One such tracking effort by Nebraska researchers has produced a different method of determining whether members of one common animal species — white-tailed deer — previously have been infected with the coronavirus and recovered, providing additional information about the extent of the virus’s spread.

Dr. Dustin Loy, director of the Nebraska Veterinary Diagnostic Center at the University of Nebraska-Lincoln, said researchers had identified the virus’s genetic material, RNA, in samples from deer, as had laboratories elsewhere in the United States.

That testing, however, captured only animals that were currently infected with the coronavirus.

“Our question was: How many had been exposed?” he said. “How broad and widespread was that in the deer populations during the peak of when it was transmitting?”

Researchers typically look for evidence of past infection by testing for antibodies in blood or blood serum, he said. The presence of antibodies indicates a person or animal has developed an immune response to an invading pathogen.

But the samples the Nebraska researchers had at their disposal came from deer harvested by hunters — and they weren’t blood or serum, but lymph nodes the Nebraska Game and Parks Commission had collected and banked as part of its effort to monitor another illness in deer, chronic wasting disease.

The researchers tapped them as part of a broader effort to look for the virus in as many species as possible. The Nebraska Department of Health and Human Services last year received a $100,000 grant to work with other agencies to expand its capacity to monitor pathogens such as the coronavirus.

So Loy’s team, with Dr. Korakrit Poonsuk, the lab’s virology lead, now with Washington State University, developed a way to test lymph nodes for antibodies.

While only 16% of the samples checked had virus detectable by the now-familiar polymerase chain reaction, or PCR, at peak in 2021, about 40% overall had antibodies to the coronavirus.

“That gave us a way to look at previous exposure,” said Loy, also a professor in UNL’s school of veterinary medicine and biomedical sciences. “Even if those animals don’t have any virus currently, the antibodies are still there and we’re able to determine that they had it at some point previously.”

The researchers published their findings last month in the Journal of Wildlife Diseases. They note that their findings also suggest that the approach might apply to detecting other pathogens in deer lymph node samples, which researchers received permission from hunters to use.

Deer, in fact, were the only animals in which the researchers found viral RNA in their broader search, he said. Altogether, they tested more than 3,500 animals representing more than 50 species — wildlife, zoo animals and pets.

“The deer seem to be the ones that stood out,” he said.

But the work emphasizes that what people may think of as human diseases also affect wildlife and other animals, he said. And they are abundant in the state.

Farms and ranches account for 90% of Nebraska’s land area and 1.2 million acres are open for hunting, trapping and fishing. The state’s three zoos together draw 2.65 million visitors a year.

Earlier in the pandemic, researchers had worried that the coronavirus could spread to animals, mutate and spill back into people.

That has not, however, proved a big threat, Loy said. Recent work indicates there were introductions of the virus from humans to deer, which was followed by circulation among deer but only a couple of cases in which the virus passed from deer to humans.

The Nebraska collaboration, he said, also demonstrates the power of team science. Some research continues in rodents.

“We really showed we can all pull together and answer a big question,” Loy said.