Effect of Aedes aegypti exposure to spatial repellent chemicals on BG-Sentinel™ trap catches.

Ferdinand V Salazar,Theeraphap Chareonviriyaphap,Lars Eisen,Christine Dureza,Nicole L Achee,Tolulope A Ojo,Atchariya Prabaripai,Suppaluck Polsomboon,John P Grieco

doi:10.1186/1756-3305-6-145

Abstract

BackgroundAn integrated approach to reduce densities of adult Aedes aegypti inside homes is currently being evaluated under experimentally controlled field conditions. The strategy combines a spatial repellent (SR) treatment (applied indoors) with the Biogents Sentinel™ (BGS) mosquito trap positioned in the outdoor environment. In essence, when combined, the goal is to create a push-pull mechanism that will reduce the probability of human-vector contact. The current study measured BGS recapture rates of Ae. aegypti test cohorts that were exposed to either SR or control (chemical-free) treatments within experimental huts. The objective was to define what, if any, negative impact SR may have on BGS trap efficacy (i.e., reduced BGS collection).MethodsAedes aegypti females were exposed to SR compounds within experimental huts in the form of either treated fabric (DDT and transfluthrin) or mosquito coil (metofluthrin). Test cohorts were released within individual screen house cubicles, each containing 4 BGS traps, following SR exposure according to treatment. Two separate test cohorts were evaluated: (i) immediate release (IR) exposed from 06:00–12:00 hours and released at 12:00 hours and (ii) delayed release (DR) exposed from12:00–18:00 hours and released at 05:30 hours the following day. BGS recapture was monitored at 09:30, 13:30 and 15:30 hours and the cumulative recapture by time point quantified.ResultsExposure of Ae. aegypti females to either DDT or metofluthrin did not significantly impact BGS capture as compared to cohorts of non-exposed females. This was true for both IR and DR exposure populations. IR cohorts exposed to transfluthrin resulted in significantly lower BGS recapture compared to matched controls but this effect was primarily due to high mosquito mortality during transfluthrin trials.ConclusionOur data indicate no more than minor and short-lived impacts (i.e., reduced attraction) on BGS trap catches following exposure to the pyrethroid compounds transfluthrin and metofluthrin and no change in recapture densities using DDT as compared to matched controls. These findings suggest a combined SR and BGS approach to vector control could function as a push-pull strategy to reduce Ae. aegypti adults in and around homes.

Highlights

An integrated approach to reduce densities of adult Aedes aegypti inside homes is currently being evaluated under experimentally controlled field conditions
There was no significant difference in Biogents SentinelTM (BGS) recapture between DDT-exposed and control cohorts for either immediate release (IR) or delayed release (DR) populations (Figure 2, Table 1)
Metofluthrin exposure There were no significant differences in BGS recapture rates among metofluthrin-exposed and both positive and negative control cohorts for either IR or DR populations

Summary

Introduction

An integrated approach to reduce densities of adult Aedes aegypti inside homes is currently being evaluated under experimentally controlled field conditions. The mechanism underlying a push-pull system includes: (i) behavioral manipulation of the target species to repel or deter (push) them away from a resource (i.e., a crop) using stimuli that renders the resource unsuitable or unattractive and (ii) a device, for example a trap, through which the target species are removed from the environment (pull) [13,14,15] Such an approach may prove effective in the control of pathogen-transmitting mosquitoes, especially in and around the home where many vector-borne pathogens are predominantly transmitted in the developing world. One clear benefit of a push-pull system is that it can be effective in settings where insecticide resistance occurs This is because the chemical doses that elicit sublethal behavioral responses, such as spatial repellency, are below that required for toxicity, thereby reducing insecticide resistance selection pressure while continuing to prevent human-vector contact [1,16,17,18]

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