With rifle season open in New Hampshire and Vermont, wildlife agencies in both states are monitoring whether COVID-19 is spreading among white-tailed deer in the Twin States.
“The concern long-term is that the deer would be a reservoir for the virus — it could eventually make its way back to people in a mutated form,” said Nick Fortin, the head deer biologist at Vermont Fish and Wildlife. Because testing is just underway, it’s unclear whether any deer here have carried COVID-19.
And in regions where the virus has been found in deer, to date, no evidence suggests that they are spreading it back to humans.
The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, better known as APHIS, approached Vermont about testing its white-tailed deer population as part of its national research on the spread of COVID-19 among the species. Vermont Fish and Wildlife prepared to test about 100 deer last weekend when the season started. The agency may continue to collect samples for testing roadkill, Fortin said.
New Hampshire had a head start on participating in APHIS’ research; it already collects blood samples from deer on behalf of the Department of Health and Human Services as it monitors the Jamestown Canyon virus — a rare disease that can spread from deer to humans through mosquitoes. New Hampshire finished collecting samples last Saturday and now awaits results from APHIS.
“We’re testing as many as we can get our hands on,” said Daniel Bergeron, the leading deer biologist at N.H. Fish and Game. “Right now there are more questions than anything,” he added. “How do they get it? How do they pass it to one another? Do they pass it to people? Is it everywhere deer are found? This is pretty much a first step.”
The USDA will amp up both testing and funding to better understand COVID-19’s spread among white-tailed deer next year, officials with both states said. The American Rescue Plan Act, passed in March, included funding for APHIS to address disease that may spread to people from wildlife — including deer.
Deer themselves do not appear to be at risk from COVID-19. The USDA Agricultural Research Service infected captive deer as part of an experiment and found no signs of illness.
And there’s “really no risk to hunters,” either, Fortin said. “It’s a respiratory disease,” he said. “A dead animal isn’t breathing on you.”
For the same reason, hunters likely did not pass the COVID-19 virus to deer, Bergeron said. He listed off theories that could explain how the virus made the jump from people to deer: Perhaps a wildlife rehabilitator unknowingly passed it on while feeding an injured doe, or perhaps a deer picked it up while drinking contaminated wastewater.
“At this point, it’s anybody’s guess,” he said. “Deer, more so in other areas, are a higher-density wildlife population. People come into more contact than with other wildlife species.”
Studies in other states showed widespread COVID-19 exposure among some white-tailed deer.
Professors at Penn State University led a study on 283 white-tailed deer in Iowa using samples taken early in the pandemic. They detected that one-third of the deer had been infected with the COVID-19 virus.
“While we lack incontrovertible evidence for spillback” from deer to humans, they argued that “our findings warrant a heightened awareness of the potential risks associated with human contact with free-living or captive deer.”
They explained that a reservoir host can promote viral mutations — especially if the virus mingles with viruses in the same family that are abundant in wildlife populations.
Pathogens like the coronavirus that can live on in multiple species, or “hosts,” are often at a “selective advantage” that may give rise to a more virulent and transmissible virus, they warned as they made the case for further study.
Meanwhile, APHIS tested 481 deer in Illinois, Michigan, New York and Pennsylvania and found COVID-19 antibodies in 33 percent of the samples. The findings could not give any reliable insight into the prevalence of COVID-19 antibodies among the nation’s approximately 30 million white-tailed deer, the agency warned.
APHIS emphasized the need for further research, and Fortin said most studies on COVID-19 infection in white-tailed deer thus far have focused on more densely populated areas than the Upper Valley.