Environmental Factors and Distribution of Urinary Schistosomiasis in Cross River State, Nigeria

摘要

The distribution patterns of many parasitic diseases are influenced by environmental factors . Schistosomiasis prevalence is governed by the suitability of environmental factors for snail vector survival. The availability of resources on environmental indices in the World Wide Web facilitated this study which determined the effect of environmental factors on schistosomiasis distribution in Cross River State, Nigeria. Questionnaires were administered in 778 primary schools to determine the schistosomiasis status of the pupils. Mean values of environmental factors (Vegetation, temperature, altitude, land use, soil type and rainfall) corresponding to the coordinates of study schools were extracted from archived, satellite sources and public domain digital databases for a period April 2009 to March 2010. The values for each of the environmental factors were displayed spatially on the Cross River State Map using Microsoft, paint brush software. The effect of the environmental variables was measured by superimposing the schistosomiasis infection map on the map of each of the factors. The number of positive schools was thereafter calculated corresponding to variations in environmental factors across the entire study area. The results showed a negative correlation between infection, vegetation and altitude. Prevalence was highest in areas with less photosynthetic activity (less vegetation). Prevalence was zero in altitudes >500 m above sea level. Land use and temperature showed a positive correlation with infection. Infection increased with corresponding increases in temperature. Infection was more in areas where intensive agricultural practices were ongoing. Infection was more in areas with deep lateritic soil type . The present study will facilitate a rapid mapping of schistosomiasis using environmental factors as guide in Nigeria.