22. Tropical Diseases Targeted for Elimination: Chagas Disease, Lymphatic Filariasis, Onchocerciasis, and Leprosy

Abstract

Ecological and socioeconomic conditions facilitate the spread of tropical diseases. Chagas disease, lymphatic filariasis, onchocerciasis, and leprosy all have been targeted for elimination. Despite successful control strategies employed to date, the pressing need for complete and sustained control of these diseases remains.

While these four tropical diseases are all parasitic infections, their causative agents, modes of transmission, and geographic distribution differ. With the exception of leprosy, all are vector–borne diseases. Leprosy and lymphatic filariasis exist in all tropical regions, whereas Chagas disease occurs only in the Americas, and onchocerciasis is found predominantly in Africa. Although information on the number of people infected by these tropical diseases is difficult to obtain, the economic impact of illness is indisputable: high medical costs, reduced income–generating capability, disrupted agricultural production, and restricted social participation.

Cost–effective interventions are available and being implemented, including control programs to eliminate domestic vector populations, improved serological screening of blood donors, early detection, annual mass drug administration, multidrug therapies, and rehabilitation to overcome activity limitations. Such interventions demonstrate that elimination of these diseases as public health problems can be achieved and that investment in tropical disease research and control can make a significant contribution to poverty reduction. The battle, however, has not yet been won: it requires ongoing support from the pharmaceutical industry (which has made large drug donations), intercountry control programs, and development of new and improved interventions to combat drug resistance.