An atypical strain of mad cow disease seems to have been the cause of two cases of mad cow disease in Texas and Alabama and researchers say the mysterious strain could appear spontaneously in cattle.

Differences between the two U.S. cases and mad cow epidemic in Britain since the 1980s are making it more difficult to understand the degenerative brain disorder, which has the medical name of bovine spongiform encephalopathy (BSE), reports the AP.

The Agriculture Department's chief veterinarian, John Clifford, says, "It's most important right now, till the science tells us otherwise, that we treat this as BSE regardless."