Mosquito Control Strategies Research Articles

Entomopathogenic fungi-based silver nanoparticles: a potential substitute of synthetic insecticides to counter behavioral and physiological immunity in Aedes aegypti mosquito (Diptera: Culicidae).

Excessive use of synthetic insecticides has resulted in environmental contamination and adverse effects on humans and other non-target organisms. Entomopathogenic fungi offer eco-friendly alternatives; however, their application for pest control requires significant advancement owing to limitations like slow killing time and effectiveness only when applied in higher amounts, whereas exposure to UV radiation, high temperature, and humidity can also reduce their viability and shelf-life. The nanoparticles synthesized using fungal extracellular extracts provide a new approach to use fungal pathogens. Our study focused on the synthesis of Metarhizium anisopliae-based silver nanoparticles (AgNPs) and evaluation of their efficiency on various physiological and behavioral parameters of the mosquito Aedes aegypti. The synthesis, size (27.6 d.nm, PDI = 0.209), zeta potential (- 24.3 mV), and shape of the AgNPs were determined through dynamic light scattering, scanning and transmission electron microscopic, and UV-visual spectroscopic analyses (432 nm). Our results showed significantly reduced survival (100% decrease in case of 3.2 and 1.8 μL/cm2 volumes, and 60% decrease in case of 0.8 μL/cm2 volume), phenoloxidase activity (t = 39.91; p = 0.0001), and gut microbiota, with increased oxidative stress and cell apoptosis in AgNPs-challenged mosquitoes. Furthermore, the AgNPs-exposed mosquitoes presented a concentration-specific decrease in flight locomotor activity (F = 17.312; p < 0.0001), whereas no significant changes in antifungal activity, self-grooming frequencies, or time spent were found. These findings enhance our understanding of mosquito responses to AgNPs exposure, and offer a more efficient mosquito control strategy using entomopathogenic fungi.

Accelerating targeted mosquito control efforts through mobile West Nile virus detection.

Different mosquito control strategies have been implemented to mitigate or prevent mosquito-related public health situations. Modern mosquito control largely relies on multiple approaches, including targeted, specific treatments. Given this, it is becoming increasingly important to supplement these activities with rapid and mobile diagnostic capacities for mosquito-borne diseases. We aimed to create and test the applicability of a rapid diagnostic system for West Nile virus that can be used under field conditions. In this pilot study, various types of adult mosquito traps were applied within the regular mosquito monitoring activity framework for mosquito control. Then, the captured specimens were used for the detection of West Nile virus RNA under field conditions with a portable qRT-PCR approach within 3-4h. Then, positive samples were subjected to confirmatory RT-PCR or NGS sequencing in the laboratory to obtain genome information of the virus. We implemented phylogenetic analysis to characterize circulating strains. A total of 356 mosquito individuals representing 7 species were processed in 54 pools, each containing up to 20 individuals. These pools were tested for the presence of West Nile virus, and two pools tested positive, containing specimens from the Culex pipiens and Anopheles atroparvus mosquito species. As a result of subsequent sequencing, we present the complete genome of West Nile virus and Bagaza virus. The rapid identification of infected mosquitoes is the most important component of quick response adulticide or larvicide treatments to prevent human cases. The conceptual framework of real-time surveillance can be optimized for other pathogens and situations not only in relation to West Nile virus. We present an early warning system for mosquito-borne diseases and demonstrate its application to aid rapid-response mosquito control actions.

Insecticide paints: a new community strategy for controlling dengue and zika mosquito vectors in Cabo Verde

BackgroundCabo Verde, an island country in West Africa, has been affected since human colonization by epidemics of vector-borne diseases with major epidemics of dengue and zika in recent years. Although there is a national program for integrated vector control, innovative strategies that reinforce routine activities and strengthen vector control are necessary to prevent the emergence or reemergence of arboviruses and new epidemics of dengue and zika. Insecticide paints are evidenced as new technologies for the formulation of insecticides in a more residual and safe way. The TINTAEDES project aimed to assess the efficacy, acceptability, and operational deployment of an insecticide paint for Aedes control.Methodology/Principal findingsLaboratory and small-scale field trials were conducted, assessing mortality through World Health Organization cone bioassays. A community-based intervention study in the neighborhoods of Várzea and Tira Chapéu in the city of Praia, Cabo Verde, was developed. The intervention is a paint self-application model by homeowners and neighborhood volunteers. The intervention was evaluated based on entomological indicators and the responses given by the residents of the painted houses to a questionnaire on the knowledge, satisfaction, and safety of insecticidal paints. A transfluthrin-based insecticide paint was effective against wild Ae. aegypti for one year in the laboratory and semi-field conditions. Residents largely perceived a reduction in mosquito presence in the treated houses (98%).ConclusionInsecticide paints are presented as an effective innovation strategy for mosquito control, which could be implemented as a reinforcement of the measures carried out by the vector control program in the city of Praia and throughout the country.

Insecticide Susceptibility and KDR Mutations in Aedes Albopictus Collected from Seven Districts of Guangyuan city, Northern Sichuan, China.

The Asian tiger mosquito, Aedes albopictus, is an important vector of chikungunya, dengue, yellow fever, and Zika viruses. Vector control remains an important means for the prevention and control of vector-borne diseases. The development of insecticide resistance has become a serious threat to the efficacy of insecticide-based control programs. To understand the resistance status and the underlying genetic mechanism in mosquitoes in Guangyuan City of Sichuan Province, China, we investigated the susceptibility of Ae. albopictus to four commonly used insecticides. We found that all the examined populations were susceptible to malathion and propoxur. However, Ae. albopictus populations in Guangyuan showed a possible resistance to the two tested pyrethroids (beta-cypermethrin and deltamethrin). Notably, phenotypic resistance to deltamethrin was detected in 2 of the 7 populations. The potential of resistance to pyrethroids was confirmed by the presence of knockdown resistance (kdr) related mutations in the voltage-gated sodium channel. Four kdr mutations (V1016G, I1532T, F1534L, and F1534S) were identified to be present alone or in combination, and their distribution displayed significant spatial heterogeneity. These findings are helpful for making evidence-based mosquito control strategies and highlight the need to regularly monitor the dynamics of pyrethroid resistance in this city.

Interactive Effects of Salinity and Mosquito Larvicides Toxicity to Larvae of Aedes Taeniorhynchus.

Understanding the influence of salinity on the efficacy of mosquito larvicides in brackish water habitats is crucial for effective salt-marsh Aedes taeniorhynchus control. This study investigated the interactive effects of salinity on the toxicity of 3 commonly used mosquito larvicides: Bacillus thuringiensis israelensis (VectoBac® 12AS), spinosad (Natular® SC), and S-methoprene (Altosid® 12AS) against Ae. taeniorhynchus larvae. Four salinity levels (0 ppt [parts per thousand], 8 ppt, 16 ppt, and 32 ppt) were tested in laboratory bioassays. The results revealed distinct responses of these larvicides to varying salinity levels. VectoBac 12AS displayed consistent efficacy across all salinity levels, indicating its suitability for brackish water habitats. In contrast, Natular 2EC exhibited increased effectiveness with higher salinity, making it a preferable choice for saline environments. Altosid 12AS showed its highest efficacy in freshwater, with reduced effectiveness as salinity increased. These findings underscore the need to consider salinity levels when selecting and applying mosquito larvicides in diverse aquatic habitats. Understanding the complex interplay between salinity and larvicide performance is essential for optimizing mosquito control strategies and mitigating mosquito-borne diseases in various environments.

AsOBP1 is required for bioallethrin repellency in the malaria vector mosquito Anopheles sinensis.

The use of insecticides, primarily pyrethroids, is a pivotal strategy for mosquito control globally. Bioallethrin, the first commercially available volatile pyrethroid, can elicit spatial (i.e., noncontact) repellency to mosquitoes through the coactivation of olfactory receptor neurons and sodium channels. However, the olfactory mechanism of the repellency elicited by bioallethrin in mosquitoes is still unclear. Here, we demonstrated the involvement of AsOBP1 in the bioallethrin repellency in Anopheles sinensis, one of the main vectors of vivax malaria in China and other Southeast Asian countries. The behavioral and electrophysiological analyses in AsOrco-/- mutant found that the spatial repellency elicited by bioallethrin depended on the odorant receptor (OR)-mediated olfactory pathway. Furthermore, the repellency was reduced in the AsOBP1-/- mutant and a pyrethroid-resistant strain, in which the expression of AsOBP1 was significantly decreased. Moreover, recombinant AsOBP1 protein bound to bioallethrin in an in vitro competition assay. These results indicate that activation of the AsOBP1-mediated olfactory pathway is an important component of bioallethrin repellency. Our research lays the foundation for further elucidation into the olfactory mechanism of bioallethrin repellency and the behavioral modifications of pyrethroid-resistant mosquitoes.

Artificial nighttime lighting impacts Plasmodium falciparum mature stage V gametocytes infectivity in Anopheles stephensi

BackgroundMalaria is one of the most important vector-borne diseases of humans with an estimated 241 million cases worldwide in 2020. As an urban and periurban mosquito species, Anopheles stephensi is exposed to artificial human stimuli like light that can alter many aspects of mosquito behaviour, physiology and metabolism. Therefore, fluctuations in the light environment may influence the host, parasite and/or mosquito biology and hence modulate risk for disease transmission. In this study, the effect of artifitial light at night on mosquito infectivity by Plasmodium falciparum during the first hours of blood digestion was tested.MethodsA total of three independent standard membrane feeding assays were performed to artificially fed septic and aseptic mosquitoes with P. falciparum infected blood. After blood feeding, females were transferred to incubators with different photoperiod cycles, so digestion occurred under day artificial light or dark. At 7 and 16 days post blood feeding, mosquitoes were dissected for midguts and salivary glands, respectively. Percentage of mosquitoes fed, percentage of prevalence and P. falciparum oocyst intensity between septic and aseptic mosquitoes in the two different photoperiod regimes, were compared using a Kruskal-Wallis test followed by a Dunn´s multiple comparison test .ResultsThe exposition of mosquitoes to light after they took an infected blood meal has a negative effect on the successful progression of P. falciparum in the mosquito midgut. Antibiotic treatment significantly incremented the number of oocysts per midgut. Photophase significantly reduced the median oocyst intensity in both septic and aseptic mosquitoes. The percentage of oocyst reduction, understood as the percentage of reduction in the mean oocyst intensity of the parasite in the mosquito midgut between photophase and scotophase, was 51% in the case of aseptic mosquitoes and 80% for septic mosquitoes, both in the photophase condition.ConclusionAlthough there are still many gaps in the understanding of parasite-mosquito interactions, these results support the idea that light can, not only, influence mosquito biting behaviour but also parasite success in the mosquito midgut. Hence, light can be considered an interesting additional mosquito-control strategy to reduce mosquito-borne diseases.

Cross-infectivity of Vorticella sp. across genera of mosquitoes for development of biological mosquito control strategies

Protists in general comprise about one-third of the parasitic species infecting arthropod vectors, the role of free-living and epibiotic ciliates on mosquitoes have been insufficiently studied either due to their low pathogenicity or facultative parasites. Studies have shown that exposure of Paramecium ciliate protists, like Vorticella species, to first instar Culex nigripalpus Theobald, larvae delayed larval development and reduced biomass of emerged adults due to competition for food sources like bacteria and other microbes essential to mosquito growth and survival. Thus, we report on the capacity of a Vorticella sp. protist’s ability to cross-infect host species and parasitize multiple mosquito larvae. The unique adapted behavior with the ability to remain on the exuviae in tree hole habitats provide a novel delivery system to develop products for target species-specific mosquitocides, larvicides, or viricides to be applied and sustained in aquatic systems.

A multiplexed, confinable CRISPR/Cas9 gene drive can propagate in caged Aedes aegypti populations

Aedes aegypti is the main vector of several major pathogens including dengue, Zika and chikungunya viruses. Classical mosquito control strategies utilizing insecticides are threatened by rising resistance. This has stimulated interest in new genetic systems such as gene drivesHere, we test the regulatory sequences from the Ae. aegypti benign gonial cell neoplasm (bgcn) homolog to express Cas9 and a separate multiplexing sgRNA-expressing cassette inserted into the Ae. aegypti kynurenine 3-monooxygenase (kmo) gene. When combined, these two elements provide highly effective germline cutting at the kmo locus and act as a gene drive. Our target genetic element drives through a cage trial population such that carrier frequency of the element increases from 50% to up to 89% of the population despite significant fitness costs to kmo insertions. Deep sequencing suggests that the multiplexing design could mitigate resistance allele formation in our gene drive system.

Efficacy of plant products in controlling disease vector mosquitoes, a review

AbstractMosquitoes pose a severe threat to the environment as vectors of numerous harmful diseases affecting humans and animals. Mosquitoes transmit pathogens that cause dengue, chikungunya, malaria, zika, yellow fever, Japanese encephalitis, and filariasis. Today's mosquito control strategies heavily rely on the use of chemical insecticides such as N,N‐diethyl‐meta‐toluamide (DEET), N,N‐diethyl mandelic acid amide (DEM), and dimethyl phthalate (DMP). However, the widespread use of chemical insecticides has resulted in pollution, bio‐magnification, and other health and environmental issues. It has also become ineffective because of the mosquitoes' aptitude to develop resistance, emphasizing the urgent need for safe, effective, and long‐lasting strategies. An alternative and promising approach to circumventing these obstacles involves the implementation of insecticides made from natural compounds found in plants. Therefore, the scientific community has shifted its focus towards plant‐based phytochemicals, oils, and extracts, as these are eco‐friendly, safe, and cost‐effective alternatives to conventional chemical insecticides. This review aims to provide details on current advances in plant‐based products (plant compounds, extracts, and essential oils), which are used to control all the life cycle stages (egg, larva, pupa, and adult) of the mosquito genera Aedes, Anopheles, and Culex. Hopefully, this review will pave the way to devise control strategies against these challenging pests.

Comparative Analysis: Larvicidal efficacy of traditional Saudi Arabian herbs and boric acid against Aedes aegypti larvae, the Dengue fever vector

Aim: This study evaluates the larvicidal properties of traditional Saudi Arabian herbs compared to Boric acid against the Aedes aegypti larval stage. Methodology: An evaluation of the larvicidal activity of eight plant extracts, as well as Boric acid, was conducted with Ae. aegypti larvae in the 3rd and 4th larval stages. Through stereo-dissecting microscope, morphological and death defects in larvae treated with Boric acid were documented. Results: The results showed that the mortality rates ranged from 59.3 to 98.3% at 30% concentration. Particularly noteworthy were Boric acid, M. chamomilla, and C. zeylanicum, demonstrating mortality rates of 100 to 89%, falling within the highly effective category. E. cardamomum, C. arabica, and A. sativum exhibited moderate efficacy (88 to 70%) whereas C. sinensis, P. nigrum and I. paraguariensis manifested relatively lower effectiveness (50 to 69%). Significantly, Boric acid showcased remarkable potency, inducing mortality rates of 28.3% even at an infinitesimal concentration of 1 ppm, accompanied by distinct malformation effects on treated larvae. These findings underscore the unparalleled larvicidal prowess of Boric acid, positioning it as a paramount choice for integrated mosquito control strategies. Interpretation: Furthermore, Boric acid accessibility, cost-effectiveness, and minimal impact on ecological systems and human health make it a compelling solution for mitigating Ae. aegypti populations, thereby fortifying our arsenal against mosquito-borne diseases. Key words: Aedes aegypti, Biological control, Boric acid, Plant extract

Dengue is a product of the environment: an approach to the impacts of the environment on the Aedes aegypti mosquito and disease cases.

Dengue is an arbovirus infection whose etiologic agent is transmitted by the Aedes aegypti mosquito. Since the early 1980s, when the circulation of the dengue virus (DENV) was confirmed in Brazil, the disease has become a growing multifactorial public health problem. This article presented the main factors that have contributed to the frequent dengue epidemics in recent years, such as the behavior of the vector, climate change, and social, political, and economic aspects. The intersection between these different factors in the dynamics of the disease is highlighted, including the increase in the mosquito population due to higher temperatures and rainy periods, as well as the influence of socioeconomic conditions on the incidence of dengue. Some mosquito control strategies are also addressed, including the use of innovative technologies such as drones and the Wolbachia bacterium, as well as the hope represented by the dengue vaccine. Nevertheless, the need for integrated and effective public policies to reduce social inequalities and the impacts of climate change on the spread of dengue is emphasized.

Mosquito Control Strategies and Insecticide Resistance of the Malaria Vector in Urbanized Land Use Types in Suame Municipality, Ghana.

Modified landscapes could create breeding habitats for mosquitoes and affect their community structure and susceptibility with implications for their management. Hence, in this study, household mosquito control methods in two urbanized landscapes; industrial and residential human settlements, in Ghana and insecticide susceptibility of the inhabiting Anopheles populations were assessed. Household knowledge and usage pattern of mosquito control methods in the modified landscapes were obtained using a questionnaire. Female adult Anopheles mosquitoes were also subjected to susceptibility tests using mosquito coils (0.08% meperfluthrin, 0.03% dimefluthrin, and 0.3% transfluthrin) and World Health Organization (WHO) insecticide test papers (0.05% deltamethrin, 4% DDT, 0.1% bendiocarb, 0.25% pirimiphos-methyl, and 5% malathion). Although insecticide-treated nets and aerosols were used for mosquito control, mosquito coils were the most common and widely preferred household method. The Anopheles mosquitoes were resistant to all the insecticides (mosquito coils and WHO test papers) except pirimiphos-methyl. Land use type did not affect insecticide resistance, but the insecticide type did. The findings indicate the effect of household insecticide usage practices on local mosquito populations and their implications for effective vector management and disease control in modified landscapes.

Chemical composition of four essential oils and their adulticidal, repellence, and field oviposition deterrence activities against Culex pipiens L. (Diptera: Culicidae)

Effective mosquito repellents can limit the transmission of vector-borne diseases to humans. Consequently, there is an urgent need to develop mosquito control strategies that prioritize eco-friendly and cost-effective repellents. Essential oils (EOs) have enormous potential for mosquito repellency. Here, cinnamon, basil, eucalyptus, and peppermint EOs were investigated for adulticide and repellency properties against Culex pipiens as well on the oviposition behavior of gravid females from laboratory (lab test) and field (field test) populations. Cinnamon oil was an effective oviposition deterrent regardless of the population and had high adulticidal activity with toxicity index of 75.00% at 24 h of exposure, relative to deltamethrin. In addition, it exhibited effective repellency at 98.01% and 71.22% at 6.67 and 1.71 µl/cm2, respectively. Peppermint oil had the least adulticidal activity with toxicity index of 6.2% at 24 h, and it resulted in low repellency at 70.90% and 50.64% at 6.67 and 1.71 µl/cm2, respectively. On average, basil and eucalyptus oils showed some adulticidal efficiency, repellency, and oviposition deterrent activity. For all treatments, the oviposition deterrent index values of gravid females from natural populations (field test) were lower than those from lab-reared (lab test) females. Different ratios of monoterpenoids, phenylpropanoids, and fatty acids in the EOs tested likely account for the activity variations observed. Our results suggest cinnamon, basil, eucalyptus, and peppermint EOs, which are widely available, economical, and eco-friendly, with good potential for mosquito control strategies.

Coffee arabica-derived copper nanoparticles: A potent larvicidal agent against Aedes aegypti mosquitoes

Mosquito-borne diseases, such as those transmitted by Aedes aegypti mosquitoes, are a major public health concern. This study examined the larvicidal activity of Coffee arabica-mediated copper nanoparticles (CuNPs) against Aedes aegypti mosquito larvae. CuNPs were synthesized from Coffee arabica extract and characterized using advanced techniques such as UV spectroscopy, FTIR, and X-ray diffraction. The extract contained bioactive compounds with antioxidant properties. Green coffee had higher total phenolic content (TPC) and total flavonoid capacity (TFC) than roasted coffee. Green coffee extract exhibited stronger antioxidant activity and lower IC50 values compared to roasted coffee extract. The larvicidal effects of green and roasted Coffee arabica extracts were assessed. Green Coffee arabica had LC50 and LC90 concentrations of 124.5 ppm and 456.5 ppm, respectively, while roasted Coffee arabica had concentrations of 73.5 ppm and 371.5 ppm. CuNPs at concentrations of 2 to 100 ppm resulted in LC50 and LC90 concentrations of 5.796 ppm and 36.595 ppm. The synthesized CuNPs demonstrated concentration-dependent mortality, with lower LC50 values compared to coffee extracts alone. Histological analysis showed tissue degradation in treated larvae, particularly in the head region. Copper nanoparticles had a detrimental effect on Artemia salina larvae, with higher concentrations leading to increased mortality. The LC50 and LC90 values for Artemia salina were determined as 344.3 ppm and 1073.2 ppm, respectively. Overall, Coffee arabica-mediated copper nanoparticles displayed potent larvicidal activity against Aedes aegypti mosquitoes, indicating their potential use in eco-friendly mosquito control strategies.

On the Origin and Evolution of the Mosquito Male-determining Factor Nix.

The mosquito family Culicidae is divided into 2 subfamilies named the Culicinae and Anophelinae. Nix, the dominant male-determining factor, has only been found in the culicines Aedes aegypti and Aedes albopictus, 2 important arboviral vectors that belong to the subgenus Stegomyia. Here we performed sex-specific whole-genome sequencing and RNAseq of divergent mosquito species and explored additional male-inclusive datasets to investigate the distribution of Nix. Except for the Culex genus, Nix homologs were found in all species surveyed from the Culicinae subfamily, including 12 additional species from 3 highly divergent tribes comprising 4 genera, suggesting Nix originated at least 133 to 165 million years ago (MYA). Heterologous expression of 1 of 3 divergent Nix open reading frames (ORFs) in Ae. aegypti resulted in partial masculinization of genetic females as evidenced by morphology and doublesex splicing. Phylogenetic analysis suggests Nix is related to femaleless (fle), a recently described intermediate sex-determining factor found exclusively in anopheline mosquitoes. Nix from all species has a conserved structure, including 3 RNA-recognition motifs (RRMs), as does fle. However, Nix has evolved at a much faster rate than fle. The RRM3 of both Nix and fle are distantly related to the single RRM of a widely distributed and conserved splicing factor transformer-2 (tra2). The RRM3-based phylogenetic analysis suggests this domain in Nix and fle may have evolved from tra2 or a tra2-related gene in a common ancestor of mosquitoes. Our results provide insights into the evolution of sex determination in mosquitoes and will inform broad applications of mosquito-control strategies based on manipulating sex ratios toward nonbiting males.

Overexpression of cytochrome P450 and esterase genes involved in permethrin resistance in larvae and adults of Culex quinquefasciatus.

Mosquitoes are important vectors of several arthropod-borne diseases, which remain a priority for epidemiological research. Mosquito vector control strategies have traditionally relied on chemical insecticides such as synthetic pyrethroids. However, the indiscriminate use of pesticides has resulted in the development of resistance in many mosquito species. In insects, resistance evolves primarily through the overexpression of one or more gene products from the cytochrome P450, carboxylesterase, and glutathione superfamilies. The current study examined the expression of cytochrome P450 CYP6M2, CYP6AA7, CYP6Z2, CYP9J34, α-Esterase, Esterase B1, and neuroactin genes in larvae and adults of a permethrin-resistant (PerRes) and susceptible (Sus) Culex quinquefasciatus strains. The results showed that the CYP6AA7 gene was overexpressed (10-fold) in larvae and adults with PerRes (p < 0.01) followed by CYPJ34 (9.0-fold) and CYP6Z2 (5.0-fold) compared to the Sus, whereas fewer changes in CYP6M gene expression were observed in PerRes adults (p < 0.05), and no expression was found in larvae. The esterase gene was overexpressed in PerRes larvae (9.0-fold) followed by adults (2.5-fold) compared to the susceptible strain. Based on data, the present study suggests that cytochrome P450, CYP6AA7, CYP6Z2, CYP9J34, α-Esterase, Esterase B1, and neuroactin genes were involved in permethrin resistance in larval and adult Cx. quinquefasciatus.

Exploring the bioactive potential leaves of Sphaeranthus indicus: Targeting immature stages of Aedes aegypti and Culex quinquefasciatus mosquito vectors through bioassay-guided screening and fraction isolation

Mosquito control is vital for combating mosquito-borne diseases, but concerns exist regarding the use of synthetic insecticides. This study aimed to explore eco-friendly alternatives derived from natural sources. The larvicidal, pupicidal, and ovicidal activities of various fractions obtained from the hexane leaf extract of Sphaeranthus indicus were investigated against two important mosquito vectors, Aedes aegypti and Culex quinquefasciatus. S. indicus leaves were extracted with hexane and column chromatography was performed with hexane, ethyl acetate, methanol, and their mixtures as eluents. Among the ten fractions (F1-F10) evaluated, fraction ‘F-4’ exhibited significant activity against third instar larvae, pupae, and eggs of both mosquito species, closely followed by ‘F-5’ . At a concentration of 10 ppm, ‘F-4’ achieved 100% mortality in larvae and displayed LC50 values of 5.08 ppm and 5.03 ppm for Ae. aegypti and Cx. quinquefasciatus larvae, respectively. The LC50 values for pupae were 6.12 ppm and 5.83 ppm for Ae. aegypti and Cx. quinquefasciatus, respectively. Regarding ovicidal activity, ‘F-4’ demonstrated percentages ranging from 63.2% to 64.8% against Ae. aegypti and Cx. quinquefasciatus eggs, respectively. These findings underscore the potent larvicidal, pupicidal, and ovicidal effects of fraction ‘F-4’ from S. indicus against the targeted mosquito species. Further research is warranted to identify the active compounds responsible for these effects and explore practical applications for sustainable mosquito control strategies.

Characterization of essential eggshell proteins from Aedes aegypti mosquitoes

BackgroundUp to 40% of the world population live in areas where mosquitoes capable of transmitting the dengue virus, including Aedes aegypti, coexist with humans. Understanding how mosquito egg development and oviposition are regulated at the molecular level may provide new insights into novel mosquito control strategies. Previously, we identified a protein named eggshell organizing factor 1 (EOF1) that when knocked down with RNA interference (RNAi) resulted in non-melanized and fragile eggs that did not contain viable embryos.ResultsIn this current study, we performed a comprehensive RNAi screen of putative A. aegypti eggshell proteins to identify additional proteins that interact with intracellular EOF1. We identified several proteins essential for eggshell formation in A. aegypti and characterized their phenotypes through a combination of molecular and biochemical approaches. We found that Nasrat, Closca, and Polehole structural proteins, together with the Nudel serine protease, are indispensable for eggshell melanization and egg viability. While all four proteins are predominantly expressed in ovaries of adult females, Nudel messenger RNA (mRNA) expression is highly upregulated in response to blood feeding. Furthermore, we identified four additional secreted eggshell enzymes that regulated mosquito eggshell formation and melanization. These enzymes included three dopachrome-converting enzymes (DCEs) and one cysteine protease. All eight of these eggshell proteins were essential for proper eggshell formation. Interestingly, their eggshell surface topologies in response to RNAi did not phenocopy the effect of RNAi-EOF1, suggesting that additional mechanisms may influence how EOF1 regulates eggshell formation and melanization.ConclusionsWhile our studies did not identify a definitive regulator of EOF1, we did identify eight additional proteins involved in mosquito eggshell formation that may be leveraged for future control strategies.

Characterization of a novel cell wall hydrolase CwlE involved in Bacillus thuringiensis subsp. israelensis mother cell lysis.

Cell wall hydrolases are ubiquitous among spore-form bacteria and essential for mother cell lysis. In this study, a novel cell wall hydrolase gene cwlE involved in mother cell lysis was characterized from Bacillus thuringiensis subsp. israelensis (Bti) strain Bt-59. cwlE was specifically expressed in Bti and located in the large plasmid carrying the insecticidal genes. The encoded CwlE protein consists of a MurNAc-LAA domain and two highly conserved catalytic residues (E26 and E151). The recombinant CwlE-His protein was able to digest the cell wall of Bti, indicating that CwlE is an N-acetylmuramoyl-L-alanine amidase. Transcriptional analysis indicated that cwlE began to express at the early stage of stationary phase and was controlled by SigE. Single mutation of cwlE gene delayed Bti mother cell lysis, while double mutation of cwlE and sigK completely blocked Bti mother cell lysis. After exposure to UV light to deactivate the crystal proteins, the level of decrease of insecticidal activity against mosquito larvae of Bt-59 (ΔcwlE-sigK) was less than that observed for Bt-59. This study elucidates the mechanism of Bti mother cell lysis and provides an effective strategy for mosquito control using Bt products with increased persistence.