Badger culls across areas less than 300km2 would be ineffective and almost certainly make matters worse, the government’s chief adviser on bovine TB has warned.

“The science says cull over large areas, very systematically and for a long period of time,” said John Bourne, chairman of the Independent Scientific Group.

The admission came after the ISG felt obliged to send a letter to stakeholders regarding the government consultation (News, 16 December).

According to the ISG two of the three badger culling options outlined in the government consultation “would seriously worsen the [TB] situation… and that the consultation paper fails to make this clear”.

“There are no scientific data to support suggestions in the consultation paper that targeted culling with co-ordinated farming groups would reduce the risk of perturbation, or that culling efficiency would decrease the edge effect in non-culled adjoining areas.”

It also dismisses as “without foundation” the claim in the consultation that differences in the edge effect [where the incidence of TB breakdowns rises in herds on the periphery of a culling zone] may be due to differences in cattle management techniques.

Instead, the ISG supports a “general” cull on the basis of supporting scientific data.

“Systematic and prolonged culling extending to areas of 300km2 or more could be expected to have an overall positive impact on cattle herd breakdown rates, if adequately resourced and co-ordinated to ensure high coverage, though the benefits may not exceed the costs,” says the ISG’s letter.

According to Prof Bourne, culling zones of 100km2 would deliver zero benefit while zones of 300km2 could yield up to a 25% reduction in the incidence of TB among cattle.

With badgers responsible for up to 50% of transmission, this “goes a long way to getting the cattle problem under control”, he said.

Robert Forster, chief executive of the National Beef Association, added his support to the ISG’s comments.

“The letter is conclusive in demonstrating the size of the task we face.

Large culling areas of 300km2 or more are exactly what it will take to stop the 18% year-on-year increase in the disease and nobody should be so naive as to believe anything less will succeed.”

But David Williams, chair of the Badger Trust, seized on the letter as a chance to rubbish claims that a badger cull would reduce the incidence of TB.

“This extraordinary letter blows a massive hole in DEFRA’s claims to be basing its policies on sound science.

It is increasingly clear that the so-called “consultation” over badger culling is simply a smokescreen for DEFRA’s vets, who are obsessed with killing wildlife and have already decided to exterminate tens of thousands of badgers.

“Killing badgers on the scale required is clearly uneconomic and logistically impossible.

DEFRA should abandon this fatally flawed consultation and get on with addressing the real problem of cattle-to-cattle transmission of tuberculosis.”

andrew.watts@rbi.co.uk