Title : Scrapie resistance gene identification using optimized TaqMan qPCR method in sheep in the Republic of Serbia
Abstract:
Scrapie is a neurodegenerative disease of sheep and goats that belongs to the group of transmissible spongiform encephalopathies (TSEs). It is caused by the accumulation of a proteinase-resistant isoform of prion protein (PrP). Susceptibility to scrapie in sheep is associated with polymorphisms of the PrP gene, specifically at codons 136, 154, and 171. The ARR allele is associated with a high level of resistance to classical scrapie, while the VRQ genotype is considered the most susceptible. Many countries have implemented eradication programs based on the use of rams with resistant genotypes. However, such a program has not been introduced in Serbia. To determine the genetic status of sheep in Serbia regarding resistance to scrapie, we optimized TaqMan probes for the real-time polymerase chain reaction (qPCR) method for the three codons. A total of 100 sheep from farms in Progar and Svilajnac were tested using blood samples, and the most frequent genotype for codon 136 was AA, for codon 154 it was RR, and for codon 171 it was QQ. The most common genotype was ARQ/ARQ, representing 34% of the tested population, while the ARR/ARR genotype, associated with high resistance, was observed in only 6% of the sheep. The results indicate that most of the examined sheep belong to genotypic groups with low genetic resistance to scrapie. This suggests that selective breeding should be considered to increase the frequency of resistant alleles in the national flock. The implementation of a selective breeding program based on genetic testing is crucial for reducing the incidence of scrapie and enhancing the overall health of the sheep population in Serbia.
