New York, September 8, 2003 (ENS): Researchers
at the University of California at San Francisco (UCSF)
say they may have found a faster, more reliable test
for identifying mad cow disease - possibly even in living
cows. Current tests can only detect the disease after
the cow dies.
Critics argue that the standard immunoassay tests used
to identify the infectious prion proteins that cause
mad cow disease are inadequate for large scale screening
of cattle. The tests can produce false readings and
may take a week to yield results.
The new test, which has already undergone animal studies,
can detect prion proteins with 100 percent accuracy
at much smaller levels than conventional tests and only
takes about five hours to produce results, according
to the UCSF researchers.
Like conventional tests, the new test is designed for
detecting prions in the brain tissue of cows only upon
autopsy. Unlike other tests, however, the new test also
shows promise for detecting the proteins in muscle tissue
and even blood while the animal is still alive.
If so, it could be used to identify precisely which
animals are infected before they show symptoms and could
help end the current practice of slaughtering whole
herds, the scientists say.
"This represents a new generation of prion tests,"
says project leader Dr. Jiri Safar, an associate adjunct
professor at University of California and a member of
the school's Institute of Neurodegenerative Diseases.
"It is the most promising test to date for accurately
detecting prion proteins."
Called the conformation-dependent immunoassay (CDI),
the test was described Friday at the 226th national
meeting of the American Chemical Society, the world's
largest scientific society.
Safar says the test has been used in a field trial
to check for signs of the disease in the brains of 11,000
slaughtered cows in Spain, the United Kingdom and Germany.
Results were compared to those from standard immunoassays
performed on the same animals. There were no discrepancies
between the tests, according to Safar.
"We had a perfect score. There were no false positives
and no false negatives," says Safar. "We can
not afford incorrect conclusions, and we did not see
that in our tests."
The research group plans to use the test on an even
larger scale among European cattle herds within the
next year, checking them for signs of the disease upon
If further tests prove successful, Safar hopes it will
eventually be used to evaluate dead cows in this country
for mad cow disease, also known as bovine spongiform
encephelopathy, or BSE.
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