Effects of Land Surface Temperature, Soil Water Content and Land Use/Cover on the Spatial Distribution of Urinary Schistosomiasis in the FCT, Nigeria Using GIS and Remote Sensing

Abstract

This study was designed and conducted to determine the effect of some environmental factors - Land Surface Temperature (LST), Land Use/Cover (LUC) and Soil Water Content (SWC) on the distribution of urinary schistosomiasis in the FCT using the Geographic Information System and Remote Sensing. The prevalence data of 14.8% was obtained from a study among 83 primary school pupils in various communities in the FCT between 2011 and 2013, using blood-in-urine as diagnostic indicator of infection. Remotely-sensed environmental data for land surface temperature, land use/cover and soil water content were downloaded from the United States Geological Survey website hosting the Moderate Resolution Imaging Spectro-Radiometer (MODIS) data specific to the geo-location of prevalence data.  These were processed and analysed in GIS using spatial intepolation and displayed as maps. Soil water content was the only significant environmental variable among the listed ones in the determination of the pattern of prevalence of urinary schistosomiasis in the FCT. These were tested using Logistic Binary Regression Analysis (Forward Stepwise – Likelihood Ratio method) and the resulting model correctly predicted the pattern of infection to the tune of 80% using the equation P = 1/1 + e^-z where P is the probability of finding infection in the FCT and z = -6.40 + (0.04 x soil water content). The highest number of schools harbouring infected pupils was in the area with high soil water content. This may be due to the fact that the bulinid intermediate snail vectors require high soil water for their survival and transmission, particularly in the FCT where there are late rains which are also not sustained for many months. This also brings the farming community into contact with the intermediate host to enhance sustained transmission of the infection. The result of this study shows that among the three variables investigated, soil with high water content was the major determining factor in the prevalence of urinary schistosomiasis in the FCT and this information is relevant in the delineation of at-risk communities for treatment and control purposes.