Behavioural and Electrophysiological Responses of Female Anopheles gambiae Mosquitoes to Volatiles from a Mango Bait

Felician C Meza,Fredros O Okumu,Joe M Roberts,Toby J A Bruce,Frederic Tripet,Islam S Sobhy

doi:10.1007/s10886-020-01172-8

Abstract

Attractive Toxic Sugar Baits (ATSB) are used in a “lure-and-kill” approach for management of the malaria vector Anopheles gambiae, but the active chemicals were previously unknown. Here we collected volatiles from a mango, Mangifera indica, juice bait which is used in ATSBs in Tanzania and tested mosquito responses. In a Y-tube olfactometer, female mosquitoes were attracted to the mango volatiles collected 24–48 h, 48–72 h and 72–96 h after preparing the bait but volatiles collected at 96–120 h were no longer attractive. Volatile analysis revealed emission of 23 compounds in different chemical classes including alcohols, aldehydes, alkanes, benzenoids, monoterpenes, sesquiterpenes and oxygenated terpenes. Coupled GC-electroantennogram (GC-EAG) recordings from the antennae of An. gambiae showed robust responses to 4 compounds: humulene, (E)-caryophyllene, terpinolene and myrcene. In olfactometer bioassays, mosquitoes were attracted to humulene and terpinolene. (E)-caryophyllene was marginally attractive while myrcene elicited an avoidance response with female mosquitoes. A blend of humulene, (E)-caryophyllene and terpinolene was highly attractive to females (P < 0.001) when tested against a solvent blank. Furthermore, there was no preference when this synthetic blend was offered as a choice against the natural sample. Our study has identified the key compounds from mango juice baits that attract An. gambiae and this information may help to improve the ATSBs currently used against malaria vectors.

Highlights

IntroductionAttractive Toxic Sugar Baits (ATSB) exploit mosquito sugar feeding behaviour to lure individuals into a trap treated with a killing agent, such an insecticide (Müller et al 2008)
Malaria, primarily vectored in sub-Saharan Africa by the Anopheles gambiae Giles (Diptera: Culicidae) mosquitoElectronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Attractive Toxic Sugar Baits (ATSB) exploit mosquito sugar feeding behaviour to lure individuals into a trap treated with a killing agent, such an insecticide (Müller et al 2008)
The current study provides clear evidence of attraction of An. gambiae to mango volatiles and identifies the key compounds involved in mediating this behaviour as terpinolene and humulene

Summary

Introduction

ATSBs exploit mosquito sugar feeding behaviour to lure individuals into a trap treated with a killing agent, such an insecticide (Müller et al 2008) J Chem Ecol (2020) 46:387–396 mosquitoes depend on plant sugar, i.e. nectar from flowers, sap from leaves and plant stems, to obtain energy for activities such as host-seeking and mating (Foster 1995; Müller and Schlein 2006). This explains why plant volatiles may be attractive to mosquitoes (Nyasembe and Torto 2014). Nyasembe et al (2018) have recently shown that An. gambiae females can detect plant derived sesquiterpenes and alkenes

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Conclusion