TEMPERATURE DATA FROM SATELLITE IMAGERY AND THE DISTRIBUTION OF SCHISTOSOMIASIS IN EGYPT

Polar orbiting environmental satellites operated by the National Ocean ographic and Atmospheric Administration acquire daytime and nighttime thermal infrared measurements of the earth's surface around the world at a spatial resolution of 1.1 km. Day-night pairs of this imagery fro m the Advanced Very High Resolution Radiometer (AVHRR) were processed to produce temperature maximum, temperature minimum, and diurnal tempe rature difference (dT) maps of the lower Nile River valley. Nile delta subsets of the dT maps for August 16, 1990 and February 14, 1991 were analyzed in detail. Values of dT at specific locations were derived u sing the median of 5 x 5 pixels centered on the latitude and longitude of 41 survey sites listed in 1935, 1983, and 1990 schistosomiasis sur veys of the Nile Delta. A Spearman correlation coefficient matrix reve aled an inverse relationship between site dT values for August 16, 199 0 and February 14, 1991 and prevalence of Schistosoma mansoni in the 1 935 and 1983 surveys. For S. haematobium, a positive association of si te dT values and prevalence was seen for 1935 only. A significant asso ciation was observed between 1935 S. mansoni prevalence and that obser ved in 1983 and 1990; S. haematobium prevalence in 1935 was not correl ated with the later surveys. The results suggest that AVHRR thermal di fference maps reflect regional hydrologic conditions that can be used as a predictor of environmental risk of schistosomiasis for control pr ogram management.