1. Mad cow comes to town!

2. Mad-cow history

3. "Abundant caution" or half-measures?

4. Making sense of the threat

5. The weirdest agent

GLOSSARY:
Bovine spongiform encephalopathy (BSE): Mad cow disease.

Chronic wasting disease: A TSE in deer and elk.

Creutzfeldt-Jakob disease (CJD): Fatal, human TSE, strikes one person in a million.

Prion: A protein that, when misshapen, can cause other prions to fold wrongly. Causes all TSEs.

Scrapie: A TSE in sheep. Known since the 1700s; does not infect people.

Transmissible spongiform encephalopathy: TSE. Infectious brain diseases caused by prions.

Variant CJD (vCJD): The "human" version of mad cow. Similar to CJD; strikes younger people.

RIGHT: Scientists can conclusively diagnose BSE -- or the human equivalent, vCJD - only after death. This picture shows the obex, just beneath the cerebellum, where prion plaques commonly form. Photo:CDC

Beef prices in Europe plunged after the mad cow epidemic. Could this happen in the United States? Data: USDA

McCarty, of the cattlemen's association, says the surveillance program was statistically designed to detect an infection level of one animal in one million, and it apparently succeeded at that.

But Greger says we will not know the true extent of the disease "until we do better testing. I'm afraid that's what the industry has been counting on. They have been resistant to increased testing for a decade, and from their perspective, it makes sense. We've been doing such lousy testing, and still incredibly are using the cannibalistic feeding processes that it's certainly no surprise to find this case -- the surprise is that we actually picked one up."

Prion researcher Aiken agrees that more testing would improve our knowledge. "Testing needs to be ramped up to include the 200,000 downers immediately or as soon as we can. The diagnostic capacity is there, we can do this." More than a dozen diagnostic tests for prion diseases are on the market.

On Jan. 1, the World Health Organization called for pre-slaughter testing of all cows aged 30 months or more.

Expert: exports important
Certainly, nobody has more to lose than cattle raisers, who were starting to enjoy high prices when Washington State loosed it's beefy bummer. If American consumers sustain their confidence in beef, the issue will largely rest on exports, and that picture is grim. "The quickest, hardest, and obvious loss is exports," says McCarty. "We export 9 to 10 percent of our product every year." More than 30 countries, including Japan, the largest market, have banned imports of U.S. beef, wrote CBS news.

On Jan. 11, the USDA cut its estimate of 2004 beef exports by 90 percent.

To McCarty, even the discovery of BSE does not represent a total failure of USDA's efforts. "Yes, keeping it out was the first goal," he says. But the government and industry both agreed on further measures. "We can't assume that it won't get in, so we need surveillance. If it gets in, we need another firewall, the feed ban, because we know that's how it spreads. Then, taking the next step, we need to do everything we can do to ensure that there is no human exposure."

One thing seems clear. Despite the hysteria about beef, despite the British experience, and despite the shifty nature of the infectious prion, it's unlikely that thousands of mad cows are lurking in American herds. The United States, in other words, is not likely to replay the disastrous British experience, says Schaefer. "I'm guardedly optimistic," he says. "I would not say there will not be another case found; that's a precarious position to take, since we do have 100 million cattle in this country. That's the guarded part of my attitude. On the other hand, the risk to our cattle industry is very low, and the risk to people is negligible" because infectious portions are excluded from human consumption.

Variant CJD, the disease humans caught by eating BSE-infected beef, appeared in Britain in 1995. Both forms of CJD are extremely rare, but how many Britons are infected without showing symptoms? Graph: U.S. Food and Drug Administration

Already, says Schaefer, the value of the 1997 feed ban appears in the fact that the two North American cases were born before the ban. "If we found a BSE case that emerged in an animal born after the feed ban was implemented, that would bring into question the adequacy of our preventive measures."

Primed for the prion fact sheet?

There are 1 2 3 4 5 pages in this feature.
Bibliography | Credits | Feedback | Search

©2004, University of Wisconsin, Board of Regents.