
The most recent case was detected in Hong Kong in January, where authorities reportedly exterminated around 2,000 pet hamsters as a precaution, after positive cases appeared at a pet store.
The coronavirus has been detected in 17 animal species since the beginning of the pandemic: cats, tigers, lions, minks, dogs, skunks, rabbits, hamsters… In total, the World Organization for Animal Health has identified 625 sources of contamination in 32 countries. Most of these animals were in zoos or enclosures where they could be tested and placed in isolation. But white-tailed deer are free-ranging and often live in urban or suburban areas. These are the first reported cases in a free-ranging wildlife population.
source of concern
All experts interviewed by The press agree on one point: the danger is real and requires “solid vigilance.”
“It is certainly worrying,” explains epidemiologist Hélène Carabin, from UdeM. Once the virus mutates, the impact the mutation will have on the virulence of the virus and its ability to transmit from human to human is very difficult to predict. But if it comes back in a virulent form that vaccines don’t work against, it’s certainly worrisome. »
Steeve Côté, Full Professor in the Biology Department at Laval University, adds: “I think the interest in these questions is justified. »
Levon Abrahamyan, professor at the Laboratory of Animal Molecular Virology at the Faculty of Veterinary Medicine at the University of Montreal, agrees.
“Are they deer reservoirs? It’s a possibility. You have to study it. If the virus adapts to a new, non-human host, that could create another opportunity for the coronavirus to circulate and evolve. This can hypothetically have unfortunate or significant consequences for humans, even if we become resistant to the old variants. »
Last July, data from a US Wildlife Research Center study showed that 40% of white-tailed deer in four US states had antibodies, suggesting they had already been infected with the virus. In another study, published in November, researchers at Park University in Pennsylvania collected blood samples from 283 deer between April 2020 and January 2021. According to the results, more than 80% of the deer had contracted the disease.
In Quebec, work was carried out in three regions last fall. In Dunham, in the eastern counties, samples were taken from 150 deer killed by hunters. Of these, 2 deer were infected and another 14 had antibodies. In Brownsburg, in the Laurentians, samples taken from 108 deer were all negative. New cases of infection have been identified in Ontario, Manitoba and Saskatchewan in recent months.
For now, the Quebec Ministry of Forests, Wildlife and Parks (MFFP) no longer conducts research on white-tailed deer. Instead, he collects samples of caribou, elk, and black bears. “We call it opportunistic surveillance. We are taking advantage of other ongoing projects, whether research, monitoring or population monitoring, to sample and maximize our efforts,” says Marianne Gagnier, a biologist at the MFFP.
As of fall 2020, the MFFP has been analyzing samples from other wildlife such as raccoons, skunks, foxes and bats. And no trace of the virus was detected in these species.
How do deer get COVID-19? It’s a mystery.
“We don’t know,” says Professor Steve Côté. But we know that deer-to-deer transmission is likely high because there are populations with high rates of infection. It is very unlikely to be a human to deer infection. There is possibly another cause of transmission. People have suggested it could be through water, but it hasn’t been verified. »
Levon Abrahamyan notes that, in the case of outbreaks in farmed mink, “direct transmission of the virus from infected humans to mink is the only definitive route of transmission identified to date.”
“But in the case of deer, it’s not clear,” he adds. Multiple activities put deer in contact with humans: breeding, field research, conservation work, national parks, animal tourism, ecotourism, wildlife rehabilitation, complementary feeding… Hunting is an important possibility. And wildlife contact with contaminated water sources is also another possibility. »
The first likely case of transmission from white-tailed deer to humans is that of the Ontario poacher, identified in the preliminary study, the report of which has not yet been published. “He is a person who has had contact with deer,” explains biologist Marianne Gagnier, co-author of the study. Chances are, she contracted the white-tailed deer virus in the area. »