Design and validation of a low-cost sugar-feeder for resource-poor insectaries

Abstract

Background The emergence of insecticide resistance in insects has led researchers to develop new control tools so that historic gains made in reducing disease transmission are not lost. Attractive targeted sugar baits (ATSBs) are a vector control tool being widely trialled to target insects that feed on plant sugars and blood. We designed a field-friendly, economical and more environmentally responsible sugar feeder for maintaining mosquito colonies and screening potential ATSB candidates. Methods We simultaneously tested, in both male and female Anopheles gambiae mosquitoes, the effect of adding three water-soluble medical and food dyes (Allura Red, fluorescein and tartrazine) to the sugar solution to identify those insects that had ingested sugar from the feeder. To test feeder efficacy to deliver a toxic substance, we assessed the killing using boric acid, which kills both male and female mosquitoes when ingested. Using microscopy techniques compatible with fieldwork, including the use of a mobile phone camera, we documented the efficacy and tissue specificity of the dyes on mosquitoes after they were continuously fed dyed sugar solutions. Results The easy-to-construct sugar feeder is an economical option for testing the efficacy of ATSB components on Anopheles gambiae mosquitoes. Allura Red AC was the preferred dye as it has low toxicity to mosquitoes and allows the researcher to quickly visualise the imbibed sugar meal within the abdomen. Feeding 1% fluorescein dye, but not 0.1%, for longer than five days induced systemic dye distribution, where the mosquito’s wing veins, antennae and legs brightly fluoresced when examined by a handheld black light torch (395-400nm emission). Discussion Developing an affordable sugar feeder to maintain insectary-reared insects and test the efficacy of ATSB candidates involves designing a dye-labelled sugar bait station that is of low-toxicity, reusable and easy to construct using components available in low resource settings such as field stations.