Research
Towards understanding the presence/absence of Human African Trypanosomosis in a focus of Côte d'Ivoire: a spatial analysis of the pathogenic system
-
* Corresponding author: Fabrice Courtin courtin.f@wanadoo.fr
1 Institut Pierre Richet (IPR), équipe « THA et glossines », s/c IRD, Rue Fleming zone 4C, 04 BP 293, Abidjan 04, Côte d'Ivoire
2 Institut de Recherche pour le Développement (IRD), Unité de Recherche UR 177, Laboratoire de Recherche et de Coordination sur les Trypanosomoses (LRCT IRD-CIRAD), TA 207/G, Campus International de Baillarguet, 34398 Montpellier cedex 5, France
3 University of Lille, USTL/LGMA (Laboratoire de Géographie des Milieux Anthropisés), UMR CNRS 8141, France
4 University of Montpellier 3, UFR sciences humaines et sciences de l'environnement, route de Mende 34199 Montpellier Cedex 5, Laboratoire de recherche GESTER (gestion des territoires et des risques), France
International Journal of Health Geographics 2005, 4:27 doi:10.1186/1476-072X-4-27
Published: 3 November 2005Abstract
Background
This study aimed at identifying factors influencing the development of Human African Trypanosomosis (HAT, or sleeping sickness) in the focus of Bonon, located in the mesophile forest of Côte d'Ivoire. A previous study mapping the main daytime activity sites of 96 patients revealed an important disparity between the area south of the town- where all the patients lived- and the area north of the town, apparently free of disease. In order to explain this disparity, we carried out a spatial analysis of the key components of the pathogenic system, i.e. the human host, the tsetse vector and the trypanosomes in their environment using a geographic information system (GIS).
Results
This approach at the scale of a HAT focus enabled us to identify spatial patterns which linked to the transmission and the dissemination of this disease. The history of human settlement (with the rural northern area exploited much earlier than the southern one) appears to be a major factor which determines the land use pattern, which itself may account for differences found in vector densities (tsetse were found six times more abundant in the southern rural area than in the northern). Vector density, according to the human and environmental context in which it is found (here an intense mobility between the town of Bonon and the rural areas), may explain the observed spatial differences in HAT prevalence.
Conclusion
This work demonstrates the role of GIS analyses of key components of the pathogenic system in providing a better understanding of transmission and dissemination of HAT. Moreover, following the identification of the most active transmission areas, and of an area unfavourable to HAT transmission, this study more precisely delineates the boundaries of the Bonon focus. As a follow-up, targeted tsetse control activities starting north of Bonon (with few chances of reinvasion due to very low densities) going south, and additional medical surveys in the south will be proposed to the Ivoirian HAT control program to enhance the control of the disease in this focus. This work also shows the evolution of HAT regarding time and environment, and the methodology used may be able to predict possible sleeping sickness development/extinction in areas with similar history and space organization.