Mycobacterium avium subsp. paratuberculosis in animal-derived foods and the environment.

Abstract This book chapter summarizes current evidence for the presence of MAP in animal-derived foods, describes the effect of various dairy processes on MAP survival, and reviews the reservoirs of MAP infection in the environment and the various mechanisms potentially aiding its survival for long periods. Viable MAP have been successfully cultured from, or MAP DNA detected in, a range of animal-derived food products and drinking water. It is difficult to conclude that humans are not being exposed to MAP-contaminated milk and dairy products on the basis of this evidence.However, whether the level of MAP exposure exceeds a safe level remains unknown. Results of culture-based studies do not paint an accurate picture of the risk of consuming viable MAP, since these methods underestimate the true number of organisms present in any particular sample. Factors such as the adverse effect of chemical decontamination on the viability of some of the MAP present and overgrowth of cultures by other bacteria potentially masking the presence of MAP colonies may also lead to underestimates of MAP presence. In recent years, more sensitive and rapid phage-based and real-time qPCR methods for detection and quantitation of MAP have been developed. Despite the fact that further validation of the phage-based assays is still needed, as these improved detection methods have been adopted for food and drinking water surveillance, a clearer picture regarding levels of MAP present in, and hence risk of human exposure to this pathogen via, animal-derived and the environment is emerging.