Badgers Responsible For Half Of Tuberculosis Found In Cattle
October 11, 2013

Badgers Responsible For Half Of Tuberculosis Found In Cattle

Lee Rannals for - Your Universe Online

A new study published in the journal PLoS Currents: Outbreaks suggests that badgers are responsible for a large number of tuberculosis (TB) cases in cattle in certain areas.

Researchers estimate that badgers ultimately account for 52 percent of cattle TB in areas where prevalence in cattle is high. However, only around six percent of infected cattle catch TB from badgers; the remaining number of cases is a result of transmission of the disease between cattle herds.

“These findings confirm that badgers do play a large role in the spread of bovine TB. These figures should inform the debate, even if they don’t point to a single way forward," Professor Christl Donnelly, from the Medical Research Council Centre for Outbreak Analysis and Modelling at Imperial, said in a statement.

Scientists have debated the role badgers play in spreading bovine TB, and whether or not the animals should be culled to control the disease. The Randomized Badger Culling Trial found that culling could reduce TB in herds inside culled areas, but may also increase TB risk in nearby areas at the same time.

Previous mathematical models were based on data from the trial, which ran from 1998 to 2005. These models were used to calculate an estimate of the proportion of TB in cattle that could ultimately be attributed to transmission from badgers.

Although the team projects that badgers could account for half of TB infection in cattle, they said that the minimum estimate could go as low as 38 percent.

Researchers estimate that if a single big cull were to occur, ranchers could expect a 16 percent reduction in cattle TB over several years in areas where TB prevalence is high. This estimate is based on if at least 70 percent of badgers were to be culled in those areas.

"This is the big question," Donnelly told The Guardian. "There are ethical, animal welfare and economic aspects, in addition to health and safety issues, that must be considered. However, science can provide quantitative predictions for many of the important 'what if we?' questions."

She said that during the Randomized Badger Culling Trial 16.6 percent of the badgers culled during those years were found to test positive for TB, indicating that about 33 percent were actually infected because the standard postmortems missed half of the infections compared with extended postmortems.

Wales rural affairs minister Elin Jones said in 2008 that badgers would need to be eradicated in certain areas in order to prevent a tuberculosis outbreak.

In 2009, thirty scientists from the British government were tested for tuberculosis after a scientist was infected from a badger. The scientists were involved in studying the spread of bovine TB for the Department of Environment, Food and Rural Affairs.