Scientists last night claimed to have produced the clearest evidence yet that bovine tuberculosis does spread between cattle and badgers. Many West Country farmers welcomed the study, but say it merely supports what they already knew.
It comes as new Defra figures released yesterday show the number of cattle slaughtered due to TB had risen again. The statistics show 24,685 cattle were slaughtered to August this year, compared with 23,477 during the same period in 2011, and 21,390 in 2010.
Scientists mapped the genetic blueprints, or genomes, of bacteria from 26 cows and four badgers during bovine TB outbreaks in Northern Ireland.
The analysis made it possible to trace changes in the bacteria’s DNA as it passed from animal to animal.
It revealed that bacteria taken from badgers and cows were closely related at the farm level.
Bacterial strains obtained from badgers and nearby cattle farms were often indistinguishable.
The findings, published in the scientific journal Public Library of Science Pathogens, shed no light on the direction of transmission – whether from badgers to cows or cows to badgers.
Lead scientist Professor Rowland Kao, from the University of Glasgow, 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.”
Bacteria from single outbreaks were usually closely related, the study showed. But different herd outbreaks were usually characterised by genetically distinct bacteria.
Controversial plans for a mass badger cull in west Somerset and Gloucestershire to curb the spread of bovine TB have been postponed until next summer.
Opponents, including the RSPCA and Queen guitarist Brian May, argue that a cull would be ineffective and inhumane.
Last night James Small, Somerset county chairman of the National Farmers’ Union said: “This is support for what most farmers already know, that there is a clear link between the spread of TB and wildlife and cattle.
“If cattle can transmit to badgers then it’s not a one-way street. Badgers can transfer it back again and all we can say as an industry is that we are tackling to the best of our ability the disease within cattle and we are still not tackling it in the wildlife.
“This proves a link between the two and we seriously need to be addressing the wildlife reservoir.”
Mr Small estimates that TB cost him £15,000 this year when the beef shorthorn suckler herd side of his business was shut down after a positive TB test in January. David Barton, who farms near Cirencester, slaughtered 44 of his 156-strong herd this year. Last night he said he would decide after tests next month whether to give up his herd.
A Defra spokesman said: “This research adds to existing scientific evidence that bTB is transmitted between cattle and badgers.
“No country in the world has successfully got to grips with the spread of this disease without tackling it in the wildlife population.”