Larvicidal, oviposition-deterrence, and excito-repellency activities of four essential oils: an eco-friendly tool against malaria vectors Anopheles coluzzii and Anopheles gambiae (Diptera: Culicidae)

Abstract

Mosquitoes are vectors of pathogens affecting humans causing morbidity, mortality and significant economic losses. Insecticides provide main-protection against vector-mosquitoes. However, synthetic insecticides, cause environmental contamination and increase vector resistance. These effects make it a priority to search for alternative means that are not deleterious to the environment and are public health acceptable. Here, we report oviposition deterrence, blood-feeding inhibition, excito-repellent effect, and larvicidal activities by essential oils (EOs) from the leaves of Lantana. camara L., Hyptis. suaveolens Poit., Hyptis. spicigera Lam, and Ocimum. canum Sims against local laboratory strains of Anopheles. gambiae s. s. and Anopheles coluzzii. All bioassays followed WHO standard protocols including minor modifications to evaluate the oviposition deterrence of gravid females, inhibition of adult blood-feeding and mortality caused by EO (essential oils), and larval susceptibility to EO. All EO tested showed strong oviposition deterrence, and the oviposition activity index ranged from −1 to - 0.75. Using a tunnel, we showed that EO have excito-repellent and blood-feeding inhibitory activities, and induced adult mortality. Engorged females tested ranged from 10.58 to 26.40%. L. camara EO had the highest larvicidal activity on both mosquito strains, and LC50 values of 102.78 and 92.20 ppm (part per million) for An. coluzzii and An. gambiae, respectively. The two mosquito strains showed similar susceptibilities to EOs. Overall, our results show that the EO used in this study could be used in developing effective and environmentally friendly approach to deter oviposition, repel mosquitoes, and control larvae.