Biopsy and Tracheobronchial Aspirates as Additional Tools for the Diagnosis of Bovine Tuberculosis in Living European Bison (Bison bonasus)

Abstract

The diagnosis of bovine tuberculosis (BTB) in living wildlife remains a complex problem, and one of particular importance in endangered species like European bison (Bison bonasus). To identify infection and avoid the unnecessary culling of such valuable individuals, current best practice requires the collection and culture of material from living animals, as mycobacteria isolation remains the gold standard in BTB diagnosis. However, such isolation is challenging due to the need for the immobilization and collection of appropriate clinical material, and because of the sporadic shedding of mycobacteria. In the present study, we evaluated the potential of sampling for the detection of BTB in a group of seven living European bison suspected of being infected with Mycobacterium caprae. The specimens were collected both as swabs from the nasal and pharyngeal cavities, tracheobronchial aspirates (TBA), ultrasound-guided biopsies from lateral retropharyngeal lymph nodes, and post mortem, from mandibular, retropharyngeal and mediastinal lymph nodes. Clinical samples were tested for mycobacterial species via mycobacteriological culture and PCR. M. caprae was isolated from collected material in two out of four living infected individuals (TBA, biopsy) and mycobacterial DNA was detected in three out of four (TBA, pharyngeal swab) bison. This is the first report of isolation of M. caprae in living European bison. Our findings demonstrate the value of diagnostic tests based on both molecular testing and culture in European bison and confirm the respiratory shedding of viable M. caprae in this host species.