Small-scale field evaluation of the entomological efficacy and the residual activity of Fludora Fusion WP-SB indoor residual spraying against Anopheles culicifacies s.l. in Gujarat, India.

Objectives: To evaluate the entomological efficacy and the residual activity of indoor residual spraying with Fludora Fusion 562.5 WP-SB, a combination formulation containing clothianidin, a neonicotinoid and deltamethrin, a pyrethroid, against the main rural malaria vector, Anopheles culicifacies s.l., in India in a small-scale trial.

Methods: In three study villages, suitable households were randomly allocated to five treatments: Fludora Fusion 562.5 WP-SB (target dose 225 mg active ingredient AI/m ); clothianidin 70 WG (target dose 200 mg AI/m ); K-Othrine 250 WG (deltamethrin, target dose 25 mg AI/m ); Ficam VC 80 WP-SB (bendiocarb, target dose 400 mg AI/m ) and unsprayed control. Insecticides were sprayed by hand compression sprayers with control flow valves and 8002E nozzles. Post-spray cone bioassays were done on insecticide-treated walls using a colonised, deltamethrin-resistant strain of An. culicifacies. Mosquitoes were collected from treated rooms by different methods. The insecticide content on filter papers collected from the sprayed walls was determined by chemical assay to assess the spray quality.

Results: The ratios of applied to target doses of insecticides were within 0.84 to 1.4, showing a good spray quality. The cone bioassays revealed residual action lasting 7 months for all insecticides without significant differences in mortality between different surfaces treated nor between the four treatment arms (P > 0.05). Considering all entomological parameters such as indoor resting density, excito-repellency, blood-feeding inhibition and delayed mortality, the overall efficacy of Fludora Fusion WG-SB was equal or better compared with other insecticides.

Conclusions: Fludora Fusion showed overall equal or better efficacy than deltamethrin and bendiocarb alone against a pyrethroid-resistant malaria vector population and can be considered as an alternative product for management of pyrethroid resistance in malaria vectors.