Detection of Mycobacterium paratuberculosis (MAP) is hampered by the slow growth of the organism and by the low numbers that they are often present in food, such as milk. Phage amplification is a novel bacteriophage-based test, which offers the opportunity to rapidly and specifically detect low numbers of MAP bacilli in milk. The test uses host specific bacteriophage to report the presence of viable MAP. Positive results are only seen if viable MAP is present and appear as plaques in lawns of a fast growing reporter helper bacteria strain that is also susceptible to the phage (such as M. smegmatis). It is expected that the MAP will be detected in 24-48 hours rather than the conventional 18 weeks taken by standard culture methods. Our study aims to develop an assay that is able to specifically and rapidly detect the presence of MAP in milk. Detection within 24 hours has been demonstrated with several culture collection strains of MAP using the phage amplification assay. We are currently exploring the effects of milk on the assay, including the identification of an inhibitor of phage attachment present in milk and the elimination of expected contaminating bacteria.