An Unusual Encounter: Mycobacterium Paratuberculosis Infection in Wild Sheep

Johne's disease (JD), paratuberculosis, is a chronic and debilitating intestinal disease affecting ruminants, caused by Mycobacterium avium subspecies paratuberculosis (MAP). Although JD has been extensively studied in domestic livestock, its prevalence and impact on wildlife in Iran, particularly among wild sheep, remain underexplored.

This study presents the first documented cases of JD in two free-ranging, 3-year-old Isfahan wild sheep (Ovis orientalis isphahanica), which exhibited weight loss, hyperthermia and neurological symptoms, including paddling movements. The sheep developed acute watery diarrhoea and severe emaciation, culminating in death. Diagnostic evaluations-including haematology, clinical chemistry, gross pathology, histopathology and microbiology-revealed hypoproteinaemia, hypoalbuminaemia, regenerative anaemia and leukocytosis, all indicative of chronic infection. Necropsy findings highlighted pulmonary congestion, mesenteric lymphadenopathy and gastrointestinal thickening, whereas histopathology showed epithelioid macrophage infiltration and substantial intestinal oedema. Molecular analysis via endpoint polymerase chain reaction (PCR) confirmed the presence of MAP DNA in tissue samples.

This report is the first to document JD in wild sheep in Iran, underscoring the potential role of MAP as a disease reservoir in wildlife. The findings emphasize the need for epidemiological surveillance of JD in wildlife and the importance of understanding its potential cross-species transmission risks.