Abstract :
Susceptibility to scrapie in sheep is largely influenced by four polymorphic amino acid positions
of the ovine PrP gene at codons 136, 141, 154 and 171. Genotyping of corresponding
DNA polymorphism can be used as a basis for selection decisions. A total of 100 Red Maasai
and 79 Black Herd Persian sheep, representative of the widely distributed breeds in Tanzania,
were genotyped by real-time PCR. Genomic DNA was extracted from buccal epithelial
cells.We report six genotypes derived from four different alleles, with the ARQ/ARQ genotype
being more frequent (p = 0.0081) in the Red Maasai than in the Black Head Persian
sheep. Our study also demonstrated higher allelic frequency (p = 0.00055) of the ARQ in the
Red Maasai than in Black Head Persian sheep, while the AHQ allelic frequency was higher
(p = 0.00086) in the Black Head Persian. All the animals were homozygous LL141. The highly
susceptible VRQ allele was not found in any of the sheep breeds examined in this study.
Both breeds were genetically low-level resistant to scrapie (NSP3). Due to absence or very
lowfrequency of the ARR allele in the two breeds, selection for genetic resistance to scrapie
through an increase of the ARR allele does not seem very relevant. If new breeds of sheep
are to be introduced for crossbreeding in Tanzania, care should be taken to avoid import
of the VRQ allele. To our knowledge, this is the first study exploring the PrP genotypes in
sub-Saharan African sheep and in the Red Maasai and Black Head Persian sheep breeds
in particular. The data provide base-line information on genetic susceptibility of the two
sheep breeds to scrapie, whichmay be useful in policy formulation for prevention and future
research on prion diseases.
