Regulators Debate U.S. Response to Mad Cow Disease
WebMD News Archive
In this case, there are some striking similarities. "We simply don't
know if there is the potential for CJD to be in the blood of donors,"
explains Steve Petteway, director of pathogen safety and research at Bayer
Corp., where groundbreaking work has been done on that subject. But studies
have shown that the infectious agent may reside in the blood of animals, which
lends credibility to the FDA's concern, he says.
To find the answer, scientists around the world are working on a test to
detect an unconventional protein called a prion, a previously unknown
infectious agent believed to be behind CJD. Prions are thought to transform
healthy molecules to a dangerous conformation, causing not only CJD but also
mink encephalopathy, scarpie in goats and sheep, chronic wasting disease of
mule deer and elk, feline spongiform encephalopathy, and bovine spongiform
encephalopathy -- or mad cow disease.
Experiments with mice in which scientists managed to transfer CJD using
prions show there is good reason to believe that prions are the cause of the
disease, says Mary Jo Schmerr, PhD, the lead scientist for prion diseases at
the National Animal Disease Center, a division of the USDA.
Based on that data, Schmerr has developed a test for animals and is now
working on a test to extract prions from concentrated human blood samples. Such
a test, she tells WebMD, would go along way toward detecting the disease in its
early stages, when treatment might still be possible.
Based on that data, others also are working on a test to confirm whether
their methods for extracting matter from the lining of the human brain and for
extracting blood components reduces the risk of inadvertently transferring the
disease from an infected person to a healthy person. So far, that work has
demonstrated the value of using animal models, and that once the prions are
removed, the disease cannot be transferred, Petteway tells WebMD.
But at least one researcher who has studied CJD for 25 years still is
disputing the official version of what causes CJD, and if he is right,
researchers may not be able to develop a reliable early screening test. Also at
question is whether government regulators can accurately assess the risk posed
by CJD, which some say may be far more prevalent than originally thought.