title: Probability of exporting infected carcasses from vaccinated pigs following a foot-and-mouth disease epidemic.
abstract: Emergency vaccination is an effective control strategy for foot-and-mouth disease (FMD) epidemics in densely populated livestock areas, but results in a six-month waiting period before exports can be resumed, incurring severe economic consequences for pig exporting countries. In the European Union, a one-month waiting period has been discussed based on negative test results in a final screening. The objective of this study was to analyze the risk of exporting FMD-infected pig carcasses from a vaccinated area: (1) directly after final screening and (2) after a six-month waiting period. A risk model has been developed to estimate the probability that a processed carcass was derived from an FMD-infected pig (P(carc)). Key variables were herd prevalence (P(H)), within-herd prevalence (P(A)), and the probability of detection at slaughter (P(SL)). P(H) and P(A) were estimated using Bayesian inference under the assumption that, despite all negative test results, > or =1 infected pigs were present. Model calculations indicated that P(carc) was on average 2.0 x 10(-5) directly after final screening, and 1.7 x 10(-5) after a six-month waiting period. Therefore, the additional waiting time did not substantially reduce P(carc). The estimated values were worst-case scenarios because only viraemic pigs pose a risk for disease transmission, while seropositive pigs do not. The risk of exporting FMD via pig carcasses from a vaccinated area can further be reduced by heat treatment of pork and/or by excluding high-risk pork products from export.
authors.affiliation: Department of Virology, Central Veterinary Institute of Wageningen UR, P.O. Box 65, 8200 AB Lelystad, The Netherlands. clazien.devos@wur.nl
authors.forename: Clazien J
authors.initials: CJ
authors.lastname: de Vos
authors.forename: Mirjam
authors.initials: M
authors.lastname: Nielen
authors.forename: Emelinda
authors.initials: E
authors.lastname: Lopez
authors.forename: Armin R W
authors.initials: AR
authors.lastname: Elbers
authors.forename: Aldo
authors.initials: A
authors.lastname: Dekker
mesh_terms: D000818:Animals; D003132:Commerce; D004196:Disease Outbreaks; D005536:Foot-and-Mouth Disease / Q000453:epidemiology / Q000517:prevention & control*; D015995:Prevalence; D011336:Probability; D013552:Swine; D013553:Swine Diseases / Q000453:epidemiology / Q000517:prevention & control*; D014765:Viral Vaccines / Q000008:administration & dosage*
chemical_list: D014765:Viral Vaccines