Our research focuses on Johne's disease and other mycobacterial diseases of animals encompassing both tuberculous and non-tuberculous infections. Johne's disease caused by Mycobacterium avium subsp. paratuberculosis (MAP) is a chronic granulomatous enteritis of ruminants characterized by persistent diarrhea, decreased milk production and progressive weight loss leading to death. Diagnosis of Johne's disease is often challenging due to the prolonged incubation period and great individual variability in subclinical and clinical disease expression. In the subclinical stage, infected animals become infectious by starting to shed MAP in their feces, thereby contributing a steady contamination to the environment and disease transmission. One of our research objectives is to develop a molecular-based test for the early detection of fecal shedders in the herd.Pathogenic mycobacteria including MAP can reside in host cells for extensive periods and have mechanisms to protect themselves against a variety of antimicrobial activities of the host immune defenses. We also focus on basic research to understand pathogenesis of mycobacterial diseases, as well as host response to infection. Other focus of our research is to monitor and characterize the epidemiology and transmission dynamics of mycobacterial diseases in domestic and wild animals.