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Background: The origin of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains unknown. However, it is likely that the virus spillover occurred from an animal reservoir to humans. Identifying animal species susceptible to SARS-CoV-2 is crucial for understanding cross-species transmission to humans. This study distinguishes itself by focusing on the susceptibility of the European bison (Bison bonasus), an endangered species, to SARS-CoV-2. The objective of this study was to investigate the occurrence of SARS-CoV-2 antibodies in a substantial number (n = 238) of both free-living and captive Polish European bison using an in-house ELISA method and virus neutralization test (VNT)., Results: The seroprevalence of SARS-CoV-2 infection was found to be 1.29% (3/232). None of the seropositive European bison tested positive in the virus neutralization test. All seropositive animals were part of captive herds., Conclusions: This study represents the first report of SARS-CoV-2 seroprevalence in both free-ranging and captive European bison in Poland. Based on these findings, the European bison appears to be a less susceptible species to SARS-CoV-2. The most probable route of transmission was from humans to European bison, as all seropositive animals belonged to captive herds with contact with indirect human sources, such as tourists and keepers., Competing Interests: Declarations. Ethics approval and consent to participate: No animal was culled or immobilized for this study. Samples were collected on the occasion when animals were culled or immobilized for other reasons. Any lethal testing was carried out by local institutions responsible for European bison management, and each culling was performed with the necessary permit. The collection and storage of serum samples from dead animals was based on the decision of the Regional Director of Environmental Protection in Warsaw: according to this decision, no permission is needed for the collection of dead animals for scientific purposes. In addition, in accordance with II Local Ethical Committee for Animal Experiments in Warsaw, no approval was needed for ante-mortem sampling, as it was conducted as part of standard veterinary care. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

The European Bison (Bison bonasus) is the largest mammal in Europe and is classified as an endangered species. Leishmaniosis is a vector-borne disease caused by the protozoan Leishmania infantum. In general, this infection has been associated with dogs, cats, and humans. However, epidemiologic studies and reports confirm that the parasite is able to infect many other mammalian species. Recent evidence has demonstrated that ruminants in endemic areas are exposed to L. infantum infection. Moreover, climate change has allowed the northward spread of vector species, causing the expansion of L. infantum infection in regions traditionally classified as nonendemic in Europe. The aim of this study was to determine the presence or absence of anti-L. infantum antibodies in serum samples from 343 European bison in Poland, collected from 2017 to 2023. For this purpose, the presence of anti-Leishmania antibodies was analyzed using an in-house multispecies ELISA. Anti-Leishmania antibodies were detected in four animals, an overall seroprevalence of 1.17%. The results provide scientific evidence of serologic exposure to the parasite in Poland, a country previously considered nonendemic for L. infantum infection., (© Wildlife Disease Association 2025.)