Abstract
BackgroundThe use of larval source management is not prioritized by contemporary malaria control programs in sub-Saharan Africa despite historical success. Larviciding, in particular, could be effective in urban areas where transmission is focal and accessibility to Anopheles breeding habitats is generally easier than in rural settings. The objective of this study is to assess the effectiveness of a community-based microbial larviciding intervention to reduce the prevalence of malaria infection in Dar es Salaam, United Republic of Tanzania.Methods and FindingsLarviciding was implemented in 3 out of 15 targeted wards of Dar es Salaam in 2006 after two years of baseline data collection. This intervention was subsequently scaled up to 9 wards a year later, and to all 15 targeted wards in 2008. Continuous randomized cluster sampling of malaria prevalence and socio-demographic characteristics was carried out during 6 survey rounds (2004–2008), which included both cross-sectional and longitudinal data (N = 64,537). Bayesian random effects logistic regression models were used to quantify the effect of the intervention on malaria prevalence at the individual level. Effect size estimates suggest a significant protective effect of the larviciding intervention. After adjustment for confounders, the odds of individuals living in areas treated with larviciding being infected with malaria were 21% lower (Odds Ratio = 0.79; 95% Credible Intervals: 0.66–0.93) than those who lived in areas not treated. The larviciding intervention was most effective during dry seasons and had synergistic effects with other protective measures such as use of insecticide-treated bed nets and house proofing (i.e., complete ceiling or window screens).ConclusionA large-scale community-based larviciding intervention significantly reduced the prevalence of malaria infection in urban Dar es Salaam.
Highlights
The Ross-Macdonald model of malaria transmission suggests that control methods that reduce adult mosquitoes’ longevity can achieve greater malaria reduction than strategies that target larval stages
A large-scale community-based larviciding intervention significantly reduced the prevalence of malaria infection in urban Dar es Salaam
Malaria prevalence was highest during the first round of data collection in 2004, with 20.8% prevalence
Summary
The Ross-Macdonald model of malaria transmission suggests that control methods that reduce adult mosquitoes’ longevity can achieve greater malaria reduction than strategies that target larval stages. Larval Source Management (LSM), such as the use of larvicides and the draining of breeding habitats, has historically been a very successful tool to reduce mosquito density [1] – examples include the elimination of Anopheles arabiensis from Egypt [2] and Brazil [3], malaria control in the Zambian copperbelt (1930–1950) [4], Dr Gorga’s work during the construction of the Panama canal [5], and the vector control program of the Tennessee Valley Authority [6]. The use of larval source management is not prioritized by contemporary malaria control programs in subSaharan Africa despite historical success. The objective of this study is to assess the effectiveness of a community-based microbial larviciding intervention to reduce the prevalence of malaria infection in Dar es Salaam, United Republic of Tanzania
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