Community-directed vector control to enhance mass drug administration for onchocerciasis elimination in Africa

摘要

ABSTRACT Onchocerciasis, or river blindness, is one of the recognized neglected tropical diseases of mankind. The disease is caused by the filarial parasite Onchocerca volvulus, which is spread by black flies (Simulium spp). In the 1980s, ivermectin was first shown to be a potent microfilaricide against O. volvulus. As a result, international programs were begun to either control or eliminate onchocerciasis, employing a strategy of mass drug administration (MDA) of ivermectin to afflicted communities. Long term MDA based programs have resulted in the elimination of onchocerciasis from some foci in Africa and almost all foci in Latin America. These successes have resulted in a change in focus from a goal of disease control of onchocerciasis to a goal of elimination, enshrined in the London Declaration on Neglected Tropical Diseases, which set a goal of eliminating onchocerciasis from Africa by 2020. Despite these successes, MDA alone will probably not be sufficient to interrupt transmission in many regions of Africa in time to meet the London Declaration goals, and may not be capable of interrupting transmission at all where vector densities are high. In such areas, it will be necessary to supplement MDA with other interventions. The experience of Uganda has demonstrated the power of utilizing a combination of vector control and ivermectin MDA, which has resulted in the interruption of transmission of O. volvulus in 9 of the country’s 17 foci in just 7 years. However, black fly control has traditionally relied upon insecticide treatment of vector breeding sites, an approach that is expensive and logistically difficult. Here we propose a different paradigm for the control of the black fly vectors of O. volvulus, that of involving the afflicted communities in this process. This project is an outgrowth of recent projects (1) to develop a black fly trap to replace human landing collections for entomological monitoring of O. volvulus transmission and, (2) to develop a remote sensing algorithm capable of predicting vector black fly breeding habitats. The first project resulted in the development of the Esperanza Window Trap (EWT), a platform constructed from locally available inexpensive materials, which equals or out performs a human landing team for the collection of vector species. The EWT can be successfully operated by local residents and has been shown to significantly reduce biting rates. In the second effort, we have conducted preliminary studies that demonstrate that enlisting local residents to remove trailing vegetation from detected vector breeding sites can reduce local biting rates by over 80%. The overall hypothesis that will be evaluated in this project through a combination of field experiments and mathematical modeling studies is that community directed vector control efforts using optimized traps, local reduction of breeding habitat or some combination of these will reduce vector biting rates to a point where O. volvulus may be eliminated by co-administration of MDA, even in areas where vector density is high.