BRAIN-DESTROYING DISEASES PUZZLE HEALTH AUTHORITIES UNKNOWNS HINDER ANALYSIS OF `MAD COW' RISKS.

Byline: Lauran Neergaard Associated Press

If there's a word that sums up ``mad cow disease'' and the similar illness that eats people's brains, it could be ``mystery.''

There's no test for these diseases - and no treatment. Nobody even knows what causes them. Nobody knows for sure that 10 fatally sick people in Britain ate any beef from infected cattle.

All those unknowns mean that even though experts believe there's very little chance that mad cow disease could spread to the United States, they can't rule out the possibility.

``It's a hard thing to explain to people,'' said Agriculture Department veterinarian Linda Detwiler.

Mad cow disease - bovine spongiform encephalopathy or BSE - was discovered in 1985 when British cows started staggering around and dying. Autopsies showed their brains were full of sponge-like holes. By the next year, Britain had an epidemic, and other European countries have sick cows, too.

No cow in the United States has ever been found to have BSE, despite rigorous checking for symptoms and thousands of autopsies.

It wasn't until 1990 that scientists noticed how similar BSE in cattle was to Creutzfeldt-Jakob or CJ disease in humans. CJ also eats holes in brains - of about one in a million people. Every year, about 250 Americans die of the rare disease. Invariably fatal, it kills about seven months after symptoms appear.

Many species, from mink to sheep, suffer similar illnesses. In sheep the disease is called scrapie.

The only link between species ever discovered is in animal feed made from ground-up sheep parts. This feed is blamed for Britain's BSE epidemic in cows - and even for several dozen deaths of house cats.

Only the brains and spines of animals have been proven infectious. Muscles, milk and other body parts are thought safe.

The only way scientists have ever found CJ disease to spread between people was from medical procedures, when someone got injections of hormones taken from corpses - a practice stopped in the 1980s - or received infected corneal transplants.

Scientists are fiercely debating whether a bacterium or a strange protein called a prion causes CJ disease.

So the world was stunned when Britain said there might be a link between 10 cases of CJ and BSE-infected cows. The British cases were unusual because, while CJ disease usually strikes older people, these 10 were all younger than 42. Some were in their 20s. There has been no CJ patient under 42 since 1978 in the United States.

U.S. scientists still aren't convinced there is a link.

``We don't know that for an absolute fact . . . despite the hysteria - and `hysteria' is the word,'' said Food and Drug Administration microbiologist Carol Vincent.

Did the victims eat infected beef? That isn't known. To infect a steak, the butcher would have to slice open the cow's spine by mistake. But Britain did allow cows' brains and other organs to be ground up in some food products before 1989, the British government noted.

In the U.S., a few drugs are made from cow organs, but the FDA certifies that they do not come from infected cows or countries with BSE.