Scientists work to stamp out mad cow
Staking out the Steak
Texas cattle ranchers will soon have a new tool in the fight against mad cow disease. The disease, bovine spongiform encephalopathy (BSE), has only been found in two cows in the U.S.--one in Texas.
A BSE epidemic in the United Kingdom in the 1980s and 1990s led to the destruction of thousands of cows and cost the British beef industry an estimated $5 billion. Texas ranchers hope to avoid those kinds of losses by watching the health of their herds carefully. A new test developed by researchers at the University of Texas Medical Branch at Galveston (UTMB) may make that easier by detecting BSE before an animal shows symptoms.
Until now, officials had to dissect the brains of infected cattle to diagnose BSE, a fatal disease that attacks the central nervous systems of cattle. UTMB researchers found a way to detect malformed proteins, or "prions," in blood that cause mad cow.
"We developed a technique that would amplify the quantity of this protein more than 10 million-fold, raising it to a detectable level," said Claudio Soto, a neurology professor who led the research.
Soto said his technique could improve detection of BSE and its counterpart disease in humans, variant Creutzfeldt-Jakob disease (vCJD), which is also fatal. BSE takes five to seven years to appear in cattle, while vCJD can take decades to appear in humans, Soto said.
"There's many advantages to having an ante-mortem test on a blood sample," said Dr. Lelve Gayle, executive director of the Texas Veterinary Medical Diagnostic Laboratory. "You could test a lot of cattle and [test] blood samples on cattle of different ages."
Scientists say the British BSE epidemic may have exposed millions of people in Europe to vCJD, which killed about 180 people worldwide by 2005.
"We don't know really how many people [were] exposed to this," said Soto. "It is of very much concern for Europe, and it should also be in the United States."
The first U.S. case of BSE occurred in a dairy cow in Washington state in December 2003. The U.S. Department of Agriculture (USDA) identified BSE in a second cow in Texas in June 2005, but meat from the animal did not enter the human food supply, according to the U.S. Food and Drug Administration (FDA).
Cows become infected with BSE by eating feed containing protein from infected cattle. Before 1997 in the U.S., portions of cows not usable for human consumption were processed into "meat and bone meal" and fed to cattle, Gayle said. In 1997, the FDA banned the use of meat and bone meal in cattle feed, so with time, the chances of finding BSE-infected cattle in the U.S. decrease, said Gayle.
In June 2004, the USDA launched the BSE enhanced surveillance program to test high-risk animals, including cattle that can't walk, are emaciated or show signs of a central nervous system disorder. By December 2005, the program had tested more than half a million cows, according to the USDA.
"I have confidence in what they're doing," said Rosalee
Coleman, second vice president of the Independent Cattlemen's Association of Texas and a cattle rancher in George West, Texas. "I think it's a receding problem because, if our science is correct, it was caused by feeding animals to animals, and we stopped doing that in 1997."
The U.S. mad cow cases haven't affected consumer demand for beef. Nationwide, demand in 2004 was up almost 8 percent from that of 2003, when the first U.S. case was reported, said Richard Wortham, executive vice president of the Texas Beef Council. Beef demand has remained strong in 2005, Wortham said.
Soto said his team is talking with companies and investors to develop commercial applications for the testing technology.
"The next step will be detecting prions in the blood of animals before they develop clinical symptoms and applying the technology to human blood samples," Soto said.