<i>Mycobacterium avium</i>ssp.<i>paratuberculosis</i>: its incidence, heat resistance and detection in milk and dairy products

Abstract

Mycobacterium avium ssp. paratuberculosis (MAP) causes Johne’s disease in cattle and other ruminants and has been implicated as a possible cause of Crohn’s disease in humans. The organism gains access to raw milk directly through excretion into the milk within the udder, and indirectly through faecal contamination during milking. MAP has been shown to survive commercial pasteurization in naturally infected milk, even at the extended holding time of 25 s. Pasteurized milk must therefore be considered a vehicle of transmission of MAP to humans. Isolation methods for MAP from milk are problematical, chiefly because of the absence of a suitable selective medium. This makes food surveillance programs and research on this topic difficult. The MAP problem can be addressed in two main ways: by devising a milk‐processing strategy that ensures the death of the organism; and/or strategies at farm level to prevent access of the organism into raw milk. Much of the research to date has been devoted to determining if a problem exists and, if so, the extent of the problem. Little has been directed at possible solutions. Given the current state of information on this topic and the potential consequences for the dairy industry, research is urgently needed so that a better understanding of the risks and the efficacy of possible processing solutions can be determined.