DNA may pinpoint source of mad cow
WASHINGTON – The government hopes DNA analysis can identify 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 beef 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 think they have found the right herd. To confirm that, they must find relatives of the dead cow and test DNA.
“We’re pretty confident that we have the herd, but we want to make sure,” Clifford said. “Testing is being done now on tissue from cows that may have been herdmates.”
Finding the herd will help track the cow’s feed and explain how the animal became infected. The mad cow disease is only known to spread through the feeding of infected cattle remains to other cattle. The U.S. has banned this practice since 1997.
When he announced the mad cow test results on 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,” said Johanns, a former governor of Nebraska, a major beef state. “They might be fed out in another state and slaughtered yet in a fourth state.”
The new case was confirmed by an internationally recognized laboratory in England. A series of tests in the U.S. had produced conflicting results.
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 Mabton, Wash. – about 180 miles southwest of Spokane – was in a dairy cow that had been imported from Canada, where three other cases have been found.
Like the 2003 case, the November cow was born before the 1997 feed ban, Johanns said.
The 2003 case prompted nearly 50 countries to impose bans on American beef, causing billions of dollars in losses for the U.S. industry.
Hours after officials confirmed the new case, Taiwan reimposed its ban. Japanese officials said they would seek more information about the new case.
Taiwan was a $76 million beef market for the U.S. in the year before the ban and had decided to resume imports two months ago. Japan was by far the biggest market, importing around $1.5 billion annually.
“There is a big difference between a suspected case and a confirmation,” Japanese Food Safety Commission member Kiyotoshi Kaneko said in an interview aired by public broadcaster NHK.
Ed Loyd, an Agriculture Department spokesman, said Saturday that officials were talking with Taiwan authorities “to assure them of the safety of U.S. beef and that our interlocking safeguards did work as they should have to protect human and animal health.”
He added, “We are hopeful that this will only be a temporary ban on U.S. beef.”
Agriculture officials said the new case presented no new risk to human or animal health. The government banned downer cows such as this one from the food supply just days after the 2003 case. The feed ban and the downer ban are among many safeguards aimed at keeping mad cow disease from getting into food or feed. The November cow was incinerated.
Also Saturday, the department said it will review whether to continue its escalated level of testing for the disease beyond 2005.
Officials ramped up testing last June in response to the first case of mad cow disease. But the higher level of testing – about 1,000 each day – was intended to last only 12 months to 18 months.
The department has screened more than 388,000 dead cattle since the escalation.
“We’ll continue to review that with the secretary,” Clifford said. “There hasn’t been any decision at this point in time to stop or to reduce the level.”
He said the new case won’t play a role in the decision.
“It’s obvious that the prevalence of the disease is extremely low,” Clifford said.
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