P22 has demonstrated high sensitivity (Se) and specificity (Sp), depending on the animal species and epidemiological situation (InfantesLorenzo, Moreno etal.,2019). sample size and seropositive bison were found in 12 of 13 sampling populations. == Conclusions == Our findings identify potential emerging threats to the European bison populace and confirm the first serological response to P22 in European bison. As Poland is currently officially free of brucellosis and bovine tuberculosis, our results require careful interpretation. Further studies are needed to establish the presence of crossreactions with atypical mycobacteria in the case of MTC and other bacteria (e.g.Yersinia enterocoliticaO:9) in the case ofBrucellaspp. Keywords:Brucellaspp, ELISA, European bison, P22, serology, tuberculosis Our findings identify two potential emerging threats to the European bison populace MLN9708 and confirm the first serological response to P22 in European bison. Antibodies MLN9708 against the MTC (P22) were detected in 7% (22/323) of the tested European bison. Antibodies againstBrucellaspp. were detected in 36% (116/323) of the tested bison. == 1. INTRODUCTION == The European bison (Bison bonasus) is an iconic Polish wildlife species, with more than a quarter of the global European bison population living in Poland. The species is currently safe from extinction, having recently changed its conservation status to Near Threatened, according to the International Union for Conservation of Nature (IUCN) (Plumb et al.,2020). The number of European bison in Poland at the end of 2021 was 206 in captivity (most herds are of a low number) and 2223 in freeliving populations located in eight different herds (Raczynski & Bobot,2022). The European bison in Poland is usually undergoing NEK5 dynamic populace development (Olech & Perzanowski,2022) that results in high local population densities; therefore, it MLN9708 is important to monitor infectious diseases and emerging threats (Klich et al.,2021,2020). Tuberculosis (TB), caused by users of theMycobacterium tuberculosiscomplex (MTC), and brucellosis, caused by the genusBrucella, not only have a considerable impact on cattle herds worldwide but also are bacterial zoonoses with significant potential impact on public health. Although Poland is usually officially free of TB and brucellosis in cattle (Regulation [(EU) 2021/620]) both are occasionally noted in Polish wildlife (Szulowski et al.,2013a; Krajewska et al.,2014). It has been suggested that European bison are highly sensitive toMycobacteriumspp. infections (Didkowska, Orowska, et al.,2021); indeed, TB has been confirmed in both captive (Didkowska, Orowska, et al.,2021) and freeliving herds of European bison in Poland MLN9708 (Welz et al.,2005). Although paratuberculosis does not seem to be an emerging problem in Polish European bison herds (Didkowska, Ptak et al.,2021), atypical mycobacteria (Mycobacterium aviumandMycobacterium xenopi) have been isolated from them (Didkowska, Orowska, et al.,2021). TB has also been recognized in European bison in a Brazilian zoo (Zimpel et al.,2017) and is endemic in American bison (Bison bison) in some North American populations (Himsworth et al.,2010; Nishi et al.,2002; Shury et al.,2015; Tessaro et al.,1990). In recent years, due to the emerging cases of TB in bison, diagnostic procedures have been extended to incorporate new methods, including serological assessments (Didkowska, Dziekan, et al.,2021). One antigen that has recently been analyzed for use in serological assessments in various mammalian species is usually P22 (Bezos et al.,2018; Casal et al.,2017; InfantesLorenzo et al.,2018; InfantesLorenzo, Dave et al.,2019; InfantesLorenzo, Moreno et al.,2019; Thomas et al 2019; ArrietaVillegas et al.,2020; FerrerasColino et al.,2022). P22 is a multiprotein complex obtained fromMycobacterium bovispurified protein derivative (BPPD) by affinity chromatography (InfantesLorenzo et al.,2017). P22 has demonstrated high sensitivity (Se) and specificity (Sp), depending on.