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 federal Centers for Disease Control announced Monday that a British man has been diagnosed with the human form of mad cow disease -the second documented U.S. case of the illness.

Health officials say the man most likely contracted variant Creutzfeldt-Jakob disease in the United Kingdom. However, he began to show symptoms while living in Houston, so he will be listed as a U.S

The Agriculture Department announces Friday there is no health risk to consumers after receiving conflicting results of a mad-cow test conducted on a bovine that was unable to walk and will seek further testing of a tissue sample of the cow.

There has only been one case of mad cow disease in The U.S., an infected dairy cow in Washington State in December 2003