Sugar feeding protects against arboviral infection by enhancing gut immunity in the mosquito vector Aedes aegypti

As mosquito females require a blood meal to reproduce, they can act as vectors of numerous pathogens, such as arboviruses (e.g. Zika, dengue and chikungunya viruses), which constitute a substantial worldwide public health burden. In addition to blood meals, mosquito females can also take sugar meals to get carbohydrates for their energy reserves. It is now recognised that diet is a key regulator of health and disease outcome through interactions with the immune system. However, this has been mostly studied in humans and model organisms. So far, the impact of sugar feeding on mosquito immunity and in turn, how this could affect vector competence for arboviruses has not been explored. Here, we show that sugar feeding increases and maintains antiviral immunity in the digestive tract of the main arbovirus vector Aedes aegypti. Our data demonstrate that the gut microbiota does not mediate the sugar-induced immunity but partly inhibits it. Importantly, sugar intake prior to an arbovirus-infected blood meal further protects females against infection with arboviruses from different families. Sugar feeding blocks arbovirus initial infection and dissemination from the gut and lowers infection prevalence and intensity, thereby decreasing the transmission potential of female mosquitoes. Finally, we show that the antiviral role of sugar is mediated by sugar-induced immunity. Overall, our findings uncover a crucial role of sugar feeding in mosquito antiviral immunity which in turn decreases vector competence for arboviruses. Since Ae. aegypti almost exclusively feed on blood in some natural settings, our findings suggest that this lack of sugar intake could increase the spread of mosquito-borne arboviral diseases.     

Effects of blood meal sources on the biological characteristics of Aedes aegypti and Culex pipiens (Diptera: Culicidae)

Mosquitoes transmit many diseases to humans and animals e.g., malaria, yellow fever, dengue, filariasis and encephalitis. The fundamental target of this search was to study the effect of three different blood meal sources (human; rabbit and pigeon) on some biological and behavioral properties of Aedes aegypti and Culex pipiens. The results have assured that the females of the mosquito Ae. aegypti that were fed on human blood meal has registered the highest feeding activity from feeding on the blood meal whereas the females of the other mosquito Cx. pipiens have shown the highest feeding activity after being fed on pigeons when compared with its feeding on other factors. The results have shown non-significant variation in the average time necessary to digest the blood meal on both mosquito species Ae. aegypti and Cx. pipiens that were fed on vertebrate hosts under laboratory conditions. Furthermore, results assured that the difference in blood meal sources has yielded distinct variation in the reproductive capacity and efficiency of both female mosquitoes under investigation where both species Ae. aegypti and Cx. pipiens already fed on human blood meal have yielded a pronounced distinctive increase in egg production (oviposition) when compared with females that were fed on pigeon or rabbit blood meal respectively. Moreover, feeding of the female mosquitoes under lab conditions on different blood meal sources did not affect the level of the hatching eggs that were laid by both mosquito females.     

Vertebrate-Aedes aegypti and Culex quinquefasciatus (Diptera)-arbovirus transmission networks: Non-human feeding revealed by meta-barcoding and next-generation sequencing

BackgroundAedes aegypti mosquito-borne viruses including Zika (ZIKV), dengue (DENV), yellow fever (YFV), and chikungunya (CHIKV) have emerged and re-emerged globally, resulting in an elevated burden of human disease. Aedes aegypti is found worldwide in tropical, sub-tropical, and temperate areas. The characterization of mosquito blood meals is essential to understand the transmission dynamics of mosquito-vectored pathogens.Methodology/principal findingsHere, we report Ae. aegypti and Culex quinquefasciatus host feeding patterns and arbovirus transmission in Northern Mexico using a metabarcoding-like approach with next-generation deep sequencing technology. A total of 145 Ae. aegypti yielded a blood meal analysis result with 107 (73.8%) for a single vertebrate species and 38 (26.2%) for two or more. Among the single host blood meals for Ae. aegypti, 28.0% were from humans, 54.2% from dogs, 16.8% from cats, and 1.0% from tortoises. Among those with more than one species present, 65.9% were from humans and dogs. For Cx. quinquefasciatus, 388 individuals yielded information with 326 (84%) being from a single host and 63 (16.2%) being from two or more hosts. Of the single species blood meals, 77.9% were from dogs, 6.1% from chickens, 3.1% from house sparrows, 2.4% from humans, while the remaining 10.5% derived from other 12 host species. Among those which had fed on more than one species, 11% were from dogs and humans, and 89% of other host species combinations. Forage ratio analysis revealed dog as the most over-utilized host by Ae. aegypti (= 4.3) and Cx. quinquefasciatus (= 5.6) and the human blood index at 39% and 4%, respectively. A total of 2,941 host-seeking female Ae. aegypti and 3,536 Cx. quinquefasciatus mosquitoes were collected in the surveyed area. Of these, 118 Ae. aegypti pools and 37 Cx. quinquefasciatus pools were screened for seven arboviruses (ZIKV, DENV 1–4, CHIKV, and West Nile virus (WNV)) using qRT-PCR and none were positive (point prevalence = 0%). The 95%-exact upper limit confidence interval was 0.07% and 0.17% for Ae. aegypti and Cx. quinquefasciatus, respectivelyConclusions/significanceThe low human blood feeding rate in Ae. aegypti, high rate of feeding on mammals by Cx. quinquefasciatus, and the potential risk to transmission dynamics of arboviruses in highly urbanized areas of Northern Mexico is discussed.     

Assessment of fitness and vector competence of a New Caledonia wMel Aedes aegypti strain before field-release

BackgroundBiological control programs involving Wolbachia-infected Aedes aegypti are currently deployed in different epidemiological settings. New Caledonia (NC) is an ideal location for the implementation and evaluation of such a strategy as the only proven vector for dengue virus (DENV) is Ae. aegypti and dengue outbreaks frequency and severity are increasing. We report the generation of a NC Wolbachia-infected Ae. aegypti strain and the results of experiments to assess the vector competence and fitness of this strain for future implementation as a disease control strategy in Noumea, NC.Methods/principal findingsThe NC Wolbachia strain (NC-wMel) was obtained by backcrossing Australian AUS-wMel females with New Caledonian Wild-Type (NC-WT) males. Blocking of DENV, chikungunya (CHIKV), and Zika (ZIKV) viruses were evaluated via mosquito oral feeding experiments and intrathoracic DENV challenge. Significant reduction in infection rates were observed for NC-wMel Ae. aegypti compared to WT Ae. aegypti. No transmission was observed for NC-wMel Ae. aegypti. Maternal transmission, cytoplasmic incompatibility, fertility, fecundity, wing length, and insecticide resistance were also assessed in laboratory experiments. Ae. aegypti NC-wMel showed complete cytoplasmic incompatibility and a strong maternal transmission. Ae. aegypti NC-wMel fitness seemed to be reduced compared to NC-WT Ae. aegypti and AUS-wMel Ae. aegypti regarding fertility and fecundity. However further experiments are required to assess it accurately.Conclusions/significanceOur results demonstrated that the NC-wMel Ae. aegypti strain is a strong inhibitor of DENV, CHIKV, and ZIKV infection and prevents transmission of infectious viral particles in mosquito saliva. Furthermore, our NC-wMel Ae. aegypti strain induces reproductive cytoplasmic incompatibility with minimal apparent fitness costs and high maternal transmission, supporting field-releases in Noumea, NC.     

Vector competence of Aedes aegypti from Havana,Cuba, for dengue virus type 1, chikungunya,and Zika viruses

BackgroundLike many countries from the Americas, Cuba is threatened by Aedes aegypti-associated arboviruses such as dengue (DENV), Zika (ZIKV), and chikungunya (CHIKV) viruses. Curiously, when CHIKV was actively circulating in the region in 2013–2014, no autochthonous transmission of this virus was detected in Havana, Cuba, despite the importation of chikungunya cases into this city. To investigate if the transmission ability of local mosquito populations could explain this epidemiological scenario, we evaluated for the first time the vector competence of two Ae. aegypti populations (Pasteur and Párraga) collected from Havana for dengue virus type 1 (DENV-1), CHIKV, and ZIKV.Methodology/Principal findingsMosquito populations were fed separately using blood containing ZIKV, DENV-1, or CHIKV. Infection, dissemination, and transmission rates, were estimated at 3 (exclusively for CHIKV), 7, and 14 days post exposure (dpe) for each Ae. aegypti population-virus combination. Both mosquito populations were susceptible to DENV-1 and ZIKV, with viral infection and dissemination rates ranging from 24–97% and 6–67% respectively. In addition, CHIKV disseminated in both populations and was subsequently transmitted. Transmission rates were low (<30%) regardless of the mosquito population/virus combination and no ZIKV was detected in saliva of females from the Pasteur population at any dpe.Conclusions/SignificanceOur study demonstrated the ability of Ae. aegypti from Cuba to transmit DENV, ZIKV, and CHIKV. These results, along with the widespread distribution and high abundance of this species in the urban settings throughout the island, highlight the importance of Ae. aegypti control and arbovirus surveillance to prevent future outbreaks.     

Sex before or after blood feeding: Mating activities of Aedes aegypti males under conditions of different densities and female blood feeding opportunities

Blood feeding and mating are critical behaviors that regulate both mosquito population maintenance and disease transmission. However, our understanding of mosquito mating systems remains incomplete. One of the most critical issues is a lack of understanding regarding how and where males and females encounter one another. This study was performed to investigate changes in key mating behaviors of Ae. aegypti relative to female blood feeding opportunities, taking into account male density. We compared courtship latency and copulation activity between single and pooled males in a range of assays performed in the presence or absence of a blood source and after blood feeding. The time taken by grouped males to initiate courtship in the presence of a host was much shorter than that in single males. There was no significant difference in courtship latency between pooled and single males in the absence of a blood source or after blood feeding. At low male density, the presence of the host and blood meal ingestion provided better conditions for copulation. At high male density, however, copulation activity was decreased after blood feeding, but remained high regardless of the presence or absence of the host. In addition to providing insight into the mating ecology of Aedes aegypti, this study indicated that the presence of a blood source influences how males encounter and copulate with females. The observation that copulation activity decreases after blood feeding when males are numerous provides new avenues for improving mass release programs of sterile mosquitoes.     

Efficacy of targeted indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-resistant Aedes aegypti

BackgroundThere is an increased need to mitigate the emergence of insecticide resistance and incorporate new formulations and modes of application to control the urban vector Aedes aegypti. Most research and development of insecticide formulations for the control of Ae. aegypti has focused on their peridomestic use as truck-mounted ULV-sprays or thermal fogs despite the widespread knowledge that most resting Ae. aegypti are found indoors. A recent modification of indoor residual spraying (IRS), termed targeted IRS (TIRS) works by restricting applications to 1.5 m down to the floor and on key Ae. aegypti resting sites (under furniture). TIRS also opens the possibility of evaluating novel residual insecticide formulations currently being developed for malaria IRS.MethodsWe evaluated the residual efficacy of chlorfenapyr, formulated as Sylando 240SC, for 12 months on free-flying field-derived pyrethroid-resistant Ae. aegypti using a novel experimental house design in Merida, Mexico. On a monthly basis, 600 female Ae. aegypti were released into the houses and left indoors with access to sugar solution for 24 hours. After the exposure period, dead and alive mosquitoes were counted in houses treated with chlorfenapyr as well as untreated control houses to calculate 24-h mortality. An evaluation for these exposed cohorts of surviving mosquitoes was extended up to seven days under laboratory conditions to quantify “delayed mortality”.ResultsMean acute (24-h) mortality of pyrethroid-resistant Ae. aegypti ranged 80–97% over 5 months, dropping below 30% after 7 months post-TIRS. If delayed mortality was considered (quantifying mosquito mortality up to 7 days after exposure), residual efficacy was above 90% for up to 7 months post-TIRS application. Generalized Additive Mixed Models quantified a residual efficacy of chlorfenapyr of 225 days (ca. 7.5 months).ConclusionsChlorfenapyr represents a new option for TIRS control of Ae. aegypti in urban areas, providing a highly-effective time of protection against indoor Ae. aegypti females of up to 7 months.     

The effects of exposure to pyriproxyfen and predation on Zika virus infection and transmission in Aedes aegypti

Zika virus (ZIKV) is an emerging mosquito-borne pathogen that can cause global public health threats. In the absence of effective antiviral medications, prevention measures rely largely on reducing the number of adult mosquito vectors by targeting juvenile stages. Despite the importance of juvenile mosquito control measures in reducing adult population size, a full understanding of the effects of these measures in determining mosquito phenotypic traits and in mosquito-arbovirus interactions is poorly understood. Pyriproxyfen is a juvenile hormone analog that primarily blocks adult emergence, but does not cause mortality in larvae. This mechanism has the potential to work in combination with other juvenile sources of mortality in nature such as predation to affect mosquito populations. Here, we experimentally evaluated the effects of juvenile exposure to pyriproxyfen and predatory mosquito Toxorhynchites rutilus on Aedes aegypti phenotypes including susceptibility to ZIKV infection and transmission. We discovered that combined effects of pyriproxyfen and Tx. rutilus led to higher inhibition of adult emergence in Ae. aegypti than observed in pyriproxyfen or Tx. rutilus treatments alone. Adult body size was larger in treatments containing Tx. rutilus and in treatments mimicking the daily mortality of predation compared to control or pyriproxyfen treatments. Susceptibility to infection with ZIKV in Ae. aegypti was reduced in predator treatment relative to those exposed to pyriproxyfen. Disseminated infection, transmission, and titers of ZIKV in Ae. aegypti were similar in all treatments relative to controls. Our data suggest that the combination of pyriproxyfen and Tx. rutilus can inhibit adult Ae. aegypti emergence but may confer a fitness advantage in survivors and does not inhibit their vector competence for ZIKV relative to controls. Understanding the ultimate consequences of juvenile mosquito control measures on subsequent adults’ ability to transmit pathogens is critical to fully understand their overall impacts.     

A survival and reproduction trade-off is resolved in accordance with resource availability by virgin female mosquitoes

The first 2-4 days after an Anopheles gambiae female mosquito emerges are critical to her survival and reproductive success. Yet, the order of behavioural events (mating, sugar feeding, blood feeding) during this time has received little attention. We discovered that among female cohorts sampled from emergence, sugar feeding had a higher probability than blood feeding of occurring first, and mating rarely occurred before a meal was taken. The night after emergence, 48% of females fed on sugar in mesocosms, and 25% fed on human blood; in the absence of sugar, 49% of females fed on human blood. After 5 days, 39% of the sugar-supplied females had blood fed and mated, and were fructose negative, whereas only 8% of the sugar-denied females had both blood fed and mated by this time. The model that best explained the transitions suggests that females made use of two distinct behavioural pathways, the most common one being to sugar-feed, then mate, and then seek blood. Other females sought blood first, then mated, and forwent a sugar meal. Lipid levels were higher in females with access to sugar than in females without access to sugar, particularly for those in later gonotrophic stages, while glycogen levels in the sugar-supplied group were higher throughout. In single-night experiments with females having had access to sucrose since emergence, those given a blood meal 1 day before spending a night with males had higher insemination rates than those not receiving the blood meal. These results indicate that the trade-off between survival and immediate reproduction is resolved by young adult females in accordance with availability of resources and gonotrophic state.     

Wolbachia infection in Aedes aegypti mosquitoes alters blood meal excretion and delays oviposition without affecting trypsin activity

Blood feeding in Aedes aegypti is essential for reproduction, but also permits the mosquito to act as a vector for key human pathogens such as the Zika and dengue viruses. Wolbachia pipientis is an endosymbiotic bacterium that can manipulate the biology of Aedes aegypti mosquitoes, making them less competent hosts for many pathogens. Yet while Wolbachia affects other aspects of host physiology, it is unclear whether it influences physiological processes associated with blood meal digestion. To that end, we examined the effects of wMel Wolbachia infection in Ae. aegypti, on survival post-blood feeding, blood meal excretion, rate of oviposition, expression levels of key genes involved in oogenesis, and activity levels of trypsin blood digestion enzymes. We observed that wMel infection altered the rate and duration of blood meal excretion, delayed the onset of oviposition and was associated with a greater number of eggs being laid later. wMel-infected Ae. aegypti also had lower levels of key yolk protein precursor genes necessary for oogenesis. However, all of these effects occurred without a change in trypsin activity. These results suggest that Wolbachia infection may disrupt normal metabolic processes associated with blood feeding and reproduction in Ae. aegypti.     

Sexual selection theory meets disease vector control: Testing harmonic convergence as a “good genes” signal in Aedes aegypti mosquitoes

BackgroundThe mosquito Aedes aegypti is a medically important, globally distributed vector of the viruses that cause dengue, yellow fever, chikungunya, and Zika. Although reproduction and mate choice are key components of vector population dynamics and control, our understanding of the mechanisms of sexual selection in mosquitoes remains poor. In “good genes” models of sexual selection, females use male cues as an indicator of both mate and offspring genetic quality. Recent studies in Ae. aegypti provide evidence that male wingbeats may signal aspects of offspring quality and performance during mate selection in a process known as harmonic convergence. However, the extent to which harmonic convergence may signal overall inherent quality of mates and their offspring remains unknown.Methodology/Principal findingsTo examine this, we measured the relationship between acoustic signaling and a broad panel of parent and offspring fitness traits in two generations of field-derived Ae. aegypti originating from dengue-endemic field sites in Thailand. Our data show that in this population of mosquitoes, harmonic convergence does not signal male fertility, female fecundity, or male flight performance traits, which despite displaying robust variability in both parents and their offspring were only weakly heritable.Conclusions/SignificanceTogether, our findings suggest that vector reproductive control programs should treat harmonic convergence as an indicator of some, but not all aspects of inherent quality, and that sexual selection likely affects Ae. aegypti in a trait-, population-, and environment-dependent manner.     

Rôle of male accessory gland substance in the regulation of blood intake by mosquitoes

The presence of male accessory gland substance during mating is shown to increase the blood intake in the adult female Aedes aegypti and Culex pipiens fatigans. Females mated with males whose accessory glands were surgically removed took significantly less blood than females mated with normal males. However, females mated with males whose seminal vesicles were surgically removed took as much blood as the controls.     

Starvation at the larval stage increases the vector competence of Aedes aegypti females for Zika virus

Aedes aegypti is the primary vector of Zika virus (ZIKV), a flavivirus which typically presents itself as febrile-like symptoms in humans but can also cause neurological and pregnancy complications. The transmission cycle of mosquito-borne arboviruses such as ZIKV requires that various key tissues in the female mosquito get productively infected with the virus before the mosquito can transmit the virus to another vertebrate host. Following ingestion of a viremic blood-meal from a vertebrate, ZIKV initially infects the midgut epithelium before exiting the midgut after blood-meal digestion to disseminate to secondary tissues including the salivary glands. Here we investigated whether smaller Ae. aegypti females resulting from food deprivation as larvae exhibited an altered vector competence for blood-meal acquired ZIKV relative to larger mosquitoes. Midguts from small ‘Starve’ and large ‘Control’ Ae. aegypti were dissected to visualize by transmission electron microscopy (TEM) the midgut basal lamina (BL) as physical evidence for the midgut escape barrier showing Starve mosquitoes with a significantly thinner midgut BL than Control mosquitoes at two timepoints. ZIKV replication was inhibited in Starve mosquitoes following intrathoracic injection of virus, however, Starve mosquitoes exhibited a significantly higher midgut escape and population dissemination rate at 9 days post-infection (dpi) via blood-meal, with more virus present in saliva and head tissue than Control by 10 dpi and 14 dpi, respectively. These results indicate that Ae. aegypti developing under stressful conditions potentially exhibit higher midgut infection and dissemination rates for ZIKV as adults, Thus, variation in food intake as larvae is potentially a source for variable vector competence levels of the emerged adults for the virus.     

Competition for Amino Acids Between Wolbachia and the Mosquito Host,Aedes aegypti

The endosymbiont Wolbachia represents a promising method of dengue control, as it reduces the ability of the primary vector, the mosquito Aedes aegypti, to transmit viruses. When mosquitoes infected with the virulent Wolbachia strain wMelPop are fed non-human blood, there is a drastic reduction in mosquito fecundity and egg viability. Wolbachia has a reduced genome and is clearly dependent on its host for a wide range of nutritional needs. The fitness defects seen in wMelPop-infected A. aegypti could be explained by competition between the mosquito and the symbiont for essential blood meal nutrients, the profiles of which are suboptimal in non-human blood. Here, we examine cholesterol and amino acids as candidate molecules for competition, as they have critical roles in egg structural development and are known to vary between blood sources. We found that Wolbachia infection reduces total cholesterol levels in mosquitoes by 15–25 %. We then showed that cholesterol supplementation of a rat blood meal did not improve fecundity or egg viability deficits. Conversely, amino acid supplementation of sucrose before and after a sheep blood meal led to statistically significant increases in fecundity of approximately 15–20 eggs per female and egg viability of 30–40 %. This mosquito system provides the first empirical evidence of competition between Wolbachia and a host over amino acids and may suggest a general feature of Wolbachia–insect associations. These competitive processes could affect many aspects of host physiology and potentially mosquito fitness, a key concern for Wolbachia-based mosquito biocontrol.     

Chikungunya Virus Transmission Potential by Local Aedes Mosquitoes in the Americas and Europe

Background

Chikungunya virus (CHIKV), mainly transmitted in urban areas by the mosquitoes Aedes aegypti and Aedes albopictus, constitutes a major public health problem. In late 2013, CHIKV emerged on Saint-Martin Island in the Caribbean and spread throughout the region reaching more than 40 countries. Thus far, Ae. aegypti mosquitoes have been implicated as the sole vector in the outbreaks, leading to the hypothesis that CHIKV spread could be limited only to regions where this mosquito species is dominant.

Methodology/Principal Findings

We determined the ability of local populations of Ae. aegypti and Ae. albopictus from the Americas and Europe to transmit the CHIKV strain of the Asian genotype isolated from Saint-Martin Island (CHIKV_SM) during the recent epidemic, and an East-Central-South African (ECSA) genotype CHIKV strain isolated from La Réunion Island (CHIKV_LR) as a well-characterized control virus. We also evaluated the effect of temperature on transmission of CHIKV_SM by European Ae. albopictus. We found that (i) Aedes aegypti from Saint-Martin Island transmit CHIKV_SM and CHIKV_LR with similar efficiency, (ii) Ae. aegypti from the Americas display similar transmission efficiency for CHIKV_SM, (iii) American and European populations of the alternative vector species Ae. albopictus were as competent as Ae. aegypti populations with respect to transmission of CHIKV_SM and (iv) exposure of European Ae. albopictus to low temperatures (20°C) significantly reduced the transmission potential for CHIKV_SM.

Conclusions/Significance

CHIKV strains belonging to the ECSA genotype could also have initiated local transmission in the new world. Additionally, the ongoing CHIKV outbreak in the Americas could potentially spread throughout Ae. aegypti- and Ae. albopictus-infested regions of the Americas with possible imported cases of CHIKV to Ae. albopictus-infested regions in Europe. Colder temperatures may decrease the local transmission of CHIKV_SM by European Ae. albopictus, potentially explaining the lack of autochthonous transmission of CHIKV_SM in Europe despite the hundreds of imported CHIKV cases returning from the Caribbean.     

Transcriptomic analysis and molecular docking reveal genes involved in the response of Aedes aegypti larvae to an essential oil extracted from Eucalyptus

BackgroundAedes aegypti (L.) is an urban mosquito, vector of several arboviruses that cause severe diseases in hundreds of million people each year. The resistance to synthetic insecticides developed by Ae. aegypti populations worldwide has contributed to failures in vector control campaigns, increasing the impact of arbovirus diseases. In this context, plant-derived essential oils with larvicidal activity could be an attractive alternative for vector control. However, the mode of action and the detoxificant response of mosquitoes to plant derived compounds have not been established, impairing the optimization of their use.Methods and findingsHere we compare gene expression in Ae. aegypti larvae after 14 hrs of exposure to Eucalyptus camaldulensis essential oil with a control group exposed to vehicle (acetone) for the same lapse, by using RNA-Seq. We found differentially expressed genes encoding for cuticle proteins, fatty-acid synthesis, membrane transporters and detoxificant related gene families (i.e. heat shock proteins, cytochromes P450, glutathione transferases, UDP-glycosyltransferases and ABC transporters). Finally, our RNA-Seq and molecular docking results provide evidence pointing to a central involvement of chemosensory proteins in the detoxificant response in mosquitoes.Conclusions and significanceOur work contributes to the understanding of the physiological response of Ae. aegypti larvae to an intoxication with a natural toxic distilled from Eucalyptus leafs. The results suggest an involvement of most of the gene families associated to detoxification of xenobiotics in insects. Noteworthy, this work provides important information regarding the implication of chemosensory proteins in the detoxification of a natural larvicide. Understanding the mode of detoxification of Eucalyptus distilled compounds could contribute to their implementation as a tool in mosquito control.     

Mark-release-recapture of male Aedes aegypti (Diptera: Culicidae): Use of rhodamine B to estimate movement,mating and population parameters in preparation for an incompatible male program

Rapid advances in biological and digital support systems are revolutionizing the population control of invasive disease vectors such as Aedes aegypti. Methods such as the sterile and incompatible insect techniques (SIT/IIT) rely on modified males to seek out and successfully mate with females, and in doing so outcompete the wild male population for mates. Currently, these interventions most frequently infer mating success through area-wide population surveillance and estimates of mating competitiveness are rare. Furthermore, little is known about male Ae. aegypti behaviour and biology in field settings. In preparation for a large, community scale IIT program, we undertook a series of mark- release-recapture experiments using rhodamine B to mark male Ae. aegypti sperm and measure mating interactions with females. We also developed a Spatial and Temporally Evolving Isotropic Kernel (STEIK) framework to assist researchers to estimate the movement of individuals through space and time. Results showed that ~40% of wild females captured daily were unmated, suggesting interventions will need to release males multiple times per week to be effective at suppressing Ae. aegypti populations. Males moved rapidly through the landscape, particularly when released during the night. Although males moved further than what is typically observed in females of the species, survival was considerably lower. These unique insights improve our understanding of mating interactions in wild Ae. aegypti populations and lay the foundation for robust suppression strategies in the future.