Abstract
The spread of pyrethroid resistance in malaria vectors and the stalling of recent progress in malaria control in Africa highlight the urgent need to deploy complementary strategies to long-lasting insecticidal nets (LLINs) to accelerate the reduction in the disease burden. Strategies such as strengthened Information, Education and Communication (IEC), Indoor Residual Spraying (IRS) and larviciding with Bacillus thuringiensis isralensis (Bti) are available but the actual benefit of their use in combination with LLINs remains to be demonstrated. The main objective of this work was to measure the additional impact of these three strategies on malaria transmission through a randomized controlled trial run in 28 villages in the health district of Korhogo, northern Côte d’Ivoire, an area of vector resistance to pyrethroids. Prior to the deployment of these strategies, my work allowed us to 1) assess the efficacy of a new larvicide formulation under semi-field conditions; 2) study vector bionomics, insecticide resistance mechanisms and malaria transmission; 3) identify and characterize Anopheles spp. breeding habitats in the study area. Data from post-intervention surveys showed 1) a reduction of vector density (69%) five months after the beginning of the IEC strategy, of sporozoïte rate (84%) and of IER (86%) in the LLIN+IEC arm relative to the LLIN alone arm; 2) a reduction of vector density at months two (72%) and four post-IRS (69%) and of EIR (62%) in the LLIN+IRS arm relative to the LLIN alone arm; 3) a reduction of vector density (95%) three months after the beginning of larviciding intervention and of IER (88%) in the LLIN + larviciding arm relative to the LLIN alone arm. These results provide evidence that IEC, IRS and larviciding are effective complementary strategies to reduce transmission intensity in Korhogo. Analysis of epidemiological data collected during the trial will allow a better understanding of the additional benefit of these strategies on the malaria burden.