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Covid is rampant among deer, study shows

Covid is rampant among deer, study shows

People have infected wild deer with Covid-19 in a handful of states, and there is evidence that the coronavirus has spread among deer, according to recent studies that outline findings that could complicate the way out of the pandemic.

Scientists swabbed the nostrils of white-tailed deer in Ohio and found evidence that humans had spread the coronavirus to deer at least six times, according to a study published last month in Nature.

About a third of the deer sampled had active or recent infections, the study says. Similar research in Iowa of tissue from road deaths and hunted deer found widespread evidence of the virus.

The research suggests that the coronavirus could take hold of a free-roaming species that is approximately in number 30 million in the US No cases of Covid spreading from deer to humans have been reported, but it is possible, scientists say.

It reminds us that human health is intertwined with that of animals and that oversight for other species could prolong the pandemic and complicate the quest to fight Covid-19.

Widespread, sustained circulation of the virus in deer could pose a risk to humans if mutations in deer create a new variant. A population of wild animals harboring the virus may also retain variants that are no longer circulating among humans and may recur later.

“The sheer possibility of these things happening and it’s unknown makes this very troubling,” said Suresh Kuchipudi, a virologist at Pennsylvania State University. “We might be surprised with a completely different variant.”

Early in the pandemic, scientists began to worry that the virus could spread from humans to other animals. a study found many mammals with receptors through which the virus can bind in their cells, with deer among those at high risk.

They started to investigate.

First, in a laboratory study, Researchers sprinkled the noses of four fawns with contagious coronavirus to test whether the virus could infect them. They also took two uninfected deer into the same room and kept them separate with a plexiglass barrier that did not reach the ceiling.

“We had four vaccinated animals and two contact animals. Everyone became infected and spread significant amounts of contagious virus. That was a surprise,” said Diego Diel, an associate professor of virology at Cornell University who led the study.

The deer likely shared the virus through nasal secretions that traveled through the air over the barrier, he said. The infected deer showed no noticeable symptoms.

Deer often travel in herds and touch noses, making transmission a concern.

So federal scientists tested blood samples of wild deer in Illinois, Michigan, New York and Pennsylvania. They eventually tested 624 samples and found that about 40 percent of the samples collected last year had antibodies that suggested a past infection.

The latest studies provide evidence of active and recent infection.

In the Ohio State University peer-reviewed study, 35.8 percent of 360 free-ranging deer tested positive via nasal swabs. The researchers were able to culture the virus for two samples, meaning they could culture live virus.

And after they assessed genetic relationships between viruses from 14 deer, “we have evidence of deer-to-deer transmission,” said one author of the study, Andrew Bowman, an associate professor of preventive veterinary medicine at Ohio State University. The researchers found six mutations in deer that are uncommon in humans.

A preprinted study led by Penn State’s Kuchipudi, the coronavirus found the coronavirus in lymph nodes of 94 of the 283 deer hunted or killed by vehicles in Iowa in 2020.

Both studies suggest that the virus has passed from humans to deer multiple times in different places. The common viral genomes circulating in humans at the time were also circulating in deer, the studies say.

Researchers can’t say for sure how the deer became infected or whether the virus will persist in the species. Deer, ubiquitous in many American communities, are among the most common large mammals in the country.

“If they keep the virus alive, that’s a very different host that we need to look at for future variants to assess whether current vaccines will be affected and how to control the spread,” Bowman said. “It complicates things considerably.”

If the virus establishes itself in the long term, scientists say there are several potential risks.

Circulation in deer allows variants that no longer infect humans, such as the alpha variant, to continue cycling in animals. That would give those species the potential to reintroduce themselves to humans, Kuchipudi said.

In another scenario, widespread transmission could allow the virus to accumulate mutations in deer and evolve differently before spreading to humans with new characteristics.

That is what happened on Dutch mink farms in 2020. After the virus spread from humans to mink, it returned with new mutations to infect humans.

The mink variety shows that “backflow is possible,” Diel said.

If deer are hosts of the coronavirus, they can also pass it on to other animals.

“Every time the virus jumps into a different species, that can lead to adaptation,” Kuchipudi said.

And in a scenario some scientists consider unlikely, the virus could recombine with other coronaviruses already identified in deer to create a hybrid virus.

“There are endemic coronaviruses in animals, some we know and a lot we don’t know,” Kuchipudi said. “Recombination could lead to a completely different variant that could be very different from the parent virus, and it could have different abilities.”

These are long-term concerns if deer are, in fact, permanent hosts. So far, researchers have not found the virus from deer to humans or discovered a new variant only in deer.

“The greatest risk to humans remains person-to-person transmission of the virus,” said Tom DeLiberto, the assistant director of the National Wildlife Research Center, which helps lead federal efforts to identify the coronavirus in wildlife. “Can that change later? Absolutely, and that’s why we’re doing these things to get a handle on what’s happening to deer.”

The American Rescue Plan Act made $6 million available to researchers to study the coronavirus in white-tailed deer. DeLiberto said researchers in 30 states are looking for the virus among deer.

Separately, scientists collect blood samples from other animals, such as coyotes, skunks and raccoons, to see if any of them have antibodies.

“If we let the virus circulate among people, we not only endanger the vulnerable sector of our population, but we could also endanger our animals and the environment,” said Kuchipudi.