Pathogens 2022, 11, 260. https://doi.org/10.3390/pathogens11020260 www.mdpi.com/journal/pathogens Communication Intra-Palpebral Tuberculin Skin Test and Interferon Gamma Release Assay in Diagnosing Tuberculosis due to Mycobacterium caprae in European Bison (Bison bonasus) Anna Didkowska 1, *, Blanka Orłowska 1 , Monika Krajewska-Wędzina 2 , Michał Krzysiak 3,4 , Małgorzata Bruczyńska 5 , Jan Wiśniewski 1 , Daniel Klich 6 , Wanda Olech 6 and Krzysztof Anusz 1 1 Department of Food Hygiene and Public Health Protection, Institute of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159, 02-776 Warsaw, Poland; blanka_orlowska@sggw.edu.pl (B.O.); jan_wisniewski1@sggw.edu.pl (J.W.); krzysztof_anusz@sggw.edu.pl (K.A.) 2 Department of Microbiology, National Veterinary Research Institute, Partyzantów 57, 24-100 Puławy, Poland; kappa2@wp.pl 3 Institute of Forest Sciences, Faculty of Civil Engineering and Environmental Sciences, Bialystok University of Technology, Wiejska 45 E, 15-351 Białystok, Poland; m.krzysiak@st.pb.edu.pl 4 Białowieża National Park, Park Pałacowy 11, 17-230 Białowieża, Poland 5 County Veterinary Inspectorate, Orezna 9, 05-501 Piaseczno, Poland; gosia639@wp.pl 6 Department of Animal Genetics and Conservation, Institute of Animal Sciences, University of Life Sciences (SGGW), Ciszewskiego 8, 02-786 Warsaw, Poland; daniel_klich@sggw.edu.pl (D.K.); wanda_olech@sggw.edu.pl (W.O.) * Correspondence: anna_didkowska@sggw.edu.pl Abstract: Despite the threat posed by tuberculosis (TB) to the protected European bison (Bison bona- sus), no validated TB tests exist for this species. This pilot study evaluates two tests based on detect- ing cellular immunity for this purpose: interferon gamma release assay (IGRA) and tuberculin skin test (TST). Ten animals were subjected to ante-mortem and post-mortem examinations. IGRA was performed using a commercial test, and the comparative TST was performed in the eyelids. The lesions were assessed post-mortem and material was collected for mycobacterial culture. The iso- lated strains were subjected to genotyping. At post-mortem examination, five out of ten individuals demonstrated both tuberculous lesions and positive culture results (Mycobacterium caprae). Com- pared to the palpebral TST, the findings of the IGRA are easier to interpret when diagnosing tuber- culosis in European bison. Keywords: ante-mortem diagnostics; tuberculosis; European bison; interferon gamma release assay (IGRA); intra-palpebral tuberculin skin test; Mycobacterium caprae; wildlife 1. Introduction While post-mortem examination remains the basis of monitoring infectious diseases in wildlife, the importance of ante-mortem diagnostics in these animals is growing. This growth has been driven by the increasing awareness and understanding of the role of wildlife as spill-over and reservoir hosts of pathogens known to pose a threat to livestock and humans, as well as the growing need to care for endangered species (both free-rang- ing and captive) and wildlife in general. Two such pathogens are Mycobacterium caprae and Mycobacterium bovis, the etiological agents of tuberculosis (TB) in mammals. Trans- mission can occur in free-ranging animals, for example, if they share pastures with in- fected livestock; it can also occur among captive animals if untested animals are intro- duced. Citation: Didkowska, A.; Orłowska, B.; Krajewska-Wędzina, M.; Krzysiak, M.; Bruczyńska, M.; Wiśniewski, J.; Klich, D.; Olech, W.; Anusz, K. Intra-Palpebral Tuberculin Skin Test and Interferon Gamma Release Assay in Diagnosing Tuberculosis due to Mycobacterium caprae in European Bison (Bison bonasus). Pathogens 2022, 11, 260. https://doi.org/10.3390/ pathogens11020260 Academic Editors: Andrew W. Byrne and Eric Morgan Received: 6 January 2022 Accepted: 16 February 2022 Published: 17 February 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).