Introduction of bovine tuberculosis to north-east England by bought-in cattle

The source of bovine tuberculosis was investigated in 31 herds in north-east England that experienced confirmed breakdowns between January 2002 and June 2004; nine of the herds had been restocked after the UK outbreak of foot-and-mouth disease in 2001. In all but one of the breakdowns the most likely source of infection was identified as one or more purchased animals. In 17 of the breakdowns, reactor animals were traced to herds from which the same combination of spoligotype and variable number tandem repeats was isolated, and in five breakdowns a different spoligotype was isolated. The most likely sources were located in Wales and the west and north of England, and included a Cheshire herd that was the most likely source of nine of the breakdowns. Three breakdowns were traced to Irish imports. Reactors in five of the breakdowns included homebred as well as purchased animals, providing evidence for the likely spread of the disease within the herds. The lack of geographical clustering of molecular types pointed to the overwhelming source of infection being cattle that had been bought-in.