Korean Journal of Veterinary Research 2009;49(2):149-155.
A simulation model for evaluating serological monitoring program of Aujeszky's disease
Ki-Yoon Chang1, Son-Il Pak2, Choi-Kyu Park3, Kyoung-Ki Lee3, Yi-Seok Joo3
1Animal Health Division, Livestock Policy Bureau, Ministry for Food, Agriculture, Forestry and Fisheries
2School of Veterinary Medicine and Institute of Veterinary Science, Kangwon National University
3National Veterinary Research and Quarantine Service
확률모형을 이용한 오제스키병 혈청학적 모니터링 프로그램 평가
장기윤1, 박선일2, 박최규3, 이경기3, 주이석3
1축산정책단, 농림수산식품부
2강원대학교 수의학부대학 및 동물의학종합연구소
3국립수의과학검역원
Abstract
The objective of this study was to analyze data from the planned national serological monitoring program for Aujeszky's disease (AD) using a simulation model to evaluate probable outcomes expected in the sample derived from the simulated herds at predefined within-herd prevalence and herd prevalence. Additionally, prevalence at animal- and herd-level estimated by the stochastic simulation model based on the distributions of the proportion of infected herds and test-positive animals was compared with those of data from a national serological survey in 2006, in which 106,762 fattening pigs from 5,325 herds were tested for AD using a commercial ELISA kit. A fixed value of 95% was used for test sensitivity, and the specificity was modeled with a minimum, most likely and maximum of 95, 97 and 99%, respectively. The within-herd prevalence and herd prevalence was modeled using Pert and Triang distributions, respectively with a minimum, most likely and maximum point values. In all calculations, population size of 1,000 was used due to lack of representative information. The mean number of infected herds and true test-positives was estimated to be 27 herds (median = 25; 95% percentile 44) and 214 pigs (median = 196; 95% percentile 423), respectively. When testing 20 pigs (mean of 2006 survey) in each herd, there was a 3.3% probability that the potential for false-positive reactions due to less than 100% specificity of the ELISA test would be detected. It was found that the model showed prevalence of 0.21% (99% percentile 0.50%) and 0.5% (99% percentile 0.99%) at animal- and herd-level, respectively. These rates were much similar to data from the 2006 survey (0.62% versus 0.83%). The overall mean herd-level sensitivity of the 2006 survey for fattening pigs was 99.9%, with only a 0.2% probability of failing to detect at least one infected herd.
Key Words: Aujeszky's disease, sensitivity, serological monitoring, stochastic model


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