Regulators Debate U.S. Response to 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.
It is entirely possible that bacteria may be the cause of CJD, says Frank
Bastian, MD, a professor of neuropathology at the University of South Alabama.
Although prions appear in people with the disease, Bastian believes that prions
are a product rather than a cause of the disease. There are bacteria that fit
the criteria, he tells WebMD. Moreover, there is no actual proof that prions
are the cause, Bastian says.
Bastian became interested in this explanation when he discovered during a
brain biopsy a microorganism that reminded him of spiroplasma, he says. Unlike
prions, spiroplasma contain both RNA and DNA, and in many ways fit a number of
criteria for the type of agent that could cause an infectious disease such CJD,
Bastian tells WebMD.
Prions may be an accurate marker, but without further research, there is a
chance that these prion-based diagnostic tests may miss less virulent forms of
the disease, Bastian says. "We simply have to do more research because we
don't know the full spectrum, and we don't have a diagnostic test," he
tells WebMD. "We could be looking at the tip of the iceberg."
But while scientists agree that there is no direct proof that prions cause
CJD, the NIH still refuses to fund Bastian's research. "They just say it's
all solved. It's the prion," he tells WebMD. Worst of all, he says, the NIH
appears to be "throwing all their eggs into one basket when it would make
more sense to spread out the research."