Abstract
The use of odor baits for surveillance and control of malaria mosquitoes requires robust dispensing tools. In this study, the residual activity of a synthetic mosquito attractant blend dispensed from nylon or low density polyethylene (LDPE) sachets was evaluated at weekly intervals for one year without re-impregnation. The potential role of bacteria in modulating the attraction of mosquitoes to odor-treated nylon that had been used repeatedly over the one year study period, without re-impregnation, was also investigated. Significantly higher proportions of female Anopheles gambiae sensu stricto mosquitoes were consistently attracted to treated nylon strips than the other treatments, up to one year post-treatment. Additional volatile organic compounds and various bacterial populations were found on the treated nylon strips after one year of repeated use. The most abundant bacteria were Bacillus thuringiensis and Acinetobacter baumannii. Autoclaving of treated nylon strips prior to exposure had no effect on trap collections of laboratory-reared female An. Gambiae (P = 0.17) or wild female An. Gambiae sensu lato (P = 0.26) and Mansonia spp. (P = 0.17) mosquitoes. Trap catches of wild female An. Funestus (P < 0.001) and other anophelines (P < 0.007) were higher when treated strips had been autoclaved prior to deployment as opposed to when the treated nylon strips were not autoclaved. By contrast, wild female Culex mosquitoes were more strongly attracted to non-autoclaved compared to autoclaved treated nylon strips (P < 0.042). This study demonstrates the feasibility of using odor baits for sampling and surveillance of malaria as well as other mosquito vectors over prolonged periods of time. Preliminary evidence points towards the potential role of bacteria in sustaining prolonged use of nylon material for dispensing synthetic attractant odorants for host-seeking malaria and other mosquito vectors but further investigations are required.
Highlights
Prospects of eliminating malaria are largely threatened by changes in the feeding and resting behavior of malaria mosquitoes, emerging resistance of Plasmodium parasites and malaria vectors to anti-malarial drugs and insecticides, respectively [1,2]
low density polyethylene (LDPE) sachets have proven suitable for the release of mosquito attractants [11,12,13], recent findings indicate that they attract fewer female Anopheles gambiae sensu stricto mosquitoes than nylon strips impregnated with similar compounds [14,15]
A total of 15,272 female An. gambiae mosquitoes were caught in all traps used over the one year study period
Summary
Prospects of eliminating malaria are largely threatened by changes in the feeding and resting behavior of malaria mosquitoes, emerging resistance of Plasmodium parasites and malaria vectors to anti-malarial drugs and insecticides, respectively [1,2]. The treated nylon strips were consistently more attractive to host-seeking An. gambiae mosquitoes than LDPE sachets containing the same attractants up to 40 nights post-treatment [15] This suggests that attractant-treated nylon strips possess a residual attraction capacity, which allows for prolonged use. This reduces the time, labour and costs needed for preparing fresh baits. It is not known whether original attractants applied on nylon strips can remain intact and active beyond the 40 post-treatment nights reported [15]. This study was designed to (a) investigate the long-lasting attraction of malaria mosquitoes to odor baits, (b) identify whether the original volatile organic compounds (VOCs) impregnated on the nylon strips remained intact up to the end of the experimental period, and (c) assess whether microbes are potentially associated with the long-lasting attraction of malaria mosquitoes to IB1-treated nylon strips
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