USDA photo by Scott Bauer
Key points:
- SARS-CoV-2 testing of white-tailed deer revealed hotspots of infection across New York state.
- Scientists detected SARS-CoV-2 variants in deer 4 to 6 months after the last detection in humans.
- The virus in the deer had up to 80 mutations compared with the human sequences.
White-tailed deer are harboring SARS-CoV-2 variants that once widely circulated but are no longer found in humans, according to new research by Cornell University scientists.
Over the course of the pandemic, deer have become infected with SARS-CoV-2 through ongoing contact with humans, possibly from hunting, wildlife rehabilitations, feeding of wild animals or through wastewater or water sources, though there is no definite answer.
For this study, researchers leveraged 5,700 samples of deer lymph tissues taken from deer killed by participating hunters as part of a New York surveillance program for chronic wasting disease in white-tailed deer. The samples were collected over two years from 2020-22, and included important information about when and where the samples were collected and each animal’s sex and age.
The testing revealed potential hotspots of infection across the state, including seven clusters where samples from a defined geographic area all contained the same variant.
When the researchers compared the genomic sequences of the variants found in deer with sequences of the same variants taken from humans across New York, they found the viruses had mutated in the deer, suggesting the variants had likely been circulating in deer for many months. By the time alpha and gamma variants were detected in deer, for example, there was no evidence of these viral strains were still circulating in humans. In fact, when they were found in deer, neither variant had been detected in humans in New York for four to six months.
“When we did sequence comparisons between those viruses recovered from white-tailed deer with the human sequences, we observed a significant number of mutations across the virus genome,” said Diego Diel, director of the Virology Laboratory at the Cornell University.
The associate professor also said some of the viruses had up to 80 mutations compared with the human sequences, providing further evidence that the viruses had likely been circulating in the deer for some time. The mutations suggest the virus has adapted to deer, possibly making it more transmissible between them.
In future work, Diel and colleagues hope to assess the effect of those mutations, including whether these changes make the virus more or less capable of binding to human receptors, information that could predict the possibility of spill back to humans from mutant variants.
Information provided by Cornell University.