Most consumers of dairy products accept that pasteurization provides a guarantee that products are safe to eat and drink. However, research  using a new highly sensitive technology has revealed that live mycobacteria can exist in retail milk even after pasteurization and explains how this may happen. Live Mycobacterium avium subspecies paratuberculosis (MAP) - which causes Johne’s disease in cattle and has been implicated in Crohn’s disease in humans - was found in just over 10% of shop-bought pasteurized milk samples that were tested in the UK. The prevalence of MAP is higher than previous studies have shown due to the high sensitivity of the new phage-based technology that was used to conduct the milk testing. In the study of 386 samples of retail-purchased milk, Actiphage was able to detect live mycobacteria at levels as low as 1-2 cells per 50ml in comparison to other tests that cannot detect cell-counts lower than 100 cells. There is a growing body of research that implicates MAP in the development of Crohn’s disease , with MAP found in the bowel tissue of a proportion of patients with the condition. Although no causal relationship between MAP and Crohn’s has been directly established the dairy industry recognizes that limiting human exposure to MAP would be sensible on a precautionary principle . Furthermore, there are clinical trials underway with anti-mycobacterial drugs that are directly assessing the benefit in Crohn’s disease. Some retailers are already removing dairy farmers from their milk pool if they are not engaged with Johne’s control plans.