Distribution of the prion protein in sheep terminally affected with BSE following experimental oral transmission.

This study has examined the distribution of PrP(Sc) in sheep by immunocytochemistry of tissues recovered from terminally affected animals following their experimental infection by the oral route with BSE. Despite a wide range of incubation period lengths, affected sheep showed a similar distribution of high levels of PrP(Sc) throughout the central nervous system. PrP(Sc) was also found in the lymphoid system, including parts of the digestive tract, and some components of the peripheral nervous system. These abundant PrP(Sc) deposits in sheep in regions outside the central nervous system are in direct contrast with cattle infected with BSE, which show barely detectable levels of PrP(Sc) in peripheral tissues. A number of genetically susceptible, challenged animals appear to have survived.