A stochastic-modeling evaluation of the foot-and-mouth-disease survey conducted after the outbreak in Miyazaki, Japan in 2000

T. Tsutsui, Nariyuki Minami, M. Koiwai, T. Hamaoka, I. Yamane, K. Shimura

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

When foot-and-mouth-disease (FMD) was identified in Miyazaki prefecture in March 2000, Japan conducted an intensive serological and clinical survey in the areas surrounding the index herd. As a result of the survey during the 21 days of the movement-restriction period, two infected herds were detected and destroyed; there were no other cases in the months that followed. To evaluate the survey used for screening the disease-control area and surveillance area, we estimated the herd-level sensitivity of the survey (HSe) through a spreadsheet model using Monte-Carlo methods. The Reed-Frost model was incorporated to simulate the spread of FMD within an infected herd. In the simulations, 4, 8 and 12 effective-contact scenarios during the 5-day period were examined. The estimated HSes of serological tests (HSeE) were 71.0, 75.3 and 76.3% under the 4, 8 and 12 contact scenarios, respectively. The sensitivity analysis showed that increasing the number of contacts beyond 12 did not improve HSeE, but increasing the number of sampled animals and delaying the dates of sampling did raise HSeES. Small herd size in the outbreak area (>80% of herds have <20 animals) seems to have helped in maintaining HSeE relatively high, although the serological inspection was carried out before sero-positive animals had a chance to increase in infected herds. The estimated herd-level specificity of serological tests (HSpE) was 98.6%. This HSpE predicted 224 false-positive herds (5th percentile estimate was 200 and 95th percentile was 249), which proved close to the 232 false-positive herds actually observed. The combined-test herd-level sensitivity (serological and clinical inspections combined; CTHSe), averaged 85.5, 87.6 and 88.1% for the 4, 8 and 12 contact scenarios, respectively. Using these CTHSes, the calculated probability that no infected herd was overlooked by the survey was ≥62.5% under the most-conservative, four-contact scenario. The probability that no more than one infected herd was overlooked was ≥89.7%.

Original languageEnglish
Pages (from-to)45-58
Number of pages14
JournalPreventive Veterinary Medicine
Volume61
Issue number1
DOIs
Publication statusPublished - 2003 Sep 30
Externally publishedYes

Fingerprint

disease surveys
Foot-and-Mouth Disease
foot-and-mouth disease
Disease Outbreaks
Serologic Tests
Japan
herds
immunologic techniques
Monte Carlo Method
Surveys and Questionnaires
animals
Monte Carlo method
herd size
frost

Keywords

  • FMD
  • Herd-level sensitivity
  • Stochastic model
  • Survey

ASJC Scopus subject areas

  • Animal Science and Zoology
  • veterinary(all)

Cite this

A stochastic-modeling evaluation of the foot-and-mouth-disease survey conducted after the outbreak in Miyazaki, Japan in 2000. / Tsutsui, T.; Minami, Nariyuki; Koiwai, M.; Hamaoka, T.; Yamane, I.; Shimura, K.

In: Preventive Veterinary Medicine, Vol. 61, No. 1, 30.09.2003, p. 45-58.

Research output: Contribution to journalArticle

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abstract = "When foot-and-mouth-disease (FMD) was identified in Miyazaki prefecture in March 2000, Japan conducted an intensive serological and clinical survey in the areas surrounding the index herd. As a result of the survey during the 21 days of the movement-restriction period, two infected herds were detected and destroyed; there were no other cases in the months that followed. To evaluate the survey used for screening the disease-control area and surveillance area, we estimated the herd-level sensitivity of the survey (HSe) through a spreadsheet model using Monte-Carlo methods. The Reed-Frost model was incorporated to simulate the spread of FMD within an infected herd. In the simulations, 4, 8 and 12 effective-contact scenarios during the 5-day period were examined. The estimated HSes of serological tests (HSeE) were 71.0, 75.3 and 76.3{\%} under the 4, 8 and 12 contact scenarios, respectively. The sensitivity analysis showed that increasing the number of contacts beyond 12 did not improve HSeE, but increasing the number of sampled animals and delaying the dates of sampling did raise HSeES. Small herd size in the outbreak area (>80{\%} of herds have <20 animals) seems to have helped in maintaining HSeE relatively high, although the serological inspection was carried out before sero-positive animals had a chance to increase in infected herds. The estimated herd-level specificity of serological tests (HSpE) was 98.6{\%}. This HSpE predicted 224 false-positive herds (5th percentile estimate was 200 and 95th percentile was 249), which proved close to the 232 false-positive herds actually observed. The combined-test herd-level sensitivity (serological and clinical inspections combined; CTHSe), averaged 85.5, 87.6 and 88.1{\%} for the 4, 8 and 12 contact scenarios, respectively. Using these CTHSes, the calculated probability that no infected herd was overlooked by the survey was ≥62.5{\%} under the most-conservative, four-contact scenario. The probability that no more than one infected herd was overlooked was ≥89.7{\%}.",
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