University of Wisconsin–Madison

Johne’s in captive deer

Research Report

Dr. Mitch Palmer and colleagues from the USDA-ARS National Animal Disease Center in Ames, IA, USA. just published an article describing diagnostic testing patterns for paratuberculosis in a captive white-tailed deer farm in the U.S. The publication titled “Characteristics of subclinical Mycobacterium avium ssp. paratuberculosis infection in a captive white-tailed deer herd“ appears in the Journal of Veterinary Diagnostic Investigations; first published online September 11, 2019.

Paratuberculosis (Johne’s disease) is caused by Mycobacterium avium ssp. paratuberculosis (MAP), and affects both domestic and wild ruminants, including cattle, goats, sheep, and deer. In cattle, most infections occur during calfhood followed by a prolonged incubation period of 1–2 y or more before cows shed culturable numbers of MAP bacilli in their feces. As disease progresses, infected animals develop protein-losing enteropathy, intractable diarrhea, and weight loss. In a cohort of 32 clinically normal deer from a herd with a history of periodic clinical paratuberculosis, we found that subclinical infection was characterized by high rates of infection, common involvement of mesenteric lymph nodes, minimal lesion formation, few intralesional acid-fast bacilli, and low-level fecal shedding of MAP. The characteristics of subclinical paratuberculosis in white-tailed deer resemble those of cattle and red deer, although microscopic lesions were less common in subclinical deer than reported for subclinical cattle, and we did not see necrotizing granulomas as described in subclinical red deer and elk.

Comment: This is another important contribution that highlights how different animal species handle MAP infections differently and that a prolonged period where animals are infectious (shedding MAP in feces) while appearing clinically normal fosters continued spread of the infection within and among animal herds. Unfortunately this article is not open access.