Following numerous reports of emaciated and scouring adult free-ranging deer in Virginia, Johne's disease was diagnosed in a 2 year old free-ranging while-tailed deer (Odocoileus virginianus) based on histopathology and culture of Mycobacterium avium subspecies paratuberculosis from frozen hepatic tissue. Clinical and pathologic findings were consistent with advanced Johne's disease: emaciation; diarrhea; severe, chronic, diffuse granulomatous colitis with acid-fast bacilli within macrophages. These findings are consistent with previous reports of Johne's disease in cervids. Subsequent targeted surveillance of nine emaciated adult deer with diarrhea as well as active surveillance of 65 asymptomatic deer for Mycobacterium avium ss. paratuberculosis using culture for multiple tissue types plus serology did not confirm any additional cases of infection. This appears to be an isolated case of Johne's disease in a free-ranging white-tailed deer, and deer from this region do not appear to represent a reservoir for the organism. The origin of infection was most likely domestic animals. Stressors such as high deer population density and low nutritional quality of the habitat may have contributed to the development of clinical disease in this case. Clinical symptoms identical to what is seen with Johne's disease in numerous animals are insufficient evidence to establish a diagnosis of widespread M. paratuberculosis infection in a free-ranging deer population.

Key words: Johne's disease, Mycobacterium avium subspecies paratuberculosis, Odocoileus virginianus, White-tailed deer.