NR AWJZ
AU McIntyre,K.M.; Gubbins,S.; Goldmann,W.; Hunter,N.; Baylis,M.
TI Epidemiological patterns of scrapie outbreaks in sheep flocks in Great Britain
QU International Conference - Prion 2006: Strategies, advances and trends towards protection of society - 3.10.-6.10.2006, Torino, Italy, Lingotto Conference Centre - Poster sessions EPI-17
PT Konferenz-Poster
AB Scrapie is an infectious disease, but one that is unusual in that the incubation period leading to clinical disease is governed by a strong host genetic component and a strong dose-response relationship. These factors can interact to yield intriguing epidemiological patterns. Here, we describe patterns in the outbreaks of confirmed classical scrapie in 30 sheep flocks. The flocks are part of a large farm-based case-control study, undertaken by the Institute for Animal Health (IAH) since 1998. Data on confirmed cases were derived from the Scrapie Notification Database (SND) held at the Veterinary Laboratories Agency (VLA), while those on flock characteristics were collected by IAH staff using a questionnaire. All flocks were blood sampled for PrP genotyping. Taking the first confirmed case as the beginning of an outbreak, the duration of epidemics varied between flocks from 1 to 9 years. Confirmed cases occurred in 6 (out of 15) PrP genotypes. These were predominantly in VRQ-bearing animals, but some cases also occurred in animals carrying the ARQ allele. The most common genotypes of cases were ARQ/VRQ and VRQ/VRQ. In most flocks, cases were confined to these two genotypes, but some flocks had markedly different affected genotypes. A measure of flock-level susceptibility was defined based on the relative frequency of genotypes in the flock and the risk of scrapie in those genotypes. The total number of cases per 1000 sheep increased significantly with flock-level susceptibility. However, no association was found between flock-level susceptibility and incidence (cases per 1000 sheep per year) or outbreak duration. The age-at-onset varied markedly within and between flocks, but certain trends were observed. In particular, it increased significantly during outbreaks, and the mean age-at-onset within a flock was similar for all genotypes, except for VRQ/VRQ where it was significantly lower. In one flock, animals of the ARQ/ARH genotype developed clinical signs at a significantly earlier age than VRQ/ARQ animals.
AD K.M. McIntyre, S. Gubbins: Institute for Animal Health, Pirbright, UK; W. Goldmann, N. Hunter: Institute for Animal Health, Neuropathogenesis Unit, Edinburgh, UK; M. Baylis: University of Liverpool Veterinary Teaching Hospitals, Neston, UK. E-mail: marie.mcintyre@bbsrc.ac.uk
SP englisch
PO Italien