U.S. mad cow cases are mysterious strain

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 for short...more