Reduction of Malaria Vector Mosquitoes in a Large Scale Intervention Trial in Rural Burkina Faso Using <i>Bti</i> Based Larval Source Management

Abstract

Background: Malaria remains one of the most important causes of morbidity and death in Sub-Saharan Africa. Along with early diagnosis and treatment of malaria cases and intermittent preventive treatment in pregnancy (IPTp), vector control is an important tool in the reduction of new cases. Alongside the use of long lasting insecticide treated bed nets (LLINs) and indoor residual spraying (IRS), targeting the vector larvae with biological larvicides such as Bacillus thuringiensis israelensis (Bti) is gaining importance as a means of reducing the number of mosquito larvae before they emerge to their adult stage. With this study, we present data corroborating the entomological impact of such an intervention in a rural African environment. Methods: The study extended over two years and researched the impact of biological larviciding with Bti on malaria mosquitoes that were caught indoors and outdoors of houses using light traps. We calculated the achieved reductions in female Anopheles mosquitoes for two different larviciding choices using a regression model. Findings: In villages that received selective treatment of the most productive breeding sites, the number of female Anopheles spp. dropped by 61% (95% CI: 54%-66%) compared to the pre-intervention period. In villages in which all breeding sites were treated, the number of female Anopheles spp. was reduced by 70% (95% CI: 64%-74%) compared to the pre-intervention period. Interpretation: We showed that malaria vector abundance can be dramatically reduced through larviciding of breeding habitats and that, in many geographical settings, they are a viable addition to current malaria control measures. Trial Registration Information: The study was registered under the trial id PACTR201611001721299 on the Pan African Clinical Trials Registry.. Funding Statement: This work was financed by Manfred Lautenschlager foundation, Wiesloch, Germany. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: The study was approved by the ethics committees of the University of Heidelberg under the certificate number S-438/2013 and additionally presented to and granted by the national ethics board of Burkina Faso in Ouagadougou and the local ethics committee at the research site in Nouna. We collected aggregated collective informed consent for the spraying activities for each village.