Badgers Can Carry Tuberculosis Across Great Distances, Study Finds

European badgers make rare, long-distance moves than can contribute to the spread of bovine tuberculosis, or bTB, according to a new study.

The short-range movements of badgers have been well studied because of the animal's role as a carrier of bTB, but little was known about when or how they move over large distances.

To learn more, a team of researchers from Ireland and Canada set up a study area spanning 755 square kilometers of County Kilkenny in the Republic of Ireland. The four-year badger movement study was the largest spatial scale badger study of its kind ever conducted in Europe.

"To study these longer distance movements, a correspondingly large study area is required. And because very long-distance movements occur infrequently, a large sampling effort is required to pick up such events," said Andrew Byrne of University College Dublin, who led the research while at University College Cork.

Byrne and his collaborators conducted their research between 2008-2012, tagging 963 badgers at their dens and measured how far they traveled when they were captured next.

On average, the badgers were found just 2.6km from their dens, but 5 percent of those tagged were found more than 7.5km away from their dens, with the longest having made a 22.1 km journey.

"These long-distance movements may be important for 'seeding' infection, if an infected animal moves to a TB-free location. Overall, long-distance dispersal of infected badgers may allow TB bacteria, Mycobacterium bovis, to survive and persist by finding new hosts despite disease control efforts," Byrne said in a statement.

The researchers contend this study was essential for accurate modeling of the spread of infection across a badger population.

Because badgers can spread bTB to livestock, there has been a controversial effort to cull badgers around Europe, especially in the United Kingdom. With enough information on badger movements, a vaccination effort could begin to make more sense than an outright culling.

"These data could be used during the design of intervention strategies aimed at stopping the spatial spread of infection across badger populations. One approach could be to vaccinate badgers across a strip creating a 'cordon sanitaire' or a biological barrier to infected badgers immigrating into a disease-free area. Our data could be used to estimate an appropriate effective width for such a barrier," Byrne said.

The research is published in the Journal of Animal Ecology.