Two recent studies; one published in December in Nature (www.nature.com/
The bioRxiv-published report details a study conducted by an interdisciplinary team of researchers led by Penn State University (PSU) scientists. The team examined 131 free-ranging white-tailed deer, all living on Staten Island, the most suburban of the 5 New York City boroughs. Nineteen tested positive for COVID antibodies, indicating that the deer had prior exposure to the virus and, according to the researchers, implying that they are vulnerable to repeated re-infections with new variants.
The report has not yet been certified by peer review, but has been published as a pre-print because of the significance of the findings, according to Suresh Kuchipudi, an American College of Veterinary Microbiologists (ACVM) board-certified specialist in virology and immunology at the Department of Veterinary and Biological Sciences at PSU. He serves as associate director of PSU’s Animal Diagnostic Laboratory where, as head of microbiology, he oversees the University’s bacteriology, virology, serology, and molecular diagnostic units. Kuchipudi has expressed concern that spillover of omicron from humans to deer could result in new and possibly vaccine-resistant mutations of the virus evolving undetected in non-human hosts and noted that one of the infected deer in the study had antibodies from a previous COVID-19 infection; indicating that deer, like humans, can experience breakthrough cases.
What’s more, the study, which was funded by the United States Department of Agriculture (USDA) National Institute of Food and Agriculture, is the first to find evidence of the omicron variant in a wild animal population. In the study published in Nature, researchers from Ohio State University (OSU), working with scientists from USDA, reported finding active COVID-19 infection in white-tailed deer from at least three different strains of the virus.
Nearly 36 percent of the deer they examined, from January through March of 2021 at six northeast Ohio locations, were infected. The findings were supported by the growth of viral isolates in the lab, indicating that the researchers had recovered viable samples of the virus; not just genetic traces. They were also able to determine that the variants infecting the deer were the same strains of the SARS-CoV-2 virus that were prevalent in Ohio COVID-19 patients at that time, based on the genomic sequencing of the samples collected. Sample collection occurred before the Delta variants became pervasive, and those variants were not detected in any of the infected deer.
An article published in Science Daily, titled COVID-19 infection detected in deer in six Ohio locations, quotes OSU associate professor of veterinary preventive medicine, Andrew Bowman, the senior author of the paper, as saying, “The working theory, based on our sequences, is that humans are giving it (the virus) to deer and, apparently we gave it to them several times. We have evidence of six different viral introductions into those deer populations. It’s not that a single population got it once and it spread.”
According to Bowman, the fact that wild deer can become infected, “leads toward the idea that we might actually have established a new maintenance host outside humans. Based on evidence from other studies, we knew they were being exposed in the wild and that in the lab we could infect them and the virus could transmit from deer to deer. Here we’re saying that in the wild they are infected. And if they can maintain it, we have a new potential source of SARS-CoV-2 coming into humans. That would mean that beyond tracking what’s in people, we’ll need to know what’s in the deer, too.”
It’s important to mention that this sampling, like the one on Staten Island, was focused on locations that are in close proximity to dense populations of people and that field samples were collected opportunistically. As such, the results are, most likely, not representative of the rate of infection across all free-ranging deer populations. At this time, there’s no evidence to suggest that the virus is being passed from deer to humans. Nonetheless, Bowman believes that viral transmission among deer “could complicate future mitigation and control plans for COVID-19.”
The Science Daily article states that Bowman believes that white-tailed deer functioning as a viral reservoir of SARS-CoV-2 would likely result in one of two outcomes. The virus could mutate in deer, potentially facilitating transmission of new strains to other species, including humans, or it could survive in deer unchanged, while simultaneously evolving in humans until people no longer have immunity to the strains infecting deer, at which time those variants could come surging back into the human population.
At this time, a lot of unknowns remain, including how the deer became infected and whether or not infected deer can pass the virus on to other species, including humans. Since the virus is shed in human excrement and detectable in wastewater, one hypothesis is that the animals initially became infected by drinking contaminated water. The USDA has previously reported COVID-19 in pets (dogs, cats), farmed animals (mink), and animals in zoos (tigers, lions, snow leopards, otters, gorillas). A recent study in Spain showed that SARS-CoV-2 infections can occur in domesticated ferrets, especially if a high viral circulation is present in the human population. (source: CDC)
Photo at top: Credit: Cornell Wildlife Health Lab