Mosquito Behavior Research Articles

Scaling artificial light at night and disease vector interactions into socio-ecological systems: a conceptual appraisal.

There is burgeoning interest in how artificial light at night (ALAN) interacts with disease vectors, particularly mosquitoes. ALAN can alter mosquito behaviour and biting propensity, and so must alter disease transfer rates. However, most studies to date have been laboratory-based, and it remains unclear how ALAN modulates disease vector risk. Here, we identify five priorities to assess how artificial light can influence disease vectors in socio-ecological systems. These are to (i) clarify the mechanistic role of artificial light on mosquitoes, (ii) determine how ALAN interacts with other drivers of global change to influence vector disease dynamics across species, (iii) determine how ALAN interacts with other vector suppression strategies, (iv) measure and quantify the impact of ALAN at scales relevant for vectors, and (v) overcome the political and social barriers in implementing it as a novel vector suppression strategy. These priorities must be addressed to evaluate the costs and benefits of employing appropriate ALAN regimes in complex socio-ecological systems if it is to reduce disease burdens, especially in the developing world. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Introduction to Techniques Used to Study Mosquito Neuroanatomy and Neural Circuitry.

Mosquitoes transmit deadly pathogens from person to person as they obtain the blood meal that is essential for their life cycle. Female mosquitoes of many species are unable to reproduce without consuming protein that they obtain from blood. This developmental stage makes them highly efficient disease vectors of deadly pathogens. They can transmit pathogens between members of the same species and different species that can provide a route for evolving zoonotic viruses to jump from animals to humans. One possible way to develop novel strategies to combat pathogen transmission by mosquitoes is to study the sensory systems that drive mosquito reproductive behaviors, in particular the neural architecture and circuits of mosquito sensory afferent neurons, the central circuits that process sensory information, and the downstream circuits that drive reproductive behaviors. The study of mosquito neuroanatomy and circuitry also benefits basic neuroscience, allowing for comparative neuroanatomy in insect species, which has great value in the current model species-heavy landscape of neuroscience. Here, we introduce two important techniques that are used to study neuroanatomy and neural circuitry-namely, immunofluorescent labeling and neural tracing. We describe how to apply these approaches to study mosquito neuroanatomy and describe considerations for researchers using the techniques.

Differences in excito-repellent behavior between susceptible and permethrin-resistant strains of Aedes aegypti upon exposure to insecticide-treated fabric.

An important component of the biological activity of pyrethroids, when used in disease vector control, is excito-repellency. In this study, behavioral differences between insecticide susceptible (Orlando) and pyrethroid resistant (Puerto Rican) strains of Aedes aegypti were explored in a round glass arena using fabrics treated with permethrin, etofenprox, deltamethrin, or DDT. Repellency was evaluated across several variables, including the time to first flight (TFF), number of landings (NOL), total flight time (TFT), and maximum surface contact (MSC), all by video analysis. Results from the Orlando strain indicated they were less likely than the Puerto Rican strain to tolerate tarsal contact with the treated fabrics. All four response variables indicated that the mosquito flight and landing behavior was most affected by pyrethroid resistance [knockdown resistance (kdr)] status. In other experiments, mosquitoes were surgically altered, with antennae ablated bilaterally, and these mosquitoes were more likely to stay on the treated surfaces for longer periods of time, irrespective of any chemical exposure. There were also differences in the responses to antennal ablation between the two strains of mosquitoes, indicating that resistance factors, probably kdr, influence the reactivity of mosquitoes to pyrethroid and DDT treatments, and that it was not completely negated by antennal ablation. These findings confirm the role of antennal olfactory components in the expression of excito-repellent behaviors, and also support the hypothesis that excito-repellency from pyrethroid/DDT exposure is probably due to a combination of sublethal neurotoxic excitation and interactions with the olfactory system. © 2023 Society of Chemical Industry.

Trapping and killing performance of a PermaNet 2.0 hybrid mosquito trapping bednet: an experimental hut evaluation

Background: Despite the huge global effort, there has been an increase in malaria morbidity and mortality in sub-Saharan Africa since 2015, from 212 million cases and 429,000 deaths in 2015 to 241 million cases and 627,000 deaths in 2020 mainly because of resistance to insecticide. Therefore, advancing innovative approaches is the only sustainable way to fight malaria. Methods: Taking advantage of the behavior of mosquitoes around the net, which is almost 70-90% concentrated on the roof, we have developed a two-compartment mosquito bednet, the so-called T-Net for mass mosquito trapping and killing. In the current study, we investigated in an experimental hut trial, the efficacy of trapping-long-lasting insecticide-treated nets (T-LLINs) against Anopheles gambiae s.l. in an insecticide resistance context. Five different arms have been considered in this study including three positive control arms e.g. PermaNet 2.0 LLIN, Tsara boost LLIN and Interceptor generation 2 (IG2) LLIN), one negative control arm using insecticide-free bednet, and one candidate arm using a hybrid-treated trapping bednet made with PermaNet 2.0 LLIN mounted with an insecticide-free compartment (T-LLIN). Results: The highest average daily mortality was recorded with the T-LLIN. In total, 678 mosquitoes were killed by T-LLIN among the 760 collected, i.e. 89.2%. Out of these, 317 were found in the trap compartment, representing 46.75% of mortality directly attributable to the mechanical effect of this net. This added value made it possible to quantify the increased in the killing effect that this net would have over the positive control arms: this would be 52% higher than the killing effect of PN2.0, 25.2% higher than that of Tsara boost and 23% higher than that of IG2. Conclusion: The current study shows potential to maximize the efficiency of the WHO-recommended LLINs by an addition of an insecticide-free trap compartment on top of the net.

How often are male mosquitoes attracted to humans?

Many mosquito species live close to humans where females feed on human blood. While male mosquitoes do not feed on blood, it has long been recognized that males of some species can be attracted to human hosts. To investigate the frequency of male mosquito attraction to humans, we conducted a literature review and human-baited field trials, as well as laboratory experiments involving males and females of three common Aedes species. Our literature review indicated that male attraction to humans is limited to a small number of species, including Ae. aegypti and Ae. albopictus. In our human-baited field collections, only 4 out of 13 species captured included males. In laboratory experiments, we found that male Ae. notoscriptus and Ae. vigilax showed no attraction to humans, while male Ae. aegypti exhibited persistent attraction for up to 30 min. Both male and female Ae. aegypti displayed similar preferences for different human subjects, suggesting that male Ae. aegypti respond to similar cues as females. Additionally, we found that mosquito repellents applied to human skin effectively repelled male mosquitoes. These findings shed light on mosquito behaviour and have implications for mosquito control programmes, particularly those involving the release or monitoring of the male mosquito population.

Host feeding preferences of malaria vectors in an area of low malaria transmission

Studying the behaviour and trophic preferences of mosquitoes is an important step in understanding the exposure of vertebrate hosts to vector-borne diseases. In the case of human malaria, transmission increases when mosquitoes feed more on humans than on other animals. Therefore, understanding the spatio-temporal dynamics of vectors and their feeding preferences is essential for improving vector control measures. In this study, we investigated the feeding behaviour of Anopheles mosquitoes at two sites in the Sudanian areas of Senegal where transmission is low following the implementation of vector control measures. Blood-fed mosquitoes were collected monthly from July to November 2022 by pyrethrum spray catches in sleeping rooms of almost all houses in Dielmo and Ndiop villages, and blood meals were identified as from human, bovine, ovine, equine and chicken by ELISA. Species from the An. gambiae complex were identified by PCR. The types and numbers of potential domestic animal hosts were recorded in each village. The Human Blood Index (HBI) and the Manly Selection Ratio (MSR) were calculated to determine whether hosts were selected in proportion to their abundance. Spatio-temporal variation in HBI was examined using the Moran’s index. A total of 1251 endophilic Anopheles females were collected in 115 bedrooms, including 864 blood fed females of 6 species. An. arabiensis and An. funestus were predominant in Dielmo and Ndiop, respectively. Of the 864 blood meals tested, 853 gave a single host positive result mainly on bovine, equine, human, ovine and chicken in decreasing order in both villages. Overall, these hosts were not selected in proportion to their abundance. The human host was under-selected, highlighting a marked zoophily for the vectors. Over time and space, the HBI were low with no obvious trend, with higher and lower values observed in each of the five months at different points in each village. These results highlight the zoophilic and exophagic behaviour of malaria vectors. This behaviour is likely to be a consequence of the distribution and use of LLINs in both villages and may increase risk of residual outdoor transmission. This underlines the need to study the feeding host profile of outdoor resting populations and how domestic animals may influence malaria epidemiology in order to tailor effective malaria vector control strategies in the two villages.

Determination of insecticide resistence associated insensitive acetylcholinesterase in Culex quinquefasciatus, Say,1823 (Diptera: Culicidae) collected in Yucatán, Mexico

Acetylcholinesterase is an enzyme whose main function is to terminate the transmission of nerve impulses in the cholinergic synapse in insects through the hydrolysis of acetylcholine. However, frequent applications of insecticides can select for individuals with an alteration in the enzyme and functional changes that result in an insensitivity to insecticides. In Mexico, the current strategy to combat insect vectors such as Culex quinquefasciatus is based mainly on the use of synthetic insecticides. The use of these chemicals in health and agricultural practices may also contribute to mosquito insensitivity to several groups of insecticides. Therefore, it is considered necessary to determine if there is any physiological mechanism associated with resistance. For this reason, the objective of this research was to identify if there is insensitivity of acetylcholinesterase to insecticides in Cx. quinquefasciatus populations, collected in urban and rural areas of the State of Yucatán, Mexico. Enzymatic tests were carried out with slight modifications to the established protocols. Areas were identified with mosquito populations showing acetylcholinesterase insensitivity to propoxur, a carbamate insecticide. We consider it important to determine the environmental factors that affect the behavior and response of mosquitoes following exposure to insecticides, and this knowledge could inform the design of efficient strategies in vector control programs.

Oviposition-Site Selection and Egg-Hatching of <em>Aedes aegypti</em> and <em>Aedes albopictus </em>(Diptera: Culicidae) in Leaf Infusions of Three Invasive Plants Found in Sri Lanka

Aedes aegypti and Aedes albopictus (Diptera: Culicidae) are the main human arboviral vectors in Sri Lanka. The oviposition behaviour of Aedes mosquitoes determines their survival and population dispersion. Using varying concentrations of plant leaf infusions is a vital technique in determining mosquito oviposition behaviour. The objective of this study was to evaluate the oviposition behavior and egg-hatching rate of Ae. aegypti and Ae. albopictus to three leaf infusions of three invasive plants found in Sri Lanka. The oviposition media were prepared using guinea grass (Megathyrsus maximus), alligator weed (Alternanthera philoxeroides) and Austroeupatorium (Austroeupatorium inulifolium). Each oviposition medium was prepared in four different concentrations: 25%, 50%, 75%, and 100%. The ovitraps were placed in a rubber plantation in Rathnapura district, Palmadulla, Sri Lanka in order to determine the oviposition site selection towards those leaf infusions. Different plant infusions have a significant effect on the oviposition and egg hatch rate of Ae. aegypti and Ae. albopictus. Accordingly, the highest number of eggs has been laid in ovitraps with a 25% concentration of M. maximus infusion. The ovitrap positivity index values were highest in A. philoxeroides at 25%, 50% and 75% concentrations; M. maximus at 25%, 50% and 100% concentrations; and A. inulifolium at 25% and 75% concentrations. Despite the type of infusion and concentration, the egg-hatching rate was highest on the second day of rearing. Ae. aegypti and Ae. albopictus responded differently to different plant infusions based on the plant species and biomass employed. The study shows that organic matter infusions composed of guinea grass improve trap effectiveness and attract females more effectively than ovitraps using aerated tap water. The use of leaf infusions of guinea grass at 25% concentration as an attractant in combination with lethal substances to control container-breeding mosquito species is suggested as a strategy in integrated pest management.

Effects of the source of information and knowledge of dengue fever on the mosquito control behavior of residents of border areas of Yunnan, China

BackgroundStrengthening the mosquito control measures undertaken by residents of an area where dengue fever is present can significantly decrease the spread of this disease. The aim of this study was to explore the effects of the source of information and knowledge of dengue fever on the mosquito control behavior of residents of areas at high risk of this disease to determine effective ways of enhancing this behavior.MethodsA survey was conducted via face-to-face interviews or questionnaires between March and May 2021 in three regions of the province of Yunnan, China. The survey included basic information about the respondents, the source(s) of their dengue fever information, the level of their dengue fever knowledge, and the measures they had implemented to control mosquitoes. Principal component analysis was used to extract the main components of the sources of information. Correlation analysis and structural equation analysis were used to explore the impact of the sources of information and residents’ dengue fever knowledge on their mosquito control behavior.ResultsPublicity achieved through mass media, including official WeChat accounts, magazines/newspapers, poster leaflets, television/radio and the Internet, had a direct effect on dengue fever knowledge and mosquito control behavior, and indirectly affected mosquito control behavior through dengue fever knowledge. Organized publicity campaigns, including information provided by medical staff and through community publicity, had a direct effect on dengue fever knowledge and indirectly affected mosquito control behavior through dengue fever knowledge. The residents’ level of dengue fever knowledge had a significant, positive, direct effect on their mosquito control behavior.ConclusionsMosquito control is an important measure for the prevention and control of outbreaks of dengue fever. An effective source of information can improve the level of dengue fever knowledge among residents and thus enhance their mosquito control behavior.Graphical

Distribution of mosquito species in various agro-ecological zones of Punjab

BackgroundThe presence and behavior of mosquitoes in various agro-ecological zones of Punjab are influenced by a combination of seasonal and topographical patterns, cropping schemes, and human settlement. These modifications have a significant impact on the occurrence of diseases. Therefore, determining the distribution of these species could help in halting their spread and disease outbreaks. MethodsUnder these prevailing conditions, surveillance studies were carried out at six zones of Punjab, to know the distribution of mosquitoes. Samples were collected in various seasons (once in winter and rainy seasons, and twice in summer), from all possible habitats, having stagnant water. ResultsOut of twenty-four (24) recorded species, three were included in Anophelinae and Culicinae, eleven from tribe Aedini, eight from Culicini and one each from Ficulbiini and Mansoniini. Sampling was done from 91 m (Ahmed Pur East) elevation to 1759 m (Fort Monroe). High and diversified population was recorded during rainy season. The Anopheline mosquitoes were found in rural as well as urban habitats, including rainfed, wet mountains and irrigated plains whereas Aedine species were confined to northern irrigated plains and mostly recorded from Changa Manga National Forest. Culicine species were more diversified and abundant, in all seasons. However, M. chamberlaini was collected from urban (rainfed lands) and rural (northern irrigated plains) settings. C. crassipes was recorded only from rainfed lands. ConclusionTwenty-four mosquito species from the Anophelinae and Culicinae subfamilies were observed in the current investigation. Anophelinae subfamily contained three species. Eleven species of Culicinae belonged to the tribe Aedini, eight to the Culicini, and one each to the Mansoniini and Ficalbiini.

Insecticide resistance of Aedes aegypti in Indonesia: a systematic review

In Indonesia, dengue hemorrhagic fever (DHF) continues to be an issue. Although there have been fewer dengue infections in the past three years, many areas of Indonesia remain dengue endemic. Insecticide use is one DHF prevention and control method that has been used for a long time. Long-term usage of insecticides can cause the vector, Aedes aegypti, to develop resistance. Insecticide resistance to Aedes aegypti in Indonesia was the focus of this study's analysis of the literature review. A systematic review using keywords based on population, interest and context (PICo) was employed in the study strategy. The databases used to find the publications were ScienceDirect, ProQuest, PubMed, Google Scholar, and Garuda from 2018 to 2022. Hence, 40 papers out of the 6,429 total articles were relevant and should be reviewed and analyzed. According to an analysis of the paper, it was discovered that Aedes aegypti mosquitoes are resistant to insecticides of the pyrethroid and organophosphate classes in various parts of Indonesia. However, it was discovered that several regions were both tolerant of and vulnerable to pyrethroids and organophosphates. If insecticides are to be utilized intolerant and vulnerable locations, monitoring and evaluation of their usage must be done, and a strategy of varying insecticide kinds and dosages and boosting community empowerment toward mosquito nest elimination behaviour must be implemented.

Efficacy of the spatial repellent product Mosquito Shield™ against wild pyrethroid-resistant Anopheles arabiensis in south-eastern Tanzania

BackgroundSpatial repellents that create airborne concentrations of an active ingredient (AI) within a space offer a scalable solution to further reduce transmission of malaria, by disrupting mosquito behaviours in ways that ultimately lead to reduced human-vector contact. Passive emanator spatial repellents can protect multiple people within the treated space and can last for multiple weeks without the need for daily user touchpoints, making them less intrusive interventions. They may be particularly advantageous in certain use cases where implementation of core tools may be constrained, such as in humanitarian emergencies and among mobile at-risk populations. The purpose of this study was to assess the efficacy of Mosquito Shield™ deployed in experimental huts against wild, free-flying, pyrethroid-resistant Anopheles arabiensis mosquitoes in Tanzania over 1 month.MethodsThe efficacy of Mosquito Shield™ transfluthrin spatial repellent in reducing mosquito lands and blood-feeding was evaluated using 24 huts: sixteen huts were allocated to Human Landing Catch (HLC) collections and eight huts to estimating blood-feeding. In both experiments, half of the huts received no intervention (control) while the remaining received the intervention randomly allocated to huts and remained fixed for the study duration. Outcomes measured were mosquito landings, blood-fed, resting and dead mosquitoes. Data were analysed by multilevel mixed effects regression with appropriate dispersion and link function accounting for volunteer, hut and day.ResultsLanding inhibition was estimated to be 70% (57–78%) [IRR 0.30 (95% CI 0.22–0.43); p < 0.0001] and blood-feeding inhibition was estimated to be 69% (56–79%) [IRR 0.31 (95% CI 0.21–0.44; p < 0.0001] There was no difference in the protective efficacy estimates of landing and blood-feeding inhibition [IRR 0.98 (95% CI 0.53–1.82; p = 0.958].ConclusionsThis study demonstrated that Mosquito Shield™ was efficacious against a wild pyrethroid-resistant strain of An. arabiensis mosquitoes in Tanzania for up to 1 month and could be used as a complementary or stand-alone tool where gaps in protection offered by core malaria vector control tools exist. HLC is a suitable technique for estimating bite reductions conferred by spatial repellents especially where direct blood-feeding measurements are not practical or are ethically limited.

Investigation on key aspects of mating biology in the mosquito Aedes koreicus.

Aedes koreicus Edwards, 1917 (Hulecoetomyia koreica) is a mosquito (Diptera: Culicidae) from Northeast Asia with a rapidly expanding presence outside its original native range. Over the years, the species has been discovered in several new countries, either spreading after first introduction or remaining localised to limited areas. Notably, recent studies have demonstrated the ability of the species to transmit zoonotic parasites and viruses both in the field and in laboratory settings. Combined with its invasive potential, the possible role of Ae. koreicus in pathogen transmission highlights the public health risks resulting from its invasion. In this study, we used a recently established population from Italy to investigate aspects of biology that influence reproductive success in Ae. koreicus: autogeny, mating behaviour, mating disruption by the sympatric invasive species Aedes albopictus Skuse, 1894, and the presence of the endosymbiont Wolbachia pipientis Hertig, 1936. Our laboratory population did not exhibit autogenic behaviour and required a bloodmeal to complete its ovarian cycle. When we exposed Ae. koreicus females to males of Ae. albopictus, we observed repeated attempts at insemination and an aggressive, disruptive mating behaviour initiated by male Ae. albopictus. Despite this, no sperm was identified in Ae. koreicus spermathecae. Wolbachia, an endosymbiotic bacterium capable of influencing mosquito reproductive behaviour, was not detected in this Ae. koreicus population and, therefore, had no effect on Ae. koreicus reproduction.

Single-Sensillum Taste Recordings in Mosquitoes.

In insects, gustatory neurons sense chemicals upon contact and directly inform many behaviors critical for survival and reproduction, including biting, feeding, mating, and egg laying. However, the taste sensory system is underexplored in many anthropophilic disease vectors such as mosquitoes, which acquire and transmit human pathogens during blood feeding from human hosts. This results in a big gap in vector biology-the study of organisms that spread disease by transmitting pathogens-because insect vectors closely interact with humans while selecting suitable individuals and appropriate bite sites for blood meals. Human sweat and skin-associated chemistries are rich in nonvolatile compounds that can be sensed by the mosquito's taste system when she lands on the skin. Taste sensory units, called sensilla, are distributed in many organs across the mosquito body, including the mouthparts, legs, and ovipositors (female-specific structures used to lay eggs). Each sensillum is innervated by as many as five taste neurons, which allow detection and discrimination between various tastants such as water, sugars, salts, amino acids, and plant-derived compounds that taste bitter to humans. Single-sensillum recordings provide a robust way to survey taste responsiveness of individual sensilla to various diagnostic and ecologically relevant chemicals. Such analyses are of immense value for understanding links between mosquito taste responses and behaviors to specific chemical cues and can provide insights into why mosquitoes prefer certain hosts. The results can also aid development of strategies to disrupt close-range mosquito-human interactions to control disease transmission. Here we describe a protocol that is curated for electrophysiological recordings from taste sensilla in mosquitoes and sure to yield exciting results for the field.

Quantification of Anopheles gambiae Olfactory Preferences under Semi-Field Conditions.

Anopheles gambiae is a highly anthropophilic (human-preferring) malaria vector that prefers to blood feed frequently and selectively on humans. This mosquito species exhibits a strong innate olfactory preference to seek out human scent over other animals, and certain humans over others-key behavioral traits with the potential to drive heterogeneity in biting risk and malaria transmission. Here, we describe the application of a large-scale, semi-field system in Zambia for the quantification of An. gambiae olfactory preferences toward whole body odor sourced from individual humans. We detail steps for modifying one-person canvas tents to duct odor from sleeping humans into a central, semi-field flight cage arena that is securely screened. Using this system, we describe a protocol to perform two-choice olfactory preference assays with two human volunteers using laboratory-reared An. gambiae and odor-guided thermotaxis assays that leverage infrared video tracking to quantify mosquito landings on heated targets baited with each body odor sample. This multichoice olfactory preference assay has the potential to be applied with expanded cohorts of humans to define the chemosensory basis of An. gambiae host preference and interindividual differences in human attractiveness to mosquitoes and to be used to quantify the effects of protective measures such as personal and spatial repellents on mosquito landing behavior.

Heritability of biting time behaviours in the major African malaria vector Anopheles arabiensis

BackgroundThe use of insecticide-treated nets for malaria control has been associated with shifts in mosquito vector feeding behaviour including earlier and outdoor biting on humans. The relative contribution of phenotypic plasticity and heritability to these behavioural shifts is unknown. Elucidation of the mechanisms behind these shifts is crucial for anticipating impacts on vector control.MethodsA novel portable semi-field system (PSFS) was used to experimentally measure heritability of biting time in the malaria vector Anopheles arabiensis in Tanzania. Wild An. arabiensis from hourly collections using the human landing catch (HLC) method were grouped into one of 3 categories based on their time of capture: early (18:00–21:00), mid (22:00–04:00), and late (05:00–07:00) biting, and placed in separate holding cages. Mosquitoes were then provided with a blood meal for egg production and formation of first filial generation (F1). The F1 generation of each biting time phenotype category was reared separately, and blood fed at the same time as their mothers were captured host-seeking. The resultant eggs were used to generate the F2 generation for use in heritability assays. Heritability was assessed by releasing F2 An. arabiensis into the PSFS, recording their biting time during a human landing catch and comparing it to that of their F0 grandmothers.ResultsIn PSFS assays, the biting time of F2 offspring (early: 18:00–21:00, mid: 22:00–04:00 or late: 05:00–07:00) was significantly positively associated with that of their wild-caught F0 grandmothers, corresponding to an estimated heritability of 0.110 (95% CI 0.003, 0.208). F2 from early-biting F0 were more likely to bite early than F2 from mid or late-biting F0. Similarly, the probability of biting late was higher in F2 derived from mid and late-biting F0 than from early-biting F0.ConclusionsDespite modest heritability, our results suggest that some of the variation in biting time is attributable to additive genetic variation. Selection can, therefore, act efficiently on mosquito biting times, highlighting the need for control methods that target early and outdoor biting mosquitoes.

Ecological and Behavioral Factors to Aid in Modelling Environmental Mosquito Control &amp; to Design Larval Robots

Abstract: The anatomical location of human pathogens in mosquitoes ranging from Plasmodium, Wucheriria, flavivirus and other viruses are in salivary glands of the mosquitoes which is important for transmission. Further Dengue virus (DENV) is known to exist from egg stage to adult stage in mosquitoes. The other important fact in mosquito borne transmission is the blood meal that renders them capable of egg laying. Hence hormonal, ecological, behavioral control of mosquitoes with environmental thyroxine, larval behavior pattern, predatory dragonfly larva, air turbulence g-force was studied. Environmental contamination of shallow water bodies with animal urine could introduce thyroxine in water bodies where mosquito larva is breeding. Modeling such an outcome, the results indicated significance influence of thyroxine on mosquito larva resulting in alteration of eclosed mosquito size, weight, sex ratio, antennal hairs. The second mode of ecological control with predatory dragonfly larva in water bodies modeled with introduced coal resulted in excellent mosquito larval control. The third mode of using air turbulence g-force (with home appliances like ceiling fan) induced mosquito control was also found to be effective in reducing the no of hatched larva when the adult mosquitoes are exposed to g-force but it did increase the longevity of male mosquitoes. Further based on mosquito larval behavior pattern, it was observed that mosquito larva does have the tendency to be social and tend to meet each other in water bodies that can be used for mosquito control by design of larval robots that can deliver larvicidal compounds on one-to-one basis.

MicroRNA Expression Prior to Biting in a Vector Mosquito Anticipates Physiological Processes Related to Energy Utilization, Reproduction and Immunity.

Understanding the molecular and physiological processes underlying biting behavior in vector mosquitoes has important implications for developing novel strategies to suppress disease transmission. Here, we conduct small-RNA sequencing and qRT-PCR to identify differentially expressed microRNAs (miRNAs) in the head tissues of two subspecies of Culex pipiens that differ in biting behavior and the ability to produce eggs without blood feeding. We identified eight differentially expressed miRNAs between biting C. pipiens pipiens (Pipiens) and non-biting C. pipiens molestus (Molestus); six of these miRNAs have validated functions or predicted targets related to energy utilization (miR8-5-p, miR-283, miR-2952-3p, miR-1891), reproduction (miR-1891), and immunity (miR-2934-3p, miR-92a, miR8-5-p). Although miRNAs regulating physiological processes associated with blood feeding have previously been shown to be differentially expressed in response to a blood meal, our results are the first to demonstrate differential miRNA expression in anticipation of a blood meal before blood is actually imbibed. We compare our current miRNA results to three previous studies of differential messenger RNA expression in the head tissues of mosquitoes. Taken together, the combined results consistently show that biting mosquitoes commit to specific physiological processes in anticipation of a blood meal, while non-biting mosquitoes mitigate these anticipatory costs.

Odour-mediated oviposition site selection in Aedes aegypti depends on aquatic stage and density

BackgroundOlfaction plays an important role in the selection and assessment of oviposition sites by mosquitoes. Volatile organic compounds (VOCs) associated with potential breeding sites affect the behaviour of gravid mosquitoes, with VOCs from aquatic stages of conspecific mosquitoes influencing and regulating oviposition. The purpose of this study was to conduct a systematic analysis of the behavioural response of gravid Aedes aegypti to conspecific aquatic stage-conditioned water, to identify the associated bioactive VOCs and to determine how blends of these VOCs regulate oviposition site selection and stimulate egg-laying.MethodsUsing a multi-choice olfactory oviposition assay, controlling for other sensory modalities, the responses of individual females to water conditioned with different densities of conspecific aquatic stages were assessed. The conditioned water samples from the most preferred density of each aquatic stage were subsequently compared to each other using the same oviposition assay and analysed using an analysis of variance (ANOVA) followed by a Tukey post-hoc test. Using combined gas chromatography and electroantennographic detection or mass spectrometry, bioactive VOCs from the preferred density of each aquatic stage were identified. Synthetic blends were prepared based on the identified ratios of bioactive VOCs in the aquatic stages, and then tested to determine the oviposition choice of Ae. aegypti in a dose-dependent manner, against a solvent control, using a dual-choice assay. This dataset was analysed using nominal logistic regression followed by an odds ratio comparison.ResultsGravid Ae. aegypti responded stage- and density-dependently to water conditioned with eggs, second- and fourth-instar larvae, and pupal exuviae, but not to water conditioned with pupae alone. Multi-choice assays demonstrated that gravid mosquitoes preferred to oviposit in water conditioned with fourth-instar larvae, over the other aquatic stage-conditioned water. Gravid Ae. aegypti were attracted, and generally stimulated, to oviposit in a dose-dependent manner to the individual identified synthetic odour blends for the different aquatic stages.ConclusionsIntraspecific VOCs regulate oviposition site selection in Ae. aegypti in a stage- and density-dependent manner. We discuss the need for further studies to evaluate the identified synthetic blends to modulate the odour-mediated oviposition of Ae. aegypti under field conditions.Graphical

Flight behaviour monitoring and quantification of aedes aegypti using convolution neural network.

Mosquito-borne diseases cause a huge burden on public health worldwide. The viruses that cause these diseases impact the behavioural traits of mosquitoes, including locomotion and feeding. Understanding these traits can help in improving existing epidemiological models and developing effective mosquito traps. However, it is difficult to understand the flight behaviour of mosquitoes due to their small sizes, complicated poses, and seemingly random moving patterns. Currently, no open-source tool is available that can detect and track resting or flying mosquitoes. Our work presented in this paper provides a detection and trajectory estimation method using the Mask RCNN algorithm and spline interpolation, which can efficiently detect mosquitoes and track their trajectories with higher accuracy. The method does not require special equipment and works excellently even with low-resolution videos. Considering the mosquito size, the proposed method's detection performance is validated using a tracker error and a custom metric that considers the mean distance between positions (estimated and ground truth), pooled standard deviation, and average accuracy. The results showed that the proposed method could successfully detect and track the flying (≈ 96% accuracy) as well as resting (100% accuracy) mosquitoes. The performance can be impacted in the case of occlusions and background clutters. Overall, this research serves as an efficient open-source tool to facilitate further examination of mosquito behavioural traits.