The microorganism, mycobacterium avium subspecies paratuberculosis, has been established in the veterinary literature to be the cause for Johne's disease, a disease causing colitis in cattle, sheep, and subhuman primate species. This disease resembles, clinically, Crohn’s disease in humans and acts very much the same. Studies in England and in Wales have shown the presence of mycobacterium paratuberculosis in milk and water supplies. It is known that infected cows secrete this bacteria in milk and hence, milk borne infection appears to be theoretically possible.
It is thought that the Mycobacteria make their way into the body’s system via cows’ milk and other dairy products. In cattle it can cause an illness called Johne's disease - a wasting, diarrhoeal condition. Until now, however, it has been unclear how this bacterium could trigger intestinal inflammation in humans.
Professor Jon Rhodes, from the University’s School of Clinical Sciences, explains: “Mycobacterium paratuberculosis has been found within Crohn’s disease tissue but there has been much controversy concerning its role in the disease. We have now shown that these Mycobacteria release a complex molecule containing a sugar, called mannose. This molecule prevents a type of white blood cells, called macrophages, from killing internalised E.Coli.”
Scientists have previously shown that people with Crohn’s disease have increased numbers of a ‘sticky’ type of E.coli and weakened ability to fight off intestinal bacteria. The suppressive effect of the Mycobacterial molecule on this type of white blood cell suggests it is a likely mechanism for weakening the body’s defence against the bacteria.
Professor Rhodes added: "We also found that this bacterium is a likely trigger for a circulating antibody protein (ASCA) that is found in about two thirds of patients with Crohn's disease, suggesting that these people may have been infected by the Mycobacterium."
As part of his research, Dr. Rioux is focusing on the MAP bacteria. He believes it's plausible the bacteria may be a trigger for Crohn's disease. A recent study showed it was present in the intestines of some Crohn's patients."It found there was a significant association, finding this mycobacterium in Crohn's patients versus those who do not have Crohn's disease...we can see the footprints of this organism associated with Crohn's disease, but we can't really prove it's at the scene of the crime so to speak," adds Dr. Rioux.The Dairy Farmers of Canada says a Guelph, Ontario study in 2002 found the bacteria in Ontario milk, though it wasn't alive. Yet a 2005 study in the United States did find live bacteria in almost 3% of retail milk sampled."It can survive pasteurization in a limited number of samples, and only in low numbers, so that would not explain the high numbers of Crohn's disease patients we have in the developed world at all," says Barkema.The Food Directorate of Health Canada calls MAP an "emerging organism of concern." At a recent meeting in Ottawa, it called for more research and testing of food products, to see just how often MAP is found in the products we consume.