An application of remotely derived climatological fields for risk assessment of vector-borne diseases: A spatial study of filariasis prevalence in the Nile delta, Egypt

This paper applies a relatively straight forward remote sensing method that is commonly used to derive climatological variables. Measurements of surfa ce reflectance and surface radiant temperature derived from Landsat Themati c Mapper data were used to create maps of fractional vegetation and surface soil moisture availability for the southern Nile delta in Egypt. These cli matological variables were subsequently used to investigate the spatial dis tribution of the vector borne disease Bancroftian filariasis in the Nile de lta where it is focally endemic and a growing problem. Averaged surface soi l moisture values, computed for a 5-km border area around affected villages , were compared to filariasis prevalence rates. Prevalence rates were found to be negligible below a critical soil moisture value of 0.2, presumably b ecause of a lack of appropriate breeding sites for the Culex Pipiens mosqui to species. With appropriate modifications to account for local conditions and vector s pecies, this approach should be useful as a means to map, predict, and cont rol insect vector-borne diseases that critically depend on wet areas for pr opagation. This type of analysis may help governments and health agencies t hat are involved in filariasis control to better focus limited resources to identifiable "high-risk" areas.