The USDA published a preprint study on 29July suggesting that 40% of white-tailed deer assessed in four U.S. states have been exposed to SARS-CoV-2 based on antibody testing (Chandler et al., 2021). These findings raise concerns that white-tailed deer could be a wildlife reservoir for SARS-CoV-2 that could result in future outbreaks in humans. The findings represent the first detection of widespread exposure to the virus in wildlife, following case studies of infected escape and wild mink in Utah in 2020 (Mallapaty, 2021; Shriner, 2021; ProMed, 2020).
Antibodies were detected in 152 samples (40%) from 2021 using a surrogate virus neutralization test (Chandler et al.,2021). Seroprevalences from highest to lowest by state were 67% in Michigan, 44% in Pennsylvania, 31% in New York, and 7% in Illinois. Minor cross-reactivity was detected between SARS and SARS-CoV-2, cross-reactivity with other human and animal coronaviruses was ruled out.
Public and scientific concerns for the findings are based on the abundance of white-tailed deer in the U.S., the close contact that the deer can have with people, and the general challenge associated with wildlife reservoirs of zoonotic diseases. Furthermore, persistent infections in a novel host could lead to adaptation, strain evolution, and re-emergence of strains with altered transmissibility, pathogenicity, and vaccine escape (Chandler et al., 2021). Cross-species transmission to other wildlife species and the concomitant risks is also a concern (Chandler et al., 2021).
The total U.S. deer population in 2017 was about 33.5 million, of which 29.5 million (88%) were white-tailed deer (Deer Friendly, 2020). Although the deer population in the U.S. is declining due to habitat loss, habitat change, fragmentation, and chronic wasting disease, these latest numbers imply a 1:10 deer to human ratio in the U.S. in 2017 (Deer Friendly, 2020; U.S. Census Bureau, 2017). Multiple activities bring deer into contact with people, including captive cervid operations, field research, conservation work, and hunting (Chandler et al., 2021).
No information of molecular or viral testing of deer for SARS-CoV-2 active infection has been indicated. Further research is needed to identify the route of transmission and the implications for human and animal health (USDA, 2021). bioRxiv.
Chandler, J. et al. (2021). SARS-CoV-2 exposure in wild white-tailed deer (Odocoileus virginianus). bioRxiv. https://doi.org/10.1101/2021.07.29.454326
Deer Friendly. (2020). The Decline of Deer Populations. Deer Friendly. Retrieved on 5 August 2021 from http://www.deerfriendly.com/decline-of-deer-populations
Mallapaty, S. (2 August 2021). The coronavirus is rife in common US deer. Nature. https://doi.org/10.1038/d41586-021-02110-8
ProMed. (11 Dec 2020). COVID-19 update (536): animal, USA (UT) wild mink, 1st case. ProMed-mail. Archive Number: 20201213.8015608. Retrieved from https://promedmail.org/promed-posts/
Shriner, S. A., Ellis, J. W., Root, J.,Roug, A., Stopak, S. R., Wiscomb, G. W....DeLiberto, T. J. (2021). SARS-CoV-2 Exposure in Escaped Mink, Utah, USA. Emerging Infectious Diseases, 27(3), 988-990. https://doi.org/10.3201/eid2703.204444.
U.S. Census Bureau. (2017). Population, Population Change, and Estimated Components of Population Change: April 1, 2010to July 1, 2019 (NST-EST2019-alldata). National Population Totals and Components of Change: 2010-2019. Retrieved from https://www.census.gov/data/tables/time-series/demo/popest/2010s-national-total.html
USDA. (2021). Questions and Answers: Results of Study on SARS-CoV-2 in White-Tailed Deer. U.S. Department of Agriculture. Retrieved from https://www.aphis.usda.gov/animal_health/one_health/downloads/qa-covid-white-tailed-deer-study.pdf
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