DC, June 24, 2005 (ENS): A second U.S. animal
has tested positive for mad cow disease, Agriculture
Secretary Mike Johanns said today. Effective immediately
the U.S. Department of Agriculture is adding a second
diagnostic test to its protocol for determining whether
suspect cattle are infected with the fatal brain wasting
The U.S. Department of Agriculture (USDA) has received
final test results from The Veterinary Laboratories
Agency in Weybridge, England, confirming that a sample
from an animal that was blocked from the food supply
in November 2004 has tested positive for bovine spongiform
encephalopathy (BSE), commonly called mad cow disease.
The suspect animal was a downer cow, one unable to
walk, so it never entered the food chain, Johanns said.
It was one of the three suspect animals whose brain
tissue had been tested three times since November, using
three different procedures. Results were positive for
one cow on one of the three tests. The other tests were
either inconclusive or negative for all three cows.
The tests performed at Weybridge confirmed BSE in the
cow that had tested positive in one U.S. test.
Johanns directed USDA scientists to work with international
experts "to thoughtfully develop a new protocol
that includes performing dual confirmatory tests in
the event of another "inconclusive" BSE screening
"We are currently testing nearly 1,000 animals
per day as part of our BSE enhanced surveillance program,
more than 388,000 total tests, and this is the first
confirmed case resulting from our surveillance,"
Effective immediately, if another BSE rapid screening
test results in inconclusive findings, the USDA will
run both an immunohistochemistry (IHC) and Western blot
confirmatory test. If results from either confirmatory
test are positive, the sample will be considered positive
for BSE, Johanns said.
Both tests are accepted by the OIE, the World Animal
"This confirmed case of BSE in no way impacts
the safety of our nation's food supply," said Johanns.
"I want to make sure we continue to give consumers
every reason to be confident in the health of our cattle
herd," the secretary said. "By adding the
second confirmatory test, we boost that confidence and
bring our testing in line with the evolving worldwide
trend to use both IHC and Western blot together as confirmatory
tests for BSE."
"I am encouraged that our interlocking safeguards
are working exactly as intended. This animal was blocked
from entering the food supply because of the firewalls
we have in place," he said. "Americans have
every reason to continue to be confident in the safety
of our beef."
Only one case of mad cow disease had been confirmed
previously in the United States, in a dairy cow in Washington
State in December 2003. Since then, preliminary tests
indicated the possibility of the disease in three cows,
but further testing had ruled out any infection.
USDA has initiated an epidemiological investigation
to determine the animal's herd of origin. That investigation
is not yet complete. The animal was born before the
United States instituted a ruminant-to-ruminant feed
ban in August 1997, which prevents the use of most mammalian
protein in cattle feed.
According to internationally accepted research, feed
containing meat-and-bone meal is the primary way BSE
is transferred to the cattle population.
The animal was selected for testing because, as a non-ambulatory
animal, it was considered to be at higher risk for BSE.
An initial screening test on the animal in November
2004 was inconclusive, triggering USDA to conduct the
internationally accepted confirmatory IHC tests. Those
test results were negative.
Earlier this month, USDA's Office of the Inspector
General recommended further testing of the seven-month-old
sample using another internationally recognized confirmatory
test, the Western blot. Unlike the IHC, the Western
blot was reactive, prompting USDA to send samples from
the animal to the Weybridge laboratory for further analysis.
The laboratory in Weybridge, England, is recognized
by the OIE as a world reference laboratory for mad cow
disease. Weybridge officials this week conducted a combination
of rapid, IHC and Western blot testing on tissue samples
from the animal in question. At the same time these
diagnostic tests were being run by Weybridge, USDA conducted
its own additional tests.
As a non-ambulatory, or "downer" animal,
the cow was prohibited from entering the human food
supply, under an interim final rule in effect since
January 2004. Research has shown that BSE is most likely
to be found in older non-ambulatory cattle, animals
showing signs of central nervous system disorders, injured
or emaciated animals, and cattle that have died for
unexplained reasons. USDA's testing program targets
these groups of animals for testing.
The system of human health protections includes the
USDA ban on specified risk materials, or SRM's, from
the food supply. SRM's are most likely to contain the
BSE agent if it is present in an animal.
Additional measures, such as a longstanding ban on
importing cattle and beef products from high-risk countries,
a ruminant-to-ruminant feed ban, U.S. slaughter practices,
and aggressive surveillance provide a series of interlocking
safeguards to protect U.S. consumers and animal health.
As the epidemiological investigation progresses, USDA
pledged to continue to communicate findings in "a
timely and transparent manner. "
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