Banned beef returns despite lack of evidence

By Debora MacKenzie BRITAIN’s ban on beef on the bone—which was imposed after the prion protein thought to cause BSE was found in nerves clinging to bones—has been lifted. But no research has been published to back the government’s claim that the prion reaches peripheral nerves too late in the incubation of the disease to be eaten by consumers, even though this is central to its decision to lift the ban. The ban was based on experiments by Gerald Wells and colleagues at the Ministry of Agriculture, Fisheries and Food’s Central Veterinary Laboratory in Surrey. The researchers fed brain tissue from BSE cases to calves. When these cattle were 36 months old, peripheral nerves near the spine were themselves infectious when injected into mice. Cattle older than 30 months may not be eaten in Britain, however, and in 1997 Britain’s Spongiform Encephalopathy Advisory Committee stated there was no infection in nerves from cattle 30 months old. Researchers familiar with the work say no tests on nerves from such younger cattle have so far been published. James Ironside, a neuropathologist at the CJD Surveillance Unit in Edinburgh, says he is surprised no one has looked more carefully for BSE in the peripheral nerves of cattle. He has found the same prion in spinal tissue and peripheral nerves of humans who died of the new variant of CJD linked to eating BSE-infected meat. Ironside used antibodies to make the protein visible under the microscope. Herbert Budka of the University of Vienna has seen prions in the peripheral nerves of people who died of classical CJD. “It is important to identify prion in peripheral nerves,” he says, “because nerves are everywhere.” British government scientists are only now testing meat, nerves and other tissues from BSE-infected cattle by injecting them into the brains of other cattle,
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