DNA tests may help find source of mad cow case
Published June 26, 2005
WASHINGTON - The government hopes DNA analysis can pinpoint the herd of the cow that tested positive for mad cow disease and lead investigators to the source of the animal's brain-wasting illness, the Agriculture Department's chief veterinarian said Saturday.
Genetic testing is needed because of mistakes in how the cow was labeled and how its tissues were stored, John Clifford said.
The cow, a "downer" that could not walk, was delivered last November to a plant where animals unfit for human consumption are killed. The department has not identified the owner or the plant.
The cow's type of breed was mislabeled, possibly because the animal had been soiled heavily with manure, and its tissues were mixed with tissues from other cows, Clifford said.
"When we went back to this particular owner, the breed we identified, he indicated he did not sell that breed. He sold another breed," Clifford said. "In addition to that, we found that after the tissues were processed, there was some mixing."
Parts from the diseased animal and four other cows were supposed to be kept in separate waste barrels, but some of the waste was combined, Clifford said.
Department officials say they think they have found the right herd. To confirm that, they must test relatives of the dead cow.
"We're pretty confident that we have the herd, but we want to make sure," Clifford said.
Finding the herd will help track the cow's feed and explain how the animal became infected. Mad cow disease is spread through the feeding of infected cattle remains to other cattle. The United States has banned this practice since 1997.
When he announced the mad cow test results Friday, Agriculture Secretary Mike Johanns pointed out that U.S. cattle "move all across the country."
"They might be born in one state; they might be fed to a certain weight in another state," Johanns said. "They might be fed out in another state and slaughtered in yet a fourth state."
The new case was confirmed by an internationally recognized laboratory in England.
U.S. officials had declared the cow to be free of the disease in November, but the department's inspector general ordered a new round of tests that came back positive and led to the British tests.
It may be the first native-born case of mad cow disease. Johanns said there is no evidence the animal was imported. The only other U.S. case, confirmed in December 2003 in Washington state, was in a dairy cow that had been imported from Canada.
[Last modified June 26, 2005, 00:35:56]
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