FARMERS illegally wrecking badger setts in an attempt to reduce bovine TB may actually exacerbate the threat posed by the disease, a study has found.

Academics from Glasgow have found that disturbing badger habitats contributes to new outbreaks of the infection in nearby herds.

The study has found the most likely reason "low-level persecution" does not have the desired effect for farmer is that disruption in the social structure of the badger population results in increased spread of bovine TB to cattle from infected animals.

Bovine Tuberculosis or bTB has proven difficult to control and eradicate in cattle, costing the UK Government more than £100 million per annum in testing, slaughter and compensation.

Although badgers are an acknowledged contributor to the persistence and spread of bTB in British and Irish cattle, culling trials in the UK and Ireland have failed to show definitive benefits.

Professor Rowland Kao, of the Boyd Orr Centre for Population and Ecosystem Health at Glasgow University, said: “What we know from the randomised badger culling trial that intense culling of badgers over a small area can have an overall negative impact on cattle btB; here, we show that badger persecution over a very broad area does not appear to reduce the risk for cattle. Further it is illegal, and may even make matters worse.”

Dr David Wright, who led the study, said: “Whilst the incidence of badger persecution was low, we hypothesised that those taking pre-emptive action against badgers may contribute to maintaining the disease."

The Institute for Global Food Security at Queen's collaborated with Glasgow University and the Agri-Food and Biosciences Institute in the research project, which was funded by the Wellcome Trust.

The study found that around five per cent of setts in Northern Ireland show signs of human interference.

Evidence included digging indicative of badger baiting, sett entrances being blocked with soil, boulders and branches or being pumped full of slurry and setts being ploughed over or having farm debris dumped on top.

Pilot culling projects in England have been branded a failure by some scientists.

The new study, published in the scientific journal Natural Scientific Reports, focused on farmers who have acted outside the law in an effort to eradicate the disease.

The researchers found the risk of bovine TB was "significantly elevated" in areas of high badger social group density and high rates of persecution through sett interference

The new study found that farm-level risk factors, including the number of cattle movements, frequency of international cattle imports, previous bovine TB history and the proximity of neighbouring farms with a bovine TB history were far more strongly associated with new outbreaks than measures of the badger population or badger persecution.

The scientists said that suggested disease control could be improved further by increased frequency and accuracy of cattle testing, development of more sensitive tests and improved farm biosecurity.

Dr Neil Reid, lecturer in Conservation Biology at Queen's University, said: "The relationship between badger persecution and bovine TB in cattle could either be because persecuting badgers perturbs the population stimulating spread of the disease or farmers are more likely to persecute badgers if their livestock have previously had a TB breakdown.

"We can't say which way round the relationship is but we can say that persecuting badgers certainly does not lower TB risk in cattle, it is illegal and may make the situation worse. Farmers should be aware of the risks incurred by disturbing badger setts."