Surprise for virologists: Ohio deer test positive

Bambi has corona. More than a third of wild white-tailed deer in the US state of Ohio tested positive for SARS-CoV-2. That’s what American researchers wrote led by vet Andrew Bowman just before Christmas in the scientific magazine Nature.

Because there are also indications that the animals transmit the virus to each other, there is a danger that an animal reservoir of SARS-CoV-2 is formed. The virus could lie dormant there, causing new outbreaks among people from time to time. There are currently no signs that this has happened yet.

Mink in Denmark

“Whether it is dangerous?” responds veterinary epidemiologist Arjan Stegeman of the Faculty of Veterinary Medicine at Utrecht University, “that’s just how you want to reason. But if a virus gets into a different host, you get a different kind of selection and mutants are created.”

That doesn’t always have to end badly, says Stegeman, referring to a virus variant that arose in minks in Denmark in 2020 and subsequently infected people. “After mid-September, no one has seen this mink variety anymore; it apparently died spontaneously.”

Also read: Danes cull mink ‘to save vaccine’

Bowman and his team collected nasal mucus samples from 360 deer shot this spring at nine locations in northeast Ohio. 129 animals tested positive for corona, mainly bucks and heavier animals. Most of the positive samples came from locations with a relatively high population density, an indication that contact with humans had given the deer the virus.

Genetic analysis of the viruses in 14 samples confirmed that view: they belonged to virus lines that were then circulating among humans. The most numerous was the B.1.2 variant, which had caused a corona wave among the population in the weeks before.

In the long term, this could drive the fight against Covid-19 in the wheels

Andrew Bowman researcher

“Our phylogenetic analysis shows that the virus is commonly transmitted from humans to deer,” Bowman said in an emailed explanation. “The SARS-CoV-2 viruses that were dominant in Ohio at the time spread independently from humans in deer populations in at least six different locations. Subsequent deer-to-deer transfer seen at three sites suggests that wild white-tailed deer have the potential to become the first non-human reservoir for SARS-CoV-2. If that happens, in the long run it could help fight Covid-19.”

Bowman found genetic changes in the deer viruses that may indicate adaptation to a new host. Worryingly, it also contained a mutation that causes an amino acid change in the spike protein, which would allow the virus to escape human antibodies. It concerns the mutation E484D, a very rare mutation that has only been seen 201 times worldwide in SARS-CoV-2, of which 71 times in the US. However, it is impossible to determine whether this mutation was introduced in human or deer transmission or whether it originated in deer.

30 million white-tailed deer

start this year has already been demonstrated experimentally that white-tailed deer are susceptible to SARS-CoV-2 and can also transmit it to each other. That was a big surprise, says Stegeman: “Many scientists thought that the virus could spread to felines and mustelids, but thought deer was weird.”

In November published U.S. Department of Agriculture researchers conducted a study that found 40 percent of wild white-tailed deer in four northern U.S. states had antibodies to SARS-CoV-2 in their blood. About 30 million white-tailed deer (Odocoileus virginianus) in the wild. In addition, there are also hundreds of deer parks where tame specimens are bred.

How does the virus get from human to deer so easily? “Hard to say,” Bowman replies. In the Naturearticle, he points out that the virus was much in wastewater during the pandemic. The deer also roam people’s yards and may eat contaminated food waste. They could also, in theory, contract it from domestic deer, which, after all, come even closer to humans because they are being cared for. But Bowman dismisses that scenario: “There are no deer farms in the study area.”

“I was surprised that there are so many corona infections among these wild deer,” says Stegeman. “You would not expect a virus to continue circulating in an animal species that does not live in large herds, but in small groups. But these deer have also been shown to be susceptible to wasting disease, a prion disease. It also continues to circulate. Perhaps it is something in this host that makes this possible.”

Lions, Tigers, Hyenas

In zoos, SARS-CoV-2 has been shown to spread to many different animal species, including lions, tigers, hyenas and gorillas. It is known that felines and great apes are susceptible to this virus. But the virus also makes unexpected leaps. At the beginning of this month, for example, it was established that two hippos in the Antwerp Zoo had contracted a corona infection.

Animals that come close to people can often pick it up, but a reservoir can only form when many animals are kept close together, as was the case with the minks. Stegeman: “We have also seen that domestic cats can pick up SARS-CoV-2 and pass it on to each other if they are housed together. But in practice this has not led to the formation of an animal reservoir, probably because cats live too far apart, usually with only one or two animals per household. Then the virus cannot survive there.”

The fact that it now seems counterintuitive to happen to deer is reason to pay more attention, also in the Netherlands. White-tailed deer are distant relatives of roe deer, which roam a lot in the Netherlands. Both species are so-called pseudodeer. SARS-CoV-2 has never been detected in deer, but Stegeman says it is wise to keep an eye on this.

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