CHRONOLOGY- Mad Cow Test Results Vary for Suspect Animal
The USDA reported late on Friday an older animal tested positive for the brain-wasting disease and would be sent to a laboratory in England next week for a final round of testing.
The USDA has refused to disclose any information about the suspect animal's origin or where it was slaughtered. The department said the carcass never entered the human food or livestock feed supply.
Following is a chronology of USDA testing on the suspect animal.
Nov. 18, 2004 -- The USDA reports a "downer" animal tested "inconclusive" for mad cow disease in two rapid, preliminary tests. A downer is an animal too sick or injured to walk at slaughter.
This is the first time two preliminary tests on the same animal returned inconclusive since the USDA began its rapid testing program on June 1, 2004.
Brain samples are sent to a USDA laboratory in Ames, Iowa, for a more sophisticated, final round of tests.
Nov. 22 -- The suspect animal tests negative for mad cow disease in a immmunohistochemistry test, or IHC, considered the "gold standard" by the USDA.
Nov. 23 -- A second IHC test on the suspect animal returns negative. After this test, the USDA expresses confidence the animal does not have BSE.
Feb. 24, 2005 -- Consumers Union urges the USDA to retest the suspect animal, using an even more sophisticated test called the "Western blot" test.
Scientists in Japan and Belgium have reported suspect cows may be negative on the IHC and still register as positive on the Western blot, the consumer group said.
Week of June 5 -- USDA's Office of Inspector General recommends the retesting of the suspect animal using the Western blot test due to the discrepancy between the rapid test kits and the IHC.
June 10 -- The suspect animal tests positive for mad cow disease using the Western blot test.