A stochastic mathematical model of the within-herd transmission dynamics of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV): fade-out and persistence.

摘要: A stochastic, mathematical model of a farrow-finish pig herd was developed and used to investigate the within-herd transmission dynamics PRRSV, examine patterns on-farm persistence fade-out. The structured represent management typical European herd. Three parameters determining natural history infection were derived from literature. Transmission chosen using PRRSV antibody data cross-sectional study 103 herds (Evans et al., 2008). seroprevalence by age generated at 21-day intervals compared field log-likelihood, accounting for accuracy ELISA test used. run various isolation practices purchased gilts, contact structure, size frequency re-introduction infectious gilts. time-dependent log-likelihood varied between in similar way observed serological values farms. Essentially they indicated two seroprevalence: which stably persistent, unstable, either recently introduced or faded-out. With 327 sows with identical management, fade-out virus occurred within 4 weeks 21.9% simulations. Without gilts sows, 250 days decreased 81.6% 14.3% sizes 75, 150, 300 600, probability >1200 4%, 13.4%, 20.4% 18.2%, respectively. Introduction rate approximately 0.37 times per year resulted persisting 32.4% simulations, 17.6% no re-introduction. Fade-out most likely occur breeding females before reached young stock. Persistence more once present piglets turn infected rearing-pigs. higher increased size, different groups ability capture variability cross-sectional, age-related suggests that processes re-introduction, play critical roles epidemiology. potential importance production is discussed.