FDA PROPOSES ANIMAL-FEED RULE TO HELP PREVENT MAD COW DISEASE.

Byline: Lawrence K. Altman The New York Times

The Food and Drug Administration on Thursday proposed a ban on the use of any tissue from a wide variety of animals in feed to prevent the spread of mad cow disease if it ever occurred in the United States.

No case of mad cow disease has been detected in the United States in 10 years of monitoring. But the agency's precautionary step is being proposed because of strong evidence that the disease can be spread through animal feed contaminated with rogue proteins known as prions.

Mad cow disease has created havoc with the economy in Britain, where it has affected more than 165,000 cattle since the neurologic ailment was first detected in England in 1986. The source of the bovine disease is thought to be animal feed from processed offal and other parts of slaughtered sheep.

Panic followed the British government's announcement last year of a tentative link between mad cow disease and an untreatable and incurable human version of an ailment known as Creutzfeldt-Jakob disease, which occurs in about one in 1 million people in the world.

British experts have reported 14 confirmed cases of a variant form of Creutzfeldt-Jakob disease, and French doctors have reported one case.

There has been no proof that mad cow disease can jump species, from cattle to humans, and there has been no evidence of an explosive outbreak of the new form of Creutzfeldt-Jakob disease in humans. Federal health officials have found no evidence of the variant form of Creutzfeldt-Jakob disease in the United States.

The proposal, to be published in The Federal Register today, will prohibit using protein from any ruminant animal in the manufacture of ruminant feeds. Ruminants are animals that chew their cuds; among them are cattle, sheep, goats, deer and elk. Mink are included in the ban because they can be affected by an ailment similar to mad cow disease.

The public will have 45 days to comment on the proposal, and then the agency expects to put the ban into effect this year, Dr. David Kessler, the commissioner of food and drugs, said in an interview.

Mad cow disease is also known as BSE, for bovine spongiform encephalopathy. It is so named because it produces holes in various areas of the brain, giving it a pitted appearance like Swiss cheese. Similar spongiform diseases affect a variety of animals.

The disease generally takes years to develop silently. But then it progresses from initial symptoms to almost certain death in a relatively short time.

Because such diseases have not been transmitted through reprocessed feed to poultry, swine and pets, such feed would be exempted from the proposed American ban, Kessler said.

Other exemptions include blood from cattle and ruminant-derived milk and gelatin, he said, because the agency has no information suggesting that milk proteins, gelatin or bovine blood proteins can potentially transmit mad-cow-like disease.