NR AXKY
AU Dobly,A.; Renard,C.; Willemarck,N.; van Poucke,M.; De Sloovere,J.; Durand,S.; Geeroms,R.; Rodeghiero,C.; Vanopdenbosch,E.; Peelman,L.J.; Roels,S.
TI Results of TSE Surveillance in the Belgian Sheep Population
QU International Conference - Prion 2007 (26.-28.9.2007) Edinburgh International Conference Centre, Edinburgh, Scotland, UK - Book of Abstracts: Epidemiology, Risk Assessment and Transmission P04.20
IA http://www.prion2007.com/pdf/Prion Book of Abstracts.pdf
PT Konferenz-Poster
AB
The European breeding program favouring scrapie resistant alleles is confronted to the appearance of atypical cases, e.g. in scrapie-resistant genotypes. In this context an overall view of the characteristics of the TSE found in sheep is essential. We therefore present latest data on TSE positive sheep found in Belgium. Since 2001, all dead or slaughtered sheep older than 18 months undergo a rapid test for TSE. All 2029 suspected and fallen stock sheep are tested with histopathology, immunohistochemistry, electron microscopy and since 2002 Western blotting. Since 2002, all sheep from positive farms have their PRNP gene genotyped to evaluate their scrapie resistance status. In the atypical cases, in addition to codons 136, 154 and 171, we also control codon 141. Furthermore we carried out 32 discriminatory diagnostics using the CEA Bio-Rad Western blotting, for which we are recognized by the CRL(QA). We also genotyped all atypical scrapie and the latest classical scrapie case for 5 extra PRNP polymorphisms associated with higher PRNP mRNA expression in blood (see poster Willemarck et al.).
From 1992, we observed 24 primary cases for a total of 77 scrapie-affected sheep from 33 farms. We observed 8 atypical cases (7 Nor98 + 1 PK sensitive). We observed sheep from all susceptibility groups except group 4 (ARR/VRQ). From 2002 to 2004, the 10 positive sheep belonged to groups 3 and 5. However since the end of 2004 they came from groups 1, 2 and 3 (N=8). This difference could be related with the replacing of classical scrapie with atypical cases. Indeed we observed a unique atypical case before 2004 and 7 atypical cases out of 8 positive sheep from 2004 onwards. All atypical scrapie sheep were homozygote L/L for codon 141, except one Nor98, which was L/F. Seven atypical cases didn't possess any of the 5 polymorphisms associated with higher PRNP mRNA expression in blood, 1 atypical case was heterozygous for all 5 polymorphisms and the classical case was homozygous for all 5 polymorphisms. The discriminatory tests on the non-atypical cases showed that all samples corresponded to classical scrapie, excluding the possibility of BSE cases in sheep in Belgium till now. Finally there were no more scrapie cases than statistically expected in herds bearing an atypical strain.
According to our results the proportion of atypical cases is increasing through time. This could be due to the selection for resistant genotype but this hypothesis needs further data to be confirmed.
AD A. Dobly, C. Renard, J. De Sloovere, S. Durand, R. Geeroms, C. Rodeghiero, E. Vanopdenbosch, S. Roels, Veterinary and Agrochemical Research Centre (CODA/CERVA), Belgium; N. Willemarck, M. van Poucke, L.J. Peelman, Ghent University, Belgium
SP englisch
PO Schottland