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A New In Vitro Bioassay System for Discovery and Quantitative Evaluation of Mosquito Repellents

Abbas Ali, Charles L. Cantrell, Ikhlas A. Khan
Journal of medical entomology 2017 v.2017 no. pp. 1-9
Aedes aegypti, bioassays, cages, collagen, deet, in vitro studies, in vivo studies, insect repellents, methyl eugenol, mosquito bites, mosquito control, new products, quantitative analysis, risk reduction, temperature, thymol
Mosquitoes vector many pathogens that cause human diseases. Repellents play a significant role in reducing the risk of these diseases by preventing mosquito bites. In this paper, we are reporting an Ali and Khan (A & K), large cage in vitro bioassay system that can effectively be used to measure repellency of compounds against mosquitoes. The system uses temperature as a landing and feeding stimulus, and collagen as a feeding substrate. The minimum effective dose (MED) of DEET (N, N-diethyl-meta-toluamide; 19.3 µg/cm2) against Aedes aegypti (L.) in a 30-cm2 treatment area from the A & K bioassay falls in the upper range of the in vivo, cloth patch bioassay (6–23 µg/cm2). Undecanoic acid and geranic acid, with MED values of 3.6 and 7.5 µg/cm2, respectively, in the A & K bioassay were active at 5.5–6.6 times lower dose than that in the in vivo bioassay. Thymol and methyl eugenol with MED values of 11.1 and 10.9 µg/cm2, respectively, were active at 3–4 times lower dose than that in the in vivo bioassay, whereas (-)-trans-p-Menthane-3,8 diol with MED value of 32.3 µg/cm2 was active at 1.3 times lower dose. Comparisons between 12-cm2 and 30-cm2 treatment areas, with similar concentration per unit area in the A & K bioassay, indicated that the MED values at 30 cm2 were 1–2 times higher. In addition to its use to identify the repellent properties of new products, the A & K bioassay can generate useful data on promising repellents to make in vivo testing and field evaluation decisions.