Korean Journal of Veterinary Research 2007;47(4):417-423.
Sample size for serological surveillance of Aujeszky's disease in Korea
Eu-Tteum Kim1, Son-Il Pak1, Choi-Kyu Park2, Chang-Hee Kweon2
1School of Veterinary Medicine and Institute of Veterinary Science, Kangwon National University
2National Veterinary Research and Quarantine Service
국내 돼지오제스키병의 혈청학적 감시활동(surveillance)을 위한 표본크기
김으뜸1, 박선일1, 박최규2, 권창희2
1강원대학교 수의학부대학 및 동물의학종합연구소
2국립수의과학검역원
Abstract
Serological surveillance programs in animal populations are becoming increasingly important to estimate prevalence of a specific disease and subsequently to document disease-free status in a region or a country. For these purposes, the programs need to be based on both theoretical and economical aspects from the designing phase. From Aujeszky's disease (AD)-eradication program point of view, group of animals (aggregates, herds) not individual animal is the more important sampling unit of concern. In this study the authors therefore attempted to compute an appropriate sample size tailored to a current surveillance program against AD, assuming that the goal of this program is either herd-level prevalence estimation or documentation of AD-freedom. For prevalence estimation, assuming a finite population with imperfect sensitivity (Se) and specificity (Sp) of ELISA kit for AD diagnosis, the number of herds present, expected herd prevalence, and desired accuracy for a certain level of confidence, sample size was estimated at herd-level in the first stage and individual animal-level in the second stage. A two-stage sampling design was used to calculate a sample size to indicate AD-freedom. In this instance, the computation was based on the possible detection of a predetermined prevalence at a certain herd-level Se and Sp. This study indicated that the sample size varied with predetermined confidence, tolerance, Se and Sp at herd- and animal-level, and within- and among-herd prevalence. In general, smaller sample size was required to estimate AD prevalence than to document of AD-freedom. Compared to individual-based samples, two-stage sampling strategy requires a larger sample size to show disease-freedom. Statistical considerations including herd-level test characteristics when designing surveillance program also are further discussed.
Key Words: aujeszky's disease, disease freedom, prevalence, sample size


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