NBA positive about TB tests

CATTLE FARMERS whose herds suffer a new TB breakdown can help scientists discover whether time spent under TB restriction can be shortened, the National Beef Association has said.

By taking part in a trial comparing the effect of skin testing with the gamma interferon blood test they can also help reduce the chance of herds suffering recurrent breakdowns, according to the NBA.

The association is keen to help the Welsh and English governments discover whether the y-IFN blood test for TB is a cost-effective diagnostic tool.

Robert Forster, NBA chief executive believes that if the skin test is used as a herd test and each remaining animal is blood sampled 8-28 days later, it could help speed up the discovery of infected animals and reduce the time taken to cleanse a herd of TB.

“This should not only mean a generally shorter time under expensive movement restriction, but could also result in the earlier identification of cattle which had only just been infected with TB,” he said.

“But this hypothesis must be proved before the combined testing regime can be accepted as standard policy for herds with confirmed breakdowns,” said Mr Forster.

But he pointed out that to do this DEFRA and the Welsh Assembly Government need to conduct comparative field trials involving around 600 herds, and so far just 125 farms have been recruited.

The NBA is worried that some farmers who could take part in the trial are put off by claims that the blood test is so much keener than the skin test that it triggers an unwelcome number of false positives.

“We have made enquiries within DEFRA and have been assured that this is not the case.

“The blood test can pick up cattle in which TB is less developed by detecting their early immune reaction, and because of this there is often a high percentage of positives that have no visible lesions which can take months, sometimes years, to develop,” said Mr Forster.

“However animals with no visible lesions must not be confused with false positives, which DEFRA tells us are usually one per cent, or less, in herds in which TB has already been confirmed.”