Scientists have found new evidence of a spontaneous occurrence of BSE in cattle. If such a sporadic form of mad cow disease exists, an eradication of the disease may not be possible. Continued active surveillance for the disease will be necessary to prevent BSE from flaring-up again.

Today's active surveillance programs target the eradication of BSE to prevent consumers from infection with variant Creutzfeldt-Jakob disease. However, the question of whether or not mad cow disease or BSE can be completely eliminated is still unanswered. A determining factor is the source of the disease. The most common theory explains the origin of the BSE epidemic with the feeding of inadequately inactivated meat and bone meal (MBM) derived from scrapie infected sheep and cattle. This theory is supported by the fact that BSE mainly occurs as one strain. If the only source of BSE is indeed infected feed, the disease can be eradicated with existing feed restrictions.

Atypical BSE strains
The recent discovery of atypical BSE strains however has raised the theory that BSE might be a spontaneously occurring disease in cattle. Until now two atypical forms which differ in their molecular properties have been defined. Recent research has now shown that the molecular properties of both atypical strains are maintained after transmission of the disease to mice. The BSE epidemic could therefore also have originated from a single spontaneous case of BSE that was then propagated to other cattle via feed stocks. Sporadic cases of BSE could also explain why many mad cow disease cases are found in animals that were born after the implementation of the MBM ban which prohibits feeding of animal remains to ruminants.
Future intensive active surveillance will have to prove if BSE can be completely eradicated or if single sporadic cases will continue to occur.