Rapid Epidemiological Mapping of Cholera in Some Parts of Abeokuta Metropolis: A GIS-Supported Post-Epidemic Assessment

Abstract

An outbreak of cholera epidemic was reported in some parts of Abeokuta city in Nigeria. Reports indicated that loss of lives was involved. This study investigates the immediate and remote sources of contamination of water supply system in the city by a GIS supported investigation. The study relied on the integration of Geographic Information System, Global Positioning System and Remote Sensing. The network of water pipelines was digitized from the master plan. The geo-ecological characteristics of the environment were captured from a high resolution (Ikonos) satellite image of the affected communities.  Water samples were collected from various points and their coordinates obtained. The water samples collected from Ogun River (abstraction point), water treatment tank and faucets within the affected communities were analyzed for the presence of Vibrio cholerae. Results revealed a high load (>180 MPN/1000ml) of cholera bacteria at the abstraction point, which reduced to < 10 MPN/1000ml in the treatment tank. As the assessment progressed from the water works farther into the communities, there was a concomitant progressive increase in cholerae contamination. The Vibrio count has risen above 180 MPN/1000ml by the time the assessment got to the cholerae endemic area. It was found that the sanitary practices of the indigenes of the area were very poor; there were no proper sewage or waste disposal systems, heaps of refuse dumps were found on pipelines. The study established pre and post epidemic water contamination in the area. Although the study could not attribute the incidence to direct negligence of water management board but rather to poor maintenance of the water facilities; which were already old, rusty and leaking. This, in conjunction with the substantiated finding on the poor sanitation of people of the area, can be said to hold a high significance for future cholerae epidemics in this part of the city.