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Background Sugar-feeding behaviour is essential for mosquito survival and reproduction, and has been exploited to develop new control strategies, such as the attractive targeted sugar baits (ATSB). This study examined the sugar-feeding habits of the dengue vector, Aedes aegypti, in semi-field conditions to determine the optimal timing (age) of sugar meals and whether the availability of sugar sources could affect blood-feeding by these mosquitoes. Methods A series of paired-choice assays were conducted in which mosquitoes were allowed to choose between a sugar meal or a blood meal directly from a rabbit. Female 1-day-old mosquitoes were given meal choices in cages I–V and observed for feeding choice in only one cage every day for 5 days starting with cages I to V. The preference of Ae. aegypti to feed on sugar or blood and the effect of sugar source availability on blood-feeding was assessed at different chronological and physiological ages. Results In the first 5 days post-emergence, there was no significant difference in mosquito preference for sugar or blood meals. However, after the first gonotrophic cycle, they had a greater preference for blood over sugar (odds ratio, OR [95% confidence interval, CI] = 9.4 [6.7–13.0]; P  < 0.001). Nulliparous Ae. aegypti females (≤ 5-day-old mosquitoes) were less likely to blood-feed if both sugar and blood sources were concurrently available (OR = 0.06 [0.02–0.16]; P  < 0.001). Conclusions Newly emerged females of Ae. aegypti mosquitoes were equally likely to choose a sugar meal or a blood meal. However, after the first gonotrophic cycle, they had a greater preference for blood over sugar. Additionally, nulliparous female mosquitoes were less likely to blood-feed when both sugar and blood sources were available. These findings provide insights into the sugar-feeding behaviour of Ae. aegypti and can inform the development and optimization of new control strategies such as using ATSB. Graphical Abstract

The house fly, Musca domestica L. (Diptera: Muscidae), is a disease vector of mechanically transmitted pathogens including bacteria, viruses, and protozoans. Opportunities for pathogen transmission can increase as fly longevity increases. Dietary preferences play an important role in insect longevity; therefore, we investigated house fly preferences, sucrose availability, and caloric constraints on house fly longevity. Experimental goals were: 1) to test the effects of calorie restriction on survival of house flies by manipulating concentrations of erythritol (low caloric content) and sucrose (high caloric content), and comparing commercial sweeteners of differing calorie content, 2) to identify house fly preferences for either erythritol or sucrose, and 3) to evaluate the insecticidal activity or toxicity of erythritol on house flies. Our data show that house flies may prefer high calorie options when given a choice and that house fly longevity likely increases as calorie content increases. Additionally, no significant differences in longevity were observed between the water only control (zero calories) and erythritol treatments. This suggests that decreased survival rates and death could be the result of starvation rather than insecticidal activity. This research furthers our understanding of house fly survival and sugar-feeding behavior.

Current methods of broad area application of contact insecticides used in mosquito control are becoming less effective, primarily due to resistance within mosquito populations. New methods that can deliver ingestible insecticides are being investigated as a means to mitigate resistance. This study evaluated insecticide delivery through toxic sugar baits (TSB) and resulting mortality of susceptible and resistant strains of Aedes aegypti. Two Ae. aegypti strains were evaluated using a 1% boric acid TSB: the susceptible Orlando 1952 (ORL) strain and the resistant Puerto Rican (PR) strain. The TSB resulted in high mortality for both ORL and PR strain of Ae. aegypti. Average mortality of female mosquitoes given TSB was 90.8% for PR and 99.3% for ORL. Our study suggests that targeting resistant mosquitoes with ingestible insecticides through TSBs could be a viable alternative to current mosquito control strategies and should be considered when developing an integrated vector management program.

During nectar feeding, mosquitoes ingest a plethora of phytochemicals present in nectar. The ecological and physiological impacts of these ingested phytochemicals on the disease vectors are poorly understood. In this study, we evaluated the effects of three nectar phytochemicals‐‐ caffeine, p‐coumaric acid, and quercetin‐‐on longevity, fecundity, and sugar‐feeding behavior of the Asian tiger mosquito (Aedes albopictus). Adult females of Ae. albopictus were provided continuous access to 10% sucrose supplemented with one of the three phytochemicals and their fecundity, longevity, and the amount of sucrose consumed determined. Transcriptome response of Ae. albopictus females to p‐coumaric acid and quercetin was also evaluated. Dietary quercetin and p‐coumaric acid enhanced the longevity of female Ae. albopictus, while caffeine resulted in reduced sugar consumption and enhanced fecundity of gravid females. RNA‐seq analyses identified 237 genes that were differentially expressed (DE) in mosquitoes consuming p‐coumaric acid or quercetin relative to mosquitoes consuming an unamended sucrose solution diet. Among the DE genes, several encoding antioxidant enzymes, cytochrome P450s, and heat shock proteins were upregulated, whereas histones were downregulated. Overall, our findings show that consuming certain nectar phytochemicals can enhance adult longevity of female Asian tiger mosquitoes, apparently by differentially regulating the expression level of genes involved in longevity and xenobiotic metabolism; this has potential impacts not only on life span but also on vectorial capacity and insecticide resistance. The study investigated the effects of nectar phytochemicals caffeine, p‐coumaric acid, and quercetin on longevity, fecundity, and sugar‐feeding behavior of female Aedes albopictus. Additionally, we did a whole‐transcriptome analysis of female Ae. albopictus consuming sucrose diets supplemented with p‐coumaric acid or quercetin to characterize their transcriptional profile. Quercetin and p‐coumaric acid significantly enhanced the longevity of the mosquitoes while caffeine consumption resulted in reduced sugar feeding and enhanced fecundity. Dietary p‐coumaric acid or quercetin led to a change in expression of genes associated with longevity regulation (superoxidase dismutase, heat shock proteins, and histones) and xenobiotic metabolism (P450s and other enzymes involved in degradation of toxins).

The project goal was to determine how a new vector control strategy that targets the sugar-feeding behavior of mosquitoes, attractive toxic sugar baits (ATSBs), can be used to more effectively control West Nile virus (WNV) vectors in the Coachella Valley, California. Three laboratory studies were conducted to determine the utility of this method for control against Culex quinquefasciatus and Culex tarsalis: 1) efficacy evaluations of 2 formulations of ATSB, microencapsulated garlic oil, and a combination of microencapsulated garlic oil and 1% boric acid; 2) choice assays to determine the attractiveness of ATSB with the microencapsulated garlic oil against attractive sugar baits (ASB; the attractant alone; without toxin) and a 10% sucrose solution; and 3) vegetation efficacy tests on 3 common plant species in the Coachella Valley, Atriplex lentiformis, Tamarix ramosissima, and Pluchea sericea. At 48 h the average mortality for Cx. quinquefasciatus was 91% after exposure to ATSB with microencapsulated garlic oil and 99% on ATSB garlic + 1% boric acid solution. Culex tarsalis averaged 86% and 91% mortality following the ATSB microencapsulated garlic oil solution and the ATSB garlic + 1% boric acid solution, respectively. Choice assays indicated that the there were differences in preferences between the solutions and between species. Both Cx. quinquefasciatus and Cx. tarsalis were found to prefer the ASB and ATSB solutions to the 10% sucrose solution. However, when comparing the ASB to ATSB, Cx. quinquefasciatus significantly preferred the ASB solution (t = 3.6, df = 25, P = 0.0008). There were no significant differences in the preference of Cx. tarsalis to feed on the ASB or ATSB solutions as indicated in the choice assays (t = 1.9, df = 25, P = 0.07). Assays indicated that applications of ATSB to the 3 common plants in the Coachella Valley resulted in high mortality in both Cx. quinquefasciatus and Cx. tarsalis. There were significant differences in the treatments compared to the control (F = 40.15, df1,2 = 4,72, P < 0.001) but no significant differences among the different plants and ATSB treatments (F = 1.06, df1,2 = 4,72, P = 0.38). Laboratory findings suggest that ATSB is effective for use against WNV vectors in California. Further evaluations are needed in the field to determine how the environment may impact ATSB applications to influence mosquito mortality and nontarget organisms in arid environments in the United States.

Sugar feeding by male mosquitoes is critical for their success in mating competition. However, the facets of sugar source finding under natural conditions remain unknown. Here, evidence obtained in Western Burkina Faso indicated that the distribution of An. gambiae s.s. (M and S molecular forms) males across different peri-domestic habitats is dependent on the availability of potential sugar sources from which they obtain more favorable sites for feeding or resting. Among field-collected anophelines, a higher proportion of specimens containing fructose were found on flowering Mangifera indica (Anacardiaceae), Dolonix regia (Fabaceae), Thevetia neriifolia (Apocynaceae), Senna siamea, and Cassia sieberiana (both Fabaceae) compared to that recorded on other nearby plants, suggesting that some plants are favored for use as a sugar source over others. Y-tube olfactometer assays with newly-emerged An. gambiae s.s. exposed to odors from individual plants and some combinations thereof showed that males use odor cues to guide their preference. The number of sugar-positive males was variable in a no-choice cage assay, consistent with the olfactory response patterns towards corresponding odor stimuli. These experiments provide the first evidence both in field and laboratory conditions for previously unstudied interactions between males of An. gambiae and natural sugar sources.

Anopheles gambiae mates in flight. Males gather at stationary places at sunset and compete for incoming females. Factors that account for male mating success are not known but are critical for the future of any genetic control strategy. The current study explored variations in nutritional reserves (sugars, glycogen, lipids, and proteins) in wild-caught swarming and resting males and evaluated the effect of body size and wing symmetry on male mating success. Our results showed that glycogen and sugar reserves are mobilized for flight. Males consume proportionally 5.9-fold as much energy derived from sugars in swarming activities than when they are at rest. Mated males were on average bigger than unmated ones (P<0.0001). A strong correlation between the left and right wings in both mated and unmated males was found and additional analysis on fluctuating asymmetry did not show any indication of mated males being more symmetrical than unmated ones. The distribution of wing size of mated males was focused around a central value, suggesting that intermediate size of males is advantageous in the An. gambiae mating system. The results are discussed in the context of sexual selection.

Background The aim of this field trial was to evaluate the efficacy of attractive toxic sugar baits (ATSB) in Mali, where sustained malaria transmission occurs despite the use of long-lasting insecticidal nets (LLINs). ATSB bait stations were deployed in seven of 14 similar study villages, where LLINs were already in widespread use. The combined use of ATSB and LLINs was tested to see if it would substantially reduce parasite transmission by Anopheles gambiae sensu lato beyond use of LLINs alone. Methods A 2-day field experiment was conducted to determine the number of mosquitoes feeding on natural sugar versus those feeding on bait stations containing attractive sugar bait without toxin (ASB)—but with food dye. This was done each month in seven random villages from April to December 2016. In the following year, in seven treatment villages from May to December 2017, two ATSB bait stations containing the insecticide dinotefuran were placed on the outer walls of each building. Vector population density was evaluated monthly by CDC UV light traps, malaise traps, pyrethrum spray (PSCs) and human landing catches (HLCs). Female samples of the catch were tested for age by examination of the ovarioles in dissected ovaries and identification of Plasmodium falciparum sporozoite infection by ELISA. Entomological inoculation rates (EIR) were calculated, and reductions between treated and untreated villages were determined. Results In the 2-day experiment with ASB each month, there was a lower number of male and female mosquitoes feeding on the natural sugar sources than on the ASB. ATSB deployment reduced CDC-UV trap female catches in September, when catches were highest, were by 57.4% compared to catches in control sites. Similarly, malaise trap catches showed a 44.3% reduction of females in August and PSC catches of females were reduced by 48.7% in September. Reductions of females in HLCs were lower by 19.8% indoors and 26.3% outdoors in September. The high reduction seen in the rainy season was similar for males and reductions in population density for both males and females were > 70% during the dry season. Reductions of females with ≥ 3 gonotrophic cycles were recorded every month amounting to 97.1% in October and 100.0% in December. Reductions in monthly EIRs ranged from 77.76 to 100.00% indoors and 84.95% to 100.00% outdoors. The number of sporozoite infected females from traps was reduced by 97.83% at treated villages compared to controls. Conclusions Attractive toxic sugar baits used against Anopheles mosquitoes in Mali drastically reduced the density of mosquitoes, the number of older females, the number of sporozoite infected females and the EIR demonstrating how ATSB significantly reduces malaria parasite transmission.

Mosquito abatement programs contend with mosquito-borne diseases, insecticidal resistance, and environmental impacts to non-target organisms. However, chemical resources are limited to a few chemical classes with similar modes of action, which has led to insecticide resistance in mosquito populations. To develop a new tool for mosquito abatement programs that control mosquitoes while combating the issues of insecticidal resistance, and has low impacts of non-target organisms, novel methods of mosquito control, such as attractive toxic sugar baits (ATSBs), are being developed. Whereas insect baiting to dissuade a behavior, or induce mortality, is not a novel concept, as it was first introduced in writings from 77 AD, mosquito baiting through toxic sugar baits (TSBs) had been quickly developing over the last 60 years. This review addresses the current body of research of ATSB by providing an overview of active ingredients (toxins) include in TSBs, attractants combined in ATSB, lethal effects on mosquito adults and larvae, impact on non-target insects, and prospects for the use of ATSB.

Effective mosquito surveillance and management depend on a thorough understanding of the biology and feeding patterns unique to species and sex. Given that a propensity to sugar feed is necessary for some mosquito surveillance and newer control strategies, we sought to document the amount of total sugar in wild Aedes aegypti (L.) and Culex quinquefasciatus (Say) captured from five different locations in the Lower Rio Grande Valley (LRGV) of South Texas over 2 yr. We used Biogents Sentinel 2 (BGS2) traps in year 1 and aspirators, BGS2, and CDC resting traps in years 2 and 3 to collect adult mosquitoes.The hot anthrone test was used to quantify total sugar content in each mosquito. Additionally, the cold and hot anthrone tests were used to distinguish fructose content from total sugars for mosquitoes captured in 2019. Overall, Ae. aegypti females had significantly lower total sugar content than Ae. aegypti males as well as both sexes of Cx. quinquefasciatus. However, the percentage of Ae. aegypti positive for fructose consumption was four to eightfold higher than Ae. aegypti previously reported in other regions. The difference between locations was significant for males of both species, but not for females. Seasonality and trapping method also revealed significant differences in sugar content of captured mosquitoes. Our results reinforce that sugar feeding in female Ae. aegypti is less than Cx. quinquefasciatus, although not absent.This study provides necessary data to evaluate the potential effectiveness of sugar baits in surveillance and control of both Ae. aegypti and Cx. quinquefasciatus mosquitoes.