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The development of an ivermectin-based attractive toxic sugar bait (ATSB) to target Anopheles arabiensis.

ABSTRACT: An increasing number of countries in sub-Saharan Africa are moving towards malaria-elimination, mostly thanks to successful vector control campaigns. However, elimination has proven challenging, resulting in the persistence of malaria transmission. It is now accepted that in order to eliminate malaria, new complementary vector control approaches must be developed. This study describes the development of a sugar-baited resting place containing a toxic dose of ivermectin for the control of Anopheles arabiensis.Dose response experiments were performed in insectary conditions to determine the LD90 of ivermectin against An. arabiensis. Over 95% of An. arabiensis were knocked down 48 h post-sugar feeding on 10% sucrose solutions containing 0.01% ivermectin. When investigating different juices as attractants, it was observed that An. arabiensis preferred orange, watermelon and commercial guava juice over pawpaw, tomato, mango or banana, but were most likely to feed on simple 10% sugar solution. Using recycled materials, different bait prototypes were tested to determine the best design to maximize sugar feeding. Baits that offered a resting place for the mosquito rather than just a surface to sugar feed were more likely to attract An. arabiensis to sugar feed. The optimized prototype was then placed in different locations within a screen-house, colour-coded with different food dyes, containing competing vegetation (Ricinus communis) and experimental huts where humans slept under bed nets. Around half of all the released An. arabiensis sugar fed on the sugar baits, and approximately 50% of all sugar fed mosquitoes chose the baits close to outdoor vegetation before entering the huts.Ivermectin is an effective insecticide for use in sugar baits. The design of the sugar bait can influence feeding rates and, therefore, efficacy. Sugar baits that offer a resting surface are more efficient and sugar feeding on the baits is maximized when these are placed close to peri-domestic vegetation. Attractive toxic sugar baited resting places may provide an additional vector control method to complement with existing strategies.

SUBMITTER: Tenywa FC

PROVIDER: S-EPMC5558776 | biostudies-other | 2017 Aug

REPOSITORIES: biostudies-other

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Project description:Attractive toxic sugar bait (ATSB) is a highly effective method which targets mosquitoes based on their sugar foraging behavior, by presenting baits of attractive compounds in combination with sugar and oral toxin to local mosquito populations. Environmental concerns and insecticide selection-pressure have prompted investigations of novel, ecologically-harmless substances which can be used as insecticides. This study examined the efficacy of microencapsulated garlic-oil as the oral toxin component of ATSB for controlling Anopheles sergentii populations inhabiting desert-surrounded wetlands in Israel. ATSB solution containing 0.4% encapsulated garlic oil was applied to local vegetation around a streamlet located in the lower Jordan Valley. To determine the propensity of bait ingestion, and assess the potential ecological impact of the method, mosquito and non-target specimens were collected and tested for the presence of natural plant- or attractive sugar bait (ASB)-derived sugars. Over the experimental period, biting-pressure values in the ATSB treatment site decreased by 97.5%, while at the control site, treated with non-toxic ASB, no significant changes were observed. Approximately 70% of the mosquitoes collected before both treatments, as well as those captured following the application of ASB at the control site, were found to have ingested sugar prior to capture. Non-target insects were minimally affected by the treatment when ATSB was applied to foliage of non-flowering plants. Of the non-Diptera species, only 0.7% of the sampled non-target insects were found to have ingested ASB-solution which was applied to green vegetation, compared with 8.5% which have foraged on ASB-derived sugars applied to flowering plants. Conversely, a high proportion of the non-target species belonging to the order Diptera, especially non-biting midges, were found to have ingested foliage-applied ASB, with more than 36% of the specimens collected determined to have foraged on bait-derived sugars. These results prove that food-grade, EPA-exempt microencapsulated garlic oil is a highly effective insecticide which can be utilized for mosquito population control. The relatively short half-life of this active ingredient makes it a suitable for use in areas where repeated application is possible, limiting the accumulation of deleterious compounds and ensuring minimal environmental impact when applied in accordance with label recommendations.

Project description:BACKGROUND:Illnesses transmitted by Aedes aegypti (Linnaeus, 1762) such as dengue, chikungunya and Zika comprise a considerable global burden; mosquito control is the primary public health tool to reduce disease transmission. Current interventions are inadequate and insecticide resistance threatens the effectiveness of these options. Dried attractive bait stations (DABS) are a novel mechanism to deliver insecticide to Ae. aegypti. The DABS are a high-contrast 28 inch2 surface coated with dried sugar-boric acid solution. Aedes aegypti are attracted to DABS by visual cues only, and the dried sugar solution elicits an ingestion response from Ae. aegypti landing on the surface. The study presents the development of the DABS and tests of their impact on Ae. aegypti mortality in the laboratory and a series of semi-field trials. METHODS:We conducted multiple series of laboratory and semi-field trials to assess the survivability of Ae. aegypti mosquitoes exposed to the DABS. In the laboratory experiments, we assessed the lethality, the killing mechanism, and the shelf life of the device through controlled experiments. In the semi-field trials, we released laboratory-reared female Ae. aegypti into experimental houses typical of peri-urban tropical communities in South America in three trial series with six replicates each. Laboratory experiments were conducted in Quito, Ecuador, and semi-field experiments were conducted in Machala, Ecuador, an area with abundant wild populations of Ae. aegypti and endemic arboviral transmission. RESULTS:In the laboratory, complete lethality was observed after 48 hours regardless of physiological status of the mosquito. The killing mechanism was determined to be through ingestion, as the boric acid disrupted the gut of the mosquito. In experimental houses, total mosquito mortality was greater in the treatment house for all series of experiments (P < 0.0001). CONCLUSIONS:The DABS devices were effective at killing female Ae. aegypti under a variety of laboratory and semi-field conditions. DABS are a promising intervention for interdomiciliary control of Ae. aegypti and arboviral disease prevention.

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The development of an ivermectin-based attractive toxic sugar bait (ATSB) to target Anopheles arabiensis.

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