Mad Cow/CJD Spread Through Spinal Cord Nerves
By Patricia Reaney
LONDON, Dec 4 (Reuters) - Consumers were up in arms and butchers and farmers vented their anger on Thursday but medical experts said Britain had no alternative but to ban beef on the bone.
Although the risk of new infection of mad cow disease is slight, they agreed that the government could not take a chance of letting contaminated beef into the food chain.
"It was certainly the right move. It would have been better to make that move years ago like in 1993 during the peak of BSE (bovine spongiform encephalopathy)," said Hans Kretzschmar, a neuropathologist at the University of Gottingen in Germany.
The scientist who has done research into prions, the brain protein that mutates and causes the disease, said Britain had no alternative after experiments showed that the agent that causes BSE and its human equivalent Creutzfeldt-Jakob disease (CJD) could be transmitted through nerves near the spinal cord.
"Knowing that the infectious agent is in there, there was no other move," he added.
Agricultural Minister Jack Cunningham wiped T-bone steaks and ribs off the British menu after expert advisers on the government's Spongiform Encephalopathy Advisory Committee (SEAC) warned that infected tissue in the dorsal root ganglia -- swellings on the nerves near the spine -- could be left in the bone.
Dr Richard Lacey, a professor at the University of Leeds and a staunch critic of Britain's handling of the BSE crisis, applauded the action, but like Kretzschmar felt it should have been done years ago.
"It was too little too late," he said. "It's ridiculous that beef, in general being consumed is safe, and the bones are dangerous."
More than a decade after BSE first broke out in British herds, nearly two years since the European Union banned all export of British beef and despite the slaughter of 1.4 million cattle over the age of 30 months, the BSE crisis continued with a new twist which left Britons confused about which parts of the animal are safe to eat.
Given the latest scientific findings, Cunningham chose what he said was the only option.
"Beef can only be allowed for consumption when there are no bones," he told a hastily arranged news conference after the shock move.
The new evidence that dorsal root ganglia (DRG), and bone marrow in cattle in a late stage of the disease, could be infected emerged after scientists fed experimental animals with a large dose of BSE by mouth.
Groups of the infected cattle were slaughtered and tissue was injected into mice. SEAC stressed that the cattle were given a heavy dose of BSE and the infected tissue was found only in cattle aged over 30 months -- older than any cattle that would be allowed into the food chain.
It emphasised that the bone marrow result was provisional and required further tests. There was no evidence that meat, muscle or blood contained the BSE infection.
SEAC estimated that "next year of the approximately 2.2 million cattle to be slaughtered for human food only three will be near enough to the end of the incubation period to raise the possibility of infectivity in their DRG."
Although there is only a five percent chance of one new case of the new strain of CJD resulting in 1998, the government felt it was still too high.
Two scientific studies published in September confirmed that mad cow disease causes the new strain of CJD, which scientists first identified in 1996, and that eating infected beef was the likely cause.
Scientists believe that BSE was caused by feeding cattle with the carcasses of sheep that died from scrapie, a related brain disease. Although Britain banned the practice in 1988, scientists suspect cattle still ate infected feed for many years.
Seeking to calm the furore caused by the latest twist in the mad cow saga, Cunningham said every requirement "that is necessary to safeguard British beef has been taken." But he admitted the crisis would probably continue into the new century.
The research that resulted in the beef on the bone move will be published in the journal Veterinary Record.

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