Essential oils of plants and their combinations as an alternative adulticides against Anopheles gambiae (Diptera: Culicidae) populations.

The persistence of malaria and the increasing of resistance of Anopheles gambiae species to chemicals remain major public health concerns in sub-Saharan Africa. Faced to these concerns, the search for alternative vector control strategies as use of essential oils need to be implemented. Here, the five essential oils (EOs) from Cymbopogon citratus, Cymbopogon nardus, Eucalyptus camaldulensis, Lippia multiflora, Ocimum americanum obtained by hydro distillation were tested according to WHO procedures on Anopheles gambiae "Kisumu" and field strains collected in "Vallee du Kou". Also, the binary combinations of C. nardus and O. americanum were examined. As results, among the EOs tested, L. multiflora was the most efficient regarding KDT50 and KDT95 and rate of morality values. Our current study showed that C8 (C.n 80% : O.a 20%) and C9 (C.n 90% : O.a 10%), were more toxic to Anopheles gambiae strain VK with the mortality rates reaching 80.7 and 100% at the 1% concentration, respectively. These two binary combinations shown a synergistic effect on the susceptible population. However, only C9 showed a synergistic effect on VK population. The bioactivity of the two EOs, Cymbopogon nardus and Ocimum americanum, was improved by the combinations at certain proportions and may constitute an alternative to pyrethroid resistance.