The virus that causes COVID-19 is now circulating in whitetail deer populations in Iowa.
A recent study tested the retropharyngeal lymph node tissue—the same type of tissue commonly used to test for chronic wasting disease—of hundreds of hunter-harvested and road-killed deer in the Hawkeye State. It showed that, between November 21, 2020 and January 10, 2021, more than 80% of sampled deer were infected with the virus.
“We weren’t really expecting to see a lot of positives, but what we found was pretty stunning,” the study’s lead author, Dr. Suresh Kuchipudi of Penn State University, told MeatEater. “During the winter months, which also coincided with the hunting season and the peak infection rates among humans in Iowa, we saw up to 80% of the tissue samples coming back positive.”
Kuchipudi and the other authors of the study also determined that the infections now circulating through Iowa’s deer herd originated in human beings.
“The geographic distribution and clusters of deer and human lineages strongly suggest multiple zooanthroponotic spillover events and deer-to-deer transmission,” the authors wrote in the study.
Zooanthroponotic spillover is a fancy term for the transmission of pathogens from humans to wild animals, or vice versa. It’s raising concerns among researchers and scientists like Kuchipudi about the possibility that whitetail deer—some 30 million strong in the United States alone—could become a major host for further mutations to the virus.
The high prevalence of SARS-CoV-2 in Iowa’s deer herd during the 2020-21 deer season is further underscored by the short window of time during which viral infection is actually detectable.
“It was reasonably expected to find antibodies,” Kuchipudi said. “But the window in which we could detect viruses is pretty short—a few days at best.”
The Iowa study is not the first to look for the presence of the SARS-CoV-2 virus in whitetail deer. The animals have been under close scrutiny since the start of the pandemic because they have a specific protein that allows coronaviruses like SARS-CoV-2 to establish an infection in a host, similar to humans.
Another study, which examined deer populations in Michigan, New York, Pennsylvania, and Illinois, showed deer with the presence of antibodies, indicating exposure but not proving infection as the Iowa study does. In Ohio, testing for the virus turned up positive results back in August 2021. Yet another, performed by the U.S. Department of Agriculture, shows that laboratory-contained deer are capable of spreading the virus amongst themselves while remaining asymptomatic.
According to Kuchipudi, there is reason to believe that other whitetail deer herds throughout the country are similarly infected. He said that further surveillance is needed in order to reveal the full scope of SARS-CoV-2 infection within deer populations.
“What we found in Iowa is not an Iowa-specific situation,” he said. “It is a widespread exposure, potentially of deer across the country, and it’s just a matter of finding it.”
Jennifer Ramsey is a wildlife veterinarian with Montana Fish, Wildlife and Parks. She and others at the agency are working to interpret the Iowa study and its implications for wildlife in Montana.
“People are worried that these deer could be a reservoir for infection back to humans,” Ramsey told MeatEater. “Would the virus, over time, be able to alter itself in deer and become more risky than it is now as far as transmission back to people?”
According to Ramsey, the risk of whitetail deer transmitting the virus back to humans appears to be low. Although a proven instance of deer-to-human transmission is yet to occur, the risk must be considered.
“Hunters should take precautions when handling harvested deer in the field, particularly tissues of the respiratory tracts such as the lungs, mouth, nasal cavity and windpipe,” Ramsey said. “Whatever risks there may be could be reduced by wearing gloves and a mask and washing your hands after handling a carcass.”
Kuchipudi echoed her sentiments.
“It’s important to note that there is still no evidence of transmission to humans from deer, but given the nature of this respiratory virus, I think it should be recommended that anyone interacting with a dead carcass, when exposure levels could be high, should wear respiratory protections like a mask.”
According to the Center for Disease Control and Prevention, there is no evidence that people can contract COVID-19 through the consumption of wild game meat.
While there are no documented cases of infection in Montana’s whitetails, (no testing has been done up to this point) Ramsey is wondering about the Iowa study’s implications for all of Montana’s wild cervids.
“They’ve not looked at any other cervids yet,” she said. “We don’t know whether mule deer, elk, or moose are similarly infectable. There’s no data to answer that question right now.”
She went on to say that testing may be needed for another of Montana’s iconic big game species: the Rocky Mountain bighorn sheep.
“We’re wondering whether other species like bighorn sheep would be susceptible to getting the virus or not,” she said. “That seems like it would be pretty valuable information to start thinking about having collected.”
Ramsey worries that testing materials may not be available in time for Montana Fish, Wildlife and Parks to utilize hunter harvest data from the current hunting season but said that upcoming capture studies should provide testing opportunities for elk and bighorn sheep.
“This winter we’ll be doing some captures of elk and bighorn sheep, and we’ll be banking some extra serum from those guys for COVID testing should the opportunity arise,” she said.
As of now, there is no evidence to suggest that the SARS-CoV-2 virus is affecting the herd health of infected deer populations.
“At least in an experimental setting, they do not show any signs of clinical disease,” Kuchipudi said, referencing the USDA’s laboratory-contained study, which showed that whitetails spread the virus amongst themselves.
But he added a caveat.
“We do not fully understand what would happen in a natural setting. For experiments, one would typically use healthy animals with no underlying conditions, and if you think about that, that’s kind of similar to what would happen in human populations. We know that the majority of people just don’t show any symptoms. If, in the natural setting, deer had any underlying conditions, all of those factors may change the outcome. We don’t know how they expressed it in the wild.”
Feature image via Matt Hansen.
