Feb. 28, 2001 -- A new round of mad cow panic is sweeping Europe -- but if a promising new blood test pans out, doctors may soon have a simple way of screening both humans and animals for the presence of the fatal brain-wasting disorder unofficially known as mad cow disease. Such a test, experts tell WebMD, could go a long way toward calming people down.
At present, though, thousands of animals are being slaughtered and disposed of each day, and billions of marks, pounds, and francs are being spent in an effort to check the spread of tainted meat that causes the human form of the disease.
Beef consumption has fallen by 50% in some European nations in recent months, as stricter testing revealed contaminated cattle in a growing number of countries. Last month, French Prime Minister Lionel Jospin was pelted with rocks by angry cattlemen, and Spanish farmers barricaded slaughterhouses and meatpacking plants for three days to protest plummeting meat prices.
Cows infected with prions, the infectious agents believed to cause mad cow disease, develop a brain disease called bovine spongiform encephalopathy (BSE). Although the condition was first identified in Great Britain during the mid-1980s, it took another decade for the first cases of a brain disease similar to BSE to be reported in humans.
These people contracted the human form of the disorder, known as variant Creutzfeldt-Jakob disease (vCJD). This fatal illness usually begins with psychiatric symptoms, such as depression and anxiety, and progresses to complete incapacitation and death. Consumption of BSE-contaminated beef is now blamed for close to 100 deaths in the U.K.
BSE and vCJD are among a group of fatal neurodegenerative diseases collectively known as transmissible spongiform encephalopathies.
"The new realization that this is not just a disease of British cattle has resulted in a frenzy of press attention and finger pointing throughout Europe," says Swiss researcher Adriano Aguzzi, MD, of the University of Zurich. "Government officials have been forced from office, and now everyone is demanding a better diagnostic test."
That demand is closer to being answered with the recent identification of a molecular footprint for the disease that could theoretically be detected in both animals and humans by using a simple blood test. The current method of testing cattle requires they be slaughtered and their brains physically inspected. People are a little better off, but confirming infection with vCJD generally still requires a painful tonsil biopsy.
"There is no simple diagnostic test for people, so we have no idea how many are infected," says pathology professor and mad cow expert Witold K. Surewicz, PhD, of Case Western Reserve University in Cleveland, Ohio. "Routine testing just isn't possible. And the process of testing cattle is also complicated. This is a pretty exciting finding which could lead to an easier and much more accurate test."
Writing in the March issue of the journal Nature Medicine, researchers from Scotland's Roslin Institute demonstrated that a protein known as erythroid differentiation-related factor (EDRF) might be overproduced in people when they contract transmissible spongiform encephalopathies such as mad cow disease. Perhaps, the researchers suggest, it may be possible to design a test for EDRF, with higher than normal levels of the protein being an indicator of likely infection.
In an editorial that appears in the same issue, Aguzzi points out that several basic questions must be answered before we'll know if EDRF will in fact be a good diagnostic marker.
For instance, he says, it is not currently known if overproduction of the protein is unique to transmissible spongiform encephalopathies, or if the same thing happens in other diseases. Researchers also must establish what a normal level of EDRF is in healthy, noninfected people.
"With all the attention being paid to this issue, and the desire for a blood test to find this infection, these questions should be answered very quickly," Aguzzi says.
Surewicz agrees and adds that these findings, while exciting, are very preliminary.
"I am certain the research will get done, because we are all desperate to find a simple test," he says. "Even if these findings turn out to be less than significant, I feel certain that there will be a simple diagnostic test. I just can't say when."