A variety of backyard wildlife, such as rabbits, mice and bats, had SARS-CoV-2 infections, potentially making evolution of this virus more unpredictable.
A new study has determined that the COVID-19 virus is widespread amongst wildlife in the United States. SARS-CoV-2, the virus that causes COVID-19, was recently detected in six common backyard species. Additionally, antibodies indicating prior exposure to the virus were found in five species. Depending upon the species, exposure rates ranged from 40-60%.
The greatest exposure to the COVID virus was found in animals near hiking trails and high-traffic public areas, suggesting that the virus passed from humans to wildlife. Genetic testing of wild animals confirmed both the presence of SARS-CoV-2 and the existence of unique viral mutations with lineages that closely matched variants circulating in humans at the time, further supporting the idea of human-to-animal transmission.
“The virus can jump from humans to wildlife when we are in contact with them, like a hitchhiker switching rides to a new, more suitable host,” said one of the study’s corresponding authors, cancer researcher Carla Finkielstein, a Professor and Director of the Molecular Diagnostics Lab and Interim Director of the Cancer Research Group at the Fralin Biomedical Research Institute at Virginia Tech.
“The goal of the virus is to spread in order to survive,” Professor Finkielstein explained. “The virus aims to infect more humans, but vaccinations protect many humans. So, the virus turns to animals, adapting and mutating to thrive in the new hosts.”
Previously, SARS-CoV-2 infections had been identified primarily in white-tailed deer and feral mink. But this new study significantly expands the number of species in which the virus has been found, pointing to areas with high human activity can serve as points of contact for transmission between humans and animals.
To do this study, Professor Finkielstein and collaborators collected 798 nasal and oral swabs from 23 common Virginia species and tested them for both active infections and for antibodies indicating previous infections. The study animals were either live-trapped in the field and released, or were being treated by wildlife rehabilitation centers. The team also collected 126 blood samples from six species and tested those.
Professor Finkielstein and collaborators identified the virus in deer mice, Virginia opossums, raccoons, groundhogs, Eastern cottontail rabbits, and Eastern red bats. Interestingly, the team collected two mice at the same site on the same day that had the exact same variant, indicating they either both got it from the same human, or one mouse infected the other. Additionally, they found one opossum was infected with a COVID variant with mutations that had never been seen before. Such mutations could make the virus more dangerous and transmissible, and could also create challenges for vaccine development.
“The virus is indifferent to whether its host walks on two legs or four. Its primary objective is survival,” Professor Finkielstein explained. “Mutations that do not confer a survival or replication advantage to the virus will not persist and will eventually disappear.”
Although the study did not find any evidence that COVID was being transmitted from animals back to humans, it underscores the need for continuing COVID surveillance in animals, and that new mutations viewed as potential threats to human health.
“This study highlights the potentially large host range SARS-CoV-2 can have in nature and really how widespread it might be,” said microbial ecologist Joseph Hoyt, an Assistant Professor of Biological Sciences at Virginia Tech. Professor Hoyt’s research focuses on the intersection of disease ecology and conservation biology.
Why was this particular study so important?
“This study was really motivated by seeing a large, important gap in our knowledge about SARS-CoV-2 transmission in a broader wildlife community,” replied Professor Hoyt. “A lot of studies to date have focused on white-tailed deer, while what is happening in much of our common backyard wildlife remains unknown.”
Although this study examined 23 common species in the state of Virginia for both active infections and antibodies indicating previous infections, many of the species that tested positive are common throughout North America. Thus, it is likely they are being exposed in other areas as well, so surveillance across a broader region is urgently needed, Professor Hoyt pointed out.
How are these wild animals getting COVID?
Professor Finkielstein and collaborators said one possible COVID source is contaminated wastewater, but they think it’s more likely that trash bins and food waste are the main sources.
“I think the big take home message is the virus is pretty ubiquitous,” said the study’s lead author, conservation biologist Amanda Goldberg, a postdoctoral researcher in the Department of Biology at Virginia Tech. “We found positives in a large suite of common backyard animals,” Dr Goldberg emphasized.
The study did not uncover any evidence that COVID was being passing from animals back to humans, so people don’t need to worry about getting the illness from any critters they might come across whilst hiking, for example.
Nevertheless, this study does indicate that surveillance for COVID should continue, the team said. More research is needed to better understand how the virus is transmitted from humans to wildlife, how it might spread within a species, and how it might spread from one species to another.
“There is a lot of work to be done to understand which species of wildlife, if any, will be important in the long-term maintenance of SARS-CoV-2 in humans,” Professor Hoyt cautioned.
“But what we’ve already learned,” Professor Finkielstein explained, “is that SARS CoV-2 is not only a human problem, and that it takes a multidisciplinary team to address its impact on various species and ecosystems effectively.”
Source:
Amanda R. Goldberg, Kate E. Langwig, Katherine L. Brown, Jeffrey M. Marano, Pallavi Rai, Kelsie M. King, Amanda K. Sharp, Alessandro Ceci, Christopher D. Kailing, Macy J. Kailing, Russell Briggs, Matthew G. Urbano, Clinton Roby, Anne M. Brown, James Weger-Lucarelli, Carla V. Finkielstein & Joseph R. Hoyt (2024). Widespread exposure to SARS-CoV-2 in wildlife communities, Nature Communications 15: 6210 | doi:10.1038/s41467-024-49891-w
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