Epidemiological and genetical differences between classical and atypical scrapie casesGesine Lühkena, Anne Buschmannb, Horst Brandta, Martin Eidenb, Martin H. Groschupb and Georg Erhardta
a Department of Animal Breeding and Genetics, Justus-Liebig University of Giessen, 35390 Giessen, Germany
b Friedrich-Loeffler Institute (FLI), Institute for Novel and Emerging Infectious Diseases, 17493 Greifswald-Insel Riems, Germany
(Received 16 June 2006; accepted 13 September 2006; published online 8 December 2006)
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 (AF141RQ) 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 (AL141RQ). 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.
Key words: sheep / classical scrapie / atypical scrapie / epidemiology / PrP polymorphisms
Corresponding author: Gesine.Luehken@agrar.uni-giessen.de
© INRA, EDP Sciences 2007