Use of demographic factors in characterization of risk areas for transmission of sleeping sickness in Cote d'Ivoire

The purpose of this study was to classify the risk for transmission of African human trypanosomiasis (sleeping sickness) according to population and settlement densities in four different areas of Zoukougbeu, Cote d'Ivoire, where the exact location of cases reported since 1990 is known. Epidemiological risk indexes were calculated from entomological data obtained from three surveys and analyzed with respect to presence of patients and occupancy rate in each area. Results indicated that there was a risk of transmission near the village of Bahigbeu II where the population density is between 30 and 40 inhabitants per km2 and settlement density is 4 per km2. There was also a risk in less inhabited areas such as Ouatigbeu where the population density is less than 30 inhabitants per km2 and dwelling density less than 4 per km2. In fact, cases are regularly reported in Ouatigbeu but never in Bahigbeu II. Based on these findings, we conclude that, while land occupancy can be considered as a risk factor for sleeping sickness, other factors such as human mobility must be taken into account to characterize risk areas and predict outbreaks.