Mosquito Attraction: Crucial Role of Carbon Dioxide in Formulation of a Five-Component Blend of Human-Derived Volatiles

Abstract

Behavioral responses of the malaria mosquito Anopheles coluzzii (An. gambiae sensu stricto molecular ‘M form’) to an expanded blend of human-derived volatiles were assessed in a dual-port olfactometer. A previously documented attractive three-component blend consisting of NH3, (S)-lactic acid, and tetradecanoic acid served as the basis for expansion. Adding 4.5 % CO2 to the basic blend significantly enhanced its attractiveness. Expansion of the blend with four human-derived C4-volatiles was then assessed, both with and without CO2. Only when CO2 was offered simultaneously, did addition of a specific concentration of 3-methyl-1-butanol or 3-methyl-butanoic acid significantly enhance attraction. The functional group at the terminal C of the 3-methyl-substituted C4 compounds influenced behavioral effectiveness. In the absence of CO2, addition of three concentrations of butan-1-amine caused inhibition when added to the basic blend. In contrast, when CO2 was added, butan-1-amine added to the basic blend strongly enhanced attraction at all five concentrations tested, the lowest being 100,000 times diluted. The reversal of inhibition to attraction by adding CO2 is unique in the class Insecta. We subsequently augmented the three-component basic blend by adding both butan-1-amine and 3-methyl-1-butanol and optimizing their concentrations in the presence of CO2 in order to significantly enhance the attractiveness to An. coluzzii compared to the three- and four-component blends. This novel blend holds potential to enhance malaria vector control based on behavioral disruption.

Eave Screening and Push-Pull Tactics to Reduce House Entry by Vectors of Malaria

“…33 It was baited with an attractive five-compound odor blend released from nylon strips, 28,30 augmented with carbon dioxide (CO 2 ) produced by the fermentation of molasses. 38 Fresh odor baits were provided at the start of the experiment and left in place throughout the entire trial as previous studies have shown that the strips remain attractive for at least 52 nights after impregnation.…”

“…[29][30][31] An ongoing large-scale intervention study explores the potential of mass-trapping malaria vectors to reduce malaria transmission on an island community in western Kenya. 32 By actively removing mosquitoes from the peridomestic environment, attractant-baited traps can provide a dual-protective effect: 1) a direct effect by reducing house entry of mosquitoes that would otherwise have entered 16,33 and 2) an indirect effect by reducing the average mosquito's life span and by depleting mosquito populations through daily removal trapping.…”

Microorganism-mediated behaviour of malaria mosquitoes

“…NH3+Lactic acid+C14+3-methyl-1-butanol+Butan-1-amine (Hiscox et al, 2014;Menger et al, 2014;van Loon et al, 2015; + CO 2 .…”

“…Significantly enhanced attraction of the SB blend to An. gambiae was achieved by adding 3-methyl-1-butanol and butan-1-amine (MB5 blend) (Hiscox et al, 2014;Menger et al, 2014;van Loon et al, 2015). These attractive blends have been developed for anthropophilic An.…”

“…These attractive blends have been developed for anthropophilic An. gambiae mosquitoes (Smallegange et al, 2005;Smallegange et al, 2009;Verhulst et al, 2011a;Verhulst et al, 2011b;van Loon et al, 2015). However, less is known about their effect on the host-seeking behaviour of other mosquito species with different host preferences.…”