There is fresh insight into the ongoing bovine tuberculosis (TB) outbreak in the U.K. regarding how the disease may be spreading among cattle herds and badger populations.
According to new research conducted by the University of Edinburgh's Roslin Institute, TB in cattle and badgers passes between members of the same species at least twice as often as it does between a cow and badger.
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 the study, which was conducted at a site where infections occur frequently in both cattle and badgers.
Roslin researchers analyzing genetic data from the bacteria that cause the disease also found that cattle are approximately 10 times more likely to catch TB from badgers than badgers are to catch it from cattle.
They said the findings of the research — which was conducted in Gloucestershire, U.K., over a 15-year period — could improve control strategies, reduce disease transmission and cut associated costs.
Bovine TB is an infectious respiratory disease of cattle that is spread mainly 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 people, deer, goats, pigs, cats and dogs. (Most human cases of TB are caused by Mycobacterium tuberculosis.)
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, Roslin said.
The researchers analyzed the entire genetic makeup of the bacteria from 230 badgers and 189 cattle using whole-genome sequencing. They combined this with detailed information on where the cattle and badgers lived, when they were infected and whether they could have had contact with one another, the institute explained.
The researchers were then able to estimate how often the two species spread TB. They found that badgers play an important role in disease maintenance in this area.
"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," said professor Rowland Kao, chair of veterinary epidemiology and data science at Roslin. "This would allow for a more targeted control of tuberculosis in cattle and badgers, aiding efforts to control the disease and reduce the impact on the badger population."
The work was led by Roslin experts, with collaborators from institutions including the U.K. Animal & Plant Health Agency, the University of Glasgow and University College Dublin.
The study, published in the journal eLife, was funded by the U.K.'s Biotechnology & Biological Sciences Research Council, the Department for the Environment, Food & Rural Affairs and the Wellcome Trust.