Evaluation of the effectiveness of a targeted community-based IRS approach for malaria elimination in an area of low malaria transmission of the central-western Senegal.

The implementation of effective malaria control strategies in the central-western Senegal, such as Indoor Residual Spraying (IRS), long-lasting insecticide-treated nets (LLIN), Seasonal malaria chemoprophylaxis (SMC) and appropriate management of malaria cases, has led to the decline of malaria transmission in the region. However, residual malaria transmission still occurring in some localities, known as hotspots villages, making challenging the achievement of the malaria elimination goal. A pilot study was undertaken between 2013 and 2014 to test the feasibility of a community-based IRS approach for malaria elimination in four targeted health districts of the Central Western Senegal. The residual efficacy of the Actellic® 300CS formulation on the sprayed surface was monitored using WHO cone test. Overall, 615 walls were tested over the two successive years, respectively 240 and 375 in 2013 and 2014 IRS campaigns. The residual efficacy of the IRS with Actellic®300 CS was longer in the second year due to the improvement of community agents spraying skill the second year thanks to the refreshing training and a better supervision by professional agent of the National Hygiene Service. The analysis of the Incidence Rate Ratio under the Poisson model shows no significant difference of IRS effectiveness according to the building type. In conclusion, the quality of training of community agents and good supervision of IRS activities play a key role in the quality and the residual efficacy of IRS campaigns. A good planning and implementation of IRS campaign ensure a high quality and a good effectiveness of spraying with the Actellic®300 CS formulation.