Abstract
BackgroundThe National Malaria Control Program (NMCP) has been using pirimiphos methyl for the first time for indoor residual spraying (IRS) in Benin. The first round was a success with a significant decrease of entomological indicators of malaria transmission in the treated districts. We present the results of the entomological impact on malaria transmission. Entomologic parameters in the control area were compared with those in intervention sites.MethodsMosquito collections were carried out in three districts in the Atacora-Dongo region of which two were treated with pirimiphos methyl (Actellic 50EC) (Tanguiéta and Kouandé) and the untreated (Copargo) served as control. Anopheles gambiae s.l. populations were sampled monthly by human landing catch. In addition, window exit traps and pyrethrum spray catches were performed to assess exophagic behavior of Anopheles vectors. In the three districts, mosquito collections were organized to follow the impact of pirimiphos methyl IRS on malaria transmission and possible changes in the behavior of mosquitoes. The residual activity of pirimiphos methyl in the treated walls was also assessed using WHO bioassay test.ResultsA significant reduction (94.25%) in human biting rate was recorded in treated districts where an inhabitant received less than 1 bite of An. gambiae per night. During this same time, the entomological inoculation rate (EIR) dramatically declined in the treated area (99.24% reduction). We also noted a significant reduction in longevity of the vectors and an increase in exophily induced by pirimiphos methyl on An. gambiae. However, no significant impact was found on the blood feeding rate. Otherwise, the low residual activity of Actellic 50 EC, which is three months, is a disadvantage.ConclusionPirimiphos methyl was found to be effective for IRS in Benin. However, because of the low persistence of Actellic 50EC used in this study on the treated walls, the recourse to another more residual formulation of pirimiphos methyl is required.
Highlights
The National Malaria Control Program (NMCP) has been using pirimiphos methyl for the first time for indoor residual spraying (IRS) in Benin
The present study aims to evaluate the persistence of the biological efficacy of Actelic 50 EC IRS and it entomologic impact on malaria transmission after large-scale implementation in areas of high resistance to pyrethroids in An. gambiae
Two members of An. gambiae complex were found in sympatry (An. gambiae and An. coluzzii) and their distribution agree with previous findings in Benin that reported both M and S forms with the predominance of S forms in savannah areas [31]
Summary
The National Malaria Control Program (NMCP) has been using pirimiphos methyl for the first time for indoor residual spraying (IRS) in Benin. Malaria is a major public health problem and Anopheles gambiae is one of the major vectors of this disease in sub-Saharan Africa [1]. The current effective vector control tools include the use of Long Lasting Insecticide Nets (LLIN) and Indoor Residual Spraying (IRS) [2]. In. The main problem with ITNs and IRS is the development of insecticide resistance, pyrethroid-resistance, which has been demonstrated in several populations of Anopheles gambiae [5,6,7,8]. The emergence of resistance in populations of An. gambiae to common classes of insecticides used in public health has been reported in many countries in Africa, including Côte d’Ivoire [5], Kenya [9], Benin [10,11], Niger [12], Burkina. Aïkpon and others [19] have recently demonstrated a decrease of An. gambiae susceptibility to bendiocarb after the IRS implementation using bendiocarb in Atacora region in Benin
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