Simulation modeling of the effect of climatic factors on bluetongue virus infection in Australian cattle herds. I. Model formulation, verification and validation

Abstract

A state transition model based on matrix formulation was used to investigate the infection of Australian cattle herds with bluetongue viruses. The model was simulated until the prevalence of bluetongue virus infection stabilized (a period of approximately 25–30 simulated years). The model behaved in an appropriate manner given the introduction of an infectious disease agent into a naive cattle population. Validation was achieved by comparing the prevalence of infection predicted by the model for a set of input climatic values with the prevalence of bluetongue virus infection observed in a serological survey of cattle herds in Queensland, Australia. No significant difference was detected (P > 0.05) and a strong correlation was found between observed and predicted prevalence of infection (r = 0.75). Sensitivity analysis was performed by systematically varying the value of input climatic parameters. The model was robust, except at very low minimum temperatures that are rarely reached in Queensland. We considered the model satisfactory for quantitatively investigating the effect of climatic factors on the infection of Australian cattle herds with bluetongue viruses.