Humans could potentially catch a new and deadly strain of Covid from deer, scientists have warned.
At least three variants of the virus have been detected in wild white-tailed deer, the species on which Walt Disney based his most-loved character Bambi.
Now a study in Ohio, USA, identified the animals as a potential reservoir for spreading more virulent strains to humans.
Professor Andrew Bowman, a senior author of the study at The Ohio State University, said: "Based on evidence from other studies, we knew they were being exposed in the wild and that in the lab we could infect them and the virus could transmit from deer to deer.
"Here, we are saying that in the wild, they are infected. And if they can maintain it, we have a new potential source of SARS-CoV-2 coming into humans.”
The trio of mutations were identified in over a third of 360 animals – at six different locations.
There was evidence of transmission between them – suggesting deer may facilitate the emergence of more lethal adaptations.
Nasal swabs were collected from the deer between January and March 2021, occurring before Delta swept the world and that variant was not present.
Genomic sequencing showed the strains matched those that were being carried by local patients with Covid.
Their continued presence would suggest the virus can 'set up shop' – and survive in wild deer.
Professor Bowman said: "The fact wild deer can become infected leads toward the idea we might actually have established a new maintenance host outside humans."
It is not known how the deer got infected, if they can infect humans and other species or how the virus behaves in the animals' body.
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Using PCR testing, they detected genetic material from at least three different strains of the virus in 129 (36%) of the deer checked.
The analysis showed B.1.2 viruses dominant in Ohio in the early months of the year spilled over multiple times into deer populations in different locations.
Professor Bowman said: "The working theory based on our sequences is humans are giving it to deer and apparently we gave it to them several times.
"We have evidence of six different viral introductions into those deer populations. It is not that a single population got it once and it spread."
Based on the findings, researchers estimated the prevalence of infection varied from 13.5 to 70% across the nine sites.
Deer functioning as a viral reservoir would result in one of two likely outcomes, Professor Bowman explained.
Covid would mutate in deer, leading to transmission of new strains to other species – including humans.
Otherwise, the virus could survive in deer unmutated while it simultaneously continues to evolve in humans.
At some point, when we don't have immunity to the strains infecting deer, those variants would come spilling back to us.
The researchers speculate white-tailed deer were infected through an environmental pathway – possibly by drinking contaminated water.
Professor Bowman said: "The extent of susceptible host species and potential new reservoirs in which the virus can reproduce, evolve and potentially spill back to the human population is not fully understood."
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