As studies show SARS-CoV-2 in deer, Wisconsin plans to start testing by winter

As evidence mounts that white-tailed deer are highly susceptible to SARS-CoV-2, the virus that causes COVID-19, researchers and health officials are scrambling to study the disease in the wild population and offer guidance to hunters.

To date there is no proof the virus sickens deer or can be transmitted from deer to humans.

But scientists say much is yet to be learned and worry about the potential for the nation's 30 million deer to act as a reservoir for an evolving virus and a source for human infection.

"It's very concerning to me," said Linda Saif, a virologist at the Ohio State University, in an interview with National Public Radio. "The question is, can it spill back from deer to humans? We don't know that yet. But if that's possible or if they could transmit it effectively to grazing livestock, then, obviously, this is a concern."

As COVID-19 spread through the human population in 2020, some researchers began looking for the disease in other animal species.

They found SARS-CoV-2 in mink, otters, tigers, lions and non-human primates, mostly in captive settings.

And in what is emerging as the most significant finding in a free-ranging wildlife population, researchers this year documented the virus in white-tailed deer. 

First the U.S. Department of Agriculture National Wildlife Disease Program published a study that showed 40% of deer sampled in January in Illinois, Michigan, New York and Pennsylvania had antibodies to COVID-19.

Separate projects then detected the SARS-CoV-2 virus in deer in two states.

In a study published Nov. 1, 33% of 280 captive and free-ranging deer in Iowa tested positive.

And in work posted online Nov. 5, 36% of 360 wild deer in an Ohio study were positive for the virus. The researchers in both cases suggested there was spillover of SARS-CoV-2 from humans to deer with deer-to-deer transmission also occurring.

"It was actually quite stunning to us," said Vivek Kapur, a veterinary microbiologist at Penn State University and co-leader of the Iowa study. "We were very surprised to see such a high number of positive samples."

Both the Ohio and Iowa studies were published without peer review. The researchers said they wanted to share their results as quickly as possible with state and federal agencies as well as the public due to the important and rapidly-evolving science related to the disease.

Officials with the USDA's Animal and Plant Inspection Service (APHIS) are leading work to test more deer for the disease in more states, including Wisconsin.

Building upon findings that white-tailed deer can be infected with SARS-CoV-2 and transmit the virus to other deer, APHIS and its state partners will begin a phased, multi-year approach this winter to understand the impacts of SARS-CoV-2 in WTD to human and animal health, said Gail Keirn, public affairs officer with USDA's National Wildlife Research Center in Fort Collins, Colorado, in a Nov. 12 email to the Milwaukee Journal Sentinel.

The work hopes to determine how widespread the virus is in U.S. whitetail populations and whether the animals can serve as a reservoir for the virus, potentially leading to new virus variants that may impact the health of deer, other animals and humans, Keirn said.

At this time, APHIS is reaching out to state fish and game agencies in multiple states to see if they are interested in participating in the effort.

The Wisconsin Department of Natural Resources is planning to be part of the project, said Tami Ryan, DNR wildlife health supervisor, but no deer have yet been tested in the Badger State for SARS-CoV-2.

There is no evidence animals, including deer, are playing a significant role in the spread of SARS-CoV-2 to people, according to APHIS officials. 

There have also been no report of clinical illness associated with SARS-CoV-2 in the deer populations APHIS surveyed. In addition, captive deer experimentally infected with SARS-CoV-2 as part of a USDA Agricultural Research Service study did not show clinical signs of illness.

Further, there is no evidence people can get COVID-19 by preparing or eating meat from an animal infected with SARS-CoV-2.

The findings of SARS-CoV-2 in whitetails will, however, likely lead to updated recommendations for deer hunters handling their kills.

An APHIS guidance document published in September said the risk of COVID-19 infection from handling a potentially infected harvested deer can be reduced by wearing gloves and masks when handling the deer and hand washing after handling the deer.

The Wisconsin Department of Health Services is planning to make an announcement regarding COVID-19 and hunting in the coming days, according to Jennifer Miller, communications specialist with the agency.

The annual Wisconsin gun deer season opens Saturday.