Orientation Behaviour of the Blood-sucking Bug Triatoma infestans to Short-chain Fatty Acids: Synergistic Effect of L-Lactic Acid and Carbon Dioxide

R B Barrozo

doi:10.1093/chemse/bjh249

Abstract

The role of short-chain fatty acids in the host-seeking behaviour of Triatoma infestans larvae was investigated using a locomotion compensator. Several short-chain fatty acids were tested alone over a wide range of doses, or in combination with L-lactic acid (L-LA; 100 microg). Bugs showed no attractive response to single carboxylic acids, but when L-LA was added to airstreams carrying specific intensities of either propionic (C3; 100 microg), butyric (C4; 1 microg) or valeric acid (C5; 1 microg), these mixtures elicited an attractive response, evincing a synergistic effect. No orientation response was observed when caproic acid (C6) was offered with L-LA at the doses tested. Two blends were created: (1) C3, C4 and C5 combined at the effective doses when added with L-LA [C3C4C5 (1)], and (2) C3, C4 and C5 combined at a third of those intensities [C3C4C5 (2)]. Both blends were tested alone, with L-LA (100 microg), with a sub-threshold concentration of CO(2) (300 p.p.m. above the ambient level), and combined with both compounds together. Oriented responses of bugs were only observed with the blend (2) added with L-LA and with the combination of this lure with CO(2). This last combination evoked a behavioural response similar in intensity to that induced by a live mouse.

Highlights

Triatomines are haematophagous bugs (Heteroptera: Reduviidae: Triatominae) that are vectors of the flagellated parasite Trypanosoma cruzi, the causative agent of Chagas’disease
Triatoma infestans larvae stimulated with two opposite odourless airstreams exhibited a non-oriented behaviour on the locomotion compensator, i.e
In the following assays we analysed whether the null attractive effect of both groups of compounds as separate stimuli could be reverted by presenting them simultaneously via an airstream

Summary

Introduction

Triatomines are haematophagous bugs (Heteroptera: Reduviidae: Triatominae) that are vectors of the flagellated parasite Trypanosoma cruzi, the causative agent of Chagas’. This trypanosomiasis constitutes one of the most serious sanitary problems in Latin America, and has an important social and economic impact on the region (Dias and Schofield, 1999). The adaptation of several species of triatomines to human habitats, which offer abundant food (blood of humans, domestic animals, associated rodents, etc.) and places that are easy to colonize (e.g. cracks and crevices in walls made of dried mud and thatched roofs), define, among other features, the vectorial importance of these bugs. Colonies of Triatoma infestans are almost exclusively established inside human dwellings and/or peridomestic structures, and this insect is the main vector of the Chagas’ disease in southern South America

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