Today in Emerging Infectious Diseases, researchers from Texas A&M University published evidence of SARS-CoV-2 Omicron XBB.1.41.1 antibodies in captive whitetail deer and found more mutations than expected compared to the same virus in humans.
SARS-CoV-2 has been found repeatedly in whitetail deer, and the animal may serve as a reservoir for the virus across North America, the authors said. In Texas, captive deer are found in more than 1,000 facilities with 100 to300 animals each. These facilities could pose a transmission risk between humans and animals.
In the study, the researchers sampled 15 deer at a private farm in Milam County in November of 2023.
“Deer were restricted to 2 pens separated by a fence and were able to have direct contact through the fence line,” the authors wrote. “This facility falls into the category of outdoor ranch, although human–deer contact rates are high in our case because of veterinary care and animal husbandry.”
11 of 15 deer showed evidence of virus
All 15 deer sampled were healthy females, and researchers collected nasal and oral swabs, rectal swabs, and blood samples.
The researchers found all 15 deer had neutralizing antibodies against SARS-CoV-2.
Only 1 rectal swab was positive for SARS-CoV-2, but 11 of the 15 (73.3%) deer showed the virus in respiratory swab samples. Six deer had infectious virus in their upper respiratory tract.
During genomic analysis, the authors found that deer-derived sequences had 15 nucleotide substitutions not found in the closest human-derived isolates, and up to 11 substitutions shared by some or none of the other deer-derived sequences. All samples were recent Omicron lineages.
The viruses detected in deer did not have unique mutations in the spike protein.
“Compared with those closely related human samples, the viruses detected in deer did not have unique mutations in the spike protein,” the authors wrote. Researchers were not able to discern how the virus entered the deer population at the private farm.
“Given the uncertain public health and animal health implications of viral maintenance within captive deer, agricultural biosecurity practices could be useful in reducing the possibility of establishing long-term animal reservoirs for the virus,” the authors concluded. “The mid- to long-term evolutionary consequences for SARS-CoV-2 circulating in nonhuman populations is unknown, and captive facilities might provide opportunities for sustained transmission at this human–deer–wildlife interface.”