A
Virginia Tech study of wildlife common in Virginia found that SARS-CoV-2, the
virus responsible for COVID-19, is widespread in animals, particularly around
areas of high human activity. The researchers identified variants consistent
with those circulating in humans at the time, and one opossum with previously
unreported viral mutations, underscoring the potential for changes that can
potentially impact humans and their immune response. Credit: Joseph
Hoyt/Virginia Tech
SARS-CoV-2,
the virus responsible for COVID-19, is widespread among wildlife species,
according to Virginia Tech research published July 29, 2024 in Nature Communications. The virus was
detected in six common backyard species, and antibodies indicating prior
exposure to the virus were found in five species, with rates of exposure
ranging from 40 to 60% depending on the species.
Genetic tracking in wild animals
confirmed both the presence of SARS-CoV-2 and the existence of unique viral
mutations with lineages closely matching variants circulating in humans at the
time, further supporting human-to-animal transmission, the study found.
The highest exposure to SARS CoV-2 was
found in animals near hiking trails and high-traffic public areas, suggesting
the virus passed from humans to wildlife, according to scientists at the Fralin
Biomedical Research Institute at VTC, the Department of Biological Sciences in
Virginia Tech's College of Science, and the Fralin Life Sciences Institute.
The findings highlight the
identification of novel mutations in SARS-CoV-2 in wildlife and the need for
broad surveillance, researchers say. These mutations could be more harmful and
transmissible, creating challenges for vaccine development.
The scientists stressed, however, that
they found no evidence of the virus being transmitted from animals to humans,
and people should not fear typical interactions with wildlife.
Investigators tested animals from 23 common Virginia species for both active infections and antibodies indicating previous infections. They found signs of the virus in deer mice, Virginia opossums, raccoons, groundhogs, Eastern cottontail rabbits, and Eastern red bats. The virus isolated from one opossum showed viral mutations that were previously unreported and can potentially impact how the virus affects humans and their immune response.
Imagine a virus is like a key, and the cells it
can infect are like locks. A virus can't infect any cell of any animal; it
needs to find a cell with the right "lock" (called a receptor) or
change its key (the viral proteins) to fit a new lock. To do this, a key needs
to change shape by acquiring mutations to fit the new lock. This is what Carla
Finkielstein and the Virginia Tech Molecular Diagnostic Lab at the Fralin
Biomedical Research Institute noted with the keys present in SARS-CoV-2 when the
virus jumped to wild species like opossums and squirrels. The key S-protein
acquired at least two mutations, displayed in yellow in this simulation, that
provided an evolutionary path for the virus to jump and transmit to other
species. Credit: Carla Finkielstein/Virginia Tech
"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 Carla Finkielstein,
professor of biological sciences at the Fralin Biomedical Research Institute at
VTC and one of the paper's corresponding authors.
"The goal of the virus is to
spread in order to survive. 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."
SARS CoV-2 infections were
previously identified in wildlife, primarily in white-tailed deer and feral
mink. The Virginia Tech study significantly expands the number of species
examined and the understanding of virus transmission to and among wildlife. The
data suggests exposure to the virus has been widespread in wildlife and that
areas with high human activity may serve as points of contact for cross-species
transmission.
"This study was really
motivated by seeing a large, important gap in our knowledge about SARS-CoV-2
transmission in a broader wildlife community," said Joseph Hoyt, assistant
professor of Biological Sciences in Virginia Tech's College of Science and
corresponding author on the paper. "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."
The research team collected 798
nasal and oral swabs across Virginia from animals either live-trapped in the
field and released, or being treated by wildlife rehabilitation centers. The
team also obtained 126 blood samples from six species. The locations were
chosen to compare the presence of the virus in animals in sites with varying
levels of human activity, from urban areas to remote wilderness.
The study also identified two mice
at the same site on the same day with the exact same variant, indicating they
either both got it from the same human, or one infected the other.
Researchers are not certain about the means of transmission from humans to animals. One possibility is wastewater, but the Virginia Tech scientists believe trash receptacles and discarded food are more likely sources.
Imagine
a virus is like a key, and the cells it can infect are like locks. A virus
can't infect any cell of any animal; it needs to find a cell with the right
"lock" (called a receptor) or change its key (the viral proteins) to
fit a new lock. To do this, a key needs to change shape by acquiring mutations
to fit the new lock. This is what Carla Finkielstein and the Virginia Tech
Molecular Diagnostic Lab at the Fralin Biomedical Research Institute noted with
the keys present in SARS-CoV-2 when the virus jumped to wild species like
opossums and squirrels. The key S-protein acquired at least two mutations,
displayed in yellow in this simulation, that provided an evolutionary path for
the virus to jump and transmit to other species. The purple part is the receptor
that's recognized by the S-protein so the virus can enter. Credit: Carla
Finkielstein/Virginia Tech
"I
think the big take home message is the virus is pretty ubiquitous," said
Amanda Goldberg, a former postdoctoral associate in Hoyt's lab, who is the
study's first author. "We found positives in a large suite of common
backyard animals."
While this study focused on the state of
Virginia, many of the species that tested positive are common wildlife found
throughout North America. It is likely they are being exposed in other areas as
well, and surveillance across a broader region is urgently needed, Hoyt said.
"The virus is indifferent to
whether its host walks on two legs or four. Its primary objective is survival.
Mutations that do not confer a survival or replication advantage to the virus
will not persist and will eventually disappear," said Finkielstein, who is
also director of the Virginia Tech Molecular Diagnostics Lab. The Roanoke lab
was established in April 2020 to expand COVID-19 testing.
"We understood the critical
importance of sequencing the genome of the virus infecting those species,"
Finkielstein said. "It was a monumental task that could only be
accomplished by a talented group of molecular biologists, bioinformaticians,
and modelers in a state-of-the-art facility. I am proud of my team and my
collaborators, their professionalism, and everything they contributed to ensure
our success."
Surveillance for these mutations should
continue and not be dismissed, the scientists said. More research is needed
about how the virus is transmitted from humans to wildlife, how it might spread
within a species, and perhaps from one species to another.
"This study highlights the
potentially large host range SARS-CoV-2 can have in nature and really how
widespread it might be," Hoyt said. "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."
"But what we've already learned," Finkielstein said, "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."
by Matt Chittum, Virginia Tech
Source: Virus that causes COVID-19 is widespread in wildlife, scientists find (phys.org)
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