A simulation model for the vector-host transmission system of a mosquito-borne avian virus, Turlock (Bunyaviridae) [Culex tarsalis]

The vector-host transmission system of Turlock (TUR) virus in Hale Co., Texas, USA, was investigated by using laboratory experimentation, field data, pertienent literature, and simulation modeling. The computer simulation model was constructed to investigate how a relatively large proportion of vectors and/or hosts can become infected with mosquito-transmitted viruses, since these infections can be associated with epidemics in humans and domestic animals. Transmission system components investigated were: randomness of transmission events; mosquito susceptibility to viral infection; ability of mosquitoes to transmit virus; survival of infected mosquitoes; and size of the mosquito population. Increasing the probability of infected mosquito survival by 10% caused more mosquito and sparrow infections than increases in all other transmission components, either separately or in their possible combinations. This increased variation may help to explain why epidemics are difficult to predict. The system modeled could not sustain itself by vector-host transmission alone. This implied that viral reintroduction is required to maintain summer transmission of viruses that are periodically undetectable in the field as is TUR virus in Hale Co., Texas.