AWWA PATH56556

The causes of Crohn's disease have been the subject of much microbiological and epidemiological interest over the last thirty years. There is some microbiological and clinical data that suggests that Mycobacterium avium subsp. paratuberculosis (MAP) is involved with the pathology of this disease, and possibly even its causation. One of the reasons for particular interest in MAP is its role on Johne's disease in herbivores, and the relative similarity of the pathology of the two conditions. However, Crohn's disease appears to have a genetic component and causation may be from multiple factors. Experimental work growing MAP from pasteurized cow's milk has lead to concerns that people may be exposed to this organism through the food chain. As many agricultural animals excrete large numbers of MAP in their faeces it is reasonable to imagine that source waters for drinking water supplies may be contaminated with this organism. Attempts at cultivation have so far not resulted in the isolation of MAP from drinking water in England. There are technical difficulties in isolation from both clinical and environmental samples that make confirmation of the causative role of MAP in Crohn's disease and the assessment of environmental exposure difficult. It is likely that water will prove to be one of a number of sources from which people are exposed to MAP. While there is little current evidence that improving drinking water treatment will have any impact on the incidence of Crohn's disease, water companies and utilities should consider whether any action is required to adopt a more precautionary approach. Includes 37 references.