NR AWJV
AU Maurella,C.; Possidente,R.; Bona,M.C.; Quasso,A.; Ariello,D.; Crescio,M.I.; Cellerino,C.; Peletto,S.; Caramelli,M.; Ru,G.
TI Born to be resistant: history of a selective culling
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-15
PT Konferenz-Poster
AB In May 2003 an outbreak of scrapie in a Biellese breed flock was confirmed in Piemonte.The flock was entirely genotyped for selective culling according to Regulation 1492/2004/EC. Owing to the low frequency of the ARR allele, the foreseen derogations (Reg. 260/2003/EC) were applied, thus delaying the destruction of susceptible animals for up to five breeding years. The aim of this work was to analyse the cumulative survival probability of each sheep associated to its own genotype. With regard to susceptibility the genotypes were grouped in three different classes according to the "National plan of genetic selection". In order to model the hazard for each individual to come down with scrapie, survival analysis techniques were applied to 1198 sheep who entered the study during a thirty-month follow up time. 53 scrapie positive sheep were detected in the study period. After the complete culling of all the VRQ carriers sheep, the origin and the end of the study were fixed respectively a day after the initial big culling (22 October 2003) and on 30 April 2006. Animals still alive at the end of the study were considered as right censored, whereas animals who left the flock because of a reason other than scrapie, were considered left censored. Follow up time was split into very small time bands (one day each) in order to suppose that only few animals died in each time band. The Kaplan - Meier estimate of the survivor function was obtained. To verify the null hypothesis (the three classes have the same probability to survive) the Logrank test was performed. In order to include in the model as covariates both age and genotype, a semi-parametric analyses (Cox proportional hazards model) was fitted. After adjustment, statistically increased risk was evident only for the susceptible genotype and the age-class 24-48 months.
AD C. Maurella, R. Possidente, M.C. Bona, M.I. Crescio, S. Peletto, M. Caramelli, G. Ru: Istituto Zooprofilattico del Piemonte, CEA, Turin, Italy; A. Quasso: ASL 19, Asti, Italy; D. Ariello: ASL 5, Rivoli, Italy; C. Cellerino: Regione Piemonte, Direzione di Sanità Pubblica, Italy. E-mail: cristiana.maurella@izsto.it
SP englisch
PO Italien