SARS-CoV-2 Serological Surveillance in Multiple Wildlife Species

Exposure to SARS-CoV-2 has been documented in a broad range of animal species, raising concerns regarding transmission within wildlife populations and their potential role as viral reservoirs for secondary zoonotic infections. Although serological surveillance of SARS-CoV-2 in animals has increased, it remains far less extensive than studies conducted in humans. Validated serological assays may serve as important tools for detecting prior SARS-CoV-2 exposure in animals. In this study, we conducted multi-species serological surveillance to assess prior exposure to SARS-CoV-2 in free-ranging wild animal populations including white-tailed deer, raccoons, fur seals, sea lions, penguins, and cormorants. A total of 589 serum samples, including samples from white-tailed deer (n = 245), raccoons (n = 147), fur seals (n = 66), sea lions (n = 14), penguins (n = 72) and cormorants (n = 45), were collected between 2022 and 2024. Samples were tested using two serological assays: an enzyme-linked immunosorbent assay targeting antibodies against the nucleocapsid protein (N-ELISA) and a surrogate virus neutralization test (sVNT) targeting antibodies against the receptor-binding domain (RBD) of the spike (S) protein. Seropositivity was determined based on established assay-specific cutoff values. Among white-tailed deer, 46 of 245 samples (18.8%) were seropositive. Of these, 38 samples were positive only by the sVNT, 7 only by N-ELISA, and only 1 sample was positive by both assays. In raccoons, 20 of 147 samples (13.6%) were positive by the sVNT and no samples were positive by N-ELISA. In contrast, among marine mammals and avian species, 3 of 197 samples (1.5%) were positive by N-ELISA, including 1 fur seal and 2 penguins, while no samples were positive by the sVNT. Overall, these findings highlight species-specific differences in SARS-CoV-2 exposure and underscore the importance of multi-species serological surveillance to better understand SARS-CoV-2 circulation, persistence, transmission, and the potential role of wildlife as reservoirs.