- The Washington Times - Sunday, June 11, 2006

ASSOCIATED PRESS

Two cases of mad cow disease in Texas and Alabama seem to have resulted from a mysterious strain that could appear spontaneously in cattle, researchers say.

Government officials are trying to play down differences between the two U.S. cases and the mad cow epidemic that has led to the slaughter of thousands of cattle in Britain since the 1980s.

It is precisely these differences that are complicating efforts to understand the brain-wasting disorder, known medically as bovine spongiform encephalopathy, or BSE.

“It’s most important right now, till the science tells us otherwise, that we treat this as BSE regardless,” said the Agriculture Department’s chief veterinarian, Dr. John Clifford.

The Texas and Alabama cases — confirmed last year and this one, respectively — are drawing international attention.

At a meeting in London last month, specialists presented research on the U.S. cases and on similar ones in Europe.

These cows appear to have had an “atypical” strain that scientists are only now starting to identify. Such cases have been described in about a dozen cows in France, Italy and other European countries, as well as in Japan.

In the two U.S. cases, researchers did not detect the telltale spongy lesions caused by prions, the misfolded proteins that deposit plaque on the brain and kill brain cells. In addition, the prions in brain tissue samples from the Texas and Alabama cows seemed to be distributed differently from what would be expected to be found in cows with the classic form.

Laboratory studies on mice in France showed that both the classic and atypical strains could be spread from one animal to another. But scientists theorize the atypical strain might have infected cattle through an unusual way.

Mad cow disease is not transmitted from cow to cow like a cold or the flu. It is thought to spread through feed, when cows eat the contaminated tissue of other cattle. That happens when crushed cattle remains are added to feed as a protein source. This once-common practice ended in the U.S. in 1997.

Humans can get a related disease, variant Creutzfeldt-Jakob Disease, in similar fashion — by eating meat contaminated with mad cow. The variant form in humans afflicts younger people; the average age at death is 28.

A more common form of Creutzfeldt-Jakob Disease — not linked to mad cow — can happen spontaneously and is reported in nearly 300 people in the U.S. each year. This form occurs mostly in older people; the average age at death is 68.

Some scientists are suggesting that the atypical strain also might happen spontaneously in cattle. The Texas and Alabama cows were older animals, as were some of the other animals in Europe with seemingly atypical cases.

Dr. Linda Detwiler, a former Agriculture Department veterinarian who consults for major food companies, cautioned against making that assumption. “I think it’s kind of early to say that would be the case,” she said.

Other theories, she said, suggest the atypical strain might come from a mutation of mad cow disease or even from a related disease in sheep.

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