PrP genotype frequencies of the most dominant sheep breed in a country free from scrapie

Polymorphisms within the prion protein (PrP) gene are associated with scrap ie susceptibility. We analysed the PrP genes of 140 Romney Marsh sheep, the dominant breed in New Zealand, a country free from scrapie. We found PrP a lleles that are associated with a high susceptibility to scrapie. Sheep wit h these PrP genotypes would probably succumb to scrapie when born and raise d in a scrapie endemic environment. These findings correspond to those obta ined in minor breeds from New Zealand. We conclude that scrapie development not only depends on host genetic factors but also requires exogenous facto rs. Our findings demonstrate the effectiveness of the measures taken by New Zealand to maintain free from scrapie.