Epidemiological and genetical differences between classical and atypical scrapie cases.

Department of Animal Breeding and Genetics, Justus-Liebig University of Giessen, 35390 Giessen, Germany.
Veterinary Research (Impact Factor: 3.38). 01/2007; 38(1):65-80. DOI: 10.1051/vetres:2006046
Source: PubMed

ABSTRACT The aim of this study was to analyze the epidemiology and prion protein (PrP) genetics in scrapie-affected sheep flocks in Germany. For this purpose, 224 German scrapie cases in sheep diagnosed between January 2002 and February 2006 were classified as classical or atypical scrapie and the amino acids at codons 136, 141, 154 and 171 were determined. Likewise, representative numbers of flock mates were genotyped. Significant epidemiological differences were observed between classical and atypical scrapie cases in regard to the numbers of scrapie-affected sheep within a flock, the sizes of flocks with only a single scrapie-positive sheep or more than one scrapie-positive sheep and the age distribution of the scrapie-positive sheep. Sheep with the ARQ/ARQ genotype had by far the highest risk for acquiring classical scrapie, but the risk for atypical scrapie was the highest for sheep carrying phenylalanine (F) at position 141 (AF(141)RQ) and/or the AHQ haplotype. However, atypical scrapie also occurred with a notable frequency in sheep with the PrP haplotypes ARR and/or ARQ in combination with Leucine at position 141 (AL(141)RQ). Furthermore, six atypical scrapie-positive sheep carried the PrP genotype ARR/ARR. The high proportion of sheep flocks affected by atypical scrapie underscores the importance of this scrapie type.

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    ABSTRACT: Scrapie is a genetically associated neurodegenerative disease caused by the accumulation of an abnormal protein. The aim of this study was to perform genotyping of some scrapie-positive cases in sheep and the flocks they come from and to compare the effect of specific polymorphisms. It is important to examine positive cases in order to determine the possible polymorphism in the PRNP gene and its possible phenotypical appearance. Seventy-nine blood samples and 7 brain samples from scrapie affected flocks were tested. Five flocks of sheep, of different size and breed, were genotyped and the results showed that 3 of the animals in flock 1 had additional polymorphism in codon 138, nucleotide 413. In two of the animals from flock 5 there was homozygous and heterozygous polymorphism in codon 138, position 414. The VRQ allele, which is associated with high susceptibility to scrapie, was found in all the flocks, except flock number 2. Our data showed that the atypical scrapie cases are not associated with polymorphism in codon 141. Additional polymorphism was also observed at codons 137, 138, 151 and 152. Strategies for eradication of scrapie have been employed.
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    ABSTRACT: RIASSUNTO Nel 1998, in Norvegia, fu descritta per la prima volta una forma atipica di scrapie ovina denominata Nor98 e ad oggi descritta in tutta Europa; nei caprini questa patologia è stata riportata in Francia, Spagna, Svizzera e Italia. I polimorfismi del gene codificante per la proteina prionica (PRNP), ormai noti per il loro coinvolgimento nella modulazio-ne della suscettibilità/resistenza alla scrapie classica, sono ugualmente importanti nella scrapie atipica ovina. In particolare è stato dimostrato il ruolo quali fattori di rischio degli alleli AHQ e AF 141 RQ. Pur essendo stata riportata la presenza dell'allele AHQ anche nei caprini affetti da scrapie atipica, non vi erano ad oggi dati che consentissero di stabilire un'associazione sta-tistica tra tale allele e la suscettibilità alla malattia. Questo lavoro descrive pertanto uno studio caso-controllo condotto su fo-colai italiani di scrapie atipica Nor98: sono stati analizzati 8 casi e 246 controlli negativi di focolaio e l'analisi statistica effet-tuata mediante test chi-quadro ha consentito di attribuire un'associazione statisticamente significativa tra l'allele AHQ e la malattia (p-value=0,002). Dai risultati ottenuti si evince come una strategia basata sull'eliminazione selettiva dei caprini portatori della mutazione H154 possa considerarsi uno strumento di controllo efficace per ridurre il rischio di malattia in sede di focolaio di scrapie atipica.

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