Transmission of SARS-CoV-2, likely from humans to free-range White-tailed Deer, have resulted in subsequent deer-to-deer transmission across the United States
Despite several concerted efforts, investigators have yet to conclusively determine whether the virus that causes Covid (SARS-CoV-2) had a zoonotic origin or was a leak from the bio-laboratory in Wuhan China. The virus became the disease COVID-19 which infected humans, and continues, in pandemic proportions. Here in Virginia, following a 2022-2023 study, several Virginia Tech researchers published their findings documenting transmission of the virus from humans to wildlife, after sampling sites across Virginia and D.C. The study appears in the July 29th issue of Nature Communications, part of the Nature portfolio. (https://www.nature.com/articles/s41467-024-49891-w)
Of particular interest in our urban area, is their finding that “areas with more human activity may serve as potential hotspots for cross-species transmission [from humans to wildlife].” And wildlife living in recreation areas and highly urbanized areas “likely have higher risk of exposure to SARS-CoV-2.” The study further summarized that “Humans and wildlife rarely come into direct contact, but numerous indirect links likely exist.” Potential sources of exposure include trash receptacles and discarded food. Wildlife in urban areas “are regularly exposed to human refuse …. which could serve as a bridge for transmission between humans, companion animals, and wild species.”
During the study researchers trapped and sampled 23 species; a variety of common backyard species. They detected the SARS-CoV2 virus in six species: deer mice, opossums, raccoons, groundhogs, cottontail rabbits, and red bats. The highest incidence of the virus was found in creatures near hiking trails and high-traffic public areas. Further the study found a close match to virus variants which were circulating in humans at the time. This suggests that humans are passing the virus to wildlife.
Health researchers were already aware of human to animal transmission. In the Spring of 2020, several animals in zoos tested positive for SARS-CoV-2, including tigers and other big cats, and gorillas. The first cases were reported in the Bronx Zoo after animals were exposed to a caretaker with COVID-19. Several well documented cases in captive animals followed. Research also shows within-species transmission in the wild and in laboratories. Various studies show “a broad diversity of mammal species have been exposed to SARS-CoV-2 in the wild. … White-tailed Deer had the most documented infections of non-captive animals.” (www.nature.com/articles/s41598-022-16071-z?)
Virginia’s Department of Wildlife Resources includes a warning to those hunting deer. “While deer do not appear to become sick or show clinical signs of disease when infected, SARS-CoV-2 may be transmitted from deer to deer. There are currently no documented cases of humans becoming infected after contact with infected white-tailed deer and there is no evidence that humans can get COVID-19 by eating wild hunted game meat. While the risk of transmission of SARS-CoV-2 from deer to humans is unknown at this time, it is believed to be low.” The DWR șite advises hunters to “continue to take standard precautions when field-dressing and processing harvested deer, regardless of concern over COVD-19 transmission.“
Olivia LoBalbo, a state and federally permitted wildlife rehabilitator with Animal Education and Rescue Organization, indicates DWR has required rehabilitators to use masks and gloves for any work with mammals for the past couple of years. The precaution prevents human to animal transmission, and potential animal to human transmission as well.
LoBalbo says that in 2020, DWR required testing any bats in rehab for Covid before release. She shares, “It was quite amusing trying to swab these tiny creatures. I had to poke them in the face enough times to make them angry and hiss at me, which is when I would quickly swab them. I rehabilitated a good number of bats, and none of them ever tested positive for COVID.”
She also says she has not had any other animals diagnosed with Covid under her care. Although “Covid symptoms are similar to those of many other common conditions, making it difficult to pinpoint one specific cause.”
Bats have been shown to carry at least three coronaviruses, however, they have not been tied to the emergence of Covid-19 despite early speculation about their role. David Lawlor, a Fairfax County Park Authority ecologist with its Natural Resources Branch, is conducting bat surveys in area parks, including Laurel Hill Park in Lorton, “to inventory bat species and confirm rare species in parks with high quality habitat.” He says his surveys do not sample bats for viruses or other diseases. He further shares, “In 2020 and 2021, DWR did not permit mist netting bats in the state due to the coronavirus and possible transmission from humans to bats. In 2022, they began issuing permits to mist net bats again. As a precaution, Park Authority staff use leather gloves covered with disposable plastic gloves when handling bats for data collection to prevent spreading [any] virus from bat to bat [and from human handlers’] as they are being handled each night. The plastic disposable gloves are changed between handling each individual bat.”
As the Virginia Tech study extract concludes, “Continued broad surveillance and more detailed ecological research will be needed to fully determine the role of wildlife communities in SARS-CoV-2 transmission and evolution.”