Residual efficacy of insecticides sprayed on different types of wall surfaces against Anopheles arabiensis in Ethiopia

Abstract

Background: Despite the available control interventions, malaria remains a major public health problem in Ethiopia. Indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) are the core vector control interventions in the country. The residual efficacy of insecticides needs to be evaluated when sprayed on different wall surfaces to determine the frequency of insecticide applications. Thus, the current study aimed to evaluate Ethiopropoxure 50% WP, Fludora Fusion, and SumiShield 50 WG insecticides at a community level in Ethiopia.

Methods: The study was conducted in five sentinel sites selected from Oromia (Wondogenet and Goro), Southern Nations, Nationalities and Peoples Region (Mirab Abaya), Afar (Melka-Werer), and Amhara (Finoteselam) regions in Ethiopia. Study villages were selected based on their history of not being covered by the IRS campaign for 12 consecutive months before the commencement of the study and households were then systematically selected from each sentinel site based on the availability of different wall types such as rough mud, smooth mud, painted, and cemented. The residual efficacy of three insecticides; Ethiopropoxure 50% WP, Fludora Fusion, and SumiShield 50 WG on different wall surfaces was measured using a standard WHO wall cone bioassay, monthly for four consecutive months. The mean percentage mortality of mosquitoes was calculated for each site, insecticide, and wall type using SPSS Version 23.  

Result: The result of the bioassay tests revealed that Ethiopropoxure 50% WP performed above 80% mortality rate after 24-hour holding time during the four test rounds in all wall types and study sites. Moreover, Fludora Fusion and SumiShield 50 WG performed above the standard determined by WHO (>80% mortality) for all wall types except for cemented wall surface after 24 hours post-exposure up to the third month. However, when the holding time was extended to 48-hour and 72-hour, both Fludora Fusion and SumiShied 50WG exerted >80% mortality for all wall types and study sites throughout the four-round test intervals.

Conclusion: The result of the wall bioassay revealed that Ethiopropoxure 50% WP, Fludora Fusion, and SumiShield 50 WG performed above the standard determined by WHO (>80% mortality) for all wall types from the initial test up to the fourth-month test interval.