Sergio Flores/The New York Times

May 1, 2022

Cornell Researchers Study COVID Transmission in White-Tailed Deer

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On Mar. 21, Dr. Mathias Martins, a researcher in the Diel Lab, which is housed in the Cornell College of Veterinary Medicine, discussed the effects of COVID-19 on the deer population in his copublished article “From Deer-To-Deer: Sars-Cov-2 Is Efficiently Transmitted And Presents Broad Tissue Tropism And Replication Sites In White-Tailed Deer.”

This study explained the infection, incubation period, transmission and recovery of SARS-CoV-2 in white-tailed deer. The researchers found that over a three to five day period,after intranasal inoculation,deer transmitted SARS CoV-2. There was no transmission after day six but was observed as early as day five. 

Intranasal inoculation is a type of in vivo inoculation, where an infection or virus is purposely introduced to the nasal passage of a test subject.

SARS-CoV2 in wildlife is not a new concept, but the Diel Lab wanted to research the duration of transmission in white-tailed deer and find commonalities between other species susceptible to COVID-19. 

 “We observed a transmission of the virus from the infected to the uninfected, and after day six, there were only a few isolated deer capable of spreading COVID,” Martins said. 

“In general, humans will transmit the virus until day six, so this is very similar to the human response, sometimes longer, which is now documented in the deer,” he added. 

The primary concern with the incidence of COVID-19 in deer is that it creates different reservoirs for mutations to breed in other species and possibly harm human and animal populations.

“After observing that the deer can become infected, we don’t really know what species that they can have contact with that they can spread COVID with. This is a huge concern in America and is an issue for Canada too, with it bordering along the U.S.,”  Martins said. 

“The animals and disease don’t know about the borders, here we have seen it in different places, and we have seen multiple spillbacks. In humans, we just transmit the virus back to the animals [deer],” he added. 

Spillback is when a human infects another animal species.

Minks are also susceptible to SARS-CoV-2. Minks in the study acquired mutations in while infected, which resulted in spillback to humans

 “We keep them in the U.S. and there were several outbreaks in these farms. While one mink mutation did not increase the severity, it was related to immune escape, meaning it decreased the ability of our immune system to fight the virus,” Martins said. 

There is not a clear answer on if COVID-19 spreads from deer to human, but Martins still suggested practicing caution because mutations can decimate wild deer populations. Variants were found circulating in deer populations in New York which means they are capable of housing possibly fatal mutations. 

The study did, however, provide a guide for further research into COVID-19 in wildlife species. 

With specific tissues, such as respiratory and lymphoid tissues, isolated as being sites of high proliferation sites of SARS-CoV-2, it will give researchers an advantage when testing other wildlife species for COVID-19.

Martins believes these results can be used as standard tissues for testing the presence COVID-19 in different wildlife in the future. 

“We can use our findings to determine tissue samples to test. The lymph nodes were great tissue samples that we determined could be used for other important tests,” Martins said.

The lab continues its research on COVID-19 in wildlife but details are not being disclosed now. 

“Right now we are researching the virus in wildlife, and the results are interesting,” Martins said. “Pretty soon, we will have some more surprising information results in terms of COVID in wildlife.”