SIMULATION STUDIES OF AFRICAN HORSE SICKNESS IN SPAIN

Factors affecting epidemics of African horse sickness in Spain were st udied using a mathematical model. The model examined the likelihood of an epidemic after the introduction of the virus, and the effectivenes s of vaccination strategies. Two host species (horses and donkeys) and one vector species (the biting midge Culicoides imicola) were include d. A stratified random sampling method (Latin hypercube sampling) was used for sensitivity analysis of the likelihood of an epidemic. System atic variation of vaccination parameters was used to consider alternat ive control strategies. In general, when an epidemic occurred most pot ential hosts became infected. The peak prevalence in C. imicola was lo w, and never exceeded 3%. The most significant factors in the likeliho od of an epidemic were vector population size, the recovery rate in ho rses and the time of year when the virus was introduced. The lag betwe en virus introduction and protection, the proportion of hosts vaccinat ed, and including donkeys in vaccination programmes where the factors that most strongly affected the success of different vaccination strat egies. These factors should be priorities for empirical research, and should be considered in the design of control strategies in areas at r isk of virus introduction.