The Efficacy of Surrogate Virus Neutralization Test ELISA Varies in the Detection of SARS-CoV-2 Antibodies with Different Postmortem White-Tailed Deer (Odocoileus virginianus) Biological Samples.

The susceptibility of white-tailed deer (WTD; Odocoileus virginianus) to SARS-CoV-2 has resulted in WTD being one of the most studied wildlife species during the COVID-19 pandemic. However, WTD specimen collections for SARS-CoV-2 research and surveillance have largely been opportunistic. Our objective was to evaluate the detection of SARS-CoV-2 neutralizing antibodies (NAbs) in WTD serum, plus two additional WTD biological sample types, using a blocking ELISA previously used for WTD serum. The two additional sample types evaluated were eluted Nobuto filter-paper strips (FPSs) from heparinized whole blood collected perimortem from 34 WTD and serosanguinous fluid collected postmortem from the thoracic cavity of 34 WTD. A true NAb prevalence of 88% was established from the serum samples. The FPS eluates performed most poorly (56% apparent prevalence; 57% sensitivity; 50% specificity), followed by serosanguinous fluid (88% apparent prevalence; 87% sensitivity; 0% specificity). Serosanguinous fluid appeared to better reflect the WTD population's true seroprevalence, although sensitivity decreased to <90% for both nonserum biological sample types. As studies are being developed to better understand the ecology of SARS-CoV-2 infections in WTD and other wildlife, it is important to consider the sample type being assessed, because sensitivity may vary greatly.