Mad Cow Disease 101 

Bret Stephens / Wall Street Journal 21dec00

BRUSSELS -- On word last week that Bavaria had confirmed its second case of mad-cow disease, German Deputy Health Minister Erwin Jordan observed that the coming panic might prove a boon to his countrymen. "I believe the amount of meat we eat is not necessarily good for our health," he said. "Certainly we could get by with less."

By and large, however, mad-cow disease inspires more alarm than joy. Part of a family of rare and so far terminal neurological maladies known as transmissible spongiform encephalopathies, the bovine variant was initially thought to be harmless to humans.

But evidence now suggests it can infect people, taking on the characteristics of a variant form of Creutzfeldt Jacob Disease, a TSE whose eventual symptoms include dementia and the loss of motor skills. There have been some 90 confirmed cases of vCJD so far, the vast majority in Britain but also a few in France. And as the German cases attest, the epidemic has the potential to spread.

Does this mean we face an epidemic of AIDS-like proportions? Almost certainly not. Yet there has been no shortage of doomsayers.

According to Richard Rhodes, author of "Deadly Feasts: Science and the Hunt for Answers in the CJD Crisis," vCJD might claim as many as 500,000 lives a year in Britain alone. Mr. Rhodes bases this "outside limit" forecast on the toll inflicted by kuru -- a TSE transmitted through human cannibalism -- on the Fore people of Papua New Guinea. At the height of that epidemic, kuru killed about 1% of the Fore, which extrapolated to Britain's population gives Mr. Rhodes his eye-popping figure.

A more reliable forecast emerges from a study carried out earlier this year by British epidemiologist Roy Anderson, who estimates that vCJD may claim between 100 and 136,000 lives over the next several decades. The latter figure is frightening. But contrast that to the 180,000 cases of lung cancer that appear annually in the U.S. alone, and one gains a clearer sense of the relative dimensions of the projected vCJD epidemic.

While it would be irresponsible to insist that vCJD poses only a trivial threat, it is equally necessary to spell out some reasons why the disease may never reach epidemic proportions:

• Most meat is safe to eat. Ever since 1996, when vCJD was first linked to eating infected cows, it has been widely assumed that all cuts of meat -- and all meat products such as gelatin -- were potential disease bearers. As a result, the British government banned beef on the bone, the European Union and the U.S. placed a quarantine on British beef, and the European Commission even took steps to force the pharmaceuticals industry to develop substitutes for gelatin capsules.

But the scare was exaggerated. "We've never been able to identify any BSE infectivity in muscle meat, and only one odd finding in bone marrow" says William Hueston of the University of Maryland. Nor does the infective agent in BSE appear in cow hides or blood, notes Paul Brown of America's National Institutes of Health, dismissing the scare about gelatin capsules and other pharmaceuticals.

Put simply, from what we know, you will never develop vCJD from eating filet mignon or high-quality hamburger, from swallowing a gelatin capsule or applying skin cream, or from chewing on a T-bone.

• Infectivity. Where there is a problem is in brain and spinal-cord tissue, which had long been used in low-quality hamburgers, meat pies and pet food. "Infectivity in the brain and spinal cord is hugely greater than anywhere else in the body," says Dr. Brown. "If brain has about 10 million infectious units in a gram, spleen might have 100, and red meat zero."

How much brain and spinal-cord tissue has made it into the human food stream is unclear, as is the amount needed to precipitate vCJD. But as Byron Caughey of the Rocky Mountain Laboratories in Hamilton, Mont., told me, "it's probably a lot harder to infect people than to infect cattle." He notes that "in transmitting BSE to mice you need 1,000- to 10,000-fold more infectivity."

There also appears to be a genetic component to human susceptibility to vCJD. So far, every person to have developed the disease had a particular genotype corresponding to about half the population, suggesting the other half may be effectively immune or will not develop symptoms for years to come. TSEs are notorious for lengthy incubation periods -- an average of 15 years for kuru -- so it is still too soon to tell the effect of genetic variations.

One thing is clear: The barrier for transmission of BSE to humans is considerably higher than it was among the kuru-afflicted Fore, who apparently acquired the disease by eating the brains of relatives.

• Geography. For the past four years, Continental Europeans believed themselves safe from BSE. With cases now reported in France, Spain, Portugal, Belgium and Germany, that is no longer true.

Still, the scope of these cases pales next to the British outbreak, in which as much as 2% of cattle may have been infected. France has so far reported about 70 cases of BSE out of a total herd of 10 million, and French authorities are now on the lookout. Starting in January, the EU plans to cull as many as 170,000 cows, in what amounts to a $4 billion exercise in consumer-confidence raising.

Much more secure from an outbreak is the U.S., which so far has reported no cases of BSE (though there have been outbreaks of TSE in elk, deer and mink). One reason is that the U.S. cattle industry was largely self-sufficient. And since 1997 the Food and Drug Administration has banned the use of cattle remains as animal feed.

• Treatment. What makes vCJD terrifying is its deadliness. But the scare has meant the disease is beginning to receive the kind of money and attention not normally devoted to so marginal a disease.

There is no known cure for vCJD. But treatments are on the horizon. Clinical trials in Germany have shown that the painkiller flupirtine significantly improved patients' cognitive abilities. Just how effective flupirtine can be over the long run remains to be seen. But it does suggest that, as with AIDS, vCJD may some day prove treatable.

Much of what I write remains speculative. Perhaps it is overly optimistic. Unlike so many other health scares, BSE and vCJD are real public-health concerns that need to be taken seriously. But it is equally crucial that the threat they pose be understood by the public, and that governments respond in measure, neither downplaying risks nor raising false alarms. "The first responsibility of good scientists is to confront public hysteria," says James Steele of the University of Texas. Given the hysteria that's already been generated by BSE, such advice could hardly be more timely.

Bret Stephens, an editorial page writer for The Wall Street Journal Europe.