Molecular screening of sheep for bovine spongiform encephalopathy

Bovine spongiform encephalopathy (BSE) may have transmitted to sheep through feed and pose a risk to human health. Sheep BSE cannot be clinically distinguished from scrapie, and conventional strain typing would be impractical on a significant scale. As human prion strains can be distinguished by differences in prion protein (PrP Sc) conformation and glycosylation we have applied PrP Sc typing to sheep. We found multiple Western blot patterns of PrP Sc in scrapie, consistent with the known scrapie strain diversity in sheep. Sheep passaged BSE showed a PrP Sc banding pattern similar to BSE passaged in other species [Collinge, J., Sidle, K.C.L., Meads, J., Ironside, J. and Hill, A.F., Nature, 383 (1996) 685–690], both in terms of fragment size following proteinase K cleavage and abundance of diglycosylated PrP. However, none of the historical or contemporary scrapie cases studied had a PrP Sc type identical to sheep BSE. While more extensive studies, including sheep of all PrP genotypes, will be required to fully evaluate these findings, these results suggest that large scale screening of sheep for BSE may be possible.