There might be, but for now there is only theory, based on an understanding of how the microbe infects dairy cattle and how it potentially can be transmitted. Collins points out that MAP not only attacks the intestinal tract of dairy cattle but that it is also present in blood and many organs of the body. The focus, however, is not on fecal matter but on lymph nodes of dairy cattle, where the bacterium can be concentrated. Weber says his group is also involved in the design of a study that will focus on the types of cooking practices that might kill MAP in ground beef. It is also plausible that MAP gets into in tap water.
Cows excrete the bacteria, and it can run into streams and city water supplies.
The next big question is whether MAP is a trigger for Crohn's disease. Here again, there is considerable debate. A review of the peer-reviewed studies to date shows that at least seven of 10 that involved testing for MAP in diseased gut tissue obtained from surgery showed a statistically significant association between a positive test and Crohn's. Others warn that any form of diagnostic tests for MAP may be limited in that they may also be picking up signs of other biological materials. Also, experts in Crohn's disease have long taken the position that the disease, whose cause is not clear, is set off by the body's immune system attacking itself, possibly due to a genetic factor, and that a microbial trigger is not necessary.