Today I want to recommend an article on animal-health-online: Israeli scientists found out that Mycobacterium avium paratuberculosis (MAP) is able to penetrate cells of the human intestinal mucosa. At the and of the article you find further links about this issue, including a video (in English) on you tube about the connection between Morbus Chron and Johnes Disease.
http://www.animal-health-online.de/gross/2009/01/13/wissenschaftler-paratuberkuloseerreger-map-dringt-aktiv-in-menschliche-darmschleimhaut-ein-und-lost-schwere-entzundungen-aus/10542/#more-10542