[back] TB tests
TB blood test has bloody results
Sunday Telegraph May 18, 2008
THE FARM run by Tony Yewdall and his son Jonny presented a chilling ; spectacle last Wednesday morning. Eleven times a gunshot signalled the killing of a cow from the Yewdalls' 450-strong pedigree Guernsey herd. Sixty nine more, 30 still in calf, were loaded onto trucks to be killed at a local abattoir. For father and son, and for their herdsman who refused to be present, it was the blackest day of their farming lives.
The reason for this mass slaughter was that last November a highly controversial new blood test, lately favoured by the Department for Environment, Food and Rural Affairs, had shown 89 of the Yewdalls' north Devon herd to be infected with TB.
But when the cattle were subjected the same day to the long-proven "skin test", only one showed a positive reaction. The discrepancy was so glaring that Tony Yewdall, twice president of the Guernsey Society, pleaded with Defra for a re-test. Local officials were sympathetic but were overruled by London, which insisted that no further tests could be allowed - and eventually all 89 animals were destroyed.
Defra claims its blood test picks up TB "in its early stages". But post mortems last week showed only five cows to have been infected. If the test was reliable, TB should by now have been raging in them all. Thus 84 healthy cows were unnecessarily killed, costing taxpayers nearly £100,000 in compensation alone. The farm's losses are estimated at £100,000 more.
This highly disturbing episode brings to a head an anguished debate raging for months over the reliability of the gamma interferon blood test, rolled out by Defra with great fanfare in October 2006. It was originally designed to be just a quick surveillance test, to be confirmed by the tried and trusted skin test, and huge sums of money hang on the difference. The epidemic of bovine TB sweeping through our dairy herds is already costing taxpayers , £90 million a year. The Government admits that within six years the total bill could reach £2 billion. Yet Defra itself admits on its website that the blood test is cruder and less "specific" than the skin test, in that it picks up the presence of diseases other than bovine TB, most not harmful to cattle at all.
Many farmers have become so alarmed by the apparent unreliability of the blood test that several, including Tony Yewdall, were recently lining up to have it ruled on by the High Court. The first case heard was that brought by a Somerset organic farm, where the original skin test had shown only 14 of 486 cows as positive. When Defra insisted on retesting with gamma interferon, this soared to 86. Official figures show that no less than 81 per cent of all cattle destroyed after being shown as positive by the blood test proved at post mortem to show no signs of the disease.
Last month, however, Mr Justice Mitting declined to discuss the scientific reliability of the two tests. Resting his judgment solely on the law, he ruled that, because the blood test had been approved by the EU, it was therefore lawful for Defra to rely on it. Even though Brussels had regarded gamma interferon as only an ancillary test, not to be relied on for a definitive diagnosis, the legal die was cast. From that moment, Tony Yewdall's cattle and tens of thousands more across Britain were doomed.
Another farmer who had been waiting to bring his own case to court was Tom Maidment of Wiltshire. Thirty-one of his cows were condemned by Defra after blood testing had shown them as positive, and he pleaded in vain with London to have them skin-tested. When his local Animal Health Office, unaware of London's refusal, ordered that skin tests be carried out, not a single animal showed any sign of TB. Defra's response was that the cows must all nevertheless be destroyed. Who gives a fig for science when someone else is footing the bill - and the courts are there to support you?