UK study finds TB 10 times more likely to transmit from badgers to cows than in reverse

Tuberculosis in cattle and badgers passes between members of the same species at least twice as often than between cow and badger, a UK and Irish study has found.

The study, published in the journal eLife, was funded by the Biotechnology and Biological Sciences Research Council, Defra and the Wellcome Trust.

The work was led by experts from the Roslin Institute, with collaborators from institutions including the Animal and Plant Health Agency, the University of Glasgow and University College Dublin and saw scientists perform whole-genome sequencing on the bacteria from 230 badgers and 189 cattle.

Using data from an undisturbed population of badgers in Woodchester Park in Gloucestershire and nearby cattle farms, this study provides the first direct evidence of transmission between badgers and cattle.

Disease spread within badger populations and within cattle herds happens at least twice as frequently as transmission from one species to the other, according to a study at a site where infections occur frequently.

Researchers also found that cattle are approximately 10 times more likely to catch TB from badgers than badgers are to catch it from cattle.

Scientists say the findings of the research – which was conducted in Gloucestershire over a 15-year period – could improve control strategies, reduce disease transmission and cut associated costs.

Transmission

Bovine TB is an infectious respiratory disease of cattle which many scientists believe is mainly spread through inhaling infectious particles in the air.

It is caused by the bacterium Mycobacterium bovis, which can also infect and cause disease in other mammals, including humans, deer, goats, pigs, cats and dogs.

Researchers combined whole-genome sequencing with detailed information on where the cattle and badgers lived, when they were infected, and whether they could have had contact with one another.

They were then able to estimate how often the two species spread TB. They found that badgers play an important role in the maintenance of the disease in this area.

Prof. Rowland Kao, chairman of Veterinary Epidemiology and Data Science, the Roslin Institute, University of Edinburgh, said: “Current approaches to controlling bovine tuberculosis only discriminate at a very coarse, regional level between areas where badgers are more likely to be involved in infecting cattle from areas where they are not.

“This work identifies genetic signatures that could guide the interpretation of similar data if collected in other, less-intensively studied areas.

“This would allow for more targeted control of tuberculosis in cattle and badgers, aiding efforts to control the disease and reduce the impact on the badger population.”