Inflammatory bowel disease is caused in part by something patients are exposed to, but what exactly is still not certain. However, an IBD cluster in the town of Forest, VA provides strong evidence that a bacterium called MAP can cause IBD — and it comes from cow poop.
The Forest cluster was documented in a 2011 study published in the journal Gut Pathogens.* The cluster included 15 children — 11 with Crohn’s disease and 4 with ulcerative colitis, in a population of 8,000 people:
This represents an incidence rate of 217 cases per 100,000 children per year; more than 47 times the expected rate.
The study authors estimate as many as 45 more adults in the area might have IBD or a similar illness.
Forest is in Virginia cattle country, and the investigators quickly homed in on a culprit: Mycobacterium avium subspecies paratuberculosis (MAP). This bacteria is common in cattle, where it causes an IBD-like disease.
MAP can be transmitted from cow to cow in a number of ways, but usually through fecal contact. This can include water contaminated with cattle feces. Humans can be exposed to MAP in similar ways:
MAP is present and may be concentrated in drinking water due to the organism’s resistance to chlorination and its growth in biofilms and on metallic water pipes. We postulate that in our outbreak, individuals inhaled aerosolized MAP from contaminated water in the river or creek tributaries near their homes.
…Nine of our eleven children with Crohn’s disease were young males at the time of their diagnosis, in distinction to previous literature suggesting boys are perhaps twice more likely than girls to develop Crohn’s disease [sic]. The marked male predominance in our patients may reflect the fact that boys are more likely to play in creeks and streams than girls, but it may also be due to immunological differences between boys and girls putting boys at risk for particular infectious illnesses.
The authors and families involved contacted the Virginia Department of Health and the Centers for Disease Control and Prevention, but neither agency did any further work on the cluster. That’s unfortunate, because there is clearly more research needed.
We don’t know what causes IBD, but the Forest cluster is strong evidence that MAP can play a role.
*The study is Pierce, E.S.; Borowitz, S.M.; and Naser, S.A. “The Broad Street pump revisited: dairy farms and an ongoing outbreak of inflammatory bowel disease in Forest, VA.” Gut Pathogens 3:20 (2011).
Photo “cow’s arse” by Flickr user rhys000 used under Creative Commons license.