Mosquito repellents from essential oils and crude extracts of plants of French Polynesia

Filariasis and Dengue Fever are two mosquito-borne diseases threatening French Polynesia. The potential vectors for transmission of these illnesses are Aedes aegypti (L.), the Yellow Fever mosquito, and Ae. polynesiensis Marks. A research program financed by the Ministry of Health of French Polynesia, the Establishment for Prevention and the Laboratory of Ecophysiology and Biotechnology of Halophytes and Marine Algae was undertaken with the ultimate goal of development of improved insect repellents and lures for insect traps. This goal is made more urgent by the threat of mosquito-borne diseases. Several natural products from terrestrial plants of French Polynesia were evaluated as spatial repellents against Ae. aegypti mosquitoes using a triple cage-dual port olfactometer and as topical repellents using a „cloth patch assay“ test with DEET as the positive control. In addition, the attraction of Ae. aegypti to L-lactic acid combined with the natural sample extracts were evaluated using the dual-port olfactometer. A total of 25 plant species have been collected by the Laboratory of Natural Products of the Institute Louis Malardé, and these have yielded 9 Essential Oils and 21 crude methanolic extracts. The fine chemical composition of some repellent essential oils were determined by gas chromatography and gas chromatography coupled with Mass Spectrometry at Malardé and at Montpellier. Their major volatile components were tested and the preliminary results are presented. Bioassays were performed with Ae. aegypti mosquitoes at the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS). This mosquito is the commonly accepted standard species for laboratory bioassays. Bioassays were conducted in with randomized sample order and distributed among the three cages of the olfactometer over three separate assay periods per day (approximately 0800, 1100, and 1300 local time). Each sample was analyzed at least times to improve the statistical precision of the results. The cloth patch repellency assays were conducted using 5–6 individuals to provide adequate precision if the duration and minimum effective dosage measures of repellent efficacy.