TB link between badgers and cattle established Farmers have long blamed badgers for spreading TB between herds, but until now there has been direct evidence that the infection can be transmitted between the two species. Now researchers have demonstrated that outbreaks of the disease in local cattle and badger populations are linked by monitoring changes in the bacteria's DNA as it spread through a group of farms in Northern Ireland. Although the findings do not prove whether the disease was spreading from badger to cattle or in the other direction, they will strengthen calls for a widespread badger cull after the government delayed a planned extermination last month. The study, sponsored by the Wellcome Trust, analysed the genes of bacteria found in 26 cows and four badgers from a number of neighbouring farms during a decade of repeated outbreaks. Writing in the PLOS Pathogens journal, they explained that bacteria isolated from badgers were almost indistinguishable from those found in cattle on nearby farms, meaning they were very closely related. The bacteria from the two species were more closely related to each other than those taken from farms a few kilometres away, meaning the link between cattle herds was weaker. Prof Rowland Kao of Glasgow University, who led the study, said: "This study provides the first direct evidence of the close relationship between tuberculosis infections in cows and local badgers, at a very local scale. However, only with a larger study might we be able to quantify the extent and direction of transmission between cattle and badgers and reliably inform disease control policies.