Mycobacterium aviumsubsp.paratuberculosisin the Catchment Area and Water of the River Taff in South Wales, United Kingdom, and Its Potential Relationship to Clustering of Crohn's Disease Cases in the City of Cardiff

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Abstract
In South Wales, United Kingdom, a populated coastal region lies beneath hill pastures grazed by livestock in whichMycobacterium aviumsubsp.paratuberculosisis endemic. The Taff is a spate river running off the hills and through the principal city of Cardiff. We sampled Taff water above Cardiff twice weekly from November 2001 to November 2002.M. aviumsubsp.paratuberculosiswas detected by IS900PCR and culture. Thirty-one of 96 daily samples (32.3%) were IS900PCR positive, and 12 grewM. aviumsubsp.paratuberculosisbovine strains. Amplicon sequences from colonies were identical to the sequence with GenBank accession no.X16293, whereas 16 of 19 sequences from river water DNA extracts had a single-nucleotide polymorphism at position 214. This is consistent with a different strain ofM. aviumsubsp.paratuberculosisin the river, which is unculturable by the methods we used. Parallel studies showed thatM. aviumsubsp.paratuberculosisremained culturable in lake water microcosms for 632 days and persisted to 841 days. Of four reservoirs controlling the catchment area of the Taff,M. aviumsubsp.paratuberculosiswas present in surface sediments from three and in sediment cores from two, consistent with deposition over at least 50 years. Previous epidemiological research in Cardiff demonstrated a highly significant increase of Crohn's disease in 11 districts. These bordered the river except for a gap on the windward side. A topographical relief map shows that this gap is directly opposite a valley open to the prevailing southwesterly winds. This would influence the distribution of aerosols carryingM. aviumsubsp.paratuberculosisfrom the river.