Mycobacterium avium subsp. paratuberculosis Infection in a Rocky Mountain Bighorn Sheep (Ovis canadensis canadensis) in Wyoming, USA, with Additional Herd Surveillance using Noninvasive Methods

Abstract: Mycobacterium avium subspecies paratuberculosis (MAP) infection (Johne's disease; paratuberculosis) is a bacterial disease primarily of domestic ruminants that causes weight loss, diarrhea, and mortality. It has been documented in North American wild ruminants previously (e.g., Rocky Mountain bighorn sheep [Ovis canadensis canadensis], Key deer [Odocoileus virginianus clavium], Rocky Mountain goat [Oreamnos americanus], tule elk [Cervus canadensis nannodes], and white-tailed deer [Odocoileus virginianus]); however, the prevalence and implications of this disease in free-ranging populations are generally unknown. In May 2021, an adult female bighorn sheep carcass was retrieved from the Encampment River Herd in southeastern Wyoming, USA. Gross and histologic examinations were performed. Lesions consistent with MAP infection were identified and included emaciation, unformed feces with perineal staining (evidence of diarrhea), chronic inflammation of the small intestine, and inflammation of the internal abdominal lymph nodes. Additionally, MAP was confirmed in a fecal sample by using PCR. A subsequent opportunistic noninvasive field investigation was initiated to ascertain MAP establishment and possible prevalence in the herd from June to August 2021. In the 73 fecal samples collected, MAP was not detected. This work encourages and guides future surveillance using noninvasive methods and highlights the need for more research into the areas of wildlife-livestock interface diseases.