US government agencies are confronting a tough test of their much-vaunted ability to maintain a safe food supply, as they scramble to block possible paths for the entry of mad cow disease into the United States. Their latest action is to extend a ban on blood donors from European countries.
Until late last year the disease, more properly known as bovine spongiform encephalopathy (BSE), was thought to be largely confined to the United Kingdom, Switzerland and Ireland. In the United Kingdom, more than 80 people have died from variant Creutzfeldt– Jakob disease (vCJD), an analogous human disease presumed to be contracted by eating infected cattle.
But the BSE panic is fanning out across Europe, with Italy the latest country to succumb (see next article). Its implications are registering with the American public for the first time, putting intense pressure on agencies charged with protecting food safety. These, primarily the Food and Drug Administration (FDA) and the United States Department of Agriculture (USDA), confront a challenge that is logistically complex, politically delicate and scientifically uncertain.
“The FDA and USDA face a tough balancing act against a frightening, little-known enemy. It's as tough as any [challenge] in the last decade,” says Arthur Caplan, director of the University of Pennsylvania's Center for Bioethics. He chairs a committee that advises the Department of Health and Human Services, the FDA's parent agency, on blood safety.
An FDA advisory committee last week recommended extending a ban on blood donors to include people who have, since 1980, spent ten years in France, Portugal or the Republic of Ireland. Previously, the 1999 ban had applied only to those who had spent six months or more in the United Kingdom between 1980 and 1996.
It is not known whether the disease can be spread through blood transfusion, although the epidemiological evidence so far makes this unlikely. But, says Paul Brown, chair of the advisory committee and director of the Laboratory of Central Nervous System Studies at the National Institute of Neurological Disorders and Stroke, “the committee chose a compromise conservative position. They are assuming there's a significant potential risk of exposure in Europe.”
The committee had been pressed unsuccessfully by the US Red Cross and others to bar donors who had spent less than six months in the United Kingdom and to extend the ban to the whole of Europe.
BSE and vCJD are caused by abnormally shaped brain proteins or prions. These cause neurological deterioration, leading to dementia, uncontrolled movement and rapid death. There is no diagnostic test for the diseases, which are confirmed by microscopic examination of the brain after death.
No cases of BSE or vCJD have been diagnosed in the United States, according to the USDA and the Centers for Disease Control and Prevention. The USDA has examined the brains of 11,900 cattle in the past decade.
“Currently we are free of mad cow disease in cows and variant CJD in humans. Every possible effort must be expended to keep us in that category,” says Sidney Wolfe, who heads the consumer watchdog Public Citizen Health Research Group in Washington DC.
Regulation of the many routes by which BSE might enter the United States is complex. The FDA monitors animal feed, blood products, vaccines and dietary supplements. The USDA is responsible for safety of meat and the health of 900 million US cattle.
“If we get BSE in this country, our cattle industry goes down the tubes,” says Jim Rogers, a spokesman for the USDA's Animal and Plant Health Inspection Service.
The FDA has no power to stop the manufacturers of dietary supplements using processed cow parts, including brain, in their products. Similarly, a USDA import ban on bovine tissues applies only if they are destined for use in food and medical products, not if they are to become dietary supplements. One nationally distributed supplement lists 17 bovine organs, including brain, as ingredients.
The United States has not imported British beef since 1985, and it banned imports of live cows from BSE-affected countries in 1989. But a recent report by a scientific advisory panel to the European Union says that tonnes of high-risk European beef products are shipped to the United States annually. They include gelatin, collagen, semen and albumin, and are used in products including cosmetics and vaccines. (In December, the FDA forbade US drug-makers to use bovine serum from BSE-affected countries in certain vaccines, but vaccines produced before the ban are still in use.)
Besides the loopholes for exports, measures to protect the US herd are sometimes disregarded. BSE is believed to have spread through the practice, now prohibited, of using cow and sheep parts in cattle feed. The FDA announced on 10 January that hundreds of US feed producers are not complying with 1997 regulations enforcing the ban.
Beyond the challenge of enforcing current regulations, the US agencies need to examine how to plug loopholes, and to determine the best way to spend limited resources fighting a dimly understood enemy. How much effort should be spent in developing a screening test for the diseases or finding a treatment, or on blocking any imported or home-grown vehicle that might spread the diseases?
Deer and elk herds in the western United States, for instance, are being afflicted in growing numbers with an analogous ailment called chronic wasting disease. Last week, the committee that extended the blood-donor ban was asked to consider if and how blood donations from people exposed to these deer and elk should be restricted. It decided there were not yet enough data to implement restrictions on them.
All of these issues “get into foreign policy questions, trade issues, regulation of hunters, which Americans hate. These are all politically tricky,” says Caplan.
At the advisory committee meeting last week, scientists complained of the lack of data on which to base their decisions — including the future curve of the epidemic in Europe, and the risk of exposure in other European countries compared with the United Kingdom. “These decisions . . . are really guesses,” said Stanley Prusiner, who won a Nobel prize in 1997 for discovering prions and elucidating how they cause disease.