‘Forgotten’ Sample Tests Positive for Mad Cow Disease

Jul. 28–The Agriculture Department said Wednesday that a “forgotten” brain sample taken in April from an ailing cow was tested last week and gave a positive but unusual reaction for mad cow disease.

The department said it is too early to call it the nation’s third case of bovine spongiform encephalopathy, or BSE. The cow’s herd has not been quarantined, nor have its progeny and similar-age livestock been traced.

Officially, the test was “nondefinitive.” The USDA said staining on the sample denoted prion proteins of BSE, but not in places where such stains usually occur.

Further testing will be conducted at laboratories in Ames, Iowa, and Weybridge, England, with results expected next week, said John Clifford, the USDA’s chief veterinarian.

The animal, killed after experiencing calving problems, was incinerated, and there was no risk to the food supply, Clifford said during a teleconference.

Clifford said early reports indicated that the cow was native-born, but he would not say where its herd was. Texas Animal Health Commission officials said they have not been contacted, The Associated Press reported. Texas has the nation’s largest cattle herd.

Clifford described the cow as being at least 12 years old, meaning it was born before a 1997 ban on feed made with rendered cattle, which is believed to be the means of transmitting the brain-wasting disease to other cattle.

Scientists believe a rare human disease, known as variant Creutzfeldt-Jakob, can be contracted by eating beef products from cattle with BSE. But the only American case involved a Florida woman who lived in Britain when such tainted products were sold. High-risk material has been banned from the human food supply since 2003 but not from chicken and hog feed, as some experts have urged. The Food and Drug Administration has delayed action on extending the ban.

The newly disclosed case is complicated by the fact that a private veterinarian did not ship the brain sample to a laboratory within 48 hours. In April, the permitted routine allowed veterinarians in remote areas to preserve the sample before sending it.

The unidentified doctor preserved the brain stem sample in formalin, a solution made with formaldehyde, but then “simply forgot” about it until mid-July, Clifford said during a teleconference.

The preservative prevents laboratories from using both a BioRad rapid screening test and a confirmatory test, known as Western blot. This leaves only one type of test, the immunohistochemistry.

It was Western blot that confirmed BSE in a Texas cow on June 10 after an immunohistochemistry test turned up negative in November.

Clifford said the latest cow was put down after its calving problems, but he did not describe it as a downer — alive but unable to walk. Downers might have central nervous system problems, including BSE, or might simply have been injured while giving birth. All downers must be killed, kept out of the food supply and tested for BSE.

Beef industry groups immediately issued statements reassuring the public that effective safeguards are in place to protect the food supply.

“Providing safe and wholesome beef remains our number one priority,” the National Cattlemen’s Beef Association said.

But Consumers Union’s top science official, Michael Hansen, said Wednesday’s disclosure “raises all sorts of problems with surveillance program.”

Referring to the test sample, he said: “Why did it sit for so many months? Why did they allow it to be preserved in formalin?”

“The fact that there is some staining, it is detecting some BSE prion protein. That’s what they are staining for,” Hansen said. As for the unusual staining, he said that could mean a rare or atypical strain of the disease.

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