Spatial distribution of mosquitoes: The context of malaria outbreaks in western Kenya highlands
During the last two decades, a series of explosive seasonal malaria outbreaks occurred in the Kenya highland areas. These outbreaks were associated with a high mortality rate and caused thousands of deaths, of which over 70% were children under the age of five. Malaria is transmitted by mosquitoes. Knowledge on the distribution of mosquitoes is important to malaria eradication and prevention. However, several gaps exist in current mosquito studies. First, few predictive models of mosquito larval habitats at a micro scale have been developed. Second, it is largely unknown how the seasonal and inter-annual change in climatic conditions affects the spatial distribution of mosquito larvae. Third, few spatial models have been developed to represent the spatial distribution of adult mosquitoes. Fourth, the quantitative relationship between the spatial distribution of the larval habitats and adult mosquitoes is rarely identified. To fill these gaps, this dissertation first developed mosquito larval habitat models to predict the spatial distribution of mosquito larval habitats utilizing mosquito data collected in a study area over three years. The prediction accuracy of the models was satisfactory. This dissertation then studied how mosquito larvae respond spatially to seasonal and inter-annual climatic variations. The results suggest that the spatial distribution of larvae demonstrates considerable seasonal and inter-annual variation. This dissertation also modeled the spatial distribution of the adult mosquitoes by using both spatial and non-spatial methods. The developed model can explain over 70% of the variation in the distribution of the adult mosquitoes. Finally, this dissertation quantified the relationship between the distribution of adult mosquitoes and mosquito larval presence sites. It was found that larval presence sites that have been repeatedly observed were significantly related to the distribution of the adult mosquitoes. The findings presented in this dissertation provide a more comprehensive understanding of the malaria vector in western Kenya highlands. These findings are important for public health decision-making related to adult mosquito surveillance and malaria control.