Something that will be walked back in the future?
Something in between?
A press release from the US Department of Agriculture (USDA) about a study looking at antibodies against SARS-CoV-2 in white-tailed deer (and an infosheet about the same study) released today makes me wonder which of these will apply. The results are potentially game-changing, but it’s so far outside of what I’d expect that we have to make sure the results are real first. Since information is currently limited to the press release and infosheet, with no specific information about the study methods or details of the results, it’s hard to draw firm conclusions. Based on the information available though, it could be a remarkable story.
We know from experimental studies that white-tailed deer are susceptible to the SARS-CoV-2 virus. So the USDA’s Animal and Plant Health Inspection Service (APHIS) set out to analyze blood samples from free-ranging white-tailed deer for antibodies against SARS-CoV-2. The method of testing isn’t stated, but the USDA has excellent labs. Samples were collected from deer in four different states (Illinois, Michigan, New York, and Pennsylvania) as part of wildlife damage management activities.
According to the USDA press release, antibodies to SARS-CoV-2 were found in 33% of 481 samples collected from white-tailed dear from January 2020 through 2021. This would indicate that these animals had been exposed to the virus sometime in the past, but the testing doesn’t tell us if there was active infection in the deer populations or if the deer could have infected others. The antibody testing only gives us a historical indication of previous exposure to the virus (or, potentially, a virus that induces similar antibodies that cross-react with the test).
Only 1/241 samples collected from deer before the COVID-19 pandemic began were positive. That was presumably a false positive result (no test is perfect, so typically we’d be quite happy with less than 1% false positives). Less than 1% positive before the pandemic and 33% positive during the pandemic after would support true infection having occurred in these deer populations.
The number raises concerns for me. The press release states that “the finding that wild white-tailed deer have been exposed to SARS-CoV-2 is not unexpected given that white-tailed deer are susceptible to the virus, are abundant in the United States, often come into close contact with people, and that, more than 114 million Americans are estimated to have been infected with COVID-19, according to the U.S. Centers for Disease Control and Prevention (CDC). ”
- All true, and good reasons to investigate exposure in deer populations. However, 33% is very high, given the limited direct contact between people and deer. Deer would have to be very susceptible and very effectively able to transmit the virus widely within the deer population for 33% to be infected.
It’s very interesting info, but more details are needed. It could be a game-changer, or a testing issue. That needs to be sorted out. Regardless, it’s a good One Health study that’s needed to help understand the ecology of this virus and potential risks.