Modelling onchocerciasis transmission and control

Abstract

In 1990 the World Health Organization (WHO) coordinated Onchocerciasis Control Programme in West Africa (OCP) used this slogan for evaluating fifteen years of control of the parasitic disease onchocerciasis and for expressing its optimism about the future. Based on the obvious success of OCP and on the availability of a safe and effective drug (ivermectin), the UNDP/World BanklWHO Special Programme for Research & Training in Tropical Diseases (TDR) has announced onchocerciasis to be one of the tropical diseases with good prospects for worldwide elimination, at least as a public health problem (the others being Chagas disease, Lymphatic filariasis, and Leprosy!). To judge slogans and statements like these, and in particular to determine under which circumstances and with what strategies they could become a realistic perspective, one should perform an integrated and detailed study of the dynamics of the disease and the impact of control. Such a study should preferably be embedded in a comprehensive quantitative approach. In the light of this, the objectives of the work reported in this thesis were (1) to develop, quantify, and validate a model for the transmission and control of onchocerciasis in West African savanna and (2) to use this model for aiding decision making in the OCP. Through achieving these objectives we have tried to contribute to a better understanding of the dynamics of the parasite that causes the illness and the impact of intervention measures, and to the as yet successful combat against the disease. In the general introduction an outline will be given of the epidemiology and control of onchocerciasis. Secondly, an overview of the achievements of the OCP in controlling the disease in West Africa will be provided. Finally, a short history will be presented of the role of quantitative modelling within OCP prior to the work reported in this thesis