Abstract
Vector control interventions including long-lasting insecticidal nets and indoor residual spraying are important for malaria control and elimination. And effectiveness of these interventions depends entirely on the high level of susceptibility of malaria vectors to insecticides. However, the insecticide resistance in majority of mosquito vector species across African countries is a serious threat to the success of vector control efforts with the extensive use of insecticides, while no data on insecticide resistance was reported from Sierra Leone in the past decade. In the present study, the polymerase chain reaction was applied for the identification of species of 757 dry adult female Anopheles gambiae mosquitoes reared from larvae collected from four districts in Sierra Leone during May and June 2018. And the mutations of kdr, rdl, ace-1 genes in An. gambiae were detected using SNaPshot and sequencing. As a result, one sample from Western Area Rural district belonged to Anopheles melas, and 748 An. gambiae were identified. Furthermore, the rdl mutations, kdr west mutations and ace-1 mutation were found. The overall frequency was 35.7%, 0.3%, 97.6% and 4.5% in A296G rdl, A296S rdl, kdrW and ace-1, respectively. The frequencies of A296G rdl mutation (P < 0.001), kdrW mutation (P = 0.001) and ace-1 mutation (P < 0.001) were unevenly distributed in four districts, respectively, while no statistical significance was found in A296S rdl mutation (P = 0.868). In addition, multiple resistance patterns were also found. In conclusion, multiple mutations involved in insecticide resistance in An. gambiae populations in Sierra Leone were detected in the kdrW, A296G rdl and ace-1 alleles in the present study. It is necessary to monitor vector susceptibility levels to insecticides used in this country, and update the insecticide resistance monitoring and management strategy.
Highlights
Malaria is one of the most widespread infectious diseases globally, with a major burden causing the death of more than 400,000 people yearly in the past three years, most of them were reported in the World Health Organization (WHO) African Region and children aged under five years (WHO, 2018; WHO, 2019; WHO, 2020)
The high malaria disease burden in this country accounted for approximately 48% of outpatient morbidity and approximately 38% of mortality in children under five years according to the national Malaria Indicator Survey 2016 (National Malaria Control Programme (NMCP) et al, 2016)
Adult female Anopheles gambiae mosquitoes were stored in the 1.5 ml Eppendorf tubes with cottons and silico gels. They were reared from larvae, which were collected from natural breeding water bodies in Kayangba community from Bo district, Magbema community from Bombali district, Lebanon community from Kono district, and Bolima community from Western Area Rural district, respectively, during May and June 2018. These four districts were selected into a four-year insecticide resistance monitoring and management program (2017-2020) which was supported by WHO to the National Malaria Control Program, Sierra Leone
Summary
Malaria is one of the most widespread infectious diseases globally, with a major burden causing the death of more than 400,000 people yearly in the past three years, most of them were reported in the WHO African Region and children aged under five years (WHO, 2018; WHO, 2019; WHO, 2020). The high malaria disease burden in this country accounted for approximately 48% of outpatient morbidity and approximately 38% of mortality in children under five years according to the national Malaria Indicator Survey 2016 (National Malaria Control Programme (NMCP) et al, 2016). Long-lasting insecticidal nets and indoor residual spraying are still two core interventions for malaria vector control. The effectiveness of these interventions depends entirely on the high level of susceptibility of malaria vectors to the insecticides. The insecticide resistance in majority of mosquito vector species across African countries is a serious threat to the success of vector control efforts with the extensive use of insecticides (https://anopheles. irmapper.com/)
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