<I>Aedes aegypti</I> (Diptera: Culicidae) Biting Deterrence: Structure-Activity Relationship of Saturated and Unsaturated Fatty Acids

Abstract

In this study we evaluated the biting deterrent effects of a series of saturated and unsaturated fatty acids against Aedes aegypti (L), yellow fever mosquito (Diptera: Culicidae) using the K & Dbioassay module system. Saturated (C6:0 to C16:0 and C18:0) and unsaturated fatty acids (C11:1 to C14:1, C16:1, C18:1, and C18:2) showed biting deterrence index (BDI) values significantly greater than ethanol, the negative control. Among the saturated fatty acids, mid chain length acids (C10:0 to C13:0) showed higher biting deterrence than short (C6:0 to C9:0) and long chain length acids (C14:0 to C18:0), except for C8:0 and C16:0 that were more active than the other short and long chain acids. The BDI values of mid chain length acids (C10:0 to C13:0) were not significantly less than N, N-diethyl-meta-toluamide (DEET), the positive control. Among the unsaturated fatty acids, C11:1 showed the highest activity (BDI = 1.05) and C18:2 had the lowest activity (BDI = 0.7). In C11:1, C12:1, and C14:1 BDI values were not significantly less than DEET. After the preliminary observations, residual activity bioassays were performed on C11:0, C12:0, C11:1, and C12:1 over a 24-h period. All the fatty acids (C11:0, C12:0, C11:1, and C12:1) and DEET showed significantly higher activity at all test intervals than the solvent control. At treatment and 1-h posttreatment, all fatty acids showed proportion not biting (PNB) values not significantly less than DEET. At 3-, 6-, and 12-h posttreatment, all fatty acids showed PNB values significantly greater than DEET. At 24-h posttreatment, only the PNB value for C12:0 was significantly higher than DEET. The dose-responses of C12:0 and DEET were determined at concentrations of 5-25 nmol/cm2. As in the residual activity bioassays, the PNB values for C12:0 and DEET at 25 nmol/cm(2) were not significantly different. However, at lower concentrations, the PNB values for C12:0 were significantly greater than DEET. These results clearly indicate that mid chain length fatty acids not only have levels of biting deterrence similar to DEET at 25 nmnol/cm(2) in our test system, but also appeared to be more persistent than DEET. In contrast, in vivo cloth patch assay system showed that the mid-chain length fatty acids, C11:0, C11:1, C12:0, and C12:1 had minimum effective dose (MED) values greater than DEET against Ae. aegypti and their relative repellency varied according to species tested. The MED values of 120 (C11:0), 145 (C12:0) and 116 (C11:1) nmol/cm(2) against Anopheles quadrimaculatus Say, indicated that these acids were not as potent as DEET with a MED of 54 nmol/cm(2). The MED ratio of the C11:0 and C11:1 for all three mosquito species indicated the C11 saturated and unsaturated acids as more repellent than their corresponding C12:0 and C12:1 homologues.

An in vitro study of the bioefficacy of essential oil blends against Aedes aegypti (Linn.) and Anopheles dirus (Peyton and Harrison) by using membrane feeding apparatus

“…Studies have shown that vanillin reduces the evaporation rate of active ingredients and therefore extends the protection time (repellency) [15]. It is believed that vanillin changes the volatile composition of essential oils and also has an effect on the gustatory processes of mosquitoes [29,30]. In this study the effect of vanillin was often more evident at increased time after application.…”

Chemical Composition, Larvicidal, and Biting Deterrent Activity of Essential Oils of Two Subspecies ofTanacetum argenteum(Asterales: Asteraceae) and Individual Constituents AgainstAedes aegypti(Diptera: Culicidae)

“…Brießy, the assay system consists of a six-well reservoir with each of the 3 by 4 cm wells containing 6 ml of blood. As described by Ali et al (2012), a feeding solution consisting of citrateÐphosphateÐ dextroseÐadenine (CPDA-1) and ATP was used instead of blood. Green ßuorescent tracer dye (www.blacklightworld.com) was used to determine the feeding by the females.…”

“…Statistical Analyses. Proportion not biting was calculated as described by Ali et al (2012). As the K&D module bioassay system can handle only four treatments along with negative and positive controls, to make direct comparisons among more than four treatments and to compensate for variation in overall response among replicates, biting deterrent activity was quantiÞed as Biting Deterrence Index (BDI).…”

Discovery and structure activity relationships of 2-pyrazolines derived from chalcones from a pest management perspective

“…Briefly, the assay system briefly consists of a six-well reservoir with each of the 3 9 4 cm wells containing 6 ml of blood. As described by Ali et al (2012), a feeding solution consisting of CPDA-1 and ATP was used instead of blood. Green fluorescent tracer dye (www.…”

“…As the K&D module bioassay system can handle only four treatments along with negative and positive controls, in order to make direct comparisons among more than four test compounds and to compensate for variation in overall response among replicates, biting deterrent activity was quantified as Biting Deterrence Index (BDI) (Ali et al, 2012). The BDIs were calculated using the following formula:…”