Brain Drain - mad cow disease

E: The Environmental Magazine, July, 1999 by Kathleen O'Neil, Fran Ryan

Can Britain's Mad Cow Disease Come Here?

At first, Doug McEwen forgot things--like, in the summer of 1998, his phone number and address. The symptoms got worse, but doctors still couldn't find anything wrong. Finally, the otherwise healthy 30-year-old quit his job, since he felt he could no longer perform well. Six months later, when he couldn't recognize his closest friends, neurologists took a biopsy of his brain, and gave him the diagnosis: Creutzfeldt-Jakob Disease (CJD).

CJD is in the family of Transmissible Spongiform Encephalopathies (TSEs), a mysterious class of degenerative diseases that produces holes in the brain, causing the tissue to appear sponge-like and creating symptoms similar to Alzheimer's. Versions of TSEs have been documented in both wild and domestic mammals, including house cats. TSEs are fatal in all cases, and there is no known cure.

According to John Stauber, founder of the Center for Media and Democracy and co-author of Mad Cow U.S.A., TSEs "probably occur in every mammalian species at some level. It's not a problem unless it can jump from one species to another." And that's precisely what happened in Britain, where a cow-based TSE known as Bovine Spongiform Encephalopathy (BSE), jumped to humans who came in contact with affected cows or ate infected meat.

Since the mid 1990s, 35 Britons have died from the human form of BSE, which is known as new-variant CJD (nvCJD). nvCJD differs from the traditional form in some striking ways. CJD is usually seen in people over the age of 60, while nvCJD victims have been in their 20s and 30s or even younger. Patients with nvCJD have experienced convulsions, deafness and blindness--uncommon symptoms in classic CJD.

Until recently, CJD infected no more than one person per million annually in the U.S. But Doug McEwen's case was one of six diagnosed in Utah during 1998, and in three of these cases the patients were 30 years old and under. Utah Department of Health Epidemiologist Gerri Dowdle believes that the increase in cases is a statistical anomaly. Ten percent of domestic CJD cases are known to be genetic, and one percent are acquired from certain surgical procedures. The rest are a mystery. "Keep in mind that statistics alone can be misleading," Dowdle says. "Given the incubation period of the disease, we expect to see clusters occur about every 20 years."

TSEs are unknown in U.S. cattle, but they have appeared in wild and captive-reared animals. Deer and elk in Utah, South Dakota and Nebraska have experienced a form of TSE called Chronic Wasting Disease (CWD), and some sections of Colorado and Wyoming have a four to six percent infection rate. Deer and elk game farms have also been infected, possibly through exposure to wild animal saliva at feeding stations. According to Tom Malmsbury, a scientist with the Colorado Department of Wildlife, "Three separate transmissibility studies are currently underway to determine if CWD can infect U.S. cattle."

Until recently, CWD was an oddity noticed only by wildlife professionals. "Everybody is concerned now because of what happened in Britain," says Tom Thorne, a veterinarian with the Wyoming Fish and Game Department. The fact that Doug McEwen was only 30 when he was diagnosed drew the attention of public health officials. When it was further discovered that he was an avid hunter and may have come into contact with CWD-infected deer, the concern became even greater. But an emphatic Dowdle points out, "There is absolutely no evidence of nvCJD occurring anywhere in the U.S"

Michael Hansen, a researcher with Consumers Union, is concerned that people in the U.S. could acquire a new variant of CJD from animal hosts. "We already know that abnormal cow proteins will recruit [and later infect] normal human proteins," says Hansen. "We need to be able to answer the simple question: `Can CWD from deer also infect humans?' There seems to be a `don't look, don't find' strategy, because this could be catastrophic to the meat industry."

Numerous laboratory studies have demonstrated that TSE from one animal can infect an animal of a different species. BSE-infected cow brains fed to or injected into mink, hamsters, monkeys and other animals have caused unique versions of that disease in each animal. And Stauber believes that CJD occurs much more frequently than is currently estimated. "According to several studies, significant percentages of people who died of dementia diseases, as many as 13 percent examined post-mortem, have CJD" he adds. "They've found that people who eat certain meats and brains have a higher chance of getting it."

Epidemiological studies of people who developed CJD in the U.S. show that they eat more animal brains and pork than the general population. Handling raw meat or animal products, including manure and milk, are also considered risk factors for contracting CJD.

Scientists have only begun to understand the method by which TSEs spread. The infectious agent is a mutant protein, called a "prion," which is smaller than any virus or bacteria. It cannot be killed by normal sterilization procedures, including chemicals or heat, and this makes it a particular problem for medical facilities. Many doctors are now using only disposable instruments for procedures on infected patients.