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Mosquito Sugar Feeding and Reproductive Energetics
... Sugar feeding increases lifespan and reproductive output, and, thus, has a potential impact on population dynamics [4]. The study of mosquito nectar foraging reveals intricate interactions between mosquitoes and flowering plants, shedding light on their ecological roles beyond disease transmission [5]. ...
... The sugars found in floral nectar, notably sucrose, which is a major component of many floral nectars, glucose, and fructose, offer the mosquito valuable resources capable of fueling energy-intensive tasks like flying and foraging [4]. Within floral nectaries rich in sucrose, mosquitoes are also exposed to various mono-and oligosaccharides, such as mannose, galactose, raffinose, maltose, and melibiose [18], several of which have been detected in mosquito midguts [4]. ...
... The sugars found in floral nectar, notably sucrose, which is a major component of many floral nectars, glucose, and fructose, offer the mosquito valuable resources capable of fueling energy-intensive tasks like flying and foraging [4]. Within floral nectaries rich in sucrose, mosquitoes are also exposed to various mono-and oligosaccharides, such as mannose, galactose, raffinose, maltose, and melibiose [18], several of which have been detected in mosquito midguts [4]. Furthermore, nectar includes amino acids, organic acids, vitamins, and minerals, all of which complement the mosquitoes' dietary needs and facilitate their physiological functions [19]. ...
Mosquitoes, males and females, rely on sugar-rich resources including floral nectar as a primary source of sugar to meet their energy and nutritional needs. Despite advancements in understanding mosquito host-seeking and blood-feeding preferences, significant gaps in our knowledge of the chemical ecology mediating mosquito-nectar associations remain. The influence of such association with nectar on mosquito behavior, and the resulting effects on their fitness are also not totally understood. It is significant that floral nectar frequently acts as a natural habitat for various microbes (e.g., bacteria and yeast), which substantially alter nectar characteristics, influencing the nutritional ecology of flower visiting insects such as mosquitoes. The role of nectar-inhabiting microbes in shaping the nectar mosquito interactions remains, however, under-researched. This review explores recent advances in understanding the role of such multitrophic interactions on the fitness and life history traits of mosquitoes and outlines future directions for research towards their control as disease vectors.
... Sugar-feeding is a fundamental behaviour of many species of mosquitoes [83]. Both male and female mosquitoes ingest sugar from a variety of sources, including floral and extrafloral nectar, fruit and seedpods, plant tissues, honeydew and ant regurgitate [77,[83][84][85]. ...
... Sugar-feeding is a fundamental behaviour of many species of mosquitoes [83]. Both male and female mosquitoes ingest sugar from a variety of sources, including floral and extrafloral nectar, fruit and seedpods, plant tissues, honeydew and ant regurgitate [77,[83][84][85]. These sugar meals provide sustenance for basic energetic demands, such as host and oviposition seeking flights [83,86]. ...
... Both male and female mosquitoes ingest sugar from a variety of sources, including floral and extrafloral nectar, fruit and seedpods, plant tissues, honeydew and ant regurgitate [77,[83][84][85]. These sugar meals provide sustenance for basic energetic demands, such as host and oviposition seeking flights [83,86]. The sugarfeeding behaviours of mosquitoes are being exploited to control them by using attractive targeted sugar baits (ATSBs) to lure mosquitoes to feed on baits laced with an oral toxin [87]. ...
The global distribution of the “Asian Tiger Mosquito”, Aedes albopictus, is rapidly expanding which has contributed to the emergence and re-emergence of dengue outbreaks. Dengue fever is an arboviral illness estimated to have increased 30-fold in the past 50 years, to a global burden of 390 million annual infections. Within the Indo-Pacific region, Ae. albopictus is now widespread. Within Australia, Ae.
albopictus populations were first found on numerous islands of the Torres Strait (Queensland, Australia) in 2005, subsequently vectoring multiple dengue outbreaks in recent years. To prevent the establishment of this species on the Australian mainland, Queensland Health implements ongoing mosquito suppression strategies on Thursday and Horn islands (these islands represent the main points of entry
from the Torres Strait onto the Australian mainland). These mosquito suppression strategies have thus far prevented the establishment of this species onto the Australian mainland. However, current manpower and funding limit extending the successful Ae. albopictus suppression strategies employed on Thursday and Horn islands to other islands in the Torres Strait.
To more effectively control Ae. albopictus, and ultimately prevent establishment on the Australian mainland, there is a need to understand how this species is being dispersed and also to strengthen mosquito surveillance and control activities. This thesis strategically addresses each of these interlinked factors: mosquito dispersal, surveillance and control. The first research chapter maps Ae. albopictus
dispersal and population genetic structure both within and between villages of the Torres Strait.
The second research chapter describes the potential of a low-powered mosquito sound trap to provide a simple and efficient surveillance tool that could be rolled out over longer periods of time and larger geographies, than the current more labour-intensive mosquito surveys. Data in the third research chapter provides a foundation for assessing the feasibility of attractive targeted sugar baits (ASTBs) for
controlling Ae. albopictus, by determining the prevalence of sugar in Ae. albopictus, a parameter critical to the success of ATSBs. Throughout the Torres Strait, Ae. albopictus exhibited weak population genetic structure, indicative of
high levels of gene flow and frequent dispersal within and between islands. Within islands, fine-scale active dispersal of Ae. albopictus occurred. Between islands, evidence of intragenerational dispersal of Ae. albopictus was observed, with dispersal of close kin within and between near and distant islands
(31–203 km apart). To improve Ae. albopictus surveillance, male Ae. albopictus can be effectively captured with the low-powered Male Aedes Sound Trap (MAST). MASTs with sound lure frequencies between 500 and 650 Hz were effective for capturing male Ae. albopictus with higher capture rates in woodland habitats than those near houses. The sugar feeding patterns of Ae. albopictus on Masig Island
showed that significantly more male than female Ae. albopictus were sugar-fed with both fructose prevalence and content higher in mosquitoes caught in the morning than the afternoon.
The outcomes of this thesis improve our understanding of Ae. albopictus dispersal in the Torres Strait and provide insights for improving surveillance and control of this mosquito. High levels of gene flow and close kin dispersal of Ae. albopictus between islands highlight the clear need for improved surveillance tools, that can be widely deployed not only in remote island settings but also on the Australian mainland. In such locations, MASTs have great potential to improve surveillance of Ae.
albopictus and to detect incursions in areas where this species is not established. There is potential to improve mosquito control throughout the Torres Strait by ATSBs. Suppression of mosquito populations could also reduce the likelihood of dispersal between islands and to the Australian mainland—both outcomes of potential benefit to the existing Ae. albopictus control program.
... An important component of mosquito ecology that has been largely overlooked to date concerns the plant feeding of mosquito females. A growing number of studies shows that Anopheles females frequently ingest plant fluids as a source of energy and nutrition [34][35][36] . Sugars, but also amino acids, minerals and vitamins from the fruit, floral and extra-floral nectar, phloem and honeydew can represent an important part of their diet. ...
... The high degree of plant selection and preference, previously demonstrated in malaria vectors 35,41,42 , has been largely attributed to chemical differences among plant species. In addition, different plants contribute different nutrients and metabolites that can have contrasting impact on mosquito live history traits 34 . A relatively understudied aspect of Anopheles ecology, which has implications for control, is how the built-in physiological plasticity to adapt to toxic compounds in their selected plant diet affect their response to insecticides. ...
... Third, plant diet can have an indirect effect on insecticide resistance through mosquito physiological condition and energetic status. Both field and laboratory based studies, have shown that plant diet can affect mosquito life history traits, such as survival 34,37 . The current study demonstrates that plant diet can also modulate the 24 h mortality in both control and deltamethrin-exposed adults. ...
Success in reducing malaria transmission through vector control is threatened by insecticide resistance in mosquitoes. Although the proximal molecular mechanisms and genetic determinants involved are well documented, little is known about the influence of the environment on mosquito resistance to insecticides. The aim of this study was to assess the effect of plant sugar feeding on the response of Anopheles gambiae sensu lato to insecticides. Adults were fed with one of four treatments, namely a 5% glucose control solution, nectariferous flowers of Barleria lupulina, of Cascabela thevetia and a combination of both B. lupulina + C. thevetia . WHO tube tests were performed with 0.05% and 0.5% deltamethrin, and knockdown rate (KD) and the 24 h mosquito mortality were measured. Plant diet significantly influenced mosquito KD rate at both concentrations of deltamethrin. Following exposure to 0.05% deltamethrin, the B. lupulina diet induced a 2.5 fold-increase in mosquito mortality compared to 5% glucose. Species molecular identification confirmed the predominance of An. gambiae (60% of the samples) over An. coluzzii and An. arabiensis in our study area. The kdr mutation L1014F displayed an allelic frequency of 0.75 and was positively associated with increased phenotypic resistance to deltamethrin. Plant diet, particularly B. lupulina, increased the susceptibility of mosquitoes to insecticides. The finding that B. lupulina -fed control individuals ( i.e. not exposed to deltamethrin) also displayed increased 24 h mortality suggests that plant-mediated effects may be driven by a direct effect of plant diet on mosquito survival rather than indirect effects through interference with insecticide-resistance mechanisms. Thus, some plant species may weaken mosquitoes, making them less vigorous and more vulnerable to the insecticide. There is a need for further investigation, using a wider range of plant species and insecticides, in combination with other relevant environmental factors, to better understand the expression and evolution of insecticide resistance.
... An important component of mosquito ecology that has been largely overlooked to date concerns the plant feeding of mosquito females. A growing number of studies shows that Anopheles females frequently ingest plant uids as a source of energy and nutrition 34,35,36 . Sugars, but also amino acids, minerals and vitamins from the fruit, oral and extra-oral nectar, phloem and honeydew can represent an important part of their diet. ...
... The high degree of plant selection and preference previously demonstrated in malaria vectors 42,43,35 has been largely attributed to chemical differences among plant species. In addition, different plants contribute different nutrients and metabolites that can have contrasting impact on mosquito live history traits 34 . A relatively understudied aspect of Anopheles ecology that has implications for control is how the built-in physiological plasticity to adapt to toxic compounds in their selected plant diet affect their response to insecticides. ...
... It has previously been demonstrated that dietary antioxidants, such as vitamin C can improve DDT phenotypic resistance in Drosophila melanogaster 56 , and it would be important to corroborate these ndings in mosquitoes. 34,38 . The current study demonstrates that plant diet can also modulate the 24 h mortality in both control and deltamethrin-exposed adults. ...
Success in reducing malaria transmission through vector control is threatened by insecticide resistance in mosquitoes. Although the proximal molecular mechanisms and genetic determinants involved are now relatively well documented, little is known about the influence of the environment on the phenotypic expression of mosquito resistance to insecticides. In particular, the extent to which mosquito plant feeding affects the phenotypic expression of insecticide resistance remains unknown. To assess the effect of plant diet on the response of mosquitoes to insecticides, larvae from the predominant vector, Anopheles gambiae sensu lato were collected in southwestern Burkina Faso and reared until adulthood. Following emergence, adults were fed with one of four treatment (5% glucose solution, nectariferous flowers of Barleria lupulina, nectariferous flowers of Cascabela thevetia and a combination of both plants Barleria lupulina + Cascabela thevetia ). WHO standard tube tests were performed with 0.05% and 0.5% deltamethrin. The measured end-point parameters were knockdown rate (KD) and the 24 h mosquito mortality. Following the bioassays, DNA was extracted from each mosquito individual for PCR identification of the siblings of the An. gambiae complex and determination of the kdr genotypic and allelic frequencies. Plant diet significantly influenced mosquito KD rate at both concentrations of deltamethrin. Following exposure to 0.05% deltamethrin, the Barleria lupulina diet induced a 2.5 fold-decrease in mosquito mortality compared to the 5% glucose treatment. The molecular data confirmed the predominance of An. gambiae (60% of the samples) over An. coluzzii and An. arabiensis . The kdr mutation L1014F displayed a high allelic frequency of 0.75 and, as expected, it was positively associated with increased resistance to deltamethrin. Plant diet, particularly B. lupulina, appears to increase the susceptibility of mosquitoes to insecticides. The finding that B. lupulina -fed control individuals ( i.e., not exposed to deltamethrin)also displayed increased 24 h mortality suggests that plant-mediated effects may be driven by direct effect of plant diet on mosquito survival rather than indirect effects through interference with insecticide-resistance mechanisms. Thus, some plant species may weaken mosquitoes, making them less vigorous and more vulnerable to the insecticide. There is a need for further investigation, using a wider range of plant species and insecticides, in combination with other relevant environmental factors, to better understand the expression and evolution of insecticide resistance
... To achieve the same deleterious phenotypes in wild populations of An. arabiensis as those observed in the lab, dsRNA must be delivered to An. arabiensis free of degradation, using field feasible applications. Sugar-feeding constitutes a vital source of sustenance for adult mosquitoes of both sexes (Foster, 1995). Within hours of emergence, both male and female mosquitoes take a sugar-meal (Foster, 1995). ...
... Sugar-feeding constitutes a vital source of sustenance for adult mosquitoes of both sexes (Foster, 1995). Within hours of emergence, both male and female mosquitoes take a sugar-meal (Foster, 1995). This behaviour could be used to administer Akirin-specific dsRNA to An. arabiensis via the oral exposure route. ...
... In nature, the most common sources of sugar for mosquitoes are floral-nectar, extrafloralnectar, honeydew, tree sap, damaged fruit, and portions of damaged leaves (McCrae et al., 1969;Foster, 1995). These plants could potentially be engineered to express hairpin RNAs that are functionally equivalent to that of the linear Akirin-specific dsRNA. ...
Anopheles arabiensis is an opportunistic malaria vector that rests and feeds outdoors, circumventing current vector control methods. Furthermore, this vector will readily feed on animal as well as human hosts. Agricultural animals are regularly vaccinated with recombinant proteins, for the control of multiple endo- and ectoparasitic infestations. Targeting An. arabiensis, while feeding on animals, can provide an additional intervention to the current vector control activities. Previously, the use of a subolesin-vaccine showed a mark reduction in tick survival and reproductive fitness. Targeting Akirin (Subolesin ortholog) in An. arabiensis, when performing CRISPR mediated interference or RNA mediated interference, reduced both vector survival and reproductive capacities. This gene regulation function made Akirin a potential antigen for vaccine development against An. arabiensis, which was further investigated. The efficacy of three recombinant Akirin vaccines was evaluated, to determine if Akirin could represent a novel target for the control of An. arabiensis. Immunisation trials were conducted based on the concept that female An. arabiensis, feeding on vaccinated hosts (balb/c mice), would ingest antibodies specific to the target antigen, affecting its function within the vector. All three antigens evaluated, namely recombinant Akirin from An. arabiensis, recombinant Akirin from Aedes albopictus and recombinant Q38 (Akirin/Subolesin chimera), successfully reduced An. arabiensis survivorship and reproductive capacities, with a vaccine efficacy of 68 to 73%. In conclusion, these results were the first to characterise the biological role of Akirin in An. arabiensis survival and reproduction, by performing CRISPRi and RNAi, using an optimised nano-injection protocol. Furthermore, these results were the first to show that blood hosts vaccinated with recombinant Akirin vaccines could aid in the suppression of An. arabiensis vector populations, through the reduction of vector survivorship and reproductive capacities. Therefore, these results provide a step towards the development of a novel target for An. arabiensis vector control
... Use of attractive toxic sugar baits (ATSB) is a relatively new and efective strategy that consists of three components: sugar as a phago-stimulant, a toxin, and an odorant for alluring feeding [3,6,7]. Te mosquitoes are attracted towards the bait because of the odour of fruit/fower juice and are killed on ingesting the toxin [8]. ATSBs, initially formulated as toxic sugar baits (TSBs) without odorant, were unable to attract mosquitoes due to the absence of an attractant [6]. ...
... Te ATSB is a mixture of three components; fruit juice, a toxin, and sugar solution; to attract for feeding and kill the adults by toxin feed. It is based on the fact that mosquitoes require a sugar diet throughout their life for energy, growth, development, mating, and egg production [8,26]. Since mosquitoes search for sugar sources in the environment, the ATSB with table sugar competes with the available sources of plant sugar and provides nourishment for survival [6]. ...
Background
The attractive toxic sugar bait (ATSB) is a promising strategy for controlling mosquitoes at the adult stage. The strategy is based on the use of a combination of fruit juice, sugar, and a toxin in order to attract and kill the adult mosquitoes. The selection of the components and optimization of their concentrations is significant for the formulation of an effective ATSB.
Methods
The present study formulated nine ATSBs and evaluated their efficacy against two laboratory strains (AND-Aedes aegypti and AND-Aedes aegypti-DL10) and two wildcaught colonized strains of Aedes aegypti (GVD-Delhi and SHD-Delhi). Initially, nine attractive sugar baits (ASBs) were prepared using a mixture of 100% fermented guava juice (attractant) with 10% sucrose solution (w/v) in 1 : 1 ratio. ATSBs were formulated by mixing each ASB with different concentrations of deltamethrin in the ratio of 9 : 1 to obtain final deltamethrin concentration of 0.003125–0.8 mg/10 mL ATSB. Cage bioassays were conducted with 50 mosquitoes for 24 h in order to evaluate the efficacy of each ATSB against the four strains of Ae. aegypti. The data were statistically analyzed using PASW software 19.0 program and 2-way ANOVA.
Results
The ATSB formulations registered 8.33–97.44% mortality against AND-Aedes aegypti and 5.15–96.91% mortality against AND-Aedes aegypti-DL10 strains of Ae. aegypti, while GVD-Delhi strain registered 2.04–95.83% mortality and SHD-Delhi strain showed 5.10–97.96% mortality. The administration of 0.8 mg of deltamethrin within 10 mL of attractive toxic sugar bait (ATSB) has led to the maximum mortality rate in adult mosquitoes.
Conclusions
The ATSBs formulated with guava juice-ASB and deltamethrin (9 : 1) showed toxin dose-dependent toxicity by all the four strains of Ae. aegypti. Most effective dosage was found as 0.8 mg deltamethrin/10 mL ATSB which imparted 96% to 98% mortality in adult mosquitoes. The investigations demonstrated the efficacy of deltamethrin-laced ATSB formulations against Ae. aegypti and highlighted the need for conduct of structured field trials and investigating the impact on disease vectors and nontarget organisms.
... In addition, only Ae. albopictus tested positive for fructose when exposed to Scaevola, goldenrod, and yarrow, and only Ae. aegypti tested positive when exposed to butterfly bush and Lantana. No positive tests from [1], a GoPro aimed at the flower [2], a water cup topped with a soaked paper towel [3], and an iButton temperature/humidity recording device [4]. ...
... We did not observe feeding activity on wave petunia, yet individuals of both species tested positive for nectar consumption and exhibited the highest carbohydrate concentrations in this study. It is, however, possible that mosquitoes fed on stems/leaves containing sugars either outside of the camera's frame, or outside of the camera's recording time at night when petunias emit a stronger scent 1,35,36 . In the headspace of Lantana, we identified β-ocimene as the most abundant volatile, which has been shown to elicit dose-dependent repellent responses in multiple aedine species, including Ae. aegypti 37,38 . ...
Feeding on plant-derived sugars is an essential component of mosquito biology, affecting key aspects of their lives such as survival, metabolism, and reproduction. Among mosquitoes, Aedes aegypti and Aedes albopictus are two invasive mosquito species in the US, and are vectors of diseases such as dengue fever, chikungunya, and Zika. These species live in heavily populated, urban areas, where they have high accessibility to human hosts as well as to plants in backyards and public landscapes. However, the range of plants that are suitable sugar hosts for these species remains to be described, despite the importance of understanding what plants may attract or repel mosquitoes to inform citizens and municipal authorities accordingly. Here, we tested whether Ae. aegypti and Ae. albopictus would sugar-feed on eleven commonly planted ornamental plant species. We confirmed feeding activity using the anthrone method and identified the volatile composition of plant headspace using gas-chromatography mass-spectroscopy. These chemical analyses revealed that a broad range of olfactory cues are associated with plants that mosquitoes feed on. This prompted us to use plant DNA barcoding to identify plants that field-caught mosquitoes feed on. Altogether, results show that native and invasive mosquito species can exploit a broader range of plants than originally suspected, including wild and ornamental plants from different phyla throughout the Spring, Summer and Fall seasons.
... For example, sugar meals are stored in the ventral diverticulum (crop) while blood meals bypass the crop and are directly sent to the midgut. Sugar meals can be stored in the crop until needed for energy-intensive activities such as flight while blood digestion typically begins within a few hours of feeding 14 . Blood digestion, unlike sucrose digestion, is also associated with significant physiological stress due to rapid shifts in temperature and pH, gut distension, heme toxicity resulting from hemoglobin digestion, and midgut redox stress [15][16][17][18][19][20][21] . ...
... The sucrose diets provided to mosquitoes in this laboratory setting are not representative of sugar meals obtained in the field. Mosquito sugar feeding behavior in natural settings is not fully understood; however, evidence suggests that mosquitoes can obtain sugar in natural settings by feeding on floral nectar, extrafloral nectar, honeydew, tree sap, rotting fruit, sugar cane trash, and even sugar-rich household waste 12,14 . The compositions of the sugar meals consumed by mosquitoes in natural settings are quite variable. ...
Immune defense is comprised of (1) resistance: the ability to reduce pathogen load, and (2) tolerance: the ability to limit the disease severity induced by a given pathogen load. The study of tolerance in the field of animal immunity is fairly nascent in comparison to resistance. Consequently, studies which examine immune defense comprehensively (i.e. considering both resistance and tolerance in conjunction) are uncommon, despite their exigency in achieving a thorough understanding of immune defense. Furthermore, understanding tolerance in arthropod disease vectors is uniquely relevant, as tolerance is essential to the cyclical transmission of pathogens by arthropods. Here, we tested the effect(s) of dietary sucrose concentration and blood ingestion on resistance and tolerance to Escherichia coli infection in the yellow fever mosquito Aedes aegypti. Resistance and tolerance were measured concurrently and at multiple timepoints. We found that mosquitoes from the restricted sugar treatment displayed enhanced resistance at all timepoints post-infection compared to those from the laboratory standard sugar treatment. Blood also improved resistance, but only early post-infection. While sucrose restriction had no effect on tolerance, we show that consuming blood prior to bacterial infection ameliorates a temporal decline in tolerance that mosquitoes experience when provided with only sugar meals. Taken together, our findings indicate that different dietary components can have unique and sometimes temporally dynamic impacts on resistance and tolerance.
... Although most mosquitoes feed on vertebrate blood, specialisation on invertebrates has also been described [7]. Next to hematophagy, males and females also feed from plants (flowers, extrafloral nectaries) to acquire carbohydrates for energy purposes [8]. The frequency of this plant-feeding depends on mosquito species, plant availability, and season [8,9] and if plant-feeding options are scarce, mosquitoes can take more and/or larger blood meals for energy repletion [4,9,10]. ...
... Next to hematophagy, males and females also feed from plants (flowers, extrafloral nectaries) to acquire carbohydrates for energy purposes [8]. The frequency of this plant-feeding depends on mosquito species, plant availability, and season [8,9] and if plant-feeding options are scarce, mosquitoes can take more and/or larger blood meals for energy repletion [4,9,10]. ...
Female mosquitoes require blood from their host for egg development. However, the relationship between the composition of host blood and mosquito reproduction, and whether and how this is linked to host selection, remain unclear. A better understanding of these issues is beneficial for mass-rearing of mosquitoes for vector control. This review provides an overview of the currently known effects of blood constituents on mosquito reproduction. Furthermore, it highlights knowledge gaps and proposes new avenues for investigation. We recommend that research efforts be focused on physiological differences between generalist and specialist mosquito species as models to investigate if and how host preference correlates with reproductive output.
... Acquiring carbohydrates is essential for both males and females and 55 can, in some species, constitute the sole source of food for adults (e.g., Toxorhynchites spp.). Males 56 feed exclusively on plant-derived sugars and recently emerged females tend to seek for sugar 57 before taking their first blood-meal, which enhances egg production [1]. In addition to 58 carbohydrates, it has been determined that mosquitoes also acquire vitamins, amino acids, and salts 59 from plant nectar [2][3][4]. ...
... 516 Interestingly, mosquitoes containing maple tree DNA were captured in July and August. 517 Therefore, it is possible that the captured Ae. albopictus mosquitoes obtained carbohydrates by 518 feeding on extra floral nectaries or from the leaves of the maple [1,44]. Alternatively, mosquitoes 519 have been observed to feed on phloem sap, and may be doing so in this case due to the maple tree's 520 high sap production [60,61]. ...
Feeding on plant-derived sugars is an essential component of mosquito biology that affects key aspects of their lives such as survival, metabolism, and reproduction. Mosquitoes locate plants to feed on using olfactory and visual cues. Aedes aegypti and Aedes albopictus are two invasive mosquito species to the US, and are vectors of diseases such as dengue fever, chikungunya, and Zika. These species live in heavily populated, urban areas, where they have a high accessibility to human hosts as well as to plants in backyards and town landscapes. Therefore, it is important to understand what plants may attract or repel mosquitoes to inform citizens and municipal authorities accordingly. Here, we analyzed Ae. aegypti and Ae. albopictus sugar-feeding behavior with eleven different commonly planted ornamental plant species. We then assessed feeding activity using the anthrone method and identified volatile composition of plant headspace using gas-chromatography mass-spectroscopy. Finally, we determined the sugar-feeding activity of field caught mosquitoes using the plant DNA barcoding technique and compared these results with the eleven ornamental species tested in the laboratory. The potential for application to disease vector control is also discussed.
... Adults of many mosquito species feed on plant uids to obtain metabolic energy and to enhance reproduction, and plants provide the only source of energy for male mosquitoes (Foster, 1995;Barredo and DeGennaro, 2020;Peach and Gries, 2020). Floral nectar is the most widely used source of plant carbohydrates, but mosquitoes may also feed on extra oral nectar or on tree sap. ...
... Mosquito feeding on plant uids is ancient, and blood-feeding may have evolved from phytophagy (Lehane, 2005;Peach and Gries, 2020). Nectar is an important source of nutrition for extant blood-feeding mosquito taxa, particularly for males and for young females before they take their rst bloodmeal (Foster, 1995;Foster and Takken, 2004;Barredo and DeGennaro, 2020). We expected young sugar-deprived females to be attracted to plant odor regardless of the presence of additional CiJA, while older females that had already sugar-fed would be more selective. ...
Adults of many mosquito species feed on plants to obtain metabolic energy and to enhance reproduction. Mosquitoes primarily rely on olfaction to locate plants and are known to respond to a range of plant volatiles. We studied the olfactory response of the yellow fever mosquito Aedes aegypti to methyl jasmonate (MeJA) and cis -jasmone (CiJA), volatile compounds originating from the octadecanoid signaling pathway that plays a key role in plant defense against herbivores. Specifically, we investigated how Ae. aegypti of different ages responded to elevated levels of CiJA in two attractive odor contexts, either derived from Lima bean plants or from human skin. Aedes aegypti females landed significantly less often on a surface with CiJA and MeJA compared to the solvent control, CiJA exerting a stronger reduction in landing than MeJA. Odor context (plant or human) had no significant main effect on the olfactory responses of Ae. aegypti females to CiJA. Mosquito age significantly affected the olfactory response, older females (7–9 d) responding more strongly to elevated levels of CiJA than young females (1–3 d) in either odor context. Our results show that avoidance of CiJA by Ae. aegypti is independent of odor background, suggesting that jasmonates are inherently aversive cues to these mosquitoes. We propose that avoidance of plants with elevated levels of jasmonates is adaptive to mosquitoes to reduce the risk of encountering predators that is higher on these plants, i.e. by avoiding ‘enemy-dense-space’.
... The nutritional reserves consist of sugar, glycogen, lipid and proteins are more important in larval and adult development are required for survival and energy purpose (Foster, 1995). This quantification of nutritional reserves was done to check that whether the R. tetraphylla extracts affects the nutritional reserves of larval or not. ...
... Van Handel (1988) and Van Handel and Day (1988) shows the nutritional requirement for larval development in mosquito and our result of control larvae comparatively match with them. When adult mosquito encloses nutritional reserves consist of lipid and glycogen accumulated during larval development (Foster, 1995). About 60 % of glycogen and sugar reserves and 35 % lipid reserves are metabolized during the females first gonotrophic cycle, acting as sources of energy and as provision for developing eggs (Zhou et al. 2004). ...
The Rauvolfia tetraphylla leaf extract with different solvents n-hexane, chloroform, acetone and methanol were tested for larvicidal, ovicidal, oviposition attractant/deterrent activities. Their effect on larval nutritional reserve against Culex quinquefasciatus was also studied. Larval mortality was observed after 24 hours exposure. The LC 50 values for n-hexane, chloroform, acetone, methanol extracts are 16.80, 91.56, 214.85, 44.68 ppm, respectively. The mean percentage hatchability of the ovicidal activity was observed 48 hours post treatment. For R. tetraphylla, methanolic extract exhibited 56 % egg hatchability at 125 ppm. The effective oviposition repellency was 100 % at 320 ppm and the oviposition activity index value-1 was shown by n-hexane extract of R. tetraphylla. The fourth instar of C. quinquefasciatus where exposed to LC 50 concentration of extracts and its on larval nutritional reserves was checked. All extracts showed moderate effect on larval nutritional reserves, i.e. changes in total concentration of sugar, glycogen, lipid and protein. The average values of total sugar, glycogen, lipid and protein are 9.47, 32.32, 54.50, 183.35 µg/larvae was found in fourth instar larvae of C. quinquefasciatus. From the all-leaf extracts, the methanol extract affects the total sugar, lipid; n-hexane extract to glycogen and acetone extract to protein of fourth instar larvae of the mosquito and decreases up to 3.39, 20.71, 11.18, 91.05 µg/larvae, respectively. These results reveal that the R. tetraphylla leaf extracts have the control potential against C. quinquefasciatus.
... Insecticide-laced attractive toxic sugar bait (ATSB) is considered a new mosquito control method based on the feeding behaviour of mosquitoes [4]. e mosquitoes feed on plant sugars (sucrose and fructose), nectar, honeydew, etc., as a source of energy for their nutrition and survival [5] and use visual and olfaction cues to locate owers and fruits [6]. Sugar-seeking mosquitoes are attracted by the volatile components of fruits and owers [7], damaged and rotted fruits [8], and various fruits, edible seeds, owers, and insect honeydew [9]. ...
... e tests showed 10-39% landings of Aedes aegypti (SHD-Delhi) strain mosquitoes on the 9 juice-ASBs, while control bait attracted 14-24% mosquitoes. e average mean value of number of mosquitoes that landed on different ASBs was recorded the highest for plum juice-ASB (19.5), followed Journal of Tropical Medicine 3 by guava (15.5) and mango juice-ASBs (12), while it was the lowest for pineapple juice-ASB (5). e values of the 3 juice-ASBs with maximum attraction potential showed significant differences with other juices (p < 0.05). ...
Background. Attractive toxic sugar bait (ATSB), based on “attract and kill” approach, is a novel and promising strategy for mosquito control. Formulation of an attractive sugar bait (ASB) solution by selecting an efficient olfaction stimulant and preparation of an optimized sugar-attractant dosage is a significant component for the success of the approach. Methods. Current study evaluated relative potential of nine ASBs, formulated by combination of sugar and fresh fruit juices (guava, mango, muskmelon, orange, papaya, pineapple, plum, sweet lemon, and watermelon) in attracting Aedes aegypti adults. Freshly extracted and 48-hour-fermented juices were combined with 10% sucrose solution (w/v) in 1 : 1 ratio. Cage bioassays were conducted against two laboratory strains (susceptible: AND-Aedes aegypti; deltamethrin-selected: AND-Aedes aegypti-DL10) and two field-collected strains (Shahdara strain of Aedes aegypti: SHD-Delhi; Govindpuri strain of Aedes aegypti: GVD-Delhi). Each of the nine ASBs was assayed, individually or in groups of three, for its attraction potential based on the relative number of mosquito landings. The data were analysed for statistical significance using PASW (SPSS) software 19.0 program. Results. The prescreening bioassay with individual ASB revealed significantly higher efficacy of ASB containing guava/plum/mango juice than that containing six other juices (p
... Plant sugar is an important part of the adult diet of both sexes of nearly all species of mosquitoes. To locate the plants producing accessible sugar, mosquitoes appear to rely heavily on their odor (Foster 1995, Peach et al. 2019, Wooding et al. 2020). These odors have been proposed as a possible means of luring them into traps or toxic bait stations without the need for electric lights, fans, human and animal kairomones, or CO 2 (Foster and Hancock 1993). ...
... Ebrahimi B. N. Njiru, and W.A. Foster, unpublished data) indicating that its effects may be broadly applicable. The lack of a sex difference in the numbers caught in the baited traps accords with other behavioral studies on attraction of mosquitoes to sugar sources and sugarrelated odors (Foster 1995). In a similar physiological state, i.e., with energy reserves either depleted or not yet accumulated and with the females neither digesting a blood meal nor holding a batch of eggs, both males and females will respond equally strongly to cues from plant-sugar sources. ...
Aedes aegypti (L.) and Aedes albopictus (Skuse) mosquitoes of both sexes were attracted to a 3-part volatile synthetic phytochemical blend but differed according to their component ratios, 7:3:2 or 1:1:1, and their initial concentrations. These arbovirus vectors were presented with the blends as baits in paired baited and blank CFG traps in a large greenhouse mesocosm. Ae. aegypti attraction was highest at a 7:3:2 blend ratio, but at a concentration half that found most effective for an anopheline mosquito species in outdoor screenhouses. Both lower and higher concentrations yielded substantially lower attraction scores for Ae. aegypti. By contrast, the few tests conducted on Ae. albopictus showed that it was not as sensitive to concentration, but again it was more responsive to the 7:3:2 ratio of components than to the 1:1:1 ratio. The two sexes of both species were represented equally in the trap catches, indicating the potential value of this and similar attractive blends for population surveillance and control of Aedes mosquitoes.
... The life cycle begins with the egg, where gravid females of Culex pipiens lay their eggs in rafts of 150-300 eggs on the surface of standing water (Wood et al. 1979, Vinogradova 2000. Culex pipiens larvae can tolerate water with high levels of organic content and are found in a wide range of larval habitats, including ponds, water-filled containers (e.g., buckets, rain barrels, cans), roadside ditches, and sewage seepage (Foster andWalker 2002, Wood et al. 1979). Eggs hatch within 2-3 days into small larvae that emerge from the lower end of the eggs. ...
... After 2 to 3 days of development in the pupal stage, adults (i.e., imago) emerge from the pupal case and gain the ability to fly shortly thereafter. Both adult males and females need sugar as a source of carbohydrate for energy, which is obtained from flower nectar, extrafloral nectar, damaged fruit, or homopteran honeydew (Foster 1995). However, only females require a blood meal as a source of protein for developing eggs (Foster and Walker 2002). ...
... ATSBs exploit the mosquito sugar feeding behaviours, by luring individuals onto a sugar-laden target that is also treated with a killing agent, such as insecticide [4]. Both male and female mosquitoes depend on plant sugars such as nectar from owers and sap from leaves and plant stems, to obtain energy [5,6]. A growing body of evidence has shown that Afrotropical malaria and dengue mosquitoes regularly feed on plant sugars in their natural environment [7]. ...
Background
Attractive targeted sugar baits (ATSBs) are one of the new promising interventions that can complement existing vector control tools. However, there is need to provide reproducible and quantitative information on the level of attractiveness of ATSBs under field conditions. To do so, we customized camera traps for close-up imaging and integrated them into a rugged ATSB monitoring station for day and night-time recording of mosquitoes landing on the baits.
Methods
The camera traps were evaluated, in a semi-field system and then in the field in rural Tanzania. In semi-field 2m x 5m x 2m net chambers, the camera trap was set up to record mosquitoes landing on either an attractive sugar bait (ASB), a blank ASB or 20% sucrose (w/v). Next, 198 mosquitoes (33 males and 33 females of Anopheles arabiensis, Anopheles funestus and Aedes aegypti) were released into each chamber and allowed to seek a sugar-meal for 72h, with the camera recording images of mosquitoes present on the ASB at 1min intervals. In the field 16 camera traps were set in 16 households, 7 with ASB attractant, 7 with ASB blank and 2 with 20% sucrose (w/v). Human landing catch (HLC) was performed on the same nights as the camera trap recordings.
Results
Under the semi-field conditions, there were significantly more mosquitoes that visited the ASBs than the blank baits, with An. funestus visiting more frequently than An. arabiensis. There were no significant differences between females and male An. arabiensis visits, but female An. funestus visited more than their conspecific males. The duration of visits did not vary between the ASB and the blanks, nor between the mosquito species. Moreover, mosquitoes visited the ASB or sucrose equally, with An. arabiensis visiting the baits more than An. funestus. Female mosquitoes visited the baits more than the males. There was no significant difference in visit duration between all species. In the field study, a mean of 70 An. arabiensis were caught per person per night by HLC compared to 1 individual recorded per night on ASBs. There were significantly more visits by mosquitoes to the ASB than the ASB blanksand sucrose solution, with more An. arabiensisvisiting the baits than An. funestus or C. quinquefasciatus. Females of all species visited baits significantly more than males. Again, the duration of visits was similar between An. arabiensis, An. funestusand C. quinquefasciatus. Ae. aegypti very rarely visited ASBs in the semi-field experiments and none were observed on baits in the field.
Conclusions
The use of camera traps to record still images of mosquitoes present on ASBs provides robust, reproducible and quantitative information on their attractiveness under different environmental conditions. Therefore, camera traps are powerful tools for evaluating and improving the ATSB technology.
... Sugars are obtained from drawing on droplets of nectar located on extrafloral tissues (extrafloral nectaries) [48] in flowers (floral nectaries), or from direct piercing of mouthparts into tissues such as stems, leaves and fruits, confirmed by content of plant cellulose residues in mosquito gut [49] and plant derived fructose in wild caught female mosquito [50]. Nectar is located by the mosquito through visual and olfactory stimuli, biased towards nectar rich plants [51]. ...
... Attractive targeted sugar bait (ATSB) is a novel vector control tool that exploits the need for both male and female mosquitoes to take sugar meal while drawing on insecticide more typically used in agriculture [8]. There have been several successful attempts to control mosquito populations using ATSB outdoors [9][10][11][12]. ...
Background
Attractive targeted sugar bait (ATSB) is a novel approach to vector control, offering an alternative mode of insecticide delivery via the insect alimentary canal, with potential to deliver a variety of compounds new to medical entomology and malaria control. Its potential to control mosquitoes was recently demonstrated in major field trials in Africa. The pyrrole chlorfenapyr is an insecticide new to malaria vector control, and through its unique mode of action—disruption of ATP mediated energy transfer in mitochondria—it may have direct action on energy transfer in the flight muscle cells of mosquitoes. It may also have potential to disrupt mitochondrial function in malarial parasites co-existing within the infected mosquito. However, little is known about the impact of such compounds on vector competence in mosquitoes responsible for malaria transmission.
Methods
In this study, ATSBs containing chlorfenapyr insecticide and, as a positive control, the anti-malarial drugs artemether/lumefantrine (A/L) were compared for their effect on Plasmodium falciparum development in wild pyrethroid-resistant Anopheles gambiae sensu stricto (s.s.) and for their capacity to reduce vector competence. Female mosquitoes were exposed to ATSB containing either sublethal dose of chlorfenapyr (CFP: 0.025%) or concentrations of A/L ranging from 0.4/2.4 mg/ml to 2.4/14.4 mg/ml, either shortly before or after taking infective blood meals. The impact of their component compounds on the prevalence and intensity of P. falciparum infection were compared between treatments.
Results
Both the prevalence and intensity of infection were significantly reduced in mosquitoes exposed to either A/L or chlorfenapyr, compared to unexposed negative control mosquitoes. The A/L dose (2.4/14.4 mg/ml) totally erased P. falciparum parasites: 0% prevalence of infection in female mosquitoes exposed compared to 62% of infection in negative controls (df = 1, χ² = 31.23 p < 0.001). The dose of chlorfenapyr (0.025%) that killed < 20% females in ATSB showed a reduction in oocyte density of 95% per midgut (0.18/3.43 per midgut).
Conclusion
These results are evidence that chlorfenapyr, in addition to its direct killing effect on the vector, has the capacity to block Plasmodium transmission by interfering with oocyte development inside pyrethroid-resistant mosquitoes, and through this dual action may potentiate its impact under field conditions.
... gambiae is attracted by CO 2 , lactic acid, acetone and 1-octen-3-ol (Dekker et al. 2002, Healy and Copland 1995, Smallegange et al. 2005, Takken et al. 1997. In nature, mosquitoes rely principally on olfaction to locate and choose oviposition (Takken and Knols 1999), nectar-feeding sites (Foster 1995) and mates (Cabrera andJaffe 2007, Nijhout andCraig 1971) to name but a few critical life-cycle behaviours. ...
... These taxa predominantly feed on the blood of terrestrial mammals, birds, reptiles or amphibians to reproduce. In mosquitoes, sugar, usually acquired from floral or extrafloral nectar, also represents an important component of their diet (Foster 1995). Some mosquitoes feed on other semi-aquatic or invertebrate species (Reeves et al. 2020), and a few are even autogenous (Gulia-Nuss et al. 2015). ...
Invasive hematophagous arthropods threaten planetary health by vectoring a growing diversity of pathogens and parasites which cause diseases. Efforts to limit human and animal morbidity and mortality caused by these disease vectors are dependent on understandings of their biology and ecology-from cellular to ecosystem levels. Here, we review research into the biology and ecology of inva-sive hematophagous arthropods globally, with a particular emphasis on mosquitoes, culminating towards management recommendations. Evolutionary history , genetics, and environmental filtering contribute to invasion success of these taxa, with life history trait and ecological niche shifts between native and invaded regions regularly documented. Pertinent vector species spread readily through active and passive means, via anthropogenic and natural mechanisms as climate changes. The rate and means of spread differ among taxa according to their capacity for entrain-ment in human vectors and physiology. It is critical to understand the role of these invaders in novel ecosystems , as biotic interactions, principally with their resources, competitors, and natural enemies, mediate patterns of invasion success. We further highlight recent advances in understanding interactions among arthropod-associated microbiota, and identify future research directions integrating arthropod microbiota to explain invasion success under changing environments. These biological and ecological facets provide an integrative perspective on the invasion history and dynamics of invasive hematophagous arthropods, helping inform on their management strategies.
... Attractive targeted sugar baits (ATSBs) are a promising new technology that is increasingly being investigated for expanding the malaria prevention toolbox [13][14][15][16][17]. The technology exploits the natural sugar-feeding behaviours essential for mosquito survival [18][19][20][21][22]. This means sugar-based solutions can be used to target mosquitoes by adding orally-ingested toxicants, which may include common pesticides, boric acid, and nucleic acids [23][24][25][26][27][28]. ...
Background
Attractive targeted sugar baits (ATSBs) control sugar-feeding mosquitoes with oral toxicants, and may effectively complement core malaria interventions, such as insecticide-treated nets even where pyrethroid-resistance is widespread. The technology is particularly efficacious in arid and semi-arid areas. However, their performance remains poorly-understood in tropical areas with year-round malaria transmission, and where the abundant vegetation constitutes competitive sugar sources for mosquitoes. This study compared the efficacies of ATSBs (active ingredient: 2% boric acid) in controlled settings with different vegetation densities.
Methods
Potted mosquito-friendly plants were introduced inside semi-field chambers (9.6 m by 9.6 m) to simulate densely-vegetated, sparsely-vegetated, and bare sites without any vegetation (two chambers/category). All chambers had volunteer-occupied huts. Laboratory-reared Anopheles arabiensis were released nightly (200/chamber) and host-seeking females recaptured using human landing catches outdoors (8.00 p.m.–9.00 p.m.) and CDC-light traps indoors (9.00 p.m.–6.00 a.m.). Additionally, resting mosquitoes were collected indoors and outdoors each morning using Prokopack aspirators. The experiments included a “before-and-after” set-up (with pre-ATSBs, ATSBs and post-ATSBs phases per chamber), and a “treatment vs. control” set-up (where similar chambers had ATSBs or no ATSBs). The experiments lasted 84 trap-nights.
Results
In the initial tests when all chambers had no vegetation, the ATSBs reduced outdoor-biting by 69.7%, indoor-biting by 79.8% and resting mosquitoes by 92.8%. In tests evaluating impact of vegetation, the efficacy of ATSBs against host-seeking mosquitoes was high in bare chambers (outdoors: 64.1% reduction; indoors: 46.8%) but modest or low in sparsely-vegetated (outdoors: 34.5%; indoors: 26.2%) and densely-vegetated chambers (outdoors: 25.4%; indoors: 16.1%). Against resting mosquitoes, the ATSBs performed modestly across settings (non-vegetated chambers: 37.5% outdoors and 38.7% indoors; sparsely-vegetated: 42.9% outdoors and 37.5% indoors; densely-vegetated: 45.5% outdoors and 37.5% indoors). Vegetation significantly reduced the ATSBs efficacies against outdoor-biting and indoor-biting mosquitoes but not resting mosquitoes.
Conclusion
While vegetation can influence the performance of ATSBs, the devices remain modestly efficacious in both sparsely-vegetated and densely-vegetated settings. Higher efficacies may occur in places with minimal or completely no vegetation, but such environments are naturally unlikely to sustain Anopheles populations or malaria transmission in the first place. Field studies therefore remain necessary to validate the efficacies of ATSBs in the tropics.
... In particular, stage specific survivorship, fecundity and abundance are critical to disease transmission. Foster (1995) studied the mosquito sugar feeding and reproductive energetic. Straif and Beier (1996) studied the effects of sugar availability on the bloodfeeding behavior of Anopheles gambiae (Diptera:Culicidae). ...
... Le cycle de vie des anophèles dure entre 7 et 14 jours depuis l'oeuf jusqu'à l'adulte. Le cycle complet est illustré en figure 4 (Carnevale et Robert, 2009 Au stade imaginal, la nutrition du mâle s'appuie uniquement sur des sources de sucre comme la sève, le miellat ou des fruits endommagés tandis que la femelle est aussi hématophage (Foster, 1995;Gary et Foster, 2004;Barredo et Degennaro, 2020). Le repas sanguin constitue un enjeu majeur en santé publique car c'est à ce moment que le moustique peut être infecté par des plasmodies et devenir infectieux après la période extrinsèque d'incubation (EIP). ...
De nos jours, la lutte anti-vectorielle s’appuie principalement sur l’utilisation des insecticides. Cependant, l’apparition de résistances au sein des populations de moustiques réduit l’efficacité de ces molécules. A l’aide d’une approche multidisciplinaire réalisée in vitro sur des neurones isolés de trois souches de moustiques Anopheles gambiae, une souche sensible (Kis) et deux souches résistantes aux insecticides de type organophosphorés/carbamates (AcerKis) et pyréthrinoïdes (KdrKis), il a été possible de montrer pour la première fois qu’il existe des mécanismes de compensation cellulaires et moléculaires associés aux résistances ace-1R sur l’acétylcholinestérase et kdr sur le canal sodium dépendant du potentiel. Ces mécanismes doivent être considérés pour adapter des stratégies de lutte chimique car ils affectent les propriétés électropharmacologiques des récepteurs cholinergiques de type nicotinique. Ils modulent l’effet de l’acétylcholine, le neurotransmetteur endogène, mais aussi de la clothianidine, un insecticide néonicotinoïde agoniste de ces récepteurs. Au contraire, l’effet du triflumézopyrime, un insecticide mésoionique antagoniste compétitif de ces récepteurs ne semble pas affecté par ces mécanismes de compensation. Cette étude a été complétée par des tests toxicologiques comparatifs réalisés in vivo sur les larves de ces trois souches. Les effets de la clothianidine et du triflumézopyrime ont été testés seuls et associés au répulsif IR3535, utilisé comme agent synergisant pour optimiser l’efficacité du traitement. Les deux association sont montré un effet synergique fort, justifiant l’intérêt de les proposer comme nouvelles stratégies de lutte.
... In this context, the mass-rearing of these species is extremely important to allow basic investigations about their biology, behavior, and vector competence, as well as to test new control strategies and determine pesticide resistance mechanisms. However, a crucial phase of mosquito rearing is blood meal administration to females to obtain gravid females and egg production (Foster, 1995). Thus, blood feeding is essential to evaluate pathogen and/or parasite transmission ability, as well as to test novel repellent substances (Romano et al., 2018). ...
Invasive mosquitoes (Diptera: Culicidae) play a key role in the spread of a number of mosquito-borne diseases worldwide. Anthropogenic changes play a significant role in affecting their distribution. Invasive mosquitoes usually take advantage from biotic homogenization and from biodiversity reduction, therefore expanding in their distribution range and abundance. In Europe, climate warming and the increasing urbanization are boosting the spread of several mosquito species of high public health importance. The present article contains a literature review focused on the biology and ecology of Aedes albopictus, Ae. aegypti, Ae. japonicus, Ae. koreicus, Ae. atropalpus and Ae. triseriatus, outlining their distribution and public health relevance in Europe. Bioecology insights were tightly connected with vector surveillance and control programs targeting these species. In the final section, a research agenda aiming for the effective and sustainable monitoring and control of invasive mosquitoes in the framework of Integrated Vector Management and One Health is presented. The WHO Vector Control Advisory Group recommends priority should be given to vector control tools with proven epidemiological impact.
... Sugar feeding plays a role in several aspects of mosquito life and both males and females frequent sugars from different natural sources (Foster 1995). In view of this, sugar has become a candidate for the oral delivery of insecticides and several studies with ATSB and TSB reported on the use of baits with 5-20% sucrose (Lea 1965, Schlein and Pener 1990, Xue and Barnard 2003, Xue et al. 2006Schlein 2008, Müller et al. 2010, Fig. 3. Engorgement of males (A) and females (B) and mortality rate of males (C) and females (D) of Ae. aegypti fed with ATSB and TSB baits with different concentrations of sucrose and ivermectin. ...
Toxins and attractants have been studied and used in sugar baits for mosquitoes. However, little importance has been given to the combination of sugar concentration, bait composition, and their relationship with mosquito engorgement and mortality. Therefore, the present study evaluated the effects of three concentrations of sucrose on baits with and without an attractant (concentrated guava juice), on engorgement and mortality rates of adult Aedes aegypti (Linnaeus, Diptera: Culicidae). Toxic sugar baits (TSB) and attractant toxic sugar baits (ATSB) containing 10, 50, and 70% sucrose and 100 ppm ivermectin (IVM) were prepared to assess engorgement and mortality rates. Subsequently, different concentrations of IVM (0.312–100 ppm) in TSB and ATSB were prepared with sucrose concentrations of 10 and 70% to determine the lethal concentrations (LC50 and LC90) values. Engorgement on the baits was observed under a stereomicroscope, and mortality was followed up to 48 h after feeding. In general, more mosquitoes engorged on TSB regardless of the sugar concentration, while higher concentrations of sugar in ATSBs resulted in higher numbers of mosquitoes engorging. A large increase in the LC90 of IVM was observed for females feeding on ATSBs and TSBs with 70% sucrose relative to those feeding on baits with lower sugar concentrations. No such effect was observed for males.
... To orient toward hosts, female mosquitoes seeking a blood meal detect a variety of chemical and physical cues including body odor, carbon dioxide (CO 2 ), moisture, heat, and visual contrast 26 ; Gibson and Torr, 1999 [26][27][28][29] . Of these sensory cues, ~4% CO 2 exhaled in breath is a potent behavioral activator and attractant for mosquitoes and is often considered to be the most important sensory cue used by these disease vectors to find humans 30 . ...
Increased outbreaks of mosquito borne diseases like the deadly parasitic disease, malaria and arboviruses like Zika,
yellow fever and dengue viruses around the world have led to increased interest in traps that could effectively be
used against mosquitoes. For example, a Google search at the time of this writing, asking, ‘which is the best way of
trapping mosquitoes?’ produced 35.5 million search results. Regardless of the interest in the subject, scientists have
yet to find a definitive answer to these questions. One area that has been exploited as a potential source of efficient
traps for mosquitoes is host odour baits. Since mosquitoes are attracted to their hosts through odours produced by
the hosts, it’s highly likely that synthetic chemical blends based on host odours could provide a solution. Most
mosquito species have 2 hosts: vertebrate animals and vascular plants. Amongst the vertebrates, most diseases
spread by mosquitoes are to humans. Considerable research has therefore been conducted on human odours that
elicit attraction in mosquitoes, with emphasis on compounds from sweat and skin. Interest on plant volatiles is cur�rently gathering pace because unlike human odours that only attract host seeking female mosquitoes, plant odours
can attract both male and female mosquitoes of all gonotrophic stages. This review article concentrates on some of
the chemical compounds in human and plant host odours that have shown a potential as attractants to mosquitoes
especially Aedes aegypti and Anopheles gambiae s.l.
... In particular, there is an urgent need for tools that remain effective against insecticide-resistant, outdoor-biting and day-time biting mosquitoes [12] Attractive targeted sugar baits (ATSBs) are a promising new technology that is increasingly being investigated for expanding the malaria prevention toolbox [13][14][15][16][17]. The technology exploits the natural sugar-feeding behaviors essential for mosquito survival [18][19][20][21][22]. This means sugar-based solutions can be used to target mosquitoes by adding orally-ingested toxicants, which may include common pesticides, boric acid, and nucleic acids [23][24][25][26][27][28]. ...
Background
Attractive targeted sugar baits (ATSBs) control sugar-feeding mosquitoes with oral toxicants, and may effectively complement core malaria interventions such as insecticide-treated nets even where pyrethroid-resistance is widespread. The technology is particularly efficacious in arid areas. However, their performance remains poorly-understood in tropical areas with year-round transmission, and where the abundant vegetation constitutes competitive sugar sources for mosquitoes. This study compared the efficacies of ATSBs (active ingredient: 2% boric acid) in controlled settings with different vegetation densities.
Methods
Potted mosquito-friendly plants were introduced inside semi-field chambers (9.6m by 9.6m each) to simulate densely-vegetated, sparsely-vegetated, and bare sites without any vegetation (two chambers/category). All chambers had volunteer-occupied huts. Laboratory-reared Anopheles arabiensis females were released nightly (200/chamber) and host-seeking mosquitoes recaptured using human landing catches outdoors (8.00pm – 9.00pm) and CDC-light traps indoors (9.00pm – 6.00am). Additionally, resting mosquitoes were collected indoors and outdoors each morning using Prokopack aspirators. The tests included a “before-and-after” set-up (with pre-ATSBs, ATSB and post-ATSB phases per chamber), and a “treatment vs. control” set-up (where similar chambers had ATSBs or no ATSBs). All tests lasted 84 trap-nights.
Results
In the initial tests when all chambers had no vegetation, the ATSBs reduced outdoor-biting by 69.7%, indoor-biting by 79.8% and the resting mosquitoes by 92.8%. In tests evaluating impact of vegetation, the efficacy of ATSBs against host-seeking mosquitoes was high in bare chambers (outdoors: 64.1% reduction; indoors: 46.8%) but modest or low in sparsely-vegetated (outdoors: 34.5%; indoors: 26.2%) and densely-vegetated chambers (outdoors: 25.4%; indoors: 16.1%). Against resting mosquitoes, the ATSBs performed modestly across settings (non-vegetated: 37.5% outdoors and 38.7% indoors; sparsely-vegetated: 42.9% outdoors and 37.5% indoors; densely-vegetated: 45.5% outdoors and 37.5% indoors). Vegetation significantly reduced the efficacy of ATSBs against outdoor-biting and indoor-biting (P < 0.001), but not resting mosquitoes.
Conclusion
While vegetation can influence the performance of ATSBs, the devices remain modestly efficacious in sparsely-vegetated and densely-vegetated settings. Higher efficacies may occur in places with minimal or completely no vegetation, but such environments are naturally unlikely to sustain Anopheles populations nor malaria transmission in the first place. Field studies therefore remain necessary to validate the efficacies of ATSBs in the tropics.
... After emerging from the pupal stage, adult females remain in the previtellogenic phase, which is associated juvenile hormone (JH) from the corpora allata stimulating primary follicles to approximately double in size by 2 days postemergence before arresting (Clifton & Noriega, 2012;Zhu & Noriega, 2016). Females in the previtellogenic phase consume nectar or other sugar sources as well as water (Foster, 1995;Baredo & DeGennaro, 2020), and also begin to seek humans or other vertebrates 3-4 days postemergence to blood-feed (Coutinho-Abreu et al., 2021). However, females remain in the previtellogenic phase indefinitely if a suitable host for blood feeding is not found. ...
Anautogenous mosquitoes must blood feed on a vertebrate host to produce eggs. Each gonadotrophic cycle is subdivided into a sugar‐feeding previtellogenic phase that produces primary follicles and a blood meal‐activated vitellogenic phase in which large numbers of eggs synchronously mature and are laid. Multiple endocrine factors including juvenile hormone (JH), insulin‐like peptides (ILPs), ovary ecdysteroidogenic hormone (OEH) and 20‐hydroxyecdysone (20E) coordinate each gonadotrophic cycle. Egg formation also requires nutrients from feeding that are stored in the fat body. Regulation of egg formation is best understood in Aedes aegypti but the role different endocrine factors play in regulating nutrient mobilization and storage remains unclear. In this study, we report that adult female Ae. aegypti maintained triacylglycerol (TAG) stores during the previtellogenic phase of the first gonadotrophic cycle while glycogen stores declined. In contrast, TAG and glycogen stores were rapidly mobilized during the vitellogenic phase and then replenishment. Several genes encoding enzymes with functions in TAG and glycogen metabolism were differentially expressed in the fat body, which suggested regulation was mediated in part at the transcriptional level. Gain of function assays indicated that stored nutrients were primarily mobilized by adipokinetic hormone (AKH) while juvenoids and OEH regulated replenishment. ILP3 further showed evidence of negatively regulating certain lipolytic enzymes. Loss of function assays further indicated AKH depends on the AKH receptor (AKHR) for function. Altogether, our results indicate that the opposing activities of different hormones regulate nutrient stores during a gonadotrophic cycle in Ae. aegypti. This article is protected by copyright. All rights reserved
... While imbibing these nutrients, they also acquired numerous shed microbes or parasites. For general body metabolism, maintenance, and flight, in addition to sterols, it has always been essential for flies to obtain carbohydrates in the form of honeydew, nectar, exudates or juices from fruits and some plants [44][45][46]. The importance of fruits in epidemiological models cannot be overemphasized. ...
An attempt has been made to provide a broad review of synanthropic flies and, not just a survey of their involvement in human pathogen transmission. It also emphasizes that the crop organ of calliphorids, sarcophagids, and muscids was an evolutionary development and has served and assisted non-blood feeding flies in obtaining food, as well as pathogens, prior to the origin of humans. Insects are believed to be present on earth about 400 million years ago (MYA). Thus, prior to the origin of primates, there was adequate time for these flies to become associated with various animals and to serve as important transmitters of pathogens associated with them prior to the advent of early hominids and modern humans. Through the process of fly crop regurgitation, numerous pathogens are still readily being made available to primates and other animals. Several studies using invertebrate-derived DNA = iDNA meta-techniques have been able to identify, not only the source the fly had fed on, but also if it had fed on their feces or the animal's body fluids. Since these flies are known to feed on both vertebrate fluids (i.e., from wounds, saliva, mucus, or tears), as well as those of other animals, and their feces, identification of the reservoir host, amplification hosts, and associated pathogens is essential in identifying emerging infectious diseases. New molecular tools, along with a focus on the crop, and what is in it, should provide a better understanding and development of whether these flies are involved in emerging infectious diseases. If so, epidemiological models in the future might be better at predicting future epidemics or pandemics.
... Mosquito sugar feeding is a necessary behavior in many species, and even in the species where it is facultative, ingestion of plant sugars typically results in higher fitness (Foster 1995). Mosquitoes seek out sugar in the form of floral and extra-floral nectaries, but also from damaged or rotting fruits, honeydew, and leaf or stem tissues Müller 1995, Müller et al. 2011). ...
Attractive toxic sugar baits (ATSBs) require target insects to locate, orient toward, and feed on an insecticidal sugar solution to control populations. Formulating these baits with different attractants and phagostimulants can increase their efficacy by causing insects to choose the ATSB over competing natural sugar sources, and to ingest more of the bait solution. We tested formulations of a 20% sodium ascorbate (SA) ATSB solution using different sugars, adenosine triphosphate (ATP), gallic acid, and six plant volatile compounds to determine their effect on adult Aedes aegypti (L.) and Anopheles stephensi Liston mortality. Baits formulated with fructose or sucrose had no effect on either species, neither did the addition of ATP. Gallic acid increased the survival of Ae. aegypti. Four of the six volatile compounds increased mortality in at least one species. We also examined An. stephensi response to baits formulated with each of the six volatile compounds. Anisaldehyde significantly increased the number of mosquitoes responding toward the SA-ATSB, but increasing the amount had no effect. Addition of anisaldehyde also significantly increased An. stephensi feeding rates on the SA-ATSB, though mosquitoes will avoid the toxic bait if a nontoxic sugar source is available. Formulation of SA-ATSBs with synthetic blends of attractive compounds can increase bait efficacy and consistency, though further research is needed to assess their performance in the field in the presence of natural sugar sources.
... Feeding on honeydew has previously been proposed as the fundamental diet of the ancestral Diptera, shaping the order as we know it today [41]. Honeydew feeding is widely reported from the Culicomorpha (Figure 2), and has also been considered as a candidate for the ancestral diet of Culicidae [13,31]. The idea that haematophagy arose from entomophagy and phytophagy, in the forms of concurrently feeding on insects and honeydew, might reconcile many contradictions in theories of the origins of haematophagy within the Culicomorpha. ...
The Culicomorpha are an infraorder of several families of blood-feeding flies, including mosquitoes (Diptera: Culicidae). Here we discuss the evolutionary origins of blood-feeding within the Culicomorpha and review literature that suggests this behaviour may have evolved from ancestral plant-feeding or a combination of plant-feeding and insect-feeding. Sialomic and life-history evidence suggest that plant-feeding, concurrent or not with insect-feeding, is parsimonious as an ancestral diet for Culicomorpha. We review the chemical parsimony observed between vertebrate headspace odours, floral headspace odours, and honeydew headspace odours, which are behaviourally attractive to many of the Culicomorpha. We also review the sensory and neural mechanisms involved in changes in olfactory attraction and we propose this observed chemical parsimony as a hypothesis for an associative mechanism which may have led to the development of blood-feeding from plant-feeding that is consistent with a “path of least resistance” for the sensory changes necessary to undergo host shifts.
... Microbiome research has expanded in mosquitoes given their medical relevance and interesting biology. As holometabolous insects, mosquitoes have distinct aquatic and terrestrial life stages, including larvae that molt through four aquatic instars before pupating on the water's surface and emerging as terrestrial adults [7,8]. All of these stages harbor gut microbial communities dominated by bacteria that can vary tremendously in diversity and abundance over time and space [9]. ...
Background
Mosquitoes harbor microbial communities that play important roles in their growth, survival, reproduction, and ability to transmit human pathogens. Microbiome transplantation approaches are often used to study host-microbe interactions and identify microbial taxa and assemblages associated with health or disease. However, no such approaches have been developed to manipulate the microbiota of mosquitoes.
Results
Here, we developed an approach to transfer entire microbial communities between mosquito cohorts. We undertook transfers between ( Culex quinquefasciatus to Aedes aegypti ) and within ( Ae. aegypti to Ae. aegypti ) species to validate the approach and determine the number of mosquitoes required to prepare donor microbiota. After the transfer, we monitored mosquito development and microbiota dynamics throughout the life cycle. Typical holometabolous lifestyle-related microbiota structures were observed, with higher dynamics of microbial structures in larval stages, including the larval water, and less diversity in adults. Microbiota diversity in recipient adults was also more similar to the microbiota diversity in donor adults.
Conclusions
This study provides the first evidence for successful microbiome transplantation in mosquitoes. Our results highlight the value of such methods for studying mosquito-microbe interactions and lay the foundation for future studies to elucidate the factors underlying microbiota acquisition, assembly, and function in mosquitoes under controlled conditions.
... ATSB control technique is based on the sugar feeding behavior of adult mosquitoes. Sugar feeding is important for survival, reproduction, and energetics (Foster 1995). Nutrient acquisitions by adult mosquitoes are from nectar resources (Muller et al. 2011, Barredo andDeGennaro 2020). ...
Eleven different carbohydrates were evaluated to determine the behavioral response of adult Anopheles quadrimaculatus Say and Aedes albopictus Skuse using an olfactometer. The carbohydrates used in the study are arabinose, fructose, glucose, maltose, melezitose, meliniose, raffinose, rhamnose, sucrose, trehalose, and turanose. The results showed that both species of mosquitoes regardless of the sex had significantly higher attraction to arabinose, maltose, meliniose, and trehalose than other 7 carbohydrates tested. Both sexes and both species responded to maltose and trehalose in considerable numbers, and the least responses were to sucrose except by male Ae. albopictus. These findings may provide insights to the development of more effective sugar-based toxic baits for the operational application in mosquito control programs.
... Male and female mosquitoes require a source of carbohydrate to obtain energy. Adult mosquitoes are able to acquire their needs of sugar from floral, extrafloral nectar, or honeydew droplets excreted by insects (Yuval 1992, Foster 1995. Thus, honeydew and plant-derived sugars are essential nutritional components for adult mosquitoes to obtain energy for flight, survival, fecundity, and maintaining nutritional reserves (Nayar andSauerman Jr 1971, Foster 1995). ...
Sugar is an essential source of nutrition for adult mosquitoes to acquire energy. Toxic sugar bait (TSB) provides a promising method for mosquito control by incorporating toxins into artificial sources of sugar (i.e., toxic baits) presented to wild populations. Spinosyns comprise a family of bacterial secondary metabolites with a unique mode of action against the insect nervous system, an appealing environmental safety profile, and potential for incorporation into sugar baits. This research evaluated acute and subacute effects of spinosad (spinosyns A and D) and spinetoram (spinosyns J and L) in sugar meals on survival, fecundity, and fertility of Aedes aegypti and Aedes albopictus. Acute toxicity of spinosyns doubled from 24 to 48 h of assessment, revealing a relatively slow and cumulative action of the formulated spinosyns. Median lethal concentrations at 48 h were lower for spinetoram than for spinosad, lower for Ae. albopictus than Ae. aegypti, and lower for males than females. When exposed to subacute LC50 concentrations of spinosad and spinetoram for 24 h, survival of males and females of both species was diminished compared with controls, fecundity of females was increased, but fertility as measured by hatch rate of eggs was decreased. The formulations may have increased the nutritive value of the sugar meals thereby boosting fecundity, while toxifying embryos, reducing fertility. The inclusion of subacute effects of spinosyns allows assessment of the broader consequences of TSB for adult mosquito control.
... Mosquito colonies are maintained and mass-reared all over the world in the context of research and mass-release control programs. Given that medically important mosquito species require a blood meal to lay eggs (Foster 1995), the initial mosquito colonies were maintained by direct feeding on vertebrates (Boyd et al. 1935, Rozeboom 1936, Munstermann 1997. As time progressed and concerns about the ethics of live animal feeding and costs arose (Bailey et al. 1978), studies have attempted to find methods of artificial feeding to replace live host feeding (Wetzel 1979, Deng et al. 2012, Luo 2014. ...
Blood sources used for insect colonies and their effects on fecundity and fertility have been studied in multiple mosquito species, but the effect of anticoagulants that prevent clotting of blood has received minimal attention. Here, we identify the effect two anticoagulants have on the mortality, fecundity, and fertility of Culex quinquefasciatus (Sebring and BCS strains) and Aedes aegypti Liverpool. Each mosquito species was provided with one of three treatments: direct feeding on live chicken (LC), blood from freshly exsanguinated chicken treated with heparin (EXS) or commercially purchased chicken blood treated with Alsever's solution (ART). No significant effect of treatment on mortality was observed. Both Cx. quinquefasciatus Sebring and BCS strains demonstrated a significant effect of treatment type on fecundity with the number of eggs laid for LC being 1.40-fold higher than EXS and 2.14-fold higher than ART for Sebring. For BCS strain mosquitoes, LC was 1.55-fold higher than ART, and EXS was 1.57-fold higher than ART, but there was no significant difference between LC and EXS. For Ae. aegypti mosquitoes, only a significant difference in mean egg counts was observed between LC and ART treatments, with LC laying 1.46-fold more eggs. No significant effect on fertility was observed among any mosquitoes for any treatment. These results demonstrate the negative effect of anticoagulants on the fecundity for multiple mosquito taxa. This may affect the ability of labs to produce large numbers of mosquitoes or colonize wild mosquito populations and should be taken into account when considering colony maintenance or vector biology research.
Background
The current rise of new innovative tools for mosquito control such as the release of transgenic mosquitoes carrying a dominant lethal gene and Wolbachia-based strategies necessitates a massive production of mosquitoes in the insectary. However, currently laboratory rearing depends on vertebrate blood for egg production and maintenance. This practice raises, ethical concerns, incurs logistical and cost limitations, and entails potential risk associated with pathogens transmission and blood storage. Consequently, an artificial blood-free diet emerges as an essential alternative to address these challenges. This study aims to evaluate the effects of a previously formulated artificial blood-free diet (herein referred to as BLOODless) on Anopheles gambiae sensu stricto (An. gambiae s.s; IFAKARA) gonotrophic parameters and fitness compared to bovine blood.
Methods
The study was a laboratory-based comparative evaluation of the fitness, fecundity and fertility of An. gambiae s.s (IFAKARA) reared on BLOODless versus vertebrate blood from founder generation (F0) to eighth generation (F8). A total of 1000 female mosquitoes were randomly selected from F0, of which 500 mosquitoes were fed with bovine blood (control group) and the other 500 mosquitoes were fed with BLOODless diet (experimental group). The feeding success, number of eggs per female, hatching rate and pupation rate were examined post-feeding. Longevity and wing length were determined as fitness parameters for adult male and female mosquitoes for both blood-fed and BLOODless -fed populations.
Results
While blood-fed and BLOODless-fed mosquitoes showed similar feeding success OR 1.12 (95% CI, 0.82–1.53; P = 0.488), significant difference emerged in their reproductive parameters. The mean number of eggs laid per female was significantly higher for blood-fed mosquitoes P < 0.001 whereas BLOODless-fed mosquitoes had significantly lower hatching rates OR 0.17 (95% CI, 0.14–0.22; P < 0.001). Wing length and longevity parameters were similar between both groups.
Conclusion
This study demonstrates the potential of the BLOODless diet as a viable and ethical alternative to vertebrate blood feeding for rearing An. gambiae s.s facilitating large-scale mosquito mass production in captivity. This breakthrough paves the way for more efficient and ethical studies aimed at combating malaria and other mosquito-borne diseases.
We evaluated miRNA and mRNA expression differences in head tissues between avid-biting vs. reluctant-biting Aedes albopictus (Skuse) females from a single population over a 20-min timescale. We found no differences in miRNA expression between avid vs. reluctant biters, indicating that translational modulation of blood-feeding behavior occurs on a longer timescale than mRNA transcription. In contrast, we detected 19 differentially expressed mRNAs. Of the 19 differentially expressed genes at the mRNA level between avid-biting vs. reluctant-biting A. albopictus, 9 are implicated in olfaction, consistent with the well-documented role of olfaction in mosquito host-seeking. Additionally, several of the genes that we identified as differentially expressed in association with phenotypic variation in biting behavior share similar functions with or are inferred orthologues of, genes associated with evolutionary variation in biting behaviors of Wyeomyia smithii (Coq.) and Culex pipiens (Lin.). A future goal is to determine whether these genes are involved in the evolutionary transition from a biting to a non-biting life history.
Background
Attractive targeted sugar bait (ATSB) is a novel approach to vector control, offering an alternative mode of insecticide delivery via the alimentary canal, with potential to deliver a variety of compounds new to medical entomology and malaria control. Its potential to control mosquitoes was recently demonstrated in major field trials in Africa. The pyrrole chlorfenapyr is an insecticide new to malaria vector control, and through its unique mode of action – disruption of ATP mediated energy transfer in mitochondria – it may have direct action on energy transfer in the flight muscle cells of mosquitoes. It may also disrupt mitochondria of malarial parasites co-existing within the infected mosquito. However, little is known about the impact of such compounds on vector competence in mosquitoes responsible for malaria transmission.
Method
In this study, we compared the effect of ATSBs containing chlorfenapyr insecticide and, as a positive control, the antimalarial drugs artemether/lumefantrine (A/L) on Plasmodium falciparum development in wild pyrethroid-resistant Anopheles gambiae s.s. for their capacity to reduce vector competence. To do this, we exposed females mosquitoes to ATSB containing sublethal dose of chlorfenapyr (CFP: 0.025%) or concentrations of A/L ranging from 0.4/2.4 mg/ml to 2.4/14.4 mg/ml, either shortly before or after infective blood meals. The impact of their component compounds on the prevalence and intensity of P. falciparum infection were compared between treatments.
Results
We showed that both prevalence and intensity of infection were significantly reduced in mosquitoes exposed to either A/L or CFP, compared to unexposed negative control mosquitoes. The A/L dose (2.4/14.4 mg per ml) totally erased P. falciparum parasites: 0% prevalence of infection in female mosquitoes exposed compared to 62% of infection in negative controls (df = 1, χ2 = 31.23 p < 0.001). The dose of CFP (0.25%) that killed < 20% females in ATSB showed a reduction in oocyte density of 95% per midgut (0.18/3.43 per midgut).
Conclusion
These results are evidence that CFP, in addition to its direct killing effect on the vector, has the capacity to block Plasmodium transmission by interfering with oocyte development inside pyrethroid-resistant mosquitoes, and through this dual action may potentiate its impact under field conditions.
Immune defense is comprised of 1) resistance: the ability to reduce pathogen load, and 2) tolerance: the ability to limit the disease severity induced by a given pathogen load. The study of tolerance in the field of animal immunity is fairly nascent in comparison to resistance. Consequently, studies which examine immune defense comprehensively (i.e., considering both resistance and tolerance in conjunction) are uncommon, despite their exigency in achieving a thorough understanding of immune defense. Furthermore, understanding tolerance in arthropod disease vectors is uniquely relevant, as tolerance is essential to the cyclical transmission of pathogens by arthropods. Here, we tested the effect(s) of dietary sucrose concentration (high or low) and blood meal (present or absent) on resistance and tolerance to Escherichia coli infection in the yellow fever mosquito Aedes aegypti . Resistance and tolerance were measured concurrently and at multiple timepoints. We found that both blood and sucrose affected resistance. Mosquitoes from the low sugar treatment displayed enhanced resistance at all timepoints post-infection compared to those from the high sugar treatment. Additionally, blood-fed mosquitoes showed enhanced resistance compared to non-blood-fed mosquitoes, but only on day 1 post-infection. Sucrose had no effect on tolerance, but the effect of blood was significant and dynamic across time. Specifically, we show that consuming blood prior to infection ameliorates a temporal decline in tolerance that mosquitoes experience when provided with only sugar meals. Taken together, our findings indicate that different dietary components can have unique and sometimes temporally dynamic impacts on resistance and tolerance. Finally, our findings 1) highlight the value of experimental and analytical frameworks which consider the explicit testing of effects on both resistance and tolerance as separate, but equally important, components of immune defense, and 2) underscore the importance of including a temporal component in studies of immune defense.
Background & objectives:
A successful blood meal acquisition process by an adult female mosquito is accomplished through salivary glands, which releases a cocktail of proteins to counteract the vertebrate host's immune homeostasis. Here, we characterize a salivary-specific Heme peroxidase family member HPX12, originally identified from Plasmodium vivax infected salivary RNAseq data of the mosquito Anopheles stephensi.
Methods:
To demonstrate we utilized a comprehensive in silico and functional genomics approach.
Results:
Our dsRNA-mediated silencing experiments demonstrate that salivary AsHPX12 may regulate pre-blood meal-associated behavioral properties such as probing time, probing propensity, and host attraction. Altered expression of the salivary secretory and antennal proteins expression may have accounted for salivary homeostasis disruption resulting in the unusual fast release of salivary cocktail proteins and delayed acquisition of blood meal in the AsHPX12 knockdown mosquitoes. We also observed a significant parallel transcriptional modulation in response to blood feeding and P. vivax infection.
Interpretation & conclusion:
With this work, we establish a possible functional correlation of AsHPX12 role in the maintenance of salivary physiological-homeostasis, and Plasmodium sporozoites survival/transmission, though the mechanism is yet to unravel.
Background
Sugar feeding behaviour is an essential aspect for mosquito survival, fitness, reproduction, and competence. Understanding the behaviour of Aedes aegypti is a fundamental phenomenon for the development of new interventions for controlling the vectors. The objective of the current study was to investigate i) the time in an Ae. aegyptimosquito’s adult life when they are most likely to sugar feed ii) if sugar sources availability limits Ae. aegypti blood feeding with the aim of informing control strategies using attractive-targeted sugar baits (ATSBs)
Methods:
The preference of Ae. aegypti to feed on sugar or blood and the effect of sugar source availability on Ae. aegypti blood feeding was studied at different chronological and physiological ages in semi-field conditions in Bagamoyo, Tanzania. Experiments were done through a series of paired–choice assays whereupon mosquitoes were allowed to choose between a sugar meal or a blood meal in the form of a rabbit.
Results
In the first five days post emergence, Aedes aegypti mosquitoes were equally likely to opt for a sugar meal or a blood meal. However, after the first gonotrophic cycle Ae. aegypti prefer to feed on blood meal (OR=9.4; 95%CI= [6.7-13.0]; p<0.001) over a sugar meal (OR=1). Moreover, a nulliparous Ae. aegypti mosquitoes are less likely to blood feed if they have both sugar and blood sources available (OR=0.06; 95%CI [0.02-0.16] p<0.001).
Conclusion
In this study, sugar meal is observed to be a part of Ae. aegypti life particularly at the younger stage (nulliparous stage). Therefore, there is potential for the development of interventions such as attractive toxic sugar baits (ATSBs).
Morphology, distribution and function of the sensilla associated with mouthparts of female mosquito, Culex pipiens (Diptera: Culicidae) were studied by using the scanning electron microscope. The female mosquito mouthpart is a piercing and sucking type and carrying many sensory organs which plays major role in host seeking, and oviposition behaviour of mosquitoes. Six types of mouthpart sensilla have been identified and described, Sensilla trichoidea, chaetica, basiconica, Capitate peg, campaniformia and squamiformia. Females mosquito were irradiated as pupae with 20, 40 and 80 Gy of gamma radiation to investigate their effect on mouthparts sensilla. Dose of 20 Gy had slight effect on the different types of the sensilla as compared with the control. Features of malformation observed in the maxillary palp segments at this radiation dose include falling of some scales (sensilla squamiformia) at certain parts of the 1st segment leaving vacuoles. At 40 Gy, the maxillary palp segments were liquefied in some areas leaving undistinguished shape. At the highest dose 80 Gy, the tip of labial palps had many tears and showed were most affected, especially, at the trichoid, basiconic and chateica sensilla. All these malformations may lead the mosquitoes to not reaching the host, impeding their ability to transmit diseases or killing the mosquitoes, and this is the main objective of this study.
Microbiota studies of Aedes aegypti and other mosquitoes generally focus on the bacterial communities found in adult female midguts. However, other compartments of the digestive tract maintain communities of bacteria which remain almost entirely unstudied. For example, the Dipteran crop stores nectar and other sugars, but few studies have looked at the microbiome of crops in mosquitoes, and only a single previous study has investigated the crop in Ae. aegypti . In this study, we used both culture-dependent and culture-independent methods to compare the bacterial communities in midguts and crops of laboratory-reared Ae. aegypti . Both methods revealed a trend towards higher abundance, but also higher variability, of bacteria in the midgut than the crop. When present, bacteria from the genus Elizabethkingia (family Weeksellaceae) dominated midgut bacterial communities. In crops, we found a higher diversity of bacteria, and these communities were generally dominated by acetic acid bacteria (family Acetobacteriaceae) from the genera Tanticharoenia and Asaia . These three taxa drove significant community structure differences between the tissues. We used FAPROTAX to predict the metabolic functions of these communities and found that crop bacterial communities were significantly more likely to contain bacteria capable of methanol oxidation and methylotrophy. Both the presence of acetic acid bacteria (which commonly catabolize sugar to produce acetic acid) and the functional profile that includes methanol oxidation (which is correlated with bacteria found with natural sources like nectar) may relate to the presence of sugar in the crop. A better understanding of what bacteria are present in the digestive tract of mosquitoes and how these communities assemble will inform how the microbiota impacts mosquito physiology and the full spectrum of functions provided by the microbiota. It may also facilitate better methods of engineering the mosquito microbiome for vector control or prevention of disease transmission.
Author summary
Bacteria inside mosquitoes’ guts have been found to have an impact on mosquito life history traits (such as longevity and fecundity) as well as their susceptibility to infection by human pathogens. Engineering these communities may provide an effective and safe way to control mosquitoes and reduce the impact of the pathogens they spread. In this work, we assayed the bacteria found in midgut and crop tissues of a medically important mosquito, Aedes aegypti . Our results show that these tissues harbor communities of bacteria that differ in composition and function and vary in abundance. Experiments like ours are important to better understand where bacteria are found in an insect’s body and how these communities assemble. This knowledge may help future researchers more successfully engineer bacterial communities in mosquitoes.
Background
Plant floral nectars contain natural sugars such as fructose, which are a primary energy resource for adult mosquitoes. Despite the importance of carbohydrates for mosquito metabolism, a limited knowledge is available about the pathways involved in sugar assimilation by mosquitoes and their associated microbiota. To this end, we used ¹³ C-metabolomic and stable isotope probing approaches coupled to high-throughput sequencing to reveal fructose-related mosquito metabolic pathways and the dynamics of the active gut microbiota following fructose ingestion.
Results
Our results revealed significant differences in metabolic pathways between males and females, highlighting different modes of central carbon metabolism regulation. Competitive and synergistic interactions of diverse fungal taxa were identified within the active mycobiota following fructose ingestion. In addition, we identified potential cross-feeding interactions between this. Interestingly, there is a strong correlation between several active fungal taxa and the presence of fructose-derived metabolites.
Conclusions
Altogether, our results provide novel insights into mosquito carbohydrate metabolism and demonstrate that dietary fructose as it relates to mosquito sex is an important determinant of mosquito metabolism; our results also further highlight the key role of active mycobiota interactions in regulating the process of fructose assimilation in mosquitoes. This study opens new avenues for future research on mosquito-microbiota trophic interactions related to plant nectar-derived sugars.
Graphical Abstract
Insecticide application for vector control is the most controversial component of a public health program due to concerns about environmental and human health safety. One approach to overcome this challenge is the use of environmentally benign active ingredients. Among the most promising emerging strategies are attractive toxic sugar baits. Sugar alcohols—naturally occurring molecules safe for human consumption but potentially toxic to insects when ingested, have received increased attention for use with this approach. For this study, we screened the toxicity of four different sugar alcohols on several mosquito species, a biting midge, and a filth fly. Sugar alcohol mortalities exceeded those in the sucrose (positive control) only group. However, only erythritol and highly concentrated xylitol induced mortalities exceeding those in the water only (negative control) treatment ranging from approximately 40–75%. Formulations containing erythritol and xylitol should be further investigated under field conditions for efficacy in reducing populations of biting flies and for assessing potential non-target impacts.
Sex is one of the important factors affecting gut microbiota. As key predators in agroforestry ecosystem, many spider species show dramatically different activity habits and nutritional requirements between females and males. However, how sex affects gut microbiota of spiders remains unclear. Here, we compared the composition and diversity of gut bacteria between female and male Pardosa astrigera based on bacterial 16S rRNA gene sequencing. Results showed that the richness of bacterial microbiota in female spiders was significantly lower than in male spiders (p < .05). Besides, β‐diversity showed a significant difference between female and male spiders (p = .0270). The relative abundance of Actinobacteriota and Rhodococcus (belongs to Actinobacteriota) was significantly higher in female than in male spiders (p < .05), whereas the relative abundance of Firmicutes and Acinetobacter (belongs to Proteobacteria) and Ruminococcus and Fusicatenibacter (all belong to Firmicutes) was significantly higher in male than in female spiders (p < .05). The results also showed that amino acid and lipid metabolisms were significantly higher in female than in male spiders (p < .05), whereas glycan biosynthesis and metabolism were significantly higher in male than in female spiders (p < .05). Our results imply that sexual variation is a crucial factor in shaping gut bacterial community in P. astrigera spiders, while the distinct differences of bacterial composition are mainly due to their different nutritional and energy requirements. Sex is a crucial factor in shaping gut bacterial community in Pardosa astrigera. The male spiders disperse more widely than the females; hence, the males had a higher bacterial diversity, while the significant differences of bacterial composition are mainly due to their different nutritional and energy requirements.
Mosquitoes transmit a wide variety of devastating pathogens when they bite vertebrate hosts and feed on their blood. However, three entire mosquito genera and many individual species in other genera have evolved a non‐biting life history in which blood is not required to produce eggs. Our long‐term goal is to develop novel interventions that reduce or eliminate the biting behavior in vector mosquitoes. A previous study used biting and non‐biting populations of a non‐vector mosquito, Wyeomyia smithii, as a model to uncover the transcriptional basis of the evolutionary transition from a biting to a non‐biting life history. Herein, we ask whether the molecular pathways that were differentially expressed due to differences in biting behavior in W. smithii are also differentially expressed between subspecies of Culex pipiens that are obligate biting (Culex pipiens pipiens) and facultatively non‐biting (Culex pipiens molestus). Results from RNAseq of adult heads show dramatic upregulation of transcripts in the ribosomal protein pathway in biting Culex pipiens, recapitulating the results in Wyeomyia smithii, and implicating the ancient and highly conserved ribosome as the intersection to understanding the evolutionary and physiological basis of blood feeding in mosquitoes. Biting Culex also strongly upregulate energy production pathways, including oxidative phosphorylation and the citric acid (TCA) cycle relative to non‐biters, a distinction that was not observed in W. smithii. Amino acid metabolism pathways were enriched for differentially expressed genes in biting vs. non‐biting Culex. Relative to biters, non‐biting Culex upregulated sugar metabolism and transcripts contributing to reproductive allocation (vitellogenin and cathepsins). These results provide a foundation for developing strategies to determine the natural evolutionary transition between a biting and non‐biting life history in vector mosquitoes.
A fundamental understanding of plant sugar feeding behaviour in vector populations can lead to the development of ecologically effective vector monitoring and control strategies. Despite previous studies on mosquito–plant interactions, relatively few have been conducted on the dengue vector Aedes aegypti (Diptera: Culicidae). The authors studied Ae. aegypti–plant interactions at two sites of varying dengue endemicity in Kenya: Kilifi (endemic) and Isiolo (non‐endemic). Using chemical and molecular assays [DNA barcoding targeting the chloroplast ribulose‐1,5 bisphosphate carboxylase/oxygenase large chain (rbcL) gene], the authors show that at the two sites plant feeding in this mosquito species: (a) varies by sex and season; (b) results in the acquisition of diverse sugars, and (c) is associated with diverse host plants in the families Fabaceae, Malvaceae, Poaceae and Rosaceae. These results reveal insights into the plant sugar feeding patterns of wild‐caught Ae. aegypti and provide a baseline for future studies on the olfactory basis for host plant attraction for the development of vector monitoring and control tools. Seasonality influences plant sugar feeding rates of Aedes aegypti in the wild. Plant feeding leads to the acquisition of diverse sugars. In nature, Ae. aegypti has a wide plant host range with a seeming preference for species in the Fabaceae and Malvaceae families.
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