Post-Mortem Evaluation of Pathological Lesions in European Bison (Bison Bonasus) in the Białowieża Primeval Forest Between 2008 and 2013

The study presents the analysis of the findings of 234 post-mortem examinations on free-ranging and captive European bison selectively culled or having fallen between 2008 and 2013 in Białowieża Primeval Forest. Pneumonia, emphysema, nephritis, bodily traumas, and intestinal lesions were observed in 106 (45.3%), 77 (32.9%), 82 (35.0%), 68 (29.1%), and 56 (23.9%) animals respectively and were the most common pathological changes. Almost half of all males (66 out of 140; 47.1%) tested showed some pathological changes of prepuce and penis, described as posthitis or balanoposthitis. Infection with liver fluke (Fasciola hepatica) and lungworm (Dictyocaulus viviparus) was observed macroscopically in 114 (48.7%) and 80 (32.9%) bison respectively. F. hepatica prevalence was associated with the emergence of other liver changes such as hepatitis and cirrhosis (P < 0.001). Similarly, the prevalence of D. viviparus coincided with pneumonia (P = 0.001), changes in the upper respiratory tract (P = 0.04), and emphysema (P < 0.001). Hepatitis, infection with F. hepatica, and pathological lesions in the male and female reproductive tracts were associated with the animals’ age. Mechanical injuries, caused by other bison or less commonly by traffic accidents, were the most common cause of death of bison below six months of age. Most pathological changes were significantly more frequent in the selectively culled animals in comparison with the ones having fallen, which confirms the desirability of elimination as a tool to improve the health and welfare of the bison population and limit the number of reservoirs of invasive and possibly infectious diseases.