Question
To ask the Secretary of State for Environment, Food and Rural Affairs pursuant to the Statement of 7 July 2008, Official Report, columns 1157-8, on bovine TB, if he will publish the evidence which underlay his evaluation of the PCR test reported to the House on 7 July 2008.
Answer
[holding answer 15 July 2008]: A number of diagnostic tests for the detection of Mycobacterium bovis (M. bovis) infection in badgers have been developed through DEFRA funded research projects at the Veterinary Laboratories Agency (VLA). The final reports of completed research projects have been published on the DEFRA website.Bovine TB is currently confirmed by culture of M. bovis in the laboratory. However, M. bovis grows very slowly so culture results can take six weeks to several months to come through. DEFRA funded VLA project SE3008 (April 1999-December 2004), 'Detection and enumeration of M. bovis from clinical and environmental samples', aimed to develop PCR-based methods that may allow rapid screening of samples from infected cattle and monitoring of the environment and badger populations for the presence of M. bovis. This research showed that while the PCR test specific for M. bovis was found to be only 50 per cent. as sensitive as the gold standard of culture, the sensitivity of the M. tuberculosis complex PCR test (i.e. a less specific PCR able to detect mycobacteria that are members of the M. tb complex) was increased from 70 per cent., to 90 per cent., by the end of the project. While such low sensitivities for M. bovis detection rules out the use of this PCR test for use on environmental samples and excretions collected from badgers, with further development and evaluation this test could be used in the laboratory to achieve faster confirmation and subsequent tracing of bTB infection in slaughterhouse cases.Work funded by DEFRA to validate the PCR test developed by Warwick University to detect M. bovis in the environment is ongoing (Project SE3231: 'Validation and epidemiological application of molecular methods for monitoring M. bovis survival and dissemination into the environment'). This is a joint project between the VLA, Warwick University and University College, London and includes validation of the test using field samples. A full project description is available on the DEFRA website. A final report on the work will be published following its completion in April 2010.If it is shown to be usable as a robust practical field test, consideration of its potential use in any bTB control policy will need to take account of the results of the Randomised Badger Culling Trial, which showed that localised culling was associated with an increase in cattle herd TB breakdowns due to the perturbation effect on badgers and increased transmission of bTB.