The Penn State researchers have been working with the Iowa Department of Natural Resources, which already conducts surveillance on chronic wasting disease, a fatal neurological illness among white-tailed deer. The first positive test results showed up in September 2020 — in two deer at different ends of the state. Between late November and early January, as the pandemic was surging in humans across Iowa, 80 percent of the deer specimens tested positive for the virus.
By then, the researchers had tested only 300 of the 5,000 lymph nodes available to them; but the evidence was overwhelming.
Such a high rate of infection, Dr. Kuchipudi said, was effectively 50 times greater than its prevalence among Iowa’s human residents during the peak of the pandemic.
What they found as they probed deeper was even more astounding. Using tests to decode the genomic makeup of each viral sample, they found similar patterns between the emergence of mutations and variants in the state’s deer population and those infecting people. Researchers said that offered stronger proof of human-to-deer transmission as well as evidence that deer were then spreading the virus to one another at a rapid clip. Mapping the location of each sample also suggested that the infections were occurring simultaneously across the state as hunting season ramped up. The study’s authors say it is unclear whether the deer were sickened by the infection.
How the virus passes from people to deer, however, is not entirely clear. Rachel Ruden, Iowa’s state wildlife veterinarian and an author of the study, said there were plenty of opportunities for transmission given that 445,000 deer roam the state.
The virus can spread when people feed deer in their backyard, through sewage discharges or maybe when an animal licks a splotch of chewing tobacco left behind by an infected hunter. “Perhaps it doesn’t take much of a loading dose to get deer infected,” she said. “But either way, all of this is a striking example that we’re all in this pandemic together.”
The study raises a multitude of questions that scientists will be keen to examine, including whether other wild animals can also carry the virus, particularly rodents like mice that live in even closer proximity to people. The more species capable of carrying the virus, the greater the chances it can evolve in ways that threaten human health.