Abstract
BackgroundThe widespread emergence of insecticide resistance in African malaria vectors remains one of the main challenges facing control programmes. Electrostatic coating that uses polarity to bind insecticide particles is a new way of delivering insecticides to mosquitoes. Although previous tests demonstrated the resistance breaking potential of this application method, studies screening and investigating the residual efficacy of a broader range of insecticides are necessary.MethodsEleven insecticide powder formulations belonging to six insecticide classes (pyrethroid, carbamate, organophosphate, neonicotinoid, entomopathogenic fungus and boric acid) were initially screened for residual activity over 4 weeks against pyrethroid resistant Anopheles gambiae sensu lato (s.l.) from the M’bé valley, central Côte d’Ivoire. Tests were performed using the eave tube assay that simulates the behavioural interaction between mosquitoes and insecticide-treated inserts. With the best performing insecticide, persistence was monitored over 12 months and the actual contact time lethal to mosquitoes was explored, using a range of transient exposure time (5 s, 30 s, 1 min up to 2 min) in the tube assays in laboratory. The mortality data were calibrated against overnight release-recapture data from enclosure around experimental huts incorporating treated inserts at the M’bé site. The natural recruitment rate of mosquitoes to the tube without insecticide treatment was assessed using fluorescent dust particles.ResultsAlthough most insecticides assayed during the initial screening induced significant mortality (45–100%) of pyrethroid resistant An. gambiae during the first 2 weeks, only 10% beta-cyfluthrin retained high residual efficacy, killing 100% of An. gambiae during the first month and > 80% over 8 subsequent months. Transient exposure for 5 s of mosquitoes to 10% beta-cyfluthrin produced 56% mortality, with an increase to 98% when contact time was extended to 2 min (P = 0.001). In the experimental hut enclosures, mortality of An. gambiae with 10% beta-cyfluthrin treated inserts was 55% compared to similar rate (44%) of mosquitoes that contacted the inserts treated with fluorescent dusts. This suggests that all host-seeking female mosquitoes that contacted beta-cyfluthrin treated inserts during host-seeking were killed.ConclusionThe eave tube technology is a novel malaria control approach which combines house proofing and targeted control of anopheline mosquitoes using insecticide treated inserts. Beta-cyfluthrin showed great promise for providing prolonged control of pyrethroid resistant An. gambiae and has potential to be deployed year-round in areas where malaria parasites are transmitted by highly pyrethroid resistant An. gambiae across sub-Saharan Africa.
Highlights
The widespread emergence of insecticide resistance in African malaria vectors remains one of the main challenges facing control programmes
Oumbouke et al Malar J (2018) 17:374 providing prolonged control of pyrethroid resistant An. gambiae and has potential to be deployed year-round in areas where malaria parasites are transmitted by highly pyrethroid resistant An. gambiae across sub-Saharan Africa
Wide-scale use of insecticide-based interventions such as indoor residual sprays (IRS) and long-lasting insecticidetreated nets (LLINs) has contributed to a substantial reduction in the global malaria burden in recent years [1, 2]. The sustainability of these approaches is being threatened by the evolution of insecticide resistance [3, 4], creating a need for more diverse vector control tools [5]
Summary
The widespread emergence of insecticide resistance in African malaria vectors remains one of the main challenges facing control programmes. The eave tube is a recent innovation that offers a novel approach for delivering insecticides to malaria mosquitoes [6]. When host-seeking mosquitoes enter a tube, they encounter an insert treated with an insecticide. The current version of the eave tube inserts uses electrostatic netting to hold powder formulations of insecticides. Mosquito contact with the netting results in very efficient transfer of powder particles such that even highly pyrethroid resistant mosquitoes can be killed with pyrethroid insecticides due to the overwhelming dose [7]. When eave tubes are combined with screening of windows and doors to reduce mosquito entry via other routes, the approach provides both physical protection and a killing effect, much like an insecticide treated net but at the level of the household
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