Malaria Vector Control in Sub-Saharan Africa: Impact and Economic Evaluation of Larviciding

Abstract

The last decade witnessed the important scaled-up of malaria control interventions in sub-Saharan Africa (SSA). There is now renewed impetus to achieve the long-term goal of malaria elimination and reducing vectorial capacity of the Anopheles mosquito is a necessary first step towards this objective. Relying solely on the two pillars of malaria vector control (i.e., insecticide-treated nets and indoor residual spraying) will be insufficient to achieve elimination in much of SSA, however. Larval Source Management, and larviciding in particular, could play an important role in areas where breeding habitats are ‘few, fixed, and findable’ or where malaria vectors exhibit exophagic and exophilic behaviors, and in settings where insecticide resistance has emerged. Yet, only few contemporary studies have investigated the effectiveness of larviciding for malaria control despite historical success. Using the wealth of data from Dar es Salaam’s Urban Malaria Control Program (2004-2008), this dissertation will first assess the impact of a community-based larviciding program on prevalence of malaria infection in 15 urban wards of Dar es Salaam (Tanzania). The cost-effectiveness of this intervention will then be estimated from both a provider and a societal perspective. Finally, in a context of accelerated malaria control, the effect of reducing malaria transmission on disease-related behavior and knowledge will be examined.

Results suggest that the larviciding intervention had a significant protective effect, decreasing by 21% the odds of being infected with malaria. Larviciding was found to be cost-effective for incidences as low as 40 infections per 1,000 individuals per year but the cost-effectiveness ratios were highly dependent on the assumed baseline malaria incidence rates. Such a successful intervention could also bring about further challenges to sustaining gains in reducing malaria transmission as the larviciding intervention was found to negatively affect bednet usage and knowledge of disease symptoms. Collectively, these results imply that larviciding should be considered as part of an Integrated Vector Management approach in SSA, if local eco-epidemiological conditions are suitable, and that there is a need to sustain behavioral change communication following successful vector control interventions.