For the last several months, a bizarre, miniaturized replay of the British mad cow crisis has gripped the United States. Except this time, there's been no cattle epidemic and no human victims. Just speculation, publicity, more speculation, more publicity.
In part, the furor was triggered by our own regulators. In early January, the Food and Drug Administration began clamping down on feed mills to ensure that safety measures intended to prevent mad cow-type diseases from circulating in this country are strictly followed. This was business as usual. It is the agency's job to consider worst-case scenarios, then to work with industry to reduce risks.
Within days of the FDA's action, however, the media speculation began. There were reports that mad cow disease might occur spontaneously and that the U.S. might have mad cow disease in its livestock feed. There were not only reports of mad cows in the U.S., but mad elk, mad deer and mad hunters. There were even rumors of mad squirrels.
As television reporters joined the fray, and pollsters were dispatched to measure our anxiety, the notional danger swung from what we eat here to what U.S. travelers might have encountered while dining in Europe. An argument erupted over the safety of blood. By late last week, the American Red Cross was disclosing plans to unilaterally disqualify thousands of Americans who had lived more than a year in Western Europe from giving blood.
Blood bank switchboards lit up with calls from donors worried about a steak and kidney pie they had eaten in England or questioning whether the semester they had spent at the Sorbonne made them ineligible to give blood.
Federal officials struggled to allay fears. The FDA has taken "very aggressive steps" to protect blood and other products, stressed Dr. Jay Epstein, director of the FDA's office of blood research and review. "These steps are directed at a theoretical risk."
How theoretical? The problem isn't that the risk of contracting mad cow disease on holiday in Europe is remote; it's that it's almost too remote to calculate. Its deadly human form is a tragedy, but outrage at this too often obscures that it is also very rare. Last year in Britain it struck one out of every two million people. To understand how mad cow disease spreads, and how to prevent it, one has to look at its larger school of disorders. This is called transmissible spongiform encephalopathies. Big name, simple meaning: transmissible, i.e., they're catching; spongiform: They leave sponge-like holes; encephalopathy: The holes appear in the brain.
Spongy-brain disease dates back to 1732, when a disease in sheep was named scrapie because the infected animals would scrape themselves. The disease, endemic in European sheep for centuries, was brought to the United States in 1947 from sheep imported from Britain. Since 1952, the U.S. Department of Agriculture has tried to contain the disease by routinely destroying affected animals. The latest destruction order, of three flocks of sheep in Vermont, generated international headlines. The sheep had been imported from Europe, and worries swirled that they had brought mad cow disease. It now appears that four sheep among many hundreds had scrapie
Sheep scrapie has never been shown to infect people, in spite of extensive epidemiological studies that looked for an association. The first hint that scrapie was part of a larger school of diseases, including some deadly to humans, came in the 1950s, when researcher Dr. Daniel Carleton Gajdusek discovered a disease endemic among the Fore-speaking tribe of Papua, New Guinea. The disease was called kuru. It means "tremble" and referred to the uncontrollable shaking of the victims.
Gajdusek, who knew of the Fore's habit of cannibalizing their dead, helped to discourage the practice, and kuru died out. Back in the United States, tipped by a veterinarian that kuru resembled a sheep disease, he performed research that found that not only was kuru a relative of scrapie, but so was a disease discovered in 1920s Germany, called Creutzfeldt-Jakob disease. In 1976, Gajdusek received a Nobel Prize for discovering the new school of diseases.
Even so, spongy-brain diseases were still quite rare in people, and only a handful of scientists worldwide were familiar with them. By the late 1970s, it was becoming clear that Creutzfeldt-Jakob disease kills about one in a million every year, and that this rate held the world over.
In Scotland, British scientists perfected a technique to strain-type these new diseases. Their work has allowed scientists to tell one type of spongy-brain disease from another. They helped record new versions as these were spotted on mink farms in Wisconsin in 1947 and elk in the Western U.S. in the late 1970s. In 1985, a fearful new strain erupted in England: bovine spongiform encephalopathy, otherwise known as "mad cow disease."
Epidemiologists speculate that by the time the new cattle disease in Britain had been named and strain-typed, an epidemic had been festering in British dairy herds for more than a decade. This is often construed as testimony to the runaway virulence of mad cow disease. In fact, mad cow disease is not carried in the wind. It requires concerted assistance from agribusiness.
Since World War II, British livestock-feed suppliers recycled meat and bone meal made from dead cows and sheep as an unlabeled "protein" constituent of dairy feed. This was thought to boost yields and increase protein content in milk. But by turning cows, in effect, into unwitting cannibals, the industry created the bovine answer to kuru in British dairy herds.
First Cases Are Diagnosed
The infectious agent had been recycled through cows and feed for more than a decade before the first cases of mad cow were diagnosed in cows in the late 1980s. By the time the epidemic became apparent, however, it was on farms throughout Britain.
British scientists struggled to pinpoint the potential risk to humans. If mad cow disease infected humans, they reasoned, it would appear in a novel form of Creutzfeldt-Jakob disease.
What they did not anticipate was an eruption in 1990 of mad cow disease in cats. The first victim of feline spongiform encephalopathy was Max, a 5-year-old Siamese in Bristol, England. The British tabloids dubbed him "Mad Max."
Researchers in Britain and the United States have found that spongy-brain diseases concentrate in the immune and central nervous system. The organ meats, brains and scraps mechanically removed from spinal cords of old dairy cows routinely went into cheap meat fillings and pet foods.
Starting in 1989, British law required the destruction of these animal parts. Even with the restrictions, another 86 cats have died since Max. But the safety controls can be seen clicking in with a sudden fall-off of cases. Eighty of the cat cases were between 1990 and 1996, with only seven cases since then.
In late 1995, a string of Creutzfeldt-Jakob cases appeared in British youths in their teens and 20s. On March 1996, British health secretary Stephen Dorrell announced the deaths of 10 young people from an illness that scientists believed to be caused by bovine spongiform encephalopathy. This "human BSE" was named "new variant Creutzfeldt-Jakob disease." The same agent had killed the cows, cats and now people. Spongy-brain experts began referring to Britons as "the human experiment."
In the six years since its emergence, there have been 90 cases of new variant Creutzfeldt-Jakob in Britain, three in France and one in Ireland. At its peak last year, it struck one in 2 million people.
The United States banned British bovine products and feed in 1989. "The most important point to make is we do not have any cases of mad cow disease recognized in the U.S., nor have we had any new variant Creutzfeldt-Jakob disease," says the FDA's Dr. Jay Epstein.
For lack of real mad cows, some news reports focused on hunters who died from Creutzfeldt-Jakob disease and intimated there was a connection with chronic wasting disease in elk. But experts who examined the hunters' brains concluded that the human and animal diseases were different strains. The hunters died from known forms of Creutzfeldt-Jakob disease, the kind found the world over. "The tentative conclusion based on this evidence is that the disease was not acquired by consuming contaminated game," says Pierluigi Gambetti, professor of neuropathology at Case Western Reserve University School of Medicine.
Beth Williams, a veterinary pathologist with the University of Wyoming who first diagnosed the elk disease in 1989, stresses that "this is not mad cow disease."
While there is no evidence that the elk disease or scrapie has affected humans, Williams also thinks we can learn from Europe's mad cow experience. "It would be foolish not to be prudent," she says. "It is prudent to get the information to hunters: Don't eat the brain, don't eat the spinal cord."
That the U.S. has so far escaped mad cow disease seems a mixture of luck and precaution. Britain was not the only country to include meat and bone meal in its dairy rations. That was a standard practice across Europe and North America. Eventually, episodes of spongy-brain disease on mink farms and the dire example of the British disaster with mad cow disease prompted the FDA to ban meat and bone meal from rations of grazing livestock in the U.S. in 1997.
Then, in January, the FDA published a report citing compliance failures by agribusiness, including some feed mills that lacked adequate safety measures for preventing meat and bone meal from getting into cattle rations. Within weeks, the agency quarantined more than 1,200 cattle in Texas--not because the animals had mad cow disease, but to send a message to the industry about the importance of complying with safety laws.
Start of Food Scare
It was a handsome show of power, but one that would soon escalate into a food scare. In mid-January, the New York Times published a front-page story that included speculation that mad cow disease arises spontaneously, probably at a rate of one in a million, and, therefore, 38 mad cows might be entering our food chain each year.
This surprised one of the country's longest-standing veterans of spongy-brain disease research. "There's no evidence for any spontaneous disease in any animal," declared Bruce Chesebro, chief of the Laboratory of Persistent Viral Diseases at the National Institutes of Health's Rocky Mountain Laboratories in Hamilton, Mont.
The problem, says Chesebro, is uncertainty. Scientists don't know what causes spongy-brain diseases in cows, cats and other animals, or in humans. Some say they are caused by viruses; others suggest the cause may be novel proteins called prions. To date, there is no test to screen blood.
This makes it tough for the FDA to design safety controls for blood testing. In 1999, the FDA's specialist committee on spongy-brain diseases recommended deferring donations from people who had lived in Britain for more than six months between 1980 and 1996.
As the same committee gathered again in January, the focus was on other European countries with appreciable levels of mad cow disease. The committee chairman, neurologist Paul Brown, underscored the unknowns to the group. "We don't know if someone is exposed if they are going to get infected. We don't know if they are infected, if they are going to have blood that is infectious. And we don't know if the blood that is infectious is going to transmit the disease."
But based on mini-outbreaks of mad cow disease in France and Portugal, the committee calculated the risk to be 20 times less than that in Britain, and voted to defer donations for Americans who have resided in Europe for more than 10 years at a time since 1980.
Last week the American Red Cross said it is considering exceeding FDA standards and banning donations from all Americans who have spent more than one continuous year in Western Europe since 1980. "Without a blood-screening test available, it's absolutely vital that we act prudently," says Chris Thomas, an American Red Cross spokesman in Washington, D.C.
The Red Cross supplies about half of this country's blood. The organization says it could make up the loss of blood by promotional efforts and blood drives.
But the other half of the blood transfused in American hospitals comes from America's Blood Centers. There, Executive Vice President Dr. Celso Bianco worries that the Red Cross is overreacting. In doing so, he adds, it risks replacing a theoretical threat with a very real one: blood shortages.
"It's such a change," he says. "We eliminate immediately about a million donations out of the 13 million we have every year. That, he says, "would have an immediate, very serious impact."
An emergency-room patient bleeding to death due to lack of blood supplies, he notes, is not a theoretical risk.
Our recent mad cow carries a salutary lesson. By viewing a remote theoretical risk through a hype-filled hall of mirrors, we became terrified. We have overreacted and prompted the danger of a real killer: blood shortages. Farm failures. Stress.
As Paul Brown, chairman of the FDA's specialist committee on spongy-brain diseases, recently put it: "There are more suicides among farmers whose herds have been slaughtered in France than there are cases of BSE [mad cow]."
To learn more about mad cow and related diseases, the Centers for Disease Control and Prevention has some information on its Web site, http://www.cdc.gov/ncidod/eid/vol7no1/brown.htm).