The spread of Covid-19 in white-tailed deer is starting to worry

Posted on November 13, 2021, 2:30 pm

Can the white-tailed deer, one of North America’s most common large mammals, become a walking bomb and transmit Covid 19 to humans? For now this is not the case. But in a new study, veterinarians at the University of Pennsylvania are concerned that the presence of the virus is strong in these deer which have also been introduced to many countries like Finland, former Czechoslovakia or even New Zealand again.

The white-tailed deer could, according to these scientists, become a “reservoir” for the virus. Clearly, it could proliferate and evolve into new forms within this species before, in theory, becoming transmissible to humans again in a way not considered by vaccines.

Rising number of deer tested positive for Covid

The presence of Covid in the deer population across the Atlantic is not a real novelty. Two studies, published in the spring and summer by the American Wildlife Research Center (NWRC), showed that these animals were heavily contaminated and transmitted the virus to each other. But what surprised and worried the researchers of this new study, which has not yet been evaluated by the scientific community, is the high proportion of infected deer. “We were very surprised to see such a large number of positive samples”, summarizes one of the authors.

In fact, if between April and December 2020, only a third of the deer were positive, that share jumped to 80% for those analyzed between November 2020 and January 2021. And to make these results a little more anxious, the deer two veterinarians discovered the presence of numerous variants that corresponded to those also identifiable in humans. All the deer studied lived freely in public spaces or in peri-urban areas, or in the middle of nature, or finally in captivity in areas reserved for hunting.

Fear of cultured mink precedent

Scientists therefore implicitly fear that we will see a repeat, with white-tailed deer, of what happened to mink farmed in many European countries, as well as China. In some very specific cases, in fact, the Covid-19 virus, after mutating, was transmitted to humans by these animals created for their skin. “As of June 2020, 214 human cases of Covid-19 have been identified in Denmark with variants of Sars-CoV-2 associated with farmed mink, including 12 cases with a single variant […] in North Jutland,” the World Health Organization (WHO) reported in November 2020.

However, if in the case of the mink the method chosen to eliminate the danger was radical with the slaughter of the animals present in the contaminated farms, the solution seems less viable in the case of the white-tailed deer. In the United States there are no less than 30 million of these deer, while there are 325,000 in Canada and 115,000 in Finland, for example.

Better monitoring of the virus in wildlife

Scientists therefore advocate greater vigilance and anticipate the appearance of variants as much as possible. And they consider it “urgent” to continue to monitor the evolution of the virus in wildlife, “especially in animals that can serve as a reservoir, such as deer. A recommendation that implicitly militates for the Anglo-Saxon concept of “One Health”, very developed on the other side of the Atlantic, and which is based on the idea that the health of the human population and animals are linked.

It also remains to be determined how these white-tailed deer are contaminated by humans. Traditionally, these animals do not live in large groups and ultimately have relatively little contact with humans, except in parks or zoos. The most relevant clue, therefore, seems to be a source of contagion that would pass through wastewater that would contaminate the water that the deer drink.

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