ABSTRACT
The distribution of Bancroftian filariasis in the Nile Delta of Egypt is highly focal. Infection prevalence rates very widely between villages and within endemic villages. Improved understanding of risk factors for filariasis may lead to more efficient programmes for surveillance and control of this largely environmental disease. Pilot GIS studies performed at Washington University [Dept. of Earth and Planetary Sciences] suggest that much of the variability in filariasis prevalence at the village level can be explained by variable ground vegetation cover, which may in turn correlate with vector density and/or longevity. Landsat thematic mapper data [1984 scenes] for Qalubia governorate on vegetation cover [a surrogate for water availability] were highly correlated with infection prevalence rates by village from Egyptian Ministry of Health night blood surveys. Case control studies have identified the following as significant risk factors for filariasis within endemic villages: crowding [persons/house], residence in houses with indoor animal sheds non-use of sanitary waste disposal, parental infection [either parent] and residence in houses facing agricultural land [peripheral houses]. Mosquito density, mosquito infection and infectivity rates are all significantly higher in [peripheral] areas of endemic villages adjacent to agricultural land. We plan to continue research on risk factors for filariasis over the coming year with multidisciplinary studies [entomology, environmental assessment and socioeconomic survey] of two closely spaced villages in the ICIDR project area with highly divergent infection prevalence rates of 2% and 12%. This study may confirm preliminary findings and lead to new insights regarding the focal distribution of filariasis in Egypt