Badgers (Meles meles), cattle and bovine tuberculosis (Mycobacterium bovis): a hypothesis to explain the influence of habitat on the risk of disease transmission in southwest England.

Badgers are believed to be responsible for a high proportion of the cases of bovine tuberculosis in cattle in southwest England where, despite the onset of badger control operations in 1975, comparatively high numbers of cattle continue to fail the tuberculin test. To determine why the disease remains a problem in these areas, data on badger densities and patterns of land use were examined. Areas subject to repeated badger control operations had greater landscape heterogeneity and a higher density of linear habitat features. These habitat features were not related to badger density, measured as the mean number of social groups per square kilometre. Environmental contamination by infected badger urine is thought to be the main mode for the transmission of bovine tuberculosis. Field studies in an area with tuberculosis in both badgers and cattle showed that badgers may urinate on pasture after crossing through a linear feature, and that the number of these crossing-point urinations increases with the number of linear features crossed. The hypothesis is presented that these crossing-point urinations are a major source of bovine tuberculosis infection in cattle, and that areas with increased numbers of linear features have greater levels of contamination of pasture with badger urine and hence increased opportunities for disease transmission.