Genetic risk assessment for atypical scrapie in Turkish native sheep breeds

Scrapie, a fatal transmissible spongiform encephalopathy (TSE), occurs in two phenotypes; classical and atypical. The aim of this study was to assess the genetic risk and identify the PRNP polymorphisms for atypical scrapie in a total of 1110 healthy sheep from 18 Turkish native sheep breeds. There were 10 alleles and 23 genotypes observed based on codons 136, 141, 154 and 171 of PRNP gene. The ALRQ allele was predominant for all breeds. The AFRQ allele, associated with the susceptibility to atypical scrapie, was detected in only I˙vesi. The other susceptible allele, ALHQ, was found at low frequencies in Akkaraman, Kangal Akkaraman, Güneykaraman, Kıvırcık, Sakız, Da˘glıc¸ and Gökc¸ eada breeds. Generally, the ALRQ/ALRQ genotype, which is resistant to atypical scrapie, was predominant in all breeds. Among the most susceptible genotypes to atypical scrapie, only ALHQ/ALHQ was found in this study. In addition, the ARR/ARR genotype, which has been reported in lots of atypical scrapie positive sheep from various countries, was detected in almost all Turkish native sheep breeds. According to our results, it is propounded that the susceptibility to atypical scrapie increased from eastern to western part of Turkey. Although it seems that Turkish native sheep breeds are safe from atypical scrapie, the occurrence of susceptible genotypes should be taken into consideration.