Prion protein gene polymorphisms in sheep with natural scrapie and healthy controls in Norway.

Abstract

Two-hundred and forty healthy sheep and 32 cases of natural scrapie in Norway were analysed for disease-linked polymorphisms in the prion protein (PrP) gene. Scrapie was strongly associated with the presence of a valine polymorphism at codon 136 (V 136 ), as 68n8 % of the cases were homozygous (VV 136 ) and 15n6 % were valine/alanine heterozygous (VA 136 ). All cases were homozygous arginine/arginine at codon 154 (RR 154 ), except two which were homozygous histidine/histidine (HH 154 ). All cases except two were homozygous glutamine/glutamine at codon 171 (QQ 171 ), the two exceptions being heterozygous glutamine/arginine (QR 171 ). More than 80 % of all scrapie cases in Norway have occurred in a Cheviot-related crossbred type of sheep called Rygja. This type of sheep, which is largely restricted to the south-western coast, carries the V 136 allele at a higher frequency than do other breeds of Norwegian sheep. Polymorphisms at codons 138 and 151 are also described.

Pregnancy status and fetal prion genetics determine PrP Sc accumulation in placentomes of scrapie-infected sheep

“…Sheep with a 171QQ genotype are susceptible to scrapie, and those with a 171QR or 171RR genotype are resistant to scrapie (11,13), with a few exceptions (26,27). The present study investigated the effects of offspring genotype and pregnancy on PrP Sc accumulation at the fetal-maternal interface of scrapie-infected sheep and possible transmission between tissues of different genotypes by using the ovine placentome as a natural chimeric model.…”

Atypical/Nor98 scrapie: properties of the agent, genetics, and epidemiology

“…Firstly, all animals were of AA 136 PrP genotype. The VRQ allele conferring susceptibility to classical scrapie in Norway [40] was completely absent from Nor98 cases although it was present in healthy flock mates. Secondly, there was an over-representation of animals carrying the AHQ allele, in HH 154 homozygous and HR 154 heterozygous genotypes.…”

PrPgenetics in ruminant transmissible spongiform encephalopathies

“…AF 141 RQ is certainly not a rare allele and homozygous AF 141 RQ/AF 141 RQ sheep are found regularly. When comparing averages from different breeds in different countries the AHQ allele frequency range appears to be 0.2% (USA) [21] to 12.5% (Norway) [68,88]. The mean of the AHQ frequency for the 20 studies (see above) is 6.3% and regional frequencies are 2.5% for Italy and Spain [1,2,4,27], 3.8% for Iceland [86], 9.6% for Greece [12,24] and 7.1% for New Zealand [14].…”

“…In the UK and in many outbreaks outside of the UK, such as in France, Ireland and Norway [25,69,88] the top group are VRQ/VRQ animals. The risk in this group is so high that scrapie was for a long time regarded as a genetic disease.…”

“…A survey conducted for this review of more than 20 studies [1,2,4,14,20,21,23,24,27,38,54,64,68,69,82,83,[86][87][88]90] reporting on sheep populations from 15 different countries in Europe, America and Asia revealed that so far all but one (Iceland) presented significant frequencies of all five major alleles (ARQ; ARR; AHQ; VRQ; ARH) in their sheep. Iceland appears not to have any ARR animals [86].…”