Ovicidal and Larvicidal Activities of Ethanolic Leaf Extracts of Three Botanicals Against the Malaria Vector - Anopheles Gambiae

Abstract

Malaria, transmitted by Anopheles gambiae, has been a major public health concern in Africa. Chemicals used in the control of A. gambiae have caused a lot of havoc in the environment and to non-target organisms. More so, a high rate of resistance by these mosquitoes has been recorded. This study evaluated the ovicidal and larvicidal activities of ethanolic leaf extracts of Duranta erecta, Tridax procumbens and Pennisetum purpureum against A. gambiae. Phytochemical analysis of these plants revealed the presence of tannins, saponins, alkanoids, flavonoids, glycosides and anthroquinone. Ground dry leaves of each plant material were concentrated in 7 litres of 95% ethanol for 72 hours followed by filtration and evaporation. D. erecta, T. procumbens and P. purpureum yielded 617.2g, 598.3g and 552g of extracts respectively. The WHO standard for mosquito bioassay was adopted and concentrations 40, 100, 140 and 200 parts per million (PPM) were tested against 20 eggs and 25 larvae using emersion method. The hatching rate and % larval mortality of the extracts were recorded in which a concentration dependent increase was observed. High ovicidal activity (low egg hatchability) was recorded in D. erecta (LC50 -10.037 PPM) followed by P. purpureum and T. procumbens with LC50 values of 17.380 and 39.198 respectively. The highest larvicidal activity was observed in D. erecta (LC50 -76.943 PPM) compared to P. purpureum and T. procumbens (LC50 - 213.410 PPM and 214.217 PPM). Evidently, D. erecta ethanolic leaf extracts showed the best efficacy in the control of A. gambiae in this study. D. erecta is an environmentally friendly alternative in reducing the use of chemicals for mosquito control.