Microorganisms Associated with Mosquito Oviposition Sites: Implications for Habitat Selection and Insect Life Histories

Assessment of the Bacterial communities associated with Anopheles gambiae larval habitats in Southern Ghana

Mosquito breeding habitats are ecosystems that comprise a complex, intimately associated micro-organism. This study aimed to determine the bacteria communities associated with Anopheles larval habitats and correlate their prevalence to the absence or presence of mosquito larvae. The 16S rRNA profiles of bacterial communities in Anopheles-positive breeding habitats (productive and semi-productive habitats) and negative habitats (non-productive) from Southern Ghana were analyzed using the Oxford Nanopore's MinION platform with water and larval samples. A total of 15 bacterial taxa were identified across all habitats based on productivity. Significantly, mosquito-positive breeding habitats (productive and semi-productive) had more bacterial diversity compared to mosquito-negative habitats (non-productive). Comparison of the composition of bacteria in the different habitat types revealed that non-productive habitats had a higher prevalence of Epsilonproteobacteria (58.1%), while Gammaproteobacteria (33.2%) and Betaproteobacteria (30.5%) were dominant in the productive and semi-productive habitats. Gammaproteobacteria and Betaproteobacteria were the most abundant bacterial classes in Anopheles larvae. Comparing the water samples to larvae microbiomes revealed distinct composition. Betaproteobacteria (58.5%) and Cytophagia (10.7%) were predominately present in the water samples, whilst Betaproteobacteria (47.9%) and Gammaproteobacteria (21.6%) were dominant in the larval samples. This study revealed a higher bacterial composition may play a role in Anopheles mosquitoes' attractiveness to a breeding habitat. These findings contribute to the understanding of which bacteria, directly or indirectly, can be linked to the absence or presence of mosquito larvae in breeding habitats and set the basis for the identification of specific bacterial taxa that could be harnessed for vector control in the future.

Variation in diet concentration and bacterial inoculum size in larval habitats shapes the performance of the Asian tiger mosquito, Aedes albopictus

BACKGROUND

Ecological niches present unique environmental and biological trademarks such as abiotic conditions, nutrient availability, and trophic interactions that may impact the ecology of living organisms. Female mosquitoes deposit their eggs in aquatic niches with fluctuating diet sources and microbial communities. However, how niche's diet and microbial composition impact mosquito performance (i.e., traits that maximize mosquito fitness) are not well understood. In this study, we focused on the Asian tiger mosquito, Aedes albopictus, one of the most invasive species in the world and a competent vector for human pathogens. To remove any external microbes, Ae. albopictus eggs were surface-sterilized then hatching larvae were exposed to a gradient of bacterial inoculum (i.e., initial microbial load) and diet concentrations while their impact on mosquito performance traits during juvenile development was measured.

RESULTS

Our results showed that Ae. albopictus larvae develop faster and give larger adults when exposed to microbiota in rearing water. However, mosquito performance, up to the adult stage, depends on both bacterial inoculum size and diet concentration in the aquatic habitat. Upon low inoculum size, larvae survived better if the diet was in sufficient amounts whereas a higher inoculum size was associated with optimal larvae survival only in the presence of the lower amount of diet. Inoculum size, and to a lesser extent diet concentration, shaped bacterial community structure and composition of larval-rearing water allowing the identification of bacterial taxa for which their abundance in larvae-rearing water correlated with niche parameters and/or larval traits.

CONCLUSIONS

Our work demonstrates that both diet concentration and bacterial inoculum size impact mosquito performance possibly by shaping bacterial community structure in the larval habitat, which accounts for a large part of the juvenile's microbiota. Host-microbe interactions influence several mosquito life-history traits, and our work reveals that niche parameters such as inoculum size and diet concentration could have numerous implications on the microbiota assembly and host evolutionary trajectory. This underlies that host-microbe-environment interactions are an important yet overlooked factor of mosquito adaptation to its local environment, with potential future implications for vector control and vector ecology. Video Abstract.

Variable effects of a fire-retardant gradient on seasonal wetland communities

Wildfires have become larger and more severe in recent decades. Fire retardant is one of the most common wildfire response tools to protect against loss of life and property. Previous studies have documented various effects of fire retardant, which commonly contains chemicals used in fertilizers, on plant and invertebrate community composition. This mesocosm study investigated the effects of fire retardant on water quality and plant and invertebrate communities in California vernal pools. This study found that fire retardant caused water quality conditions to shift from oligotrophic to eutrophic with strong correlations between fire retardant and phosphates, nitrates, conductivity, and chlorophyll-a. Algal cover increased with added fire-retardant concentration. Shifts in invertebrate and plant communities occurred even at relatively low fire-retardant concentrations. Abundance of passive dispersers (crustaceans) peaked at medium concentrations of fire retardant, but time also influenced the relationship between fire retardant and passive invertebrate abundance. Active disperser (insects) abundance increased with increasing fire-retardant concentration and invertebrate richness peaked at medium concentrations. This study informs land managers, government agencies, and the public of the side-effects of fire-retardant use on populations, communities, and water quality of freshwater ecosystems.

Environmental yeasts differentially impact the development and oviposition behavior of the Asian tiger mosquito Aedes albopictus

BACKGROUND

While the Asian tiger mosquito (Aedes albopictus), a known vector of many arboviruses, establishes symbiotic associations with environmentally acquired yeasts, their impact on mosquito biology remains poorly investigated. To better understand these associations, we hypothesized that waterborne yeasts colonizing the larval gut differentially support mosquito development based on their capacity to produce riboflavin or recycle nitrogen waste into proteins by secreting uricase, as B vitamins and amino acids are crucial for mosquito development. To address this hypothesis, we used axenic and gnotobiotic insects to gauge the specific impact of different environmental yeasts on Ae. albopictus development and survival. We then evaluated whether the observed variations across yeast species could be linked to differential uricolytic activities and varying quantities of riboflavin and proteins in insecta. Finally, given that mosquito oviposition site selection favors conditions that enhance offspring performance, we tested whether yeasts that promote faster development mediate oviposition site selection by gravid females.

RESULTS

Differences in mosquito development times were observed based on the environmental yeast used. Yeasts like Rhodotorula mucilaginosa and Aureobasidium pullulans promoted rapid development and were associated with improved survival. Conversely, yeasts such as Torulaspora delbrueckii and Martiniozyma asiatica, which led to slower development, produced smaller adults. Notably, R. mucilaginosa, which promoted the fastest development, provided high riboflavin intakes and enhance nitrogenous waste recycling and protein synthesis through strong uricolytic-ureolytic activity. Behavioral experiments indicated that yeasts promoting rapid development "attract gravid females.

CONCLUSIONS

Our findings highlight that a set of environmental yeasts present in natural larval breeding sites can be associated with improved mosquito development and survival by enhancing nutritional intake, thereby attracting gravid females. Variations in mosquito development time are likely linked to the differential levels of riboflavin production and nitrogenous waste recycling capacities among yeast species. This study opens new perspectives on the trophic interactions between mosquitoes and their mycobiota, emphasizing the importance of nitrogen-containing molecules such as essential amino acids, proteins, or vitamins provided by the mycobiota. Video Abstract.

The type of environment has a greater impact on the larval microbiota of Anopheles arabiensis than on the microbiota of their breeding water

Mosquito larvae of the genus Anopheles develop entirely in water, frequently visiting the surface for air. The aquatic environment plays a key role in shaping their microbiota, but the connection between environmental characteristics of breeding sites and larval microbiota remains underexplored. This study focuses on Anopheles arabiensis, which inhabits the surface microlayer (SML) of breeding sites, a zone with high particle density. We hypothesized that the SML could allow us to capture the diversity of the surrounding environment, and in turn its influence on the larval microbial communities. To test this, we collected A. arabiensis larvae and SML samples from various breeding sites categorized by environmental features. Our results confirm that breeding site characteristics are significant drivers of the bacterial species present in mosquito larvae. Additionally, we found that the larval micro-environment selectively shapes its microbiota, highlighting a dynamic interplay between environmental and internal factors. Interestingly, specific bacterial families were associated with the presence or absence of larvae in breeding sites, suggesting potential ecological roles. These findings expand our understanding of vector-mosquito microbiota, emphasizing the importance of breeding site features in shaping larval microbial communities and providing a foundation for future research on mosquito ecology and control strategies.

Fungi from Anopheles darlingi Root, 1926, larval breeding sites in the Brazilian Amazon

The fungi present in the breeding waters of mosquitoes have been scarcely investigated. This work explored the diversity of cultivable fungi present in the breeding sites of the South American malaria vector mosquito Anopheles darlingi. Water samples were collected from four sites located in the municipalities of Coari and São Gabriel da Cachoeira and four different culture media were used for the isolation of fungi. Two-hundred-and-six fungal strains were isolated and morphologically similar fungi were grouped into 30 morphotypes. Their taxonomic identities were assigned by macro and microscopic observations and sequencing of rDNA internal transcribed spacers (ITS1-5.8S-ITS2). Representatives of 26 morphotypes were identified at the genus level, one only at the family level, and three were not identified. The identified morphotypes belong to the phyla, Ascomycota (80.6%), Basidiomycota (11.7%), and Mucoromycota (2.4%), distributed in five classes, ten orders, 25 families, and 26 genera. This study fills a considerable knowledge gap about the fungi present in the breeding sites of An. darlingi mosquitoes.

MosAIC: An annotated collection of mosquito-associated bacteria with high-quality genome assemblies

Mosquitoes transmit medically important human pathogens, including viruses like dengue virus and parasites such as Plasmodium spp., the causative agent of malaria. Mosquito microbiomes are critically important for the ability of mosquitoes to transmit disease-causing agents. However, while large collections of bacterial isolates and genomic data exist for vertebrate microbiomes, the vast majority of work in mosquitoes to date is based on 16S rRNA gene amplicon data that provides limited taxonomic resolution and no functional information. To address this gap and facilitate future studies using experimental microbiome manipulations, we generated a bacterial Mosquito-Associated Isolate Collection (MosAIC) consisting of 392 bacterial isolates with extensive metadata and high-quality draft genome assemblies that are publicly available, both isolates and sequence data, for use by the scientific community. MosAIC encompasses 142 species spanning 29 bacterial families, with members of the Enterobacteriaceae comprising 40% of the collection. Phylogenomic analysis of 3 genera, Enterobacter, Serratia, and Elizabethkingia, reveal lineages of mosquito-associated bacteria isolated from different mosquito species in multiple laboratories. Investigation into species' pangenomes further reveals clusters of genes specific to these lineages, which are of interest for future work to test for functions connected to mosquito host association. Altogether, we describe the generation of a physical collection of mosquito-associated bacterial isolates, their genomic data, and analyses of selected groups in context of genome data from closely related isolates, providing a unique, highly valuable resource for research on bacterial colonisation and adaptation within mosquito hosts. Future efforts will expand the collection to include broader geographic and host species representation, especially from individuals collected from field populations, as well as other mosquito-associated microbes, including fungi, archaea, and protozoa.

Vision guides the twilight search for oviposition sites of the Asian tiger mosquito, Aedes albopictus

BACKGROUND

Oviposition site selection is an important component of vector mosquito reproductive biology. The Asian Tiger mosquito, Aedes albopictus, is a major and important vector of arboviruses including Dengue. Previous studies documented the preference of gravid females for small, dark-colored water containers as oviposition sites, which they sought during the twilight period (dusk) of their locomotor activity. Vision plays an important role in this behavior, and factors such as the shape, size, and color of the container, light intensity, polarization, spectrum, and other visual cues guide the search for suitable oviposition sites, but the mechanistic factors driving this behavior are unclear.

METHODOLOGY/PRINCIPAL FINDINGS

We blindfolded adult female compound eyes and observed the effects of a lack of vision on the ability to discriminate and utilize preferred oviposition sites. Furthermore, the transcriptomes of blindfolded mosquitoes were screened to identify genes with vision-sensitive expression profiles and gene-editing was used to create non-functional mutations in two of them, rhodopsin-like (mutation designated 'rho-l△807') and kynurenine hydroxylase (mutation designated 'khw'). Behavioral tests of both mutant and control strains revealed that the rho-l△807 mutant mosquitoes had a significant decrease in their ability to search for preferred oviposition sites that correlated with a reduced ability to recognize long-wavelength red light. The khw mutant mosquitoes also had a reduced ability to identify preferred oviposition sites that correlated with reductions in their ability to respond to variations in daily brightness and their ability to discriminate among different color options of the containers and background monochromatic light.

CONCLUSIONS/SIGNIFICANCE

This study underscores the importance of visual cues in the oviposition site selection behavior of adult female Ae. albopictus. We demonstrate that wild-type rho-l and kh gene products play a crucial role in this behavior, as mutants exhibit altered sensitivity or recognition of light intensity and substrate colors.

Pollution gradients shape microbial communities associated with Ae. albopictus larval habitats in urban community gardens

The Asian tiger mosquito Aedes albopictus is well adapted to urban environments and takes advantage of the artificial containers that proliferate in anthropized landscapes. Little is known about the physicochemical, pollutant, and microbiota compositions of Ae. albopictus-colonized aquatic habitats and whether these properties differ with noncolonized habitats. We specifically addressed this question in French community gardens by investigating whether pollution gradients (characterized either by water physicochemical properties combined with pollution variables or by the presence of organic molecules in water) influence water microbial composition and then the presence/absence of Ae. albopictus mosquitoes. Interestingly, we showed that the physicochemical and microbial compositions of noncolonized and colonized waters did not significantly differ, with the exception of N2O and CH4 concentrations, which were higher in noncolonized water samples. Moreover, the microbial composition of larval habitats covaried differentially along the pollution gradients according to colonization status. This study opens new avenues on the impact of pollution on mosquito habitats in urban areas and raises questions on the influence of biotic and abiotic interactions on adult life-history traits and their ability to transmit pathogens to humans.

Synthetic Alfalfa Infusion Odour Attracts Gravid Culex quinquefasciatus Under Laboratory Conditions

Gravid culicine mosquitoes rely on olfactory cues for selecting breeding sites containing organic detritus. While this capacity of the mosquitoes is used for surveillance and control, the current methodology is unwieldy, unreliable and expensive in time and labour. This study evaluated the dose-dependent attraction and oviposition response of gravid Culex quinquefasciatus to alfalfa infusions. Through combined chemical and electrophysiological analyses, bioactive volatile organic compounds (VOCs) in the headspace of alfalfa infusions, eliciting attraction, were identified. While phenolic and indolic compounds were the most abundant bioactive VOCs, additional VOCs, including a monoterpene, were required to elicit a significant behavioural response to the synthetic odour blend of alfalfa infusions. Comparative analysis with the commercially available mosquito oviposition pheromone (MOP) was also conducted demonstrating that this standardised synthetic alfalfa infusion odour blend offers a promising lure for targeted surveillance and control of Culex mosquitoes, which may contribute to disease prevention and public health protection.

The complexities of blood-feeding patterns in mosquitoes and sandflies and the burden of disease: A minireview

Mosquitoes and sandflies exhibit a wide range of blood feeding patterns, targeting a wide range of vertebrate species, including birds, mammals, reptiles, and amphibians, for proteins vital for egg development. This broad host range increases the opportunity for them to acquire pathogens of numerous debilitating-and-fatal diseases from various animal reservoirs, playing a significant role in disease crossover between animals and humans, also known as zoonotic transmission. This review focuses on the intricate blood-feeding habits of these dipteran vectors, their sensory systems and the complex dance between host and pathogen during disease transmission. We delve into the influence of blood sources on pathogen spread by examining the insect immune response and its intricate interplay with pathogens. The remarkable sense of smell guiding them towards food sources and hosts is explored, highlighting the interplay of multiple sensory cues in their navigation. Finally, we examine the challenges in mosquito control strategies and explore innovations in this field, emphasizing the need for sustainable solutions to combat this global health threat. By understanding the biology and behaviour of these insects, we can develop more effective strategies to protect ourselves and mitigate the burden of vector-borne diseases.

Gustatory receptor 11 is involved in detecting the oviposition water of Asian tiger mosquito, Aedes albopictus

BACKGROUND

Aedes albopictus is a major arbovirus vector with small stagnant water containers being its oviposition sites. Mosquitoes search for these sites based on their olfactory cues (odor and moisture emanating from the water at the oviposition site), visual cues (size and color of the site), and gustatory cues (ion and nutrient concentration in that water). The gustatory mechanism through which mosquitoes search for oviposition sites remains unknown.

METHODS

To investigate the role of taste receptors in Ae. albopictus oviposition site selection, we developed a laboratory model. This model assessed mosquito behavior in locating and detecting oviposition sites, using a location index to quantify site preference and detection time to measure response to water presence. We compared oviposition site-searching efficiency between mosquitoes with blocked and unblocked appendages, targeting the taste organs. Transcriptome sequencing was conducted to identify differentially expressed genes between water-exposed and unexposed mosquitoes. CRISPR/Cas9 technology was then employed to generate a mutant strain with a targeted gene knockout.

RESULTS

There was no significant difference between the blocked and unblocked groups in the location index. In contrast, the detection time of the unblocked group differed significantly from all other groups, including those with blocked foreleg tarsus, midleg tarsus, hindleg tarsus, all tibia, and all tarsus. Transcriptome sequencing analyses of water-exposed and unexposed mosquitoes revealed that the taste-related gene gustatory receptor 11(gr11) was differentially expressed. This gene was knocked out with CRISPR/Cas9 technology to generate a pure mutant strain with 2- and 4-bp deletions, which exhibited a significantly longer detection time than the wild-type strain.

CONCLUSIONS

This study reveals the role of Ae. albopictus gr11 in water detection at oviposition sites, thereby providing a theoretical basis and scientific guidelines for managing the breeding sites of these mosquitoes.

The odorant-binding protein genes obp67 and obp56d-like encode products that guide oviposition site selection in the Asian tiger mosquito, Aedes albopictus

Aedes albopictus is an important vector of arboviruses and prefers small containers of stagnant water as oviposition sites. One of the mechanisms mosquitoes use to search for suitable oviposition sites is relying on odor cues from prospective sites and their surroundings. The genetic and molecular bases of this behavior are not known for Ae. albopictus. Oviposition site-searching behavior can be separated into 2 stages: container location and water detection. We applied a glue compound to the antennae and the maxillary palps of adult females to mask their ability to detect molecules that may guide them to preferred oviposition sites. Treatment of the antennae significantly reduces the location index (P < 0.001), indicating a decreased ability to find oviposition sites, whereas no significant difference was observed in mosquitoes with maxillary palps treated with the same glue compound (P > 0.05). The detection time, measured as the duration from contact with the water surface to the deposition of the first egg, was extended in mosquitoes with treated antennae or maxillary palps, supporting the conclusion that olfaction is involved in the detection of oviposition site. Transcriptomic analysis identified differentially expressed olfactory-related genes, including obp67, obp56d-like, obp19d-like and obp67-like. RNA interference (RNAi)-mediated knockdown of obp67 and obp56d-like significantly affected the location index and detection time, respectively. Cas9/guide RNA-mediated knockout of obp56d-like resulted in a prolonged detection time, compared with the wild type (P < 0.05). These findings help to elucidate aspects of the olfactory mechanisms involved in Ae. albopictus oviposition site selection, and provide a basis for the development of mosquito surveillance and control strategies.

Mitigating the Public Health Issues Caused by the Filarial Vector, Culex quinquefasciatus (Diptera: Culicidae) Through Phytocontrol and Larval Source Marker Management

Failure of conventional mosquito control strategies to curb the population of vectors have made the humans vulnerable to serious medical problems transmitted by them. This effect has been compounded by global climate change enabling the mosquitoes to cross geographical boundaries and cause trouble in regions where they were initially not found. As such, the scientific community has been compelled to devise alternative and innovative strategies of mosquito control that can be integrated with the conventional practices to implement multi-phasic approach of vector management. Culex quinquefasciatus is one such mosquito species that is reported to be one of the primary vectors of lymphatic filariasis and many other diseases of global health concern. However, not much is known about its breeding habitat ecology and microbial properties that have enabled the species to achieve reproductive success in urbanized habitats. The current investigation was carried out at Digha, West Bengal, India. The region, despite being endemic for lymphatic filariasis, has rarely been explored for its mosquito diversity and/or their breeding habitat characteristics. Therefore, these were attempted. For survey and sampling, seven villages were chosen, namely, Duttapur, Jatimati, Champabani, Padima, Gobindabasan, Bhagibaharampur and Palsandapur. The study showed that Cx. quinquefasciatus is the dominant mosquito species at the sampling sites with the highest density of their larvae being recorded from man-made structures like drains and pools close to human habitations and livestock. The study was, therefore, restricted to Cx. quinquefasciatus. Seasonal abundance showed that they were most prevalent in the monsoon followed by summer. The physicochemical characterization showed their larvae to prefer almost neutral pH (6.9 to 7.3), low chloride concentration (98 to 258 ppm) and turbidity. As far as other parameters are concerned, they were tolerant towards a wide range allowing them to adapt varied habitats in the study areas. The bacterial profiling of their natural habitat waters revealed the presence of Paenibacillus nanensis DGX1(OQ690670), Bacillus cereus DGX2(OQ690675), Bacillus sp. DGX3(OQ690700) and Escherichia coli DGX4(OQ690701). Bacillus cereus was found to have high oviposition attractant properties in oviposition assays. Bacillus cereus was also obtained from the midgut of third instar larvae indicating that they had entered from the surrounding medium and colonized the larval gut. Subsequent tests exhibited the roles of B. cereus in larval development. Numerous plant products have been reported either as insecticides for killing larvae or adult mosquitoes or as repellents for mosquito biting and the best alternatives for mosquito control. Larvicidal potential of emulsified neem oil formulation against the field collected 3rd instar larvae of Culex quinquefasciatus mosquito under laboratory conditions was also evaluated. The information thus obtained can be pooled to generate larval source markers and larval source management practices by altering their habitats that cannot be removed. Furthermore, the time of implementation of these strategies can also be planned.

Heritability and preadult survivorship costs of ectoparasite resistance in the naturally occurring Drosophila-Gamasodes mite system

Our understanding of the evolutionary significance of ectoparasites in natural communities is limited by a paucity of information concerning the mechanisms and heritability of resistance to this ubiquitous group of organisms. Here, we report the results of artificial selection for increasing ectoparasite resistance in replicate lines of Drosophila melanogaster derived from a field-fresh population. Resistance, as ability to avoid infestation by naturally co-occurring Gamasodes queenslandicus mites, increased significantly in response to selection and realized heritability (SE) was estimated to be 0.11 (0.0090). Deployment of energetically expensive bursts of flight from the substrate was a main mechanism of host resistance that responded to selection, aligning with previously documented metabolic costs of fly behavioral defenses. Host body size, which affects parasitism rate in some fly-mite systems, was not shifted by selection. In contrast, resistant lines expressed significant reductions in larva-to-adult survivorship with increasing toxic (ammonia) stress, identifying an environmentally modulated preadult cost of resistance. Flies selected for resistance to G. queenslandicus were also more resistant to a different mite, Macrocheles subbadius, suggesting that we documented genetic variation and a pleiotropic cost of broad-spectrum behavioral immunity against ectoparasites. The results demonstrate significant evolutionary potential of resistance to an ecologically important class of parasites.

Effects of bacterial composition and aquatic habitat metabolites on malaria vector larval availability in irrigated and non-irrigated sites of Homa Bay county, western Kenya

Gravid Anopheles malaria vectors depend on both chemical and physical (including microbial) cues for selection of preferred habitats for oviposition. This study focused on assessing the effects of bacterial composition and habitat metabolites on malaria vector larval availability in irrigated and non-irrigated potential larval sources. Water samples were collected from larval positive and negative habitats in the irrigated and non- irrigated areas of Homa Bay county. Bacteria cultured from the water samples were subjected to Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) for species identification. DNA was extracted from the colonies and polymerase chain reaction (PCR) and sequencing done. Finally, the metabolite composition of larval positive and negative habitats was determined. MALDI-TOF MS results revealed that Bacillus was the only genera identified from larval sources in the non-irrigated zone. In the irrigated area, Shigella was the dominant genera (47%) while Escherichia coli was the abundant species (13/51). Of the sequenced isolates, 65% were Bacillus. Larvicidal isolates Brevibacillus brevis, Bacillus subtilis, and Exiguobacterium profundum were isolated and grouped with Bacillus mojavensis, Bacillus tequilensis, Bacillus stercoris, and Brevibacillus agri. Irrigated areas with larvae had reduced crude fat (0.01%) and protein content (0.13%) in comparison to those without larvae. In irrigated and non- irrigated areas, larval presence was evident in habitats with high total chlorophyll content (1.12 μg/g vs 0.81μg/g and 3.37 μg/g vs 0.82). Aquatic habitats with larvae in both irrigated and non-irrigated areas exhibited higher sugar concentration than habitats without larvae; however, when compared, non-irrigated areas with larvae had higher sugar concentration than similar habitats in irrigated areas. In addition, substantial concentrations of Manganese, Calcium, and Copper were found in aquatic habitats containing larvae in both irrigated and non-irrigated areas. These results allow for prospective examination as potential larvicidal or adulticidal agents and could be considered when designing potential vector control interventions.

Impact of Human Activities on Disease-Spreading Mosquitoes in Urban Areas

Urbanization is one of the leading global trends of the twenty-first century that has a significant impact on health. Among health challenges caused by urbanization, the relationship of urbanization between emergence and the spread of mosquito-borne infectious diseases (MBIDs) is a great public health concern. Urbanization processes encompass social, economic, and environmental changes that directly impact the biology of mosquito species. In particular, urbanized areas experience higher temperatures and pollution levels than outlying areas but also favor the development of infrastructures and objects that are favorable to mosquito development. All these modifications may influence mosquito life history traits and their ability to transmit diseases. This review aimed to summarize the impact of urbanization on mosquito spreading in urban areas and the risk associated with the emergence of MBIDs. Moreover, mosquitoes are considered as holobionts, as evidenced by numerous studies highlighting the role of mosquito-microbiota interactions in mosquito biology. Taking into account this new paradigm, this review also represents an initial synthesis on how human-driven transformations impact microbial communities in larval habitats and further interfere with mosquito behavior and life cycle in urban areas.

Odor-mediated response of gravid Aedes aegypti to mosquito-associated symbiotic bacteria

Complex oviposition decisions allow gravid Aedes aegypti mosquitoes to select suitable sites for egg-laying to increase the probability that their progeny will thrive. The bacterial communities present in larval niches influence mosquito oviposition behavior, and gravid mosquitoes transmit key microbial associates to breeding sites during oviposition. Our study evaluated whether symbiotic Klebsiella sp., which are strongly associated with mosquitoes, emit volatiles that affect mosquito oviposition decisions. Dual-choice behavioral assays demonstrated that volatile organic compounds emitted by Klebsiella sp. induce a preference in oviposition decisions by Ae. aegypti. Bacterial headspace volatiles were sampled by solid-phase microextraction, and subsequent combined gas chromatography and electroantennogram detection analysis, revealed that the antennae of gravid females detect two compounds present in the Klebsiella sp. headspace. These compounds were identified by gas chromatography and mass spectrometry as 2-ethyl hexanol and 2,4-di‑tert-butylphenol. The binary blend of these compounds elicited a dose-dependent egg-laying preference by gravid mosquitoes. We propose that bacterial symbionts, which are associated with gravid mosquitoes and may be transferred to aquatic habitats during egg-laying, together with their volatiles act as oviposition cues indicating the suitability of active breeding sites to conspecific females.

Evaluation of a mosquito home system for controlling Aedes aegypti

BACKGROUND

Dengue is a significant public health issue that is caused by Aedes spp. mosquitoes. The current vector control methods are unable to effectively reduce Aedes populations and thus fail to decrease dengue transmission. Hence, there is an urgent need for new tools and strategies to reduce dengue transmission in a wide range of settings. In this study, the Mosquito Home System (MHS) and Mosquito Home Aqua (MHAQ) formulations were assessed as commercial autodissemination traps in laboratory and small-scale field trials.

METHOD

Multiple series of laboratory and small-scale field trials were performed to assess the efficacy of MHS and MHAQ exposed to Ae. aegypti. In the laboratory trials, various parameters such as fecundity, fertility, wing size, oviposition preferences, residual effects, and MHAQ transference to other containers through controlled experiments were tested. For small-scale field trials, the efficacy of the MHS and MHAQ approaches was determined to ascertain whether wild mosquitoes could transfer the MHAQ formulation from MHS stations to ovitraps.

RESULTS

The data revealed that Ae. aegypti was highly susceptible to low concentrations of MHAQ formulations and had a residual effect of up to 3 months, with MHAQ exposure affecting fecundity, fertility, and mosquito wing size. In the oviposition studies, gravid females strongly preferred the hay infusion compared to tap water and MHAQ during egg-laying in the laboratory. Nevertheless, the use of commercial MHAQ by MHS was highly attractive in field settings compared to conventional ovitraps among local Aedes spp. mosquitoes. In addition, MHAQ horizontal transfer activities in the laboratory and small-scale field trials were demonstrated through larval bioassays. These findings demonstrated the potential of MHAQ to be transferred to new containers in each study site.

CONCLUSION

This study provided proof of principle for the autodissemination of MHAQ. Through further refinement, this technique and device could become an effective oviposition trap and offer an alternative preventive tool for vector control management.