Population Structure of Schistosomes and Host Snails

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DESCRIPTION (provided by the applicant): Interactions between schistosomes and their snail hosts play an important role in the evolutionary development of host and parasite genetic systems. Gene flow, genetic drift and selection all potentially act on these systems, driving co-evolutionary trajectories and dictating disease dynamics. Assessing the degree and structure of genetic heterogeneity of both hosts and parasites is an essential first step in predicting the epidemiology of infectious diseases. The recent characterization of allelic microsatellite markers for Schistosoma mansoni and Biomphalaria glabrata provides us with an opportunity to study population structure of both parasite and host on a local spatial scale. Specific aims of this project include: 1) Determining the relative nature of population subdivision for schistosomes and snails based on allelic data from microsatellites, and assessing how that genetic variation changes on both spatial and temporal scales; and 2) Correlating microsatellite allelic heterogeneity with biomarkers for schistosome virulence and snail resistance to assess relationships between genetic variation and phenotypic expressions of epidemiological importance. Knowledge of the distribution of host and parasite genetic diversity within and among individual hosts, and within and among populations, will allow us to estimate parasite gene flow, assess the importance of multiple parasite genotypes on schistosome virulence, and begin to understand the interplay among micro-evolutionary forces that drive disease dynamics. Results will yield evolutionary insights into the epidemiological process, help to identify genetic consequences of control strategies, and complement concurrent immuno-epidemiology studies of humans in endemic Brazilian communities.