Attraction of Culex mosquitoes to aldehydes from human emanations

Helena M Leal,Justin K Hwang,Walter S Leal,Kaiming Tan

doi:10.1038/s41598-017-18406-7

Helena M Leal, Justin K Hwang + Show 2 more

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https://doi.org/10.1038/s41598-017-18406-7

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Journal: Scientific Reports	Publication Date: Dec 1, 2017
Citations: 23	License type: open-access

Affiliation: University of California, Davis

Abstract

Anecdotes related to preferential mosquito bites are very common, but to date there is no complete explanation as to why one out of two people systematically receives more mosquito bites than the other when both are equally accessible. Here we tested the hypothesis that two constituents of skin emanations, 6-methyl-5-heptan-2-one (6-MHO) and geranylacetone (GA), are natural repellents and may account for differential attraction in different ratios. We studied skin emanations from two human subjects, confirmed in behavioral assays that female southern house mosquitoes are significantly more attracted to subject A (attractant) than to subject N (non-attractant), and tested their 6-MHO/GA ratios in a dual-choice olfactometer. Although repelling at high doses, 6-MHO/GA mixtures were not active at the levels emitted by human skin. We found, however, differential attraction elicited by the aldehydes in the ratios produced by subjects A and N. When tested in a dose commensurate with the level released from human skin and in the ratio produced by subject A, the aldehyde mixture significantly attracted mosquitoes. By contrast, an aldehyde mixture at the same ratio released by subject N did not attract mosquitoes. We, therefore, hypothesized that aldehydes may play a role in the commonly observed differential attraction.

Highlights

Female mosquitoes feed on humans and other vertebrates to acquire nutrients and unwittingly transmit disease-causing agents when their contaminated, needle-like mouthparts make contact with the victim’s blood stream[1,2]
We compared two human subjects, designated subjects A and N, to reflect the reported observation that subject A attracted more mosquitoes than subject N attracted. By analyzing their skin emanations and measuring the behavior of female southern house mosquitos in response to synthetic blends or their “intact” body odors, we confirmed that 6-MHO/GA mixtures repel mosquitoes, but the amounts and ratios of 6-MHO/GA produced by the study subjects do not explain their differential attraction
The aldehydes octanal, nonanal, and decanal elicited mosquito attraction when presented in the ratio produced by subject A, but not in the ratio produced by subject N

Summary

OPEN Attraction of Culex mosquitoes to aldehydes from human emanations

Anecdotes related to preferential mosquito bites are very common, but to date there is no complete explanation as to why one out of two people systematically receives more mosquito bites than the other when both are accessible. Differential attraction elicited by the aldehydes in the ratios produced by subjects A and N. When tested in a dose commensurate with the level released from human skin and in the ratio produced by subject A, the aldehyde mixture significantly attracted mosquitoes. Regardless of the public interest in the subject, scientists have yet to find out a definitive answer to these questions It is well established, that host location is mediated by physical and chemical cues, heat[3], moisture[4], visual cues[5], and, more importantly, odorants (skin emanations)[6]. No evidence is available that suggests that CO2 mediates differential attraction, i.e., carbon dioxide emission levels do not explain the common observation that mosquitoes systematically prefer one person to another. The aldehydes octanal, nonanal, and decanal elicited mosquito attraction when presented in the ratio produced by subject A, but not in the ratio produced by subject N

Results and Discussion

Materials and Methods

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