Epidemiological investigation of confirmed disease outbreaks indicates that breakdowns are attributable either to bought-in cattle, reactivation of the disease in animals exposed at an early stage in their lives (residual infection), wildlife (mainly badger) sources or secondary or consequential breakdowns arising from lateral spread from the primary breakdowns.
A major research project is under way which should provide more accurate data on the wildlife contribution to overall herd breakdowns.
The combined operational expenditure on the TB brucellosis programmes since 1990 is as follows: £46.6 million (1990), £41.5 million (1991), £42.2 million (1992), £39.1 million (1993), £43.4 million (1994), £47.0 million (1995) and £40.3 million (1996). It is estimated that brucellosis accounts for one sixth of the expenditure annually.