| Mysterious mad cow cases found texas alabama { June 12 2006 } Original Source Link: (May no longer be active) http://www.chron.com/disp/story.mpl/nation/3960683.htmlhttp://www.chron.com/disp/story.mpl/nation/3960683.html
June 12, 2006, 1:42AM Mad cow cases in Texas, Alabama called mysterious The strain found may form in cattle spontaneously, researchers say
By LIBBY QUAID Associated Press
WASHINGTON - 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.
But 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," the Agriculture Department's chief veterinarian, John Clifford, said.
The Texas and Alabama cases are drawing international attention. At a meeting in London last month, experts presented research on the 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 identified in about a dozen cows in Europe and others 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 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 in 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.
Humans can get a related disease, variant Creutzfeldt-Jakob Disease, in similar fashion by eating meat contaminated with BSE. Mad cow in humans typically afflicts younger people; the average age at death is 28.
A more common form of CJD not linked to mad cow can happen spontaneously and is reported in nearly 300 people in the U.S. each year. This form infects mostly older people; the average age at death is 68.
Some scientists are raising the possibility 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.
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