JERUSALEM -- Israeli researchers have developed a simple urine test that can identify so-called mad cow disease before symptoms appear, a finding that could prevent large-scale culling of unaffected cattle and lead to screening tests for the human variant of the brain-wasting disease.
Until now, the only definitive way to test for bovine spongiform encephalopathy (BSE, commonly known as mad cow disease) -- or for the variant of Creutzfeldt-Jakob disease, known as vCJD, that humans can catch -- has been to examine the brain after death.
Yesterday, researchers said they have developed a urine test that can identify the nerve protein particle, or prion, that causes the fatal disease before any signs of the illness appear.
"The goal and hope is to develop a test that could be widely used for the detection of the disease," said Ruth Gabizon, head of the research team at Jerusalem's Hadassah University Hospital.
"This could avert the necessity of killing herds of cattle upon the discovery of one affected cow."
Urine samples from hamsters, cattle and humans known to be infected all revealed the presence of prions before any clinical signs manifested, said the researchers, whose work is reported in the current issue of the Journal of Biological Chemistry.
The researchers said examination of human urine could also prevent the danger of infection via blood donations, although so far no direct link has been established between blood or organ donations and the transmission of vCJD.
Widespread urine tests among humans could also help determine whether the number of carriers is in the hundreds, the thousands, or even the hundreds of thousands, as some scientists fear.
"Regular screening of cattle may be able to wipe out BSE in animals within a few years, but from data available so far it appears that the incubation period of CJD in humans is about 30 years," said Dr. Gabizon, adding: "That's why it is so important to screen all blood and organ donors because it can lie dormant for so long."
Dr. Gabizon said talks are under way with commercial investors in the United States and Europe to develop a simple version of the urine test so that all cattle and human patients, including potential blood and organ donors, could be screened as a matter of course.
More than 100 people, most of them in Britain, have died in Europe in recent years after eating beef infected with BSE, and many more are expected to fall victim to it, as the disease can be carried for decades before any of its symptoms begin to appear.
BSE was first detected in England in 1985 in cows that contracted the disease through feed that was made from sheep infected with scrapie.
Since then, millions of cows have been destroyed across Europe as a preventive measure after outbreaks were discovered.
Although it has not been proven that blood from people who carry Creutzfeldt-Jakob disease can transmit the virus on to others, the possibility has raised concern.
The Canadian Blood Service has banned donations from people who spent more than six months in the United Kingdom and France between 1980 and 1996, and recently an advisory panel to the U.S. government recommended a similar ban.
Dr. Gabizon has been researching prions at Hadassah Hospital since 1988.
Previously, she studied prion disease with Nobel Prize-winning scientist Stanley Prusiner at the University of California.
Prions -- the nerve proteins that cause BSE, CJD or related diseases such as scrapie -- are normally benign, but can take on a misshapen form that can cause holes to form in the brain.