Besnoitia spp. Infection of the Testis, Peritesticular Structures, and Udder Skin in Migratory Caribou (Rangifer tarandus).

We investigated the prevalence, cyst density, and any associated pathologic changes of Besnoitia spp. in the testis, peritesticular structures, and udder skin of migratory caribou (Rangifer tarandus). Possible risk factors for infection, cyst density, and inflammation were investigated. Samples from 149 male and 229 female caribou were collected from seven different herds across Canada, Alaska (US), and Greenland, 2007-09. Biopsies were taken from the udder skin in females and from the epididymis, scrotal skin, testis (seminiferous tubules and tunica albuginea), and spermatic cord in males. The cyst density (cysts per square millimeters) of Besnoitia spp. in each tissue, as well as the type of associated inflammation, were determined by histopathologic examination. Individual (age class) and environmental (season and herd) risk factors were investigated for infection, cyst density, and inflammation. Besnoitia spp. cysts were detected in 22.2, 20.4, 11.2, 31.3, 10.4, and 8.0% of the sections of epididymis, scrotal skin, seminiferous tubules, spermatic cord, tunica albuginea, and udder skin, respectively. The median cyst densities varied from 0.07 cysts/mm2 in the seminiferous tubules to 1.02 cysts/mm2 in the udder skin. Age class and season were risk factors for infection, so adults and subadults were more at risk than calves, and infection was more prevalent in the fall months (September to December) relative to other seasons. Subadults, however, demonstrated a higher cyst density compared with adults and calves. During the winter months, a higher risk of inflammation was present compared with other seasons. Overall, the intensity of inflammation was light to mild, and both pericystic and concomitant inflammation were commonly present. Further research should determine whether these parasitic cysts and the associated inflammation influence the functionality of the testis, peritesticular structures, and udder and thus reproduction.