Covid is endemic among deer, research shows


Humans have infected wild deer with Covid-19 in a handful of US states and there is evidence the virus has spread between deer, recent studies show, which describes findings that could complicate exit from the pandemic.

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

About a third of the deer sampled had active or recent infection, according to the study. Similar research in Iowa on tissue from the road and hunted deer has found widespread evidence of the virus.

Research suggests that the coronavirus could take hold in a free-range species of around 30 million in the United States. No cases of the spread of Covid from deer to humans have been reported, but it is possible, scientists say.

It is a reminder that human health is closely linked to that of animals and that inattention to other species could prolong the pandemic and complicate the quest to control the Covid.

Widespread and 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 could also retain variants that are no longer circulating among humans now, and allow them to return later.

“The mere possibility that these things are happening and that they are unknown makes it very disturbing,” said Suresh Kuchipudi, a virologist at Pennsylvania State University. “We could be taken by surprise with a completely different variant. ”

At the start of the pandemic, scientists feared the virus could pass from humans to other animals. A study found many mammals with receptors that could allow the virus to bind in their cells, with deer among those at high risk.

They started to investigate.

First, in a laboratory study, researchers sprayed four fawns’ noses with infectious coronavirus to test if the virus could infect them. They also brought two uninfected deer into the same room, keeping them separated by a plexiglass barrier that did not reach the ceiling.

“We had four inoculated animals and two contact animals. Everyone was infected and shed significant amounts of infectious virus. It was a surprise, ”said Diego Diel, associate professor of virology at Cornell University, who helped lead the research.

The deer likely shared the virus through nasal secretions that passed through the barrier through the air, he said. The infected deer did not show noticeable symptoms.

Deer often travel in herds and touch the nose, making transmission a problem.

So, federal scientists tested blood samples wild deer in Illinois, Michigan, New York and Pennsylvania. They eventually tested 624 samples, finding that around 40% of the samples collected in 2021 had antibodies suggesting a past infection.

The latest studies provide evidence of an active and recent infection.

In the peer-reviewed study from Ohio State University, 360 deer in the wild underwent nasal swabs, with 35.8% testing positive. The researchers were able to grow the virus for two samples, meaning they could grow a live virus.

And after examining the genetic relationships between viruses in 14 deer, “we have evidence that deer-to-deer transmission occurs,” said Andrew Bowman, associate professor in the Department of Preventive Veterinary Medicine at Ohio State University, and author of the study. Researchers have found six mutations in deer that are rare in humans.

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

Both studies suggest that the virus has spread from humans to deer in multiple locations and on multiple occasions. Common viral genomes circulating in humans at the time were also circulating in deer, studies show.

Researchers cannot say for sure how deer became infected or whether the virus will persist in the species. Deer – ubiquitous in many American communities – are among the most abundant large mammals in the United States

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

If the virus becomes established over the long term, scientists say it poses several potential risks.

Circulation in deer could allow variants that no longer infect humans – like the alpha variant, for example – to continue cycling in animals. This would give these strains the potential to reintroduce themselves to people later, Kuchipudi said.

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

That’s what occurred in Dutch mink farms in 2020. After the virus spread from humans to mink, it returned to infect humans and had new mutations.

The mink variant shows that “the fallout is possible,” Diel said.

If deer are hosts for the coronavirus, they could also transmit the virus to other animals.

“Anytime the virus jumps into a different species, it could lead to adaptation,” Kuchipudi said.

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

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

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

“The greatest risk to people remains person-to-person transmission of the virus,” said Tom DeLiberto, deputy director of the National Wildlife Research Center, which is helping lead federal efforts to identify the coronavirus in wildlife. “Could that change later?” Absolutely, and that’s why we’re doing these things to figure out what’s happening to deer.

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

Separately, scientists are collecting blood samples from other animals such as coyotes, skunks, and raccoons to see if any of these creatures have antibodies.

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


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