Many wild backyard animals, such as rabbits, mice, and bats, have been infected with SARS-CoV-2, potentially making the evolution of this virus more unpredictable.
Wild rabbits have been infected with COVID-19. (Public domain via PickPik)
A new study has determined that the COVID-19 virus is prevalent among 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 on the species, exposure rates ranged from 40 to 60 percent.
Animals most exposed to the COVID-19 virus were near hiking trails and busy public places, suggesting that the virus jumped 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 the variants circulating in humans at the time, further supporting the idea of human-to-animal transmission.
“The virus can jump from humans to wild animals when we come into contact with them, like a hitchhiker changing routes for a new, more suitable host,” said one of the study’s corresponding authors, cancer researcher Carla Finkielstein, professor and director of the Molecular Diagnostics Laboratory and interim director of the Cancer Research Group at Virginia Tech’s Fralin Biomedical Research Institute.
“The goal of the virus is to spread to survive,” says Professor Finkielstein. “The virus aims to infect more humans, but vaccines protect many humans. So the virus turns to animals, adapts and mutates to thrive in the new hosts.”
FIGURE 1: Prevalence of SARS-CoV-2 RNA and neutralizing antibodies in wild communities. … (+)
Until now, SARS-CoV-2 infections had been identified mainly in wild white-tailed deer and mink. But this new study significantly expands the number of species in which the virus has been detected, highlighting that areas with high human activity can serve as contact points for transmission between humans and animals.
To conduct the study, Finkielstein and his colleagues collected 798 nasal and oral swabs from 23 common Virginia species and tested them for active infections and antibodies indicating past infections. The animals studied were either live-caught in the field and released, or had been treated at wildlife rehabilitation centers. The team also collected 126 blood samples from six species and analyzed them.
Professor Finkielstein and his collaborators identified the virus in deer mice, Virginia opossums, raccoons, marmots, cottontail rabbits and eastern red bats. Interestingly, the team collected two mice from the same site on the same day that had the exact same variant, indicating that they either both contracted it from the same human or that one mouse infected the other. Additionally, they found that 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 doesn’t care whether its host walks on two or four legs. Its primary goal is survival,” says Professor Finkielstein. “Mutations that don’t give the virus a survival or replication advantage will not persist and will eventually disappear.”
Although the study found no evidence that COVID is transmitted from animals to humans, it highlights the need to continue surveillance of COVID in animals and to consider new mutations as potential threats to human health.
“This study highlights the broad host range that SARS-CoV-2 can have in nature and its true magnitude,” said Joseph Hoyt, a microbial ecologist and assistant professor of biological sciences at Virginia Tech. Hoyt’s research focuses on the intersection of disease ecology and conservation biology.
Why was this particular study so important?
“This study was motivated by the recognition of a significant gap in our knowledge about SARS-CoV-2 transmission in the broader wildlife community,” Hoyt responded. “Many studies to date have focused on white-tailed deer, while what is happening in much of our shared wildlife remains unknown.”
Although this study examined 23 species common in the state of Virginia for both active infections and antibodies indicating past infections, many of the species that tested positive are common throughout North America. It is therefore likely that they are also exposed in other regions, which is why surveillance across a broader region is urgently needed, Hoyt said.
How do these wild animals contract COVID?
Professor Finkielstein and his colleagues said one possible source of COVID is contaminated sewage, but they think it is more likely that garbage and food waste are the main sources.
“I think the main takeaway is that the virus is pretty ubiquitous,” said the study’s lead author, conservation biologist Amanda Goldberg, a postdoctoral researcher in Virginia Tech’s Department of Biology. “We found positive cases in a lot of common backyard animals,” Dr. Goldberg said.
The study found no evidence that COVID spreads from animals to humans, so people don’t need to worry about contracting the disease from animals they might encounter while hiking, for example.
Still, this study indicates that COVID-19 surveillance needs to continue, the team said. More research is needed to better understand how the virus transmits from humans to wildlife, how it can spread within a species, and how it can spread from one species to another.
“There is still much work to be done to understand which wildlife species, if any, will be important in the long-term maintenance of SARS-CoV-2 in humans,” warned Professor Hoyt.
“But what we have already learned,” Professor Finkielstein explained, “is that SARS-CoV-2 is not just a human problem, and that it takes a multidisciplinary team to effectively address its impact on diverse species and ecosystems.”
Source:
French 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, and Joseph R. Hoyt (2024). Widespread exposure to SARS-CoV-2 in wild communities, Nature Communications 15: 6210 | doi:10.1038/s41467-024-49891-w
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