In what may emerge as a potential worry for health authorities across the world, amidst the receding Covid-19 pandemic, scientists have discovered white-tailed deer in Ohio, USA, acting as a reservoir for SARS-CoV2 virus where it is mutating fast. According to the study published in Nature Communications on Monday, viral variants in the Ohio region seem to undergo evolution at a rate approximately three times faster in these deer than in humans.
A team of scientists gathered 1,522 nasal swabs from free-roaming deer in 83 out of Ohio's 88 counties between November 2021 and March 2022. The findings showed that over 10% of the samples tested positive for the SARS-CoV-2 virus. Furthermore, a positive case was detected in 59% of the counties under examination.
The genomic analysis of these samples highlighted that at least 30 instances of infections in deer were traced back to human transmission. This unexpected level of interspecies transmission has raised concerns among the scientific community. "Generally, interspecies transmission is viewed as a rare occurrence. However, our study documented 30 instances of spillovers. It seems the virus is moving quite readily between people and animals," said Andrew Bowman, co-senior author of the study and associate professor of veterinary preventive medicine at The Ohio State University.
The evidence indicates a bidirectional transmission between humans and deer, rather than a one-way flow. This insight emphasizes the need for understanding and surveillance in the realm of zoonotic infections, also known as zoonoses, are diseases that can be transmitted from animals to humans. The cumulative findings suggest that white-tailed deer are acting as a reservoir for the SARS-CoV-2 virus, facilitating its ongoing mutation. This situation raises concerns about the virus's potential to spread to other wildlife and even livestock.
The research, undertaken by Bowman and his colleagues, was initiated after the detection of SARS-CoV-2 infections in white-tailed deer at nine Ohio locations in December 2021. The study was expanded across the state to determine whether this phenomenon was localized, only to discover that numerous areas had positive cases.
In addition to active infections, the researchers found evidence of past exposure through blood samples containing antibodies. This indicated that an estimated 23.5% of Ohio's deer population had been infected at some point.
The study’s genetic analysis of the virus revealed a close match between the delta variants found in deer and those dominant in the human population during that period. This suggests that spillover events were occurring and that transmission within the deer population was occurring in clusters across multiple counties. The implications extend beyond immediate infections. The rate of virus evolution in deer was found to outpace that in humans, which could lead to new variants that may or may not be responsive to existing countermeasures.
The study, funded by the National Institute of Allergy and Infectious Diseases and Ohio State's Infectious Diseases Institute, highlighted the importance of ongoing surveillance and research in tackling these challenges at the intersection of human and animal health.
Despite the mystery surrounding the exact means of transmission between humans and white-tailed deer, the scientists said that it remains clear that the potential for virus circulation within animals poses a significant risk. The research team emphasized that vigilance is necessary, as a virus adapted to deer could become a bridge for transmission to other animal hosts, both domestic and wild.