Frequencies of PrP Genotypes in Meat Breeds of Japanese Sheep and Trail of Selective Breeding in Experimental Sheep Flock

Abstract

ABSTRACT. The selection of sheep with scrapie-resistant PrP genotypes is one of the control measures for transmissible spongiform encephalopathies in ruminants. In this study, we investigated the frequencies of PrP genotypes in meat breeds in Japan. The nationwide surveillance revealed that nearly half of the Suffolk sheep, a major meat breed in Japan, carried scrapie-susceptible AQ/AQ and AQ/VQ genotypes. In addition, the VQ haplotype, which confers high susceptibility to scrapie within sheep, was also found in Poll Dorset sheep. A trial of selective breeding using sires with scrapie-resistant PrP genotypes AQ/AR and AR/AR could raise the ratio of scrapie-resistant sheep from less than 50% to 80% within 3 years. However, the use of sires with the AR/AR genotype and the selection of ewes would be required to achieve a higher ratio of scrapie-resistant sheep. KEY WORDS: prion, scrapie, transmissible spongiform encephalopathy.

Protective effect of the T112 PrP variant in sheep challenged with bovine spongiform encephalopathy

“…The M112T variant of the sheep PRNP gene has been reported previously in scrapie-free sheep (Ikeda et al, 1995;Heaton et al, 2003;Gombojav et al, 2004;Goldmann et al, 2005;Lan et al, 2006;Ohara et al, 2007;Serrano et al, 2007;Babar et al, 2009), sheep infected naturally with classical scrapie (Laplanche et al, 1993;Ikeda et al, 1995;Saunders et al, 2006;Vaccari et al, 2007), sheep challenged orally with scrapie (Laegreid et al, 2008) and in various breeds of sheep (Goldmann et al, 2005;Serrano et al, 2007;Babar et al, 2009). The Goldmann et al (2005) study estimated that the TARQ allele accounts for 7 % of ARQ alleles in 41 UK sheep flocks examined.…”

Transmission of atypical scrapie to homozygous ARQ sheep

“…In Japan, the classical scrapie-susceptible ARQ/ARQ and ARQ/VRQ PRNP genotypes predominate among Suffolk sheep [33]. However, the risk to homozygous ARQ sheep of contracting atypical scrapie remains unknown.…”