Vector ecology of West Nile virus on the Southern High Plains, USA

Background/Question/Methods   On the Southern High Plains of Texas, USA, the two most abundant mosquito species are Aedes vexans and Culex tarsalis. The occurrence and abundance of these two species is seasonal and they are important vectors for West Nile virus (WNV). Both species amplify and likely bridge WNV to mammal populations (e.g., horses, humans). Both species occupy overlapping, but different niches. Aedes vexans is generally considered a floodwater species, while Cx. tarsalis usually prefers organically polluted water for egg laying. The purpose of this study was to determine the effects of weather on the occurrence and abundance of each species. We used an information-theoretics approach to compare competing models that predicted occurrence or abundance of each species through time. Logistic regression models were used to predict the occurrence, and multiple linear regressions were used to predict the abundance of each species. Within these models, we also tested a nested hypothesis that average daily wind speed would be important in predicting the abundance and occurrence of each species due to our trapping methods. Our field observations are part of a 7-year WNV monitoring project in Lubbock, County, TX.

Results/Conclusions   We found that temperature, relative humidity, and wind speed were all important for predicting the occurrence of both vector species through time. For Ae. vexans, the best model (based upon ΔAICc values) included temperature, relative humidity, and wind speed. The global model, which also included precipitation, was the second best model. For Cx. tarsalis, the global model was the best model and the second best model included temperature, relative humidity, and wind speed. None of our models predicted abundance well, but temperature is likely important in determining the population abundance of various species.