Sample size for serological surveillance of Aujeszky's disease in Korea

국내 돼지오제스키병의 혈청학적 감시활동(surveillance)을 위한 표본크기

  • Kim, Eu-Tteum (School of Veterinary Medicine and Institute of Veterinary Science, Kangwon National University) ;
  • Pak, Son-Il (School of Veterinary Medicine and Institute of Veterinary Science, Kangwon National University) ;
  • Park, Choi-Kyu (National Veterinary Research and Quarantine Service) ;
  • Kweon, Chang-Hee (National Veterinary Research and Quarantine Service)
  • 김으뜸 (강원대학교 수의학부대학 및 동물의학종합연구소) ;
  • 박선일 (강원대학교 수의학부대학 및 동물의학종합연구소) ;
  • 박최규 (국립수의과학검역원) ;
  • 권창희 (국립수의과학검역원)
  • Accepted : 2007.11.16
  • Published : 2007.12.30


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.


Supported by : 국립수의과학검역원


  1. 국립수의과학검역원. 2006년 1/4분기 가축전염병중앙예찰협의회자료. pp.31-32, 국립수의과학검역원, 안양, 2006
  2. 국립수의과학검역원. 2007년 1/4분기 가축전염병중앙예찰협의회자료. pp.31-32, 국립수의과학검역원, 안양, 2007
  3. 농림부. 농림통계연보. 농림부, 과천, 2006
  4. Audige L, Beckett S. A quantitative assessment of the validity of animal-health surveys using stochastic modelling. Prev Vet Med 1999, 38, 259-276
  5. Cameron AR, Baldock FC. A new probability formula for surveys to substantiate freedom from disease. Prev Vet Med 1998, 34, 1-17
  6. Cameron AR, Baldock Fe. Two-stage sampling in surveys to substantiate freedom from disease. Prev Vet Med 1998, 34, 19-30
  7. Commission of the European Communities. Council Directive 97/12/EC of 17 March 1997 amending and updating Directive 64/432/EEC on health problems affecting intra-community trade in bovine animals and swine. Off J Eur Commun 1997, 109, 1-37
  8. Donald A. Prevalence estimation using diagnostic tests when there are multiple, correlated disease states in the same animal or farm. Prev Vet Med 1993, 15, 125-145
  9. Humphry RW, Cameron A, Gnnn GJ. A practical approach to calculate sample size for herd prevalence surveys. Prev Vet Med 2004, 65, 173-188
  10. Martin SW, Shoukri MM, Thorburn MA. Evaluating the health status of herds based on tests applied to individuals. Prev Vet Med 1990, 14, 33-43
  11. Office International des Epizooties (OlE). Terrestrial Animal Health Code 2006. 5th ed. pp. 101-498, Paris, 2006
  12. Office International des Epizooties (OlE). Recommended standards for epidemiological surveillance systems for rinderpest. Rev Sci Tech 1998, 17, 825-828
  13. Rogan WJ, Gladen B. Estimating prevalence from the results of a screening test. Am J Epidemiol 1978, 107, 71-76
  14. Straw BE, Taylor DJ, D'Allaire S, Mengeling, WL. Diseases of Swine. 8th ed. pp. 233-246, Iowa State University Press, Ames, 1999
  15. Stark KDC, Mortensen S, Olsen AM, Barfod K, Botner A, Lavritsen DT, Strandbygard B. Designing serological surveillance programmes to document freedom from disease with special reference to exotic viral diseases of pigs in Denmark. Rev Sci Tech 2000, 19, 715-724
  16. Wagner B, Salman MD. Strategies for two-stage sampling designs for estimating herd-level prevalence. Prev Vet Med 2004, 66, 1-17