Scientists at the University of Glasgow and the Agri-Food and Biosciences Institute in Northern Ireland used next-generation genome sequencing technology (NGS) to trace mutations of the bovine TB bacteria – Mycobacterium bovis – as it passed between animals over a 10-year period.
They found that bacterial isolates found in badgers were often “indistinguishable” from those found in cattle on nearby farms, which the authors said provided evidence of transmissions between the two hosts. However, they added that the role of the badger population in cattle infection was still unclear, because TB can also be spread by cattle to badgers.
Professor Rowland Kao, a Wellcome Trust Senior Research Fellow at the University of Glasgow who led the study, said: “While the study was small, it provides the first direct evidence that the epidemic in the two species are closely linked at the farm scale and highlights the potential for use of NGS as a tool for disentangling the impact of badgers and cattle on TB.
“However, only a larger study will allow us to quantify the extent and direction of transmission between cattle and badgers and reliably inform disease control policies.”
The research, which was journal PLoS Pathogens, comes as new Defra figures revealed that the number of cattle slaughered due to TB between January and August has increased for the third consecutive year. According to the data, 24,685 cattle were slaughtered in the first eight months of 2012, compared to 23,477 in the same period in 2011, and 21,390 in 2010.
However, the Badger Trust insisted the study did not provide any evidence that culling badgers would help eradicate TB in cattle. The charity said it has been known for some time that the disease can exist in both species in the same area, but added that previous research had shown that culling did not lead to “meaningful” reductions in TB infection in nearby cattle herds.
David Williams, chairman of the Badger Trust, said: “The question is not whether badgers get bTB or even whether it passes between them and cattle but how to eradicate the epidemic. Killing badgers cannot do that and may make matters worse, This disastrous mess clearly has its historic roots in the cattle industry and was spread by careless and stubborn behaviour over many years.
“This new work is valuable in verifying an important aspect of the scientific background to bTB in this country but it is not proof that badgers give bTB to cattle or that the opposite is the case.”