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Title: Electrophysical and behavioral characterization of bioactive compounds of four essential oils against Anopheles gambiae and prospects for their use as bednet treatments

Author
item DELETRE, EMILIE - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item CHANDRE, FABRICE - National Council For Scientific Research-Cnrs
item Williams, Livy
item DUMENIL, CLAIRE - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item MENUT, CHANTAL - University Of Montpellier
item MARTIN, THIBAUD - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2015
Publication Date: 6/11/2015
Citation: Deletre, E., Chandre, F., Williams III, L.H., Dumenil, C., Menut, C., Martin, T. 2015. Electrophysical and behavioral characterization of bioactive compounds of four essential oils against Anopheles gambiae and prospects for their use as bednet treatments. Parasites & Vectors. 8:316. 1-14.

Interpretive Summary: Mosquito bites are integral to the transmission of many diseases, e.g., malaria and yellow fever, that result in serious illness and death of millions of humans every year. This has led to the development of strategies to reduce the frequency of human bites by mosquitoes. Historically, these strategies have emphasized insecticides and synthetic repellents. Recent concerns about the development of insecticide resistance by mosquitoes, and interest in more environmentally-friendly mosquito control methods have led to research on bednets treated with repellents derived from plant essential oils in as an approach to mitigate the impact of mosquitoes in sub-Saharan Africa. Our objectives were to identify the active compounds of four plant essential oils, characterize their biological activity, and examine their potential to repel mosquitoes when applied to bednets. We evaluated the odors of the active compounds in physiological and behavioral experiments, as well as the toxic effects, against Anopheles gambiae mosquitoes. Results between the physiological, behavioral, and toxicity experiments were not always consistent, but several of the single compounds did exhibit repellency, irritancy or toxicity in the mosquitoes. Generally, the biological activity of essential oils appeared complex, suggesting interactions between individual compounds, some of which might be present in minute amounts, and the insect under study. Our results also suggested that the mechanisms that mediate repellency differ from those that control irritancy and toxicity. Based on our studies, several of the compounds merit further research as alternative bednet treatments.

Technical Abstract: Laboratory and field studies have shown that repellent, irritant and toxic effects of common public health insecticides reduce human-vector contact and thereby interrupt disease transmission. One of the more effective strategies to reduce disease risk involves the use of long-lasting treated bednets. However, development of insecticide resistance in mosquito populations makes it imperative to find alternatives to these insecticides. Our previous study identified four essential oils as alternatives to pyrethroids: Thymus vulgaris, Cymbopogon winterianus, Cuminum cyminum, Cinnamomum zeylanicum. The objectives of this study were to identify active compounds of these essential oils, to characterize their biological activity, and to examine their potential as a treatment for bed nets. We evaluated the electrophysiological, behavioural (repellency, irritancy) and toxic effects of the major compounds of these oils against Anopheles gambiae strain ‘Kisumu’. Aldehydes elicited the strongest responses and monoterpenes the weakest responses in electroantennogram (EAG) trials. However, EAG responses did not correlate consistently with results of behavioral assays. In behavioral and toxicity studies, several of the single compounds did exhibit repellency, irritancy or toxicity in An. gambiae; however, the activity of essential oils did not always correlate with activity expected from the major components. On the contrary, the biological activity of essential oils appeared complex, suggesting interactions between individual compounds and the insect under study. Data also indicated that the three effects appeared independent, suggesting that repellency mechanism(s) may differ from mechanisms of irritancy and toxicity. Based on the bioassays reported here, some of the compounds merit consideration as alternative bednet treatments.