HUMAN POPULATION GROWTH IMPACT ON S. HAEMATOBIUM

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Urinary schistosomiasis, caused by infection with the parasitic trematode S. haematobium, is a significant cause of human morbidity and mortality throughout Africa and the Mideast. The long-term goal of this project is to define means for effective interruption of parasite transmission from intermediate host Bulinus snails to definitive human hosts. While dynamic modeling predicts that mass treatment of S. haematobium-infected human populations should substantially reduce parasite transmission, suppression of transmission has, in practice, proven difficult to achieve with drug treatment alone. It appears that wide variability in human water use and contamination and seasonal variability in snail population density serve to perpetuate S. haematobium transmission under marginal conditions. It is also likely that increasing human population density serves to increase infection levels through all stages of the parasite life cycle. It is hypothesized that parasite latency in the intermediate snail r-appreciated 'capacitance'for perpetuating transmission. These dynamic effects must be addressed in attempting to achieve interruption of S. haematobium transmission in a highly endernic/enzootic environment, such as that found in Coast Province, Kenya. The specific aims of the project are: 1) to determine the impact of human population growth and climate variation on patterns of S. haematobium transmission in an endemic region over a multi-year period (1984-2005); 2) To establish molecular PCR monitoring systems for more precise measurement of human/snail/human dynamics of S. haematobium transmission at field sites; 3) To develop and test mathematical models of S. haematobium transmission, in both small- and large-scale settings, which can be used to define optimal targets for control intervention; and 4) To train scientists from S haematobium-endemic areas in the use of PCR detection techniques, GIS analysis, and remote sensing techniques for the design and implementation of focused parasite control programs.