Larvicidal and Synergistic Properties of Fixed Oils Derived from Plants and their Capacity to inhibit Pupation and Emergence of Malaria Vector (Anopheles gambiae)

Abstract

Malaria vectors have evolved resistance to almost all WHO-recommended insecticides, which compromises vector control. This study aimed to evaluate the insecticidal activity of four doses of fixed oils from Jatropha curcas and Ricinus communis on Anopheles gambiae in western Burkina Faso. Biological tests of susceptibility to oil doses were carried out on two populations of the An. gambiae complex from August to October 2022 using the WHO standard protocol. The synergistic or antagonistic effects of the extracts’ combinations were evaluated by comparing “sums of effects” to “effects of sums” according to the WHO protocol. R software enabled probit and ANOVA analyses. All oils showed larvicidal activity on susceptible strains of An. gambiae, Kisumu. The LC50 of the combination of the two oils was lower (54.09±1.03 ppm), followed by the oil of J. curcas (58.8±1.03 ppm) and that of R. communis (139.0±1.04 ppm) on the field strain of An. gambiae. J. curcas oil was more toxic on both strains, leading to 100% mortality at 48h and 72h of exposure. Synergistic insecticidal effects after 24h and additive effects after 48h of the combined oil at 50 and 150 ppm resulted in 41.75% to 91.66% mortality of larvae and reduced pupation from 2.66% to 0.00% and reduced the emergence of An. gambiae from 1.16 to 0.00%. J. curcas and R. communis’ oils contain linalool, tannins, alkaloids, saponins, and terpenes. Applying J. curcas or R. communis oil or a combined oil at 50 and 150 ppm as a spray could constitute an effective strategy for integrated control of An. gambiae mosquitoes.