SARS-CoV-2 not detected in Vermont wildlife monitoring study

Recent research posted in Bio Rxiv* Surveillance for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in wildlife in Vermont, USA (USA).

study: A 2021-2022 Vermont wildlife survey revealed no detectable SARS-CoV-2 viral RNA. Image Credit: TomReichner/Shutterstock.com

*Important Notices: Bio Rxiv We publish a non-peer-reviewed, preliminary scientific report and should not be taken as conclusive, to guide clinical practice/health-related actions, or to be treated as established information.

Background

Natural infections with SARS-CoV-2 in animals have been reported. Animals that facilitate virus transmission within their species become reservoirs for the virus, leading to evolutionary changes that pose risks if reintroduced into humans.

This scenario has been documented on a mink farm. In the Netherlands he had five outbreaks recorded in 2020, with more than half of his mink farms having SARS-CoV-2 infections.

Sequencing data showed multiple spillover and spillback events between mink and humans. A recent study showed that a member of the North American deer family is susceptible to her SARS-CoV-2.

Studies have reported wildlife infections with SARS-CoV-2 in several states in the United States and Canada, but there is no information for Vermont.

Research and Findings

In the current study, researchers conducted SARS-CoV-2 surveillance in Vermont animals. Surveys were conducted statewide during the 2021 hunting and trapping season and the 2022 hunting season. They sampled gray/red foxes, fishers, coyotes, bobcats, white-tailed deer, black bears, and otters.

Deer were given priority in sampling. 470 samples were most sampled (deer) in 2022 compared to 17 samples in 2021.

At the end of the 2021 season, RNA was extracted from the samples and reverse transcription quantitative polymerase chain reaction (RT-qPCR) was performed to detect SARS-CoV-2 RNA using the N1 and N2 primer sets.

No viral RNA was detected in any of the 2021 samples. Of 472 samples in 2022, 133 were positive for both primers. mean period threshold (C_T.) were 36.6 and 38 for N1 and N2, respectively. Additionally, multiple samples were positive for one of the primers. 28 were N1 positive and 56 were N2 positive.

This sudden high positive rate in the 2022 sample, high mean C_T. Absence of values ​​and samples of C_T. < 30 and C_T. N2 is less than 33, indicating possible contamination.Another lab at the University of Vermont in vitro A project involving expression of the SARS-CoV-2 nucleocapsid.

A DNA construct with N1/N2 primer recognition sequences existed in the laboratory. The team therefore assessed whether the positive test results were genuine or due to contamination. Researchers obtained environmental swabs from common laboratory items/surfaces.

All swabs positive for N1 and N2, C_T. The value reaches 23.6. Negative controls were not amplified in reactions. They then performed qPCR to determine whether the contamination was viral DNA or RNA.On average, qPCR positive controls (clinical SARS-CoV-2 samples) were 5.4 cycles higher in C_T. For N1 than RT-qPCR.

Two positive control samples with N2 primers were undetectable by qPCR, but C_T. One positive control, N2 positive, was 1.8 cycles higher.

C._T. Values ​​for all laboratory samples were consistent between qPCR and RT-qPCR testing, suggesting viral DNA contamination. Additionally, the team compared his RT-qPCR and qPCR reactions on selected positive samples from deer.

SARS-CoV-2 nucleic acids are detectable and consistent C_T. value between tests. This suggests that the first positive results in animal samples are likely DNA contamination.

Therefore, the DNA constructs used in the lab lacked the E gene sequence, so the team repeated the RT-qPCR test using the envelope (E) gene primer set. All 2022 samples were undetectable with this primer set. This suggests that Vermont wildlife is free of SARS-CoV-2 RNA.

Conclusion

In summary, this study did not detect SARS-CoV-2 in Vermont wildlife. This was surprising as previous studies had reported prevalence of over 30% and seroprevalence of over 40% in white-tailed deer.

Vermont’s sparse population and relatively low incidence of coronavirus disease 2019 (COVID-19) may have reduced the risk of SARS-CoV-2 transmission from humans to deer.

While the findings are encouraging, they are unlikely to continue indefinitely, especially as cases are increasingly being reported in nearby wildlife. Surveillance should be implemented throughout.

*Important Notices: Bio Rxiv We publish a non-peer-reviewed, preliminary scientific report and should not be taken as conclusive, to guide clinical practice/health-related actions, or to be treated as established information.