Suspicion of a Mad Cow Case Proves Unfounded, Tests Find - NYT 11/24/

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Suspicion of a Mad Cow Case Proves Unfounded, Tests Find

 

November 24, 2004

By DONALD G. McNEIL Jr.

 

 

 

A cow that tested positive last week in preliminary tests

for mad cow disease has tested negative in the follow-up,

the Agriculture Department announced yesterday.

 

 

The government's National Veterinary Services Laboratories

in Ames, Iowa, examined the cow's brain twice with what is

called an immunohistochemistry test, which officials

describe as the "gold standard," and the result was

negative both times, the department said.

 

 

"Negative results from both IHC tests makes us confident

that the animal in question is indeed negative," said John

Clifford, deputy administrator of the department's Animal

and Plant Health Inspection Service.

 

 

The department did not disclose the age, location or other

information about the animal. In announcing the preliminary

results last week, it said the meat had never entered the

food supply.

 

 

One regular critic of the department, Dr. Michael K.

Hansen, a senior research associate at Consumers Union,

expressed skepticism at the latest results and suggested

that further tests be conducted by sending samples to

Britain, which has far more experience with the disease.

 

 

Noting that the rapid, preliminary test on the animal had

been done more than once, Dr. Hansen said, "We feel it's

highly unusual to get this result given the low rate of

false positives when the Bio-Rad test is repeated."

 

 

Bio-Rad Laboratories, a California company, produces the

rapid test used by the department, which says 121,000

animals have been examined with it since June 1.

 

 

For unexplained reasons, the department has refused to

disclose most details of its testing in this case. A

spokeswoman said last week that the Bio-Rad test had been

run three times and been positive each time, but yesterday

the department suggested that it had been run only twice.

 

 

Dr. Hansen said he would like to hear the details of the

follow-up test, in particular which regions of the brain

were examined. Only the obex, near the brainstem, is

typically used in the rapid test, while the whole brain

should be sent for IHC testing since prions, the misfolded

proteins that cause mad cow disease, tend to clump in a

variety of the brain's regions.

 

 

Other frequent critics of the department's mad-cow policies

accepted the Iowa results.

 

 

One, Carol Tucker Foreman of the Consumer Federation of

America, called them "good news and a relief for everyone."

Another, Dr. Peter Lurie of Public Citizen, said he felt

that the Bio-Rad test was so highly sensitive that it

tended to "err toward overdiagnosis."

 

http://www.nytimes.com/2004/11/24/politics/24cow.html?ex=1102315701&ei=1&en=330

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