Badger culling to control TB in cattle has mixed effects

According to a letter published in Nature, widespread culling of badgers caused a 19 per cent reduction in the incidence of cattle TB in the areas culled, but also led to a 29 per cent increase of TB in surrounding areas. The researchers suggest the increase is caused by the remaining badgers roaming more widely.

The team had previously found that localised ’reactive’ culling increased TB incidence in cattle by 27 per cent. Ecological data suggests that increased badger movement caused both increases in TB incidence. Where badger population densities were reduced by culling, their usual territorial organisation broke down and the remaining badgers travelled longer distances potentially encountering more cattle.

Professor Christl Donnelly, from Imperial College London and first author, said: “The fact that widespread culling has both simultaneous negative and positive effects could have important implications for policies to control TB in cattle. Although we believe very large culling areas would act to reduce TB, it is not clear whether this would prove economically and environmentally sustainable.”

Bovine tuberculosis can have serious consequences for cattle herds, and if found to be infected, cattle are compulsorily slaughtered. Although the infection can be spread from cattle to humans, the risk is extremely low due to routine testing of cattle for infection and pasteurisation of milk and milk products.