Because of the long incubation period, the ability to diagnose the presence of a BSE infection prior to the onset of the clinical disease would enhance the efficacy of surveillance and prevention programs. Because there is no fully characterized immune response to BSE or scrapie, diagnosis in live animals has been thought to be possible only when clinical signs are evident and must be confirmed by histopathology at post mortem, or brain biopsy of moribund patients. Recently published research suggests antemortem tests for the TSE agent may be possible.