British beef blues

Curious cause

Down deer, ill elk

Can't happen here?

Laughing death in New Guinea

Identifying disease agents

Menacing microbes

Glossary

Creutzfeld-Jacob disease normally affects only old people. But the variant you catch from mad cow meat destroys the brains of young people.

Back in the UK
PAGE UPDATED 8 FEB 2001 In 1986, cows in Great Britain began drooling and staggering. Some were pathologically nervous, others bizarrely aggressive. When the "mad cows" died, as they inevitably did, their brains were shot through with holes.

The ailment, popularly known as mad cow disease, was called bovine spongiform encephalopathy, or BSE (Want The Why Files guide to mad-cow lingo?).

The frightening disease raised an immediate question: Was it safe to eat British beef?

The obvious parallels to scrapie, a similar illness in sheep led scientists to suspect the cows had been sickened by eating feed containing sheep byproducts. The issue is controversial. A recent independent report from bse.org says BSE probably arose from a mutation in a cow in the 1970s. But Judd Aiken, who studies TSEs at the University of Wisconsin-Madison, says the cause "may never be known... but I have no difficulty with the concept that it could have been an adaptation of sheep scrapie."

In any case, a second speculation about mad cow -- that it spread when cows ate feed containing cattle byproducts -- remains the accepted explanation for the bovine epidemic, which affected at least 170,000 cows.

Tragically, a third speculation -- that eating mad cow meat would expose humans to disease -- has also proven accurate. For a decade after the disease appeared in the United Kingdom, the government assured the public that a "species barrier" would prevent infections just as it had protected people who ate those sick sheep.

Between 1986 and 1996, despite warnings from some scientists and food-safety types, an unknown number of mad cows were slaughtered and sent to the dinner table (see "Tracking the Human... " in the bibliography).

10 cases that shook the world
Then, in 1996, the U.K. government acknowledged eating contaminated meat as the "most likely explanation" reason why 10 young people had Creutzfeldt-Jakob disease (CJD). The "variant CJD" (vCJD) struck younger people and caused a different pattern of brain damage, but as in CJD, everybody died.

The reaction to the government's "Sorry for our beastly error!" was as tumultuous as a mad cow in a china shop. Fast-food restaurants started importing beef. Anger over the erroneous reassurances helped topple the Conservative government. The European Union banned imports of British beef, and the country's cattle business was essentially slaughtered. The government shelled about $7.5 billion to kill and dispose of 4.7 million cows that were old enough to have developed the illness.

The government also changed rules on animal feed, preventing the "feeding like to like" system that perpetuated the epidemic. The control measures worked, and mad cow is disappearing from British herds.

But the human death toll, already above 80, is rising 23 percent per year, as the slow-acting, untreatable disease continues to emerge.

Because variant CJD remains undetectable for an unknown number of years, we could be seeing the start of a major epidemic. A recent estimate said the human death toll would range between 10.000 and 136,000 in the United Kingdom -- with the lower range considered more likely. But until the death rate starts dropping, all such predictions are essentially guesstimates (see "Tracking the Human..." in the bibliography).

Scrapie, a sheep disease, was the first TSE to be identified. This disease does not seem to infect humans. Courtesy USDA. Agricultural Research Service.

Mad sheep
Long before there were mad cows, there were mad sheep. Since at least the 1700s, some sheep in England and France suffered a hideous, deadly brain disease. Farmers named the strange staggering illness "scrapie" because the sheep scratched -- or scraped -- an insatiable itch in their dying months.

Scrapie came and went, flaring and waning, striking some breeds more than others, even occasionally infecting goats.

When scientists examined the brains of dead sheep, they saw sponge-like holes. In their jargon-friendly way, they called the disease "spongiform encephalopathy" -- spongy brain disease. Using the simple but unpalatable technique of injecting pureed brains of sick animals into healthy animals, scientists proved that scrapie could pass between animals -- from sheep to sheep, and from sheep to other livestock and lab animals. Ergo "transmissible spongiform encephalopathy," or TSE.

Scrapie was odd.

It was clearly infectious, but it did not seem to sicken mutton-eating humans.

The sheep did not mount an immune response to scrapie.

The disease agent was immune to heat and chemicals that kill all known pathogens. But scrapie remained a kind of scientific backwater until the 1980s, when mad cows started making headlines.

What on Earth could cause this weirdo brain disease?