Abstract
BackgroundThe current study shows the results of three years of IRS entomological monitoring (2016, before intervention; 2017 and 2018, after intervention) performed in Alibori and Donga, northern Benin.MethodsMosquito collections were performed on a monthly basis using human landing catches and pyrethrum spray catches in six districts including four treated with Actellic 300 CS (Kandi, Gogounou, Djougou and Copargo) and two untreated (Bembèrèkè and Kouandé) which served as control sites. Key transmission indicators of Anopheles gambiae (s.l.) as well as the residual activity of Actellic 300 CS assessed through WHO cone tests, were determined.ResultsThe residual efficacy duration of Actellic 300 CS after the two IRS campaigns (2017 and 2018) was 4–5 months (May–September). The parity rate and the sporozoite index of An. gambiae (s.l.) were 36.62% and 0.71%, respectively, after the first spray round in treated areas compared to 57.24% and 3.7%, respectively, in the control areas (P < 0.0001). The same trend was observed after the second spray round. After the first spray round, each person received 1.6 infective bites/month (ib/m) in the treated areas against 12.11 ib/m in the control areas, resulting in a reduction rate of 86.78%. Similarly, the entomological inoculation rate was 1.5 ib/m after the second spray round in the treated areas vs 9.75 ib/m in the control areas, corresponding to a reduction of 84.61%. A decrease in the parity rate (46.26%), sporozoite index (85.75%) and EIR (87.27%) was observed for An. gambiae (s.l.) after the first round of IRS (June–October 2017) compared to the pre-intervention period (June–October 2016). The density of An. gambiae (s.l.) ranged between 0.38–0.48 per house in treated areas vs 1.53–1.76 An. gambiae (s.l.) per house respectively after the first and second IRS rounds.ConclusionsThis study showed the positive impact of IRS in reducing key entomological parameters of malaria transmission in Alibori and Donga. However, the considerable blood-feeding rate of An. gambiae (s.l.) in spray areas, stress the need for the population to sleep under long-lasting insecticidal nets (LLINs) in addition, to prevent from mosquito bites which did not succeed in resting on sprayed walls.
Highlights
The current study shows the results of three years of indoor residual spraying (IRS) entomological monitoring (2016, before intervention; 2017 and 2018, after intervention) performed in Alibori and Donga, northern Benin
According to the World Health Organization (WHO), of the 663 million malaria cases prevented in sub-Saharan Africa between 2001 and 2015 through vector control interventions, 79% were through long-lasting insecticidal nets (LLIN) and IRS [5]
Residual effect of Actellic 300 micro-encapsulated formulation (CS) on treated walls from 2017 and 2018 Figure 2 shows the monthly variation of mortality rates in 2017 (Fig. 2a) and 2018 (Fig. 2b), after exposure of An. gambiae Kisumu to cement and mud walls sprayed with Actellic 300CS in the districts of Djougou and Copargo
Summary
The current study shows the results of three years of IRS entomological monitoring (2016, before intervention; 2017 and 2018, after intervention) performed in Alibori and Donga, northern Benin. According to the World Health Organization (WHO), of the 663 million malaria cases prevented in sub-Saharan Africa between 2001 and 2015 through vector control interventions, 79% were through LLINs and IRS [5]. This historic progress in the fight against malaria is partly due to the efforts of the USA Government through the Presidents Malaria Initiative (PMI) [6]. The decrease in susceptibility of mosquitoes to bendiocarb in the same region [14] has favored the switch from this insecticide to pirimiphosmethyl, which showed good performance in experimental huts trials [15]
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