Malaria incidence in Amazonian Peru has been increasing since 2011. The mainstays of vector control, indoor residual spray (IRS) and long-lasting insecticidal nets (LLINs) are only partly effective against the behaviorally and ecologically plastic major vector, Nyssorhynchus (formerly Anopheles) darlingi, a species that rests outdoors and takes blood meals indoors and outdoors. Attractive toxic sugar baits (ATSBs) lure vector mosquitoes into feeding on a combination of attractive sugars and an oral insecticide, the latter killing mosquitoes soon after they have fed. The biological basis of ATSBs is that both male and female mosquitoes require carbohydrate sources, usually as nectar, throughout their lives. Males require sugar for reproductive success; females for flight and to maximize survival and egg production. This proposal will examine the understudied sugar-feeding behavior of wild populations of Ny. darlingi and, in a biosphere, test responses of colony Ny. darlingi to volatile organic compounds (VOCs), both those that have been successful for other malaria vectors, and those from local plants. First, we will quantify, in wild male and female Peruvian Ny. darlingi, proportions of fructose, determine time and place of highest frequency of sugar-feeding, and estimate age structure of each population. Mosquitoes will be collected with barrier screen traps and resting boxes to provide maximum baseline data. We expect to detect 1) both males and females taking sugar- meals; 2) higher proportion of newly-emerged (nulliparous) females will take sugar versus those that have previously laid eggs (parous); and 3) early evening will be the preferred female sugar- feeding time. These data will guide determination of time and location for optimal placement of ATSBs initially in the biosphere experiments and ultimately in the field. Secondly, in the biosphere we will test known blends of VOCs for attractiveness to our colony Ny. darlingi using baited traps and compare the preferred blend against the most common natural plant sugar sources identified in the field sites. We will then determine the effective concentrations of the oral insecticide boric acid that can kill Ny. darlingi, and test in combination with the preferred attractant as an ATSB prototype. Our novel insights into behavior and chemical ecology of Ny. darlingi will facilitate new avenues of investigation toward the elimination of malaria transmission in the Amazon.
The overall goal of the Amazonia ICEMR is to organize a comprehensive approach to understanding the combined socio-demographic and biological features of Amazonian malaria towards the ultimate goal of regional control and elimination of Plasmodium falciparum and P. vivax. This revision project focuses on the development of sugar baits in a quasi-real world experimental biosphere to test new approaches to malaria vector control.
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