PrP polymorphisms in Brazilian sheep

Ovine scrapie, a fatal, neurodegenerative disorder of the transmissible spongiform encephalopathies group is an emerging disease in Brazilian sheep. The disorder is due to the deposition of a conformationally altered form (PrPSc) of the normal prion protein (PrPC) in the central nervous and lymphoreticular systems. Mutations at codons 171 (Q, R, H, or K) and 136 (V or A) in the ovine prion gene (PrP), influence scrapie incidence, the codon 171 being the major determinant of susceptibility. This paper analyzed 301 sheep of Hampshire Down and Suffolk breeds in relation to codon 136 and 171. Genomic DNA was obtained from blood and genotypes were screened using polimerase chain reaction and restriction endonuclease digestion. The AA and QQ genotypes were the most frequent in Suffolk breed, while AA and QR were the more common in H. Down sheep. Considering both codons simultaneously the AAQQ genotype was the most frequent in Suffolk and AAQR in H. Down. Up to 90% of the animals had medium to high risk of developing the disease. This data could be used as a guide for selection procedures to reduce the risk of scrapie in Brazilian sheep flocks.