Tories push DEFRA for more PCR research

The Tory Party is pressing DEFRA secretary Hilary Benn to adopt a test which can identify disease infected badger setts as a mainstay in the fight against bovine tuberculosis.

Shadow junior DEFRA minister Jim Paice explained that if it could be demonstrated that only diseased setts would be targeted then the Polymerase Chain Reaction test could be vital in helping to defuse public opposition to a cull.

Explaining the political difficulty the government faces Mr Paice said: “Farmers need to understand that any government making a decision on badgers needs to take account of public opinion.  The PCR could help diffuse public opposition to a cull if it could be persuaded only diseased setts would be targeted: the PCR test would enable us to do that.”

But it would not be achieved without cost to the farming industry, he said.  “There will be expense and inconvenience to farmers, but you can’t expect government to shoulder it all.”  No government, he added, would stand by while allowing the cost to continue escalating as it is.

He said the Tories had always favoured a comprehensive strategy that sought to address disease spread in both cattle and wildlife.  Speaking about the final report of the Independent Scientific Group on cattle TB he said DEFRA should accept its recommendations.

“The government has seen this coming for a number of years.  It should get on and accept the recommendations of the report regarding cattle measures and just consult on the detail of how to implement them.  Then it should trial the PCR test to consider its usefulness, if it proves unhelpful we are no worse off, but it could be extremely beneficial to policy.

The test is not new.  The British army is currently using a version in Iraq and America has made widespread use of it in its efforts to identify deer populations infected with TB.

In the UK its use in identifying infected badger setts is being pioneered by researchers at Warwick University.

In an academic paper published last year the researchers claim to have detected MTBC (a group of M. tuberculosis strains that includes M. bovis) in soil of badger setts on 78% of 60 farms sampled and in 56% of badger latrines on nine farms sampled.  The biologists then carried out a second test to ensure the strain detected was indeed M. bovis. 

On contaminated farms an average 43% of setts and 29% of latrines tested positive.  These results led the researchers to conclude that once the organism is excreted in to the environment by cattle, badgers, or other wildlife, it could act as a source for further transmission.

However, Orin Courtenay, one of the researchers at Warwick, warned that the test is not conclusive proof and observers should not consider it a panacea to tackling the issue of TB.

The suitability of the test in identifying infectious sources of TB is also questioned by Chris Cheeseman, a wildlife ecologist at the Central Science Laboratory, who described the attention surrounding the PCR test as “completely over-hyped”.

Although the test can confirm the presence of M. bovis in soil, questions remain over its ability to distinguish between live M. bovis DNA and dead DNA.

“Finding M. bovis-positive soil near a badger sett does not necessarily mean that the bacteria came from a badger,” said Dr Cheeseman.  “Even if it were possible to show it came from a badger it does not mean that the badger responsible came from that social group. 

“Forays are common, especially by boars in the breeding season – our genetic research has shown that 54% of cubs born are sired by boar badgers from other social groups.”

“A targeted culling strategy employing a diagnostic technique like PCR would result in piece meal culling which would be a recipe for perturbation.  This could spread and worsen the overall disease situation,” he added.