Investigating the Presence of SARS CoV-2 in Free-Living and Captive Animals

Due to SARS CoV-2 recombination rates, number of infected people and recent reports of environmental contamination, the possibility of SARS CoV-2 transmission to animals can be expected. We tested samples of dominant free-living and captive wildlife species in Croatia for the presence of anti-SARS CoV-2 antibodies and viral RNA. In total, from June 2020 until February 2021, we tested blood, muscle extract and fecal samples of 422 free-living wild boars (Sus scrofa), red foxes (Vulpes vulpes) and jackals (Canis aureus); blood and cloacal swabs of 111 yellow-legged gulls (Larus michahellis) and fecal samples of 32 zoo animals. A commercially available ELISA (ID.Vet, France) and as a confirmatory test, a surrogate virus neutralization test (sVNT; GenScript, Netherlands) were used. Fecal samples were tested for the presence of viral RNA by a real-time RT-PCR protocol. Fifteen out of 533 (2.8%) positive ELISA results were detected; in wild boars (3.9%), red foxes (2.9%) and jackals (4.6%). However, the positive findings were not confirmed by sVNT. No viral RNA was found. In conclusion, no spillover occurred within the investigated period (second COVID-19 wave). However, further investigation is needed, especially regarding wildlife sample features for serological tests.