Wildlife Biologists Prioritize Monitoring Wild Animals for SARS-CoV-2

The Covid-19 pandemic is driven by human-to-human transmission, but the virus is known to infect animal species

An image of a white tailed deer standing in snow-covered woods looking straight into the camera
Out of the deer tested in Iowa between September 2020 and January 2021, a third of total white-tailed deer had SARS-coV-2. Joseph A. Maker via Wikimedia Commons under CC BY SA 3.0

In Minnesota's northern forests, researchers are sneaking into the dens of hibernating black bears, capturing deer in nets, and trapping wolves and moose to get a quick swab of their snouts—all in an effort to track the spread of SARS-CoV-2, the virus that causes Covid-19, in wildlife, Laura Ungar writes in a feature for the Associated Press.

The coronavirus pandemic has highlighted how closely animal and human health are intertwined. Although the exact origins of the virus have not been pinpointed, researchers suspect it may have leapt from bats to humans, directly or through an intermediate animal vector. Although SARS-CoV-2 is known to infect animal species, the Covid-19 pandemic is driven by human-to-human transmission. While current research shows that wildlife does not play a significant role in spreading the virus to humans, experts are still concerned about the virus spreading between animal populations, which may facilitate the emergence of new virus variants. 

Last month, the World Health Organization (WHO) along with the Food and Agriculture Organization (FAO) and the Organization for Animal Health—formerly the Office International des Epizooties (OIE)—released a joint statement calling on global wildlife agencies prioritizing monitoring SARS-CoV-2 infections in wildlife to prevent the formation of animal reservoirs. In a reservoir, the virus can mutate and emerge as different strains. So far, domestic animals, big cats, minks, ferrets, North American white-tailed deer, and great apes have been observed infected with the virus. According to the statement, cases of farmed mink and pet hamsters have shown to be capable of infecting humans with SARS-CoV-2.

“If the virus can establish itself in a wild animal reservoir, it will always be out there with the threat to spill back into the human population,” Matthew Aliota, an emerging pathogen biologist at the University of Minnesota who is involved with tracking efforts in the state, tells AP. After swabbing of the animal’s noses, biologists send the samples to Aliota’s laboratory in St. Paul, Minnesota. Results from the tests may reveal which animals are getting infected and could spread virus to other woodland creatures, like red foxes and raccoons, AP reports.

E.J. Issac, a fish and wildlife biologist at the reservation home to the Grand Portage Ojibwe, tells AP that he expects stakes will be higher this spring when animals awaken from hibernation and intermingle with other animals’ and roam to different regions.

Currently, wildlife in at least 24 American states have contracted the virus. White-tailed deer appear to be a prominent potential reservoir species. University of Pennsylvania microbiologist Andrew Marques, who co-authored the study, told NPR's Ari Daniel that the rate of transmission is "absolutely stunning when we consider the positivity rate in humans." (In March when the study was published, coronavirus rates in a city like Philadelphia were about three percent in humans, per NPR.)

Between September 2020 and January 2021, researchers in Iowa tested 151 wild white-tailed deer and 132 captive deer, according to a study published in PNAS in January. Of those, 33 percent tested positive for SARS-CoV-2. During the same timeframe, the United States Department of Agriculture collected 481 samples from deer in Illinois, New York, Michigan, and Pennsylvania, and also found about third of those deer had coronavirus antibodies present in their systems. 

More recently in fall and winter 2021, researchers in Pennsylvania also identified a 20 percent coronavirus positivity rate in deceased white-tail deer that were hunted or involved in vehicle collisions, per NPR; both of which are instances when human-animal interaction is more likely. They were also able to sequence the genome of seven samples and found the Delta strain was present, which marked the first observations of the lineage in deer, according to the study.

A Canadian study published on the preprint server bioRxiv in February this year identified a person who may have contracted a mutated strain of the virus from an infected white-tailed deer, per AP. This study is currently undergoing peer-review by an external panel of experts, per the WHO statement.

“We are encroaching on animal habitats like we have never before in history,” Aliota tells AP. “Spillover events from wild animals into humans are, unfortunately I think, going to increase in both frequency and scope.”

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