Many infectious diseases around the world are becoming increasingly prevalent due to changing environmental conditions, such as climate change and land use change. It is important to understand better the factors that influence the prevalence of organisms carrying these diseases. In this project, I will quantify the influence of several factors, including biodiversity and nutrient input, on the prevalence of disease vector species in lake, pond and stream ecosystems. With these relationships, I will then develop, test and apply a global model that predicts vector species occurrence and abundance as function of various abiotic and biotic freshwater ecosystem characteristics.