Mosquito-Borne Diseases Emergence/Resurgence and How to Effectively Control It Biologically

A systematic review on malaria and dengue vaccines for the effective management of these mosquito borne diseases: Improving public health

Insect vector-borne diseases (VBDs) pose significant global health challenges, particularly in tropical and subtropical regions. The WHO has launched the "Global Vector Control Response (GVCR) 2017-2030" to address these diseases, emphasizing a comprehensive approach to vector control. This systematic review investigates the potential of malaria and dengue vaccines in controlling mosquito-borne VBDs, aiming to alleviate disease burdens and enhance public health. Following PRISMA 2020 guidelines, the review incorporated 39 new studies out of 934 identified records. It encompasses various studies assessing malaria and dengue vaccines, emphasizing the significance of vaccination as a preventive measure. The findings indicate variations in vaccine efficacy, duration of protection, and safety considerations for each disease, influencing public health strategies. The review underscores the urgent need for vaccines to combat the increasing burden of VBDs like malaria and dengue, advocating for ongoing research and investment in vaccine development.

Assessment of biorational larvicides and botanical oils against Culex quinquefasciatus Say (Diptera: Culicidae) larvae in laboratory conditions

Mosquitoes are known vectors that transmit deadly diseases to millions of people across the globe. The reliance on synthetic insecticides has been the sole way to combat mosquito vectors for decades. In recent years, the extensive use of conventional insecticides in mosquito suppression has led to significant pesticide resistance and serious human health hazards. In this light, investigating the potential application of biorational compounds for vector management has drawn significant attention. We, hereby, evaluated the efficacy of three microbial derivative biorational insecticides, abamectin, spinosad, and buprofezin, and two botanical oils, neem (Azadirachta indica A. Juss) and karanja oil (Pongamia pinnata Linn.) against the Culex quinquefasciatus under laboratory conditions. The fourth-instar C. quinquefasciatus larvae were exposed to different concentrations of the selected larvicides and lethality was estimated based on LC50 and LT50 with Probit analysis. All larvicides showed concentration-dependent significant effects on survival and demonstrated larvicidal activity against C. quinquefasciatus larvae. However, abamectin exerted the highest toxicity (LC50 = 10.36 ppm), exhibited statistically significant effects on C. quinquefasciatus larval mortality, followed by spinosad (LC50 = 21.32 ppm) and buprofezin (LC50 = 56.34 ppm). Abamectin caused larval mortality ranged from 30.00 to 53.33 % and 53.00-70.00 % at 06 and 07 h after treatment (HAT), respectively. In the case of botanicals, karanja oil (LC50 = 216.61 ppm) was more lethal (more than 1.5 times) and had a shorter lethal time than neem oil (LC50 = 330.93 ppm) and showed a classic pattern of relationship between concentrations and mortality over time. Overall, the present study highlighted the potential of deploying new generation biorational pesticides and botanicals in mosquito vector control programs.

Transgene removal using an in cis programmed homing endonuclease via single-strand annealing in the mosquito Aedes aegypti

While gene drive strategies have been proposed to aid in the control of mosquito-borne diseases, additional genome engineering technologies may be required to establish a defined end-of-product-life timeline. We previously demonstrated that single-strand annealing (SSA) was sufficient to program the scarless elimination of a transgene while restoring a disrupted gene in the disease vector mosquito Aedes aegypti. Here, we extend these findings by establishing that complete transgene removal (four gene cassettes comprising ~8-kb) can be programmed in cis. Reducing the length of the direct repeat from 700-bp to 200-bp reduces, but does not eliminate, SSA activity. In contrast, increasing direct repeat length to 1.5-kb does not increase SSA rates, suggesting diminishing returns above a certain threshold size. Finally, we show that while the homing endonuclease Y2-I-AniI triggered both SSA and NHEJ at significantly higher rates than I-SceI at one genomic locus (P5-EGFP), repair events are heavily skewed towards NHEJ at another locus (kmo), suggesting the nuclease used and the genomic region targeted have a substantial influence on repair outcomes. Taken together, this work establishes the feasibility of engineering temporary transgenes in disease vector mosquitoes, while providing critical details concerning important operational parameters.

Comparison of the cytotoxicity and zebrafish embryo toxicity of insect repellent ingredients: p-Menthane-3,8-diol synthesized by green chemistry from Eucalyptus citriodora and N,N-diethyl-meta-toluamide

Bio-sourced insect repellents are becoming more popular due to their safer applications. Known for its strong fly-repellent property, Cis, trans-para-menthane-3,8-diol (PMD) is the main component of the lemon eucalyptus essential oil and is synthesized from citronellal. In April 2005, US Centers for Disease Control approved two fly repellents that do not contain N,N-diethyl-meta-toluamide (DEET), including PMD. Due to the intentional and pervasive human exposure caused by DEET as insect repellent, concerns have been raised about its toxicological profile and potential harm to people. We hypothesized PMD would have a different toxicological profile than DEET. We synthesized PMD from Eucalyptus citriodora using green chemistry methods and analyzed its structures by 1H-NMR,13C-NMR, and GC/MS spectral methods. We used MTS assay to determine the percentage inhibition of PMD and DEET on keratinocyte (human epidermal keratinocyte [HaCaT]) cells. The xCelligence system was used and followed at real time. Effects of PMD and DEET on zebrafish embryo development were monitored and levels of lipid peroxidation, glutathione-S-transferase (GST), superoxide dismutase (SOD), and acetylcholinesterase (AchE) were evaluated at 72 h post-fertilization using spectrophotometric methods. Our results showed that while DEET inhibited human keratinocyte cell growth, while imporved cell viability and proliferation was exposed in PMD exposed group. In zebrafish embryos, PMD was less toxic in terms of development, oxidant-antioxidant status, and AChE activities than DEET. Based on these results we suggest an efficient method using green chemistry for the synthesis of PMD, which is found to be less toxic in zebrafish embryos and human keratinocyte cells.

A DNA barcode reference library of Croatian mosquitoes (Diptera: Culicidae): implications for identification and delimitation of species, with notes on the distribution of potential vector species

BACKGROUND

Mosquitoes pose a risk to human health worldwide, and correct species identification and detection of cryptic species are the most important keys for surveillance and control of mosquito vectors. In addition to traditional identification based on morphology, DNA barcoding has recently been widely used as a complementary tool for reliable identification of mosquito species. The main objective of this study was to create a reference DNA barcode library for the Croatian mosquito fauna, which should contribute to more accurate and faster identification of species, including cryptic species, and recognition of relevant vector species.

METHODS

Sampling was carried out in three biogeographical regions of Croatia over six years (2017-2022). The mosquitoes were morphologically identified; molecular identification was based on the standard barcoding region of the mitochondrial COI gene and the nuclear ITS2 region, the latter to identify species within the Anopheles maculipennis complex. The BIN-RESL algorithm assigned the COI sequences to the corresponding BINs (Barcode Index Number clusters) in BOLD, i.e. to putative MOTUs (Molecular Operational Taxonomic Units). The bPTP and ASAP species delimitation methods were applied to the genus datasets in order to verify/confirm the assignment of specimens to specific MOTUs.

RESULTS

A total of 405 mosquito specimens belonging to six genera and 30 morphospecies were collected and processed. Species delimitation methods assigned the samples to 31 (BIN-RESL), 30 (bPTP) and 28 (ASAP) MOTUs, with most delimited MOTUs matching the morphological identification. Some species of the genera Culex, Aedes and Anopheles were assigned to the same MOTUs, especially species that are difficult to distinguish morphologically and/or represent species complexes. In total, COI barcode sequences for 34 mosquito species and ITS2 sequences for three species of the genus Anopheles were added to the mosquito sequence database for Croatia, including one individual from the Intrudens Group, which represents a new record for the Croatian mosquito fauna.

CONCLUSION

We present the results of the first comprehensive study combining morphological and molecular identification of most mosquito species present in Croatia, including several invasive and vector species. With the exception of some closely related species, this study confirmed that DNA barcoding based on COI provides a reliable basis for the identification of mosquito species in Croatia.

TNF signaling mediates cellular immune function and promotes malaria parasite killing in the mosquito Anopheles gambiae

Tumor Necrosis Factor-α (TNF-α) is a proinflammatory cytokine and a master regulator of immune cell function in vertebrates. While previous studies have implicated TNF signaling in invertebrate immunity, the roles of TNF in mosquito innate immunity and vector competence have yet to be explored. Herein, we confirm the identification of a conserved TNF-α pathway in Anopheles gambiae consisting of the TNF-α ligand, Eiger, and its cognate receptors Wengen and Grindelwald. Through gene expression analysis, RNAi, and in vivo injection of recombinant TNF-α, we provide direct evidence for the requirement of TNF signaling in regulating mosquito immune cell function by promoting granulocyte midgut attachment, increased granulocyte abundance, and oenocytoid rupture. Moreover, our data demonstrate that TNF signaling is an integral component of anti-Plasmodium immunity that limits malaria parasite survival. Together, our data support the existence of a highly conserved TNF signaling pathway in mosquitoes that mediates cellular immunity and influences Plasmodium infection outcomes, offering potential new approaches to interfere with malaria transmission by targeting the mosquito host.

Influence of insular conditions on wing phenotypic variation in two dominant mosquito vectors, Aedes albopictus and Armigeres subalbatus (Diptera: Culicidae), in the border archipelagos of Thailand

Insects geographically separated into island and mainland populations often exhibit phenotypic variations, a phenomenon known as insular conditions. These conditions can lead to rapid evolutionary changes that affect the morphological characteristics of mosquito vectors. Nevertheless, studies that specifically examine phenotype differences between island and mainland mosquito populations have been limited. In this study, wing variation in size and shape was investigated using the geometric morphometric (GM) technique in two dominant mosquito vectors, Aedes albopictus and Armigeres subalbatus, in the Ranong and Trat archipelagos of Thailand. Significant differences in average wing centroid size (CS) were found in 6 out of 15 population pairs for Ae. albopictus (p < 0.05) and in 5 population pairs for Ar. subalbatus (p < 0.05). After removing the allometric effect, canonical variate analyses (CVA) based on wing shape analysis revealed overlap across all populations for both Ae. albopictus and Ar. subalbatus. However, the statistical analysis indicated that Ar. subalbatus exhibited wing shape differences across all populations (p < 0.05), and most Ae. albopictus populations also displayed distinct wing shapes (p < 0.05), except for the populations from Chang Island and the mainland of Ranong, which showed no significant differences (p > 0.05). These findings enhance our understanding of mosquito adaptability in island regions and provide valuable data for the surveillance and monitoring of vector evolution.

Systematic review of clinical manifestations, management and outcome following accidental ingestion of liquid mosquito repellent vaporiser in children

BACKGROUND

Pyrethroid-based mosquito repellents are widely used to control mosquito-borne diseases. Liquid mosquito-repellent vaporisers are effective modes of pyrethroid delivery but can also pose significant health risks if ingested or used improperly.

OBJECTIVE

This systematic review was performed to assess the demographic distribution, clinical presentation, management strategies and outcomes in children resulting from accidental ingestion of liquid mosquito repellent vaporiser.

METHODS

The study adheres to the reporting standards outlined in the PRISMA Statement for Systematic Reviews and was prospectively registered with PROSPERO (record # CRD42023413937) to enhance transparency and minimise reporting bias. A comprehensive search was conducted on PubMed, Scopus and Google Scholar using specific MeSH terms related to insecticides, mosquito repellents, pyrethroids, ingestion, poisoning, toxicity and prevention. The reference lists of the included studies were also reviewed for additional relevant articles. The inclusion criteria involved studies published in peer-reviewed journals between 2000 and 2023 that focused on children under 18 years old with a history of mosquito-repellent ingestion based on primary data.

RESULTS

Twelve studies met the inclusion criteria; these were primarily case reports from India, China and the UAE. Male children were predominantly affected, and symptoms included vomiting, convulsions, cough and respiratory distress. Management primarily involved supportive and symptomatic measures, including atropine for salivation and antiepileptic drugs for seizures. Respiratory support was provided for respiratory complications.

CONCLUSION

Despite the known risks and diverse presentations of pyrethroid poisoning caused by liquid mosquito repellent vaporiser in children, the limited substantial evidence in the literature underscores the urgent need for comprehensive research to refine management approaches and enhance preventive measures.

Influence of microbiota-driven natural antibodies on dengue transmission

Dengue has had a significant global health impact, with a dramatic increase in incidence over the past 50 years, affecting more than 100 countries. The absence of a specific treatment or widely applicable vaccine emphasizes the urgent need for innovative strategies. This perspective reevaluates current evidence supporting the concept of dual protection against the dengue virus (DENV) through natural antibodies (NAbs), particularly anti-α-Gal antibodies induced by the host's gut microbiome (GM). These anti-α-Gal antibodies serve a dual purpose. Firstly, they can directly identify DENV, as mosquito-derived viral particles have been observed to carry α-Gal, thereby providing a safeguard against human infections. Secondly, they possess the potential to impede virus development in the vector by interacting with the vector's microbiome and triggering infection-refractory states. The intricate interplay between human GM and NAbs on one side and DENV and vector microbiome on the other suggests a novel approach, using NAbs to directly target DENV and simultaneously disrupt vector microbiome to decrease pathogen transmission and vector competence, thereby blocking DENV transmission cycles.

Insights and Challenges for the Development of Mosquito Control Action Thresholds Using Historical Mosquito Surveillance and Climate Datasets

Strategies to advance action threshold development can benefit both civilian and military vector control operations. The Anastasia Mosquito Control District (AMCD) has curated an extensive record database of surveillance programs and operational control activities in St. Johns County, Florida, since 2004. A thorough exploratory data analysis was performed on historical mosquito surveillance and county-wide climate data to identify climate predictors that could be used in constructing proactive threshold models for initiating control of Aedes, Culex, and Anopheles vector mosquitoes. Species counts pulled from Centers for Disease Control and Prevention (CDC) light trap (2004-2019) and BG trap (2014-2019) collection records and climate parameters of temperature (minimum, maximum, average), rainfall, and relative humidity were used in two iterations of generalized linear models. Climate readings were incorporated into models 1) in the form of continuous measurements, or 2) for categorization into number of "hot," "wet," or "humid" days by exceedance of selected biological index threshold values. Models were validated with tests of residual error, comparison of model effects, and predictive capability on testing data from the two recent surveillance seasons 2020 and 2021. Two iterations of negative binomial regression models were constructed for 6 species groups: container Aedes (Ae. aegypti, Ae. albopictus), standing water Culex (Cx. nigripalpus, Cx. quinquefasciatus), floodwater Aedes (Ae. atlanticus, Ae. infirmatus), salt-marsh Aedes (Ae. taeniorhyncus, Ae. sollicitans), swamp water Anopheles (An. crucians), and a combined Total Mosquitoes group. Final significant climate predictors varied substantially between species groups. Validation of models with testing data displayed limited predictive abilities of both model iterations. The most significant climate predictors for floodwater Aedes, the dominant and operationally influential species group in the county, were either total precipitation or frequency of precipitation events (number of "wet" days) at two to four weeks before trap collection week. Challenges hindering the construction of threshold models were discussed. Insights gained from these models provide initial feedback for streamlining the AMCD mosquito control program and analytical recommendations for future modelling efforts of interested mosquito control programs, in addition to generalized guidance for deployed armed forces personnel with needs of mosquito control but lacking active surveillance programs.

A Non-Active-Site Inhibitor with Selectivity for Zika Virus NS2B-NS3 Protease

Flavivirus infection usually results in fever accompanied by headache, arthralgia, and, in some cases, rash. Although the symptoms are mild, full recovery can take several months. Flaviviruses encode seven nonstructural proteins that represent potential drug targets for this viral family. Focusing on the Zika virus NS2B-NS3 protease, we uncovered a unique inhibitor, MH1, composed of aminothiazolopyridine and benzofuran moieties. MH1 inhibits ZVP with a biochemical IC50 of 440 nM and effectively blocks cleavage of ZVP substrates in cells. Surprisingly, MH1 inhibits the other flaviviral proteases at least 18-fold more weakly. This same phenomenon was observed in assays of the viral cytopathic effect, where only Zika virus showed sensitivity to MH1. This selectivity was unexpected since flaviviral proteases have high similarity in sequence and protein structure. MH1 binds at an allosteric site, as demonstrated by its ability to stabilize ZVP synergistically with an active site inhibitor. To understand its selectivity, we constructed a series of hybrid proteases composed of select segments of ZVP, which is sensitive to MH1, and dengue virus protease, which is essentially insensitive to MH1. Our results suggest that MH1 binds to the NS3 protease domain, disrupting its interaction with NS2B. These interactions are essential for substrate binding and cleavage. In particular, the unique dynamic properties of NS2B from Zika seem to be required for the function of MH1. Insights into the mechanism of MH1 function will aid us in developing non-active-site-directed, pan-flaviviral inhibitors, by highlighting the importance of evaluating and considering the dynamics of the NS2B regions.

Metatranscriptomic Sequencing of Medically Important Mosquitoes Reveals Extensive Diversity of RNA Viruses and Other Microbial Communities in Western Australia

Mosquitoes harbor a wide diversity of microorganisms, including viruses that are human pathogens, or that are insect specific. We used metatranscriptomics, an unbiased high-throughput molecular approach, to describe the composition of viral and other microbial communities in six medically important mosquito species from across Western Australia: Aedes vigilax, Culex annulirostris, Cx. australicus, Cx. globocoxitus, Cx. pipiens biotype molestus, and Cx. quinquefasciatus. We identified 42 viral species, including 13 novel viruses, from 19 families. Culex mosquitoes exhibited a significantly higher diversity of viruses than Aedes mosquitoes, and no virus was shared between the two genera. Comparison of mosquito populations revealed a heterogenous distribution of viruses between geographical regions and between closely related species, suggesting that geography and host species may play a role in shaping virome composition. We also detected bacterial and parasitic microorganisms, among which Wolbachia bacteria were detected in three members of the Cx. pipiens complex, Cx. australicus, Cx. pipiens biotype molestus, and Cx. quinquefasciatus. In summary, our unbiased metatranscriptomics approach provides important insights into viral and other microbial diversity in Western Australian mosquitoes that vector medically important viruses.

Fine-scale monitoring of insecticide resistance in Aedes aegypti (Diptera: Culicidae) from Sri Lanka and modeling the phenotypic resistance using rational approximation

BACKGROUND

The unplanned and intensified use of insecticides to control mosquito-borne diseases has led to an upsurge of resistance to commonly used insecticides. Aedes aegypti, the main vector of dengue, chikungunya, and Zika virus, is primarily controlled through the application of adulticides (pyrethroid insecticides) and larvicides (temephos). Fine spatial-scale analysis of resistance may reveal important resistance-related patterns, and the application of mathematical models to determine the phenotypic resistance status lessens the cost and usage of resources, thus resulting in an enhanced and successful control program.

METHODS

The phenotypic resistance for permethrin, deltamethrin, and malathion was monitored in the Ae. aegypti populations using the World Health Organization (WHO) adult bioassay method. Mosquitoes' resistance to permethrin and deltamethrin was evaluated for the commonly occurring base substitutions in the voltage-gated sodium channel (vgsc) gene. Rational functions were used to determine the relationship between the kdr alleles and the phenotypic resistant percentage of Ae. aegypti in Sri Lanka.

RESULTS

The results of the bioassays revealed highly resistant Ae. aegypti populations for the two pyrethroid insecticides (permethrin and deltamethrin) tested. All populations were susceptible to 5% malathion insecticide. The study also revealed high frequencies of C1534 and G1016 in all the populations studied. The highest haplotype frequency was detected for the haplotype CC/VV, followed by FC/VV and CC/VG. Of the seven models obtained, this study suggests the prediction models using rational approximation considering the C allele frequencies and the total of C, G, and P allele frequencies and phenotypic resistance as the best fits for the area concerned.

CONCLUSIONS

This is the first study to our knowledge to provide a model to predict phenotypic resistance using rational functions considering kdr alleles. The flexible nature of the rational functions has revealed the most suitable association among them. Thus, a general evaluation of kdr alleles prior to insecticide applications would unveil the phenotypic resistance percentage of the wild mosquito population. A site-specific strategy is recommended for monitoring resistance with a mathematical approach and management of insecticide applications for the vector population.

Mosquitocidal Susceptibility and Non-Target Effects of Tricholoma equestre Mushroom (Agaricomycetes) on the Immature Stages of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus

The worldwide scientific community is well aware that mosquitoes are the sole agents responsible for transmitting various dreadful diseases and critical illnesses caused by vector-borne pathogens. The primary objective of this current research was to evaluate the effectiveness of methanol extract from Tricholoma equestre mushroom in controlling the early life stages of Culex quinquefasciatus Say, Anopheles stephensi Liston, and Aedes aegypti (Linnaeus in Hasselquist) mosquitoes. The larvae, pupae and eggs of these mosquitoes were exposed to four different concentrations (62.5 to 500 ppm). After 120 h of treatment, the methanol extract of T. equestre exhibited ovicidal activity ranging from 66% to 80% against the eggs of the treated mosquitoes. It also demonstrated promising larvicidal and pupicidal activity with LC50 values of 216-300 and 230-309 ppm against the early life stages of all three mosquito species. Extensive toxicity studies revealed that the methanol extract from T. equestre had no harmful effects on non-target organisms. The suitability index (SI) or predator safety factor (PSF) indicated that the methanol extract did not harm Poecilia reticulata Peters 1859, (predatory fish), Gambusia affinis S. F. Baird & Girard 1853, dragonfly nymph and Diplonychus indicus Venkatesan & Rao 1871 (water-bug). Gas chromatography-mass spectrometry (GCMS) analysis identified key compounds, including 3-butenenitrile, 2-methyl-(25.319%); 1-butanol, 2-nitro-(18.87%) and oxalic acid, heptyl propyl ester (21.82%) which may be responsible for the observed activity. Furthermore, the formulation based on the methanol extract demonstrated similar effectiveness against all treated mosquitoes at the laboratory level and was found to be non-toxic to mosquito predators. This groundbreaking research represents the first confirmation that methanol extract from T. equestre could be effectively employed in preventing mosquito-borne diseases through mosquito population control programs.

MosChito rafts as a promising biocontrol tool against larvae of the common house mosquito, Culex pipiens

Mosquito control is of paramount importance, in particular, in light of the major environmental alterations associated with human activities, from climate change to the altered distribution of pathogens, including those transmitted by Arthropods. Here, we used the common house mosquito, Culex pipiens to test the efficacy of MosChito raft, a novel tool for mosquito larval control. MosChito raft is a floating hydrogel matrix, composed of chitosan, genipin and yeast cells, as bio-attractants, developed for the delivery of a Bacillus thuringiensis israeliensis (Bti)-based bioinsecticide to mosquito larvae. To this aim, larvae of Cx. pipiens were collected in field in Northern Italy and a novel colony of mosquito species (hereafter: Trescore strain) was established. MosChito rafts, containing the Bti-based formulation, were tested on Cx. pipiens larvae from the Trescore strain to determine the doses to be used in successive experiments. Thus, bioassays with MosChito rafts were carried out under semi-field conditions, both on larvae from the Trescore strain and on pools of larvae collected from the field, at different developmental stages. Our results showed that MosChito raft is effective against Cx. pipiens. In particular, the observed mortality was over 50% after two days exposure of the larvae to MosChito rafts, and over 70-80% at days three to four, in both laboratory and wild larvae. In conclusion, our results point to the MosChito raft as a promising tool for the eco-friendly control of a mosquito species that is not only a nuisance insect but is also an important vector of diseases affecting humans and animals.

Pyruvate kinase is post-translationally regulated by sirtuin 2 in Aedes aegypti mosquitoes

We previously demonstrated that Aedes aegypti pyruvate kinase (AaPK) plays a key role in the regulation of both carbon and nitrogen metabolism in mosquitoes. To further elucidate whether AaPK can be post-translationally regulated by Ae. aegypti sirtuin 2 (AaSirt2), an NAD+-dependent deacetylase that catalyzes the removal of acetyl groups from acetylated lysine residues, we conducted a series of analysis in non-starved and starved female mosquitoes. Transcriptional and protein profiles of AaSirt2, analyzed by qPCR and western blots, indicated that the AaSirt2 is differentially modulated in response to sugar or blood feeding in mosquito tissues dissected at different times during the first gonotrophic cycle. We also found that AaSirt2 is localized in both cytosolic and mitochondrial cellular compartments of fat body and thorax. Multiple lysine-acetylated proteins were detected by western blotting in both cellular compartments. Furthermore, western blotting of immunoprecipitated proteins provided evidence that AaPK is lysine-acetylated and bound with AaSirt2 in the cytosolic fractions of fat body and thorax from non-starved and starved females. In correlation with these results, we also discovered that RNAi-mediated knockdown of AaSirt2 in the fat body of starved females significantly decreased AaPK protein abundance. Notably, survivorship of AaSirt2-deficient females maintained under four different nutritional regimens was not significantly affected. Taken together, our data reveal that AaPK is post-translationally regulated by AaSirt2.

Aedes albopictus microbiota: Differences between wild and mass-reared immatures do not suggest negative impacts from a diet based on black soldier fly larvae and fish food

The "Sterile Insect Technique" (SIT), a promising method to control Aedes albopictus, the Asian tiger mosquito, is gaining increasing interest. Recently, the role of microbiota in mosquito fitness received attention, but the link between microbiota and larval diet in mass rearing programs for SIT remains largely unexplored. We characterized the microbiota of four larval instars, pupae and eggs of non-wild (NW) lab-reared Ae. albopictus fed with a diet based on Black soldier fly (Hermetia illucens) larvae powder and fish food KOI pellets. We compared it with wild (W) field-collected individuals and the bacterial community occurring in rearing water-diet (DIET). A total of 18 bacterial classes with > 0.10% abundance were found overall in the samples, with seven classes being especially abundant. Overall, the microbiota profile significantly differed among NW, W and DIET. Verrucomicrobiae were significantly more abundant in W and DIET, Bacteroidia were more abundant in NW and DIET, and Gammaproteobacteria were only more abundant in W than in DIET. W-eggs microbiota differed from all the other groups. Large differences also appeared at the bacterial genus-level, with the abundance of 14 genera differing among groups. Three ASVs of Acinetobacter, known to have positive effects on tiger mosquitoes, were more abundant in NW than in W, while Serratia, known to have negative or neutral effects on another Aedes species, was less abundant in NW than in W. The bacterial community of W-eggs was the richest in species, while dominance and diversity did not differ among groups. Our data show that the diet based on Black soldier fly powder and fish food KOI influences the microbiota of NW tiger mosquito immature stages, but not in a way that may suggest a negative impact on their quality in SIT programs.

Insecticide resistance: Status and potential mechanisms in Aedes aegypti

Aedes aegypti, an important vector in the transmission of human diseases, has developed resistance to two commonly used classes of insecticides, pyrethroids and organophosphates, in populations worldwide. This study examined sensitivity/resistance to chlorpyrifos, fenitrothion, malathion, deltamethrin, permethrin, and β-cyfluthrin, along with possible metabolic detoxification and target site insensitivity, in three Aedes aegypti mosquito strains. The resistant strain (PR) had developed high levels of resistance to all three pyrethroid insecticides compared to a susceptible population, with 6, 500-, 3200- and 17,000-fold resistance to permethrin, β-cyfluthrin, and deltamethrin, respectively. A newly emerged Ae. aegypti population collected from St. Augustine, Florida (AeStA) showed elevated levels of resistance to malathion (12-fold) and permethrin (25-fold). Synergists DEF (S,S,S,-tributyl phosphorotrithioate) and DEM (diethyl maleate) showed no or minor effects on insecticide resistance in both the AeStA and PRG20strains, but PBO (piperonyl butoxide) completely abolished resistance to both malathion and permethrin in AeStA and partially suppressed resistance in PR. The voltage-gated sodium channel sequences were examined to explore the mechanism that only partially inhibited the suppression of resistance to PBO in PR. Two mutations, V1016G/I and F1534C substitutions, both of which are associated with the development of pyrethroid resistance, were identified in the PRG20 strain but not in AeStA. These results suggest that while cytochrome P450 mediated detoxification may not be solely responsible, it is the major mechanism governing the development of resistance in AeStA. Both P450 mediated detoxification and target site insensitivity through the mutations in the voltage-gated sodium channel contribute to the high levels of resistance in the PRG20 strain.

Current advances in microbiome sciences within the US Department of Defense: part 2 - enabling technologies and environmental microbiomes

Microbiomes involve complex microbial communities wherein the micro-organisms interact with one another as well as their associated hosts or environmental niches. Much of the characterisation of these communities and the associations have been achieved through 'omics' technologies, such as metagenomics, metaproteomics and metametabolomics, and model systems. Recent research in host-associated microbiomes has been aimed at understanding the role microbes may play in host fitness or conversely how host activities/conditions may perturb the microbial community, which can further affect host health. These studies have led to the investigation of detection, intervention or modulation methods, which may serve to provide benefits to the host and advance our understanding of microbiome associations. With the clear implications on human health and disease, the US Department of Defense (DoD) has made microbiome research a priority, with the founding of the Tri-Service Microbiome Consortium (TSMC) to enhance collaboration, coordination,and communication of microbiome research among DoD organisations and partners in academia and industry. DoD microbiome research focuses mainly on the following themes: (1) human health and performance, (2) environmental microbiomes and (3) enabling technologies. This review provides an update of current DoD microbiome research efforts centred on enabling technologies and environmental microbiomes and highlights innovative research being done in academia and industry that can be leveraged by the DoD. These topics were also communicated and further discussed in the Fifth Annual TSMC Symposium. This paper forms part of the special issue of BMJ Military Health dedicated to personalised digital technology for mental health in the Armed Forces.

Optimized high-yield preparation of alkaline-solubilizable crystalline inclusion of the Bacillus thuringiensis Cry4Aa δ-endotoxin expressed in Escherichia coli

The native Cry4Aa δ-endotoxin produced exclusively in Bacillus thuringiensis during sporulation as a ∼130-kDa inactive protoxin is confined within the parasporal crystalline inclusion that dissolves at alkaline pH in the midgut lumen of mosquito larvae. Here, the recombinant Cry4Aa toxin over-expressed in Escherichia coli at 30 °C as an alkaline-sobubilizable inclusion was found inevitably lost during isolation from the cell lysate (pH ∼6.5) of which host cells were pre-suspended in distilled water (pH ∼5.5). When 100 mM KH₂PO₄ (pH 5.0) was used as host cell-suspending buffer, the cell lysate's pH became more acidic (pH 5.5), allowing the expressed protoxin to be entirely retained in the form of crystalline inclusion rather than a soluble form, and thus high-yield recovery of the partially purified inclusion was obtained. Upon dialysis of the alkaline-solubilized protoxin against the KH₂PO₄ buffer, the protoxin precipitate was efficiently recovered and still exhibited high toxicity to Aedes aegypti mosquito larvae. Additionally, the precipitated protoxin was completely resolubilized in 50 mM Na₂CO₃ buffer (pH 9.0) and proteolytically processed by trypsin to produce the 65-kDa activated toxin comprising ∼47- and ∼20-kDa fragments. In silico structural analysis suggested that His¹⁵⁴, His³⁸⁸, His⁵³⁶ and His⁵⁷² were involved in a dissolution of the Cry4Aa inclusion at pH 6.5, conceivably through interchain salt bridge breakage. Altogether, such an optimized protocol described herein was effective for the preparation of alkaline-solubilizable inclusions of the recombinant Cry4Aa toxin in large amounts (>25 mg per liter culture) that would pave the way for further structure-function relationship studies of different Cry toxins.

Human skin bacterial microbiota homeostasis: A delicate balance between health and disease

As the largest organ of the body, the skin acts as a barrier to prevent diseases and harbors a variety of beneficial bacteria. Furthermore, the skin bacterial microbiota plays a vital role in health and disease. Disruption of the barrier or an imbalance between symbionts and pathogens can lead to skin disorders or even systemic diseases. In this review, we first provide an overview of research on skin bacterial microbiota and human health, including the composition of skin bacteria in a healthy state, as well as skin bacterial microbiota educating the immune system and preventing the invasion of pathogens. We then discuss the diseases that result from skin microbial dysbiosis, including atopic dermatitis, common acne, chronic wounds, psoriasis, viral transmission, cutaneous lupus, cutaneous lymphoma, and hidradenitis suppurativa. Finally, we highlight the progress that utilizes skin microorganisms for disease therapeutics, such as bacteriotherapy and skin microbiome transplantation. A deeper knowledge of the interaction between human health and disease and the homeostasis of the skin bacterial microbiota will lead to new insights and strategies for exploiting skin bacteria as a novel therapeutic target.

Choice Modeling for the Commercial Cultivation of Underutilized Aromatic Plants for Producing Mosquito Repellents: Targeting Rural Sector Income Generation

Tropical countries face considerable economic losses due to mosquito-borne diseases which can be effectively combatted using plant-based mosquito repellents. Therefore, using a questionnaire survey, we selected the 25 top-ranked common but underutilized aromatic plants with mosquito repellent ability in Sri Lanka to investigate the rural sector's willingness to cultivate and supply them. Cinnamomum verum, Citrus aurantiifolia, Citrus sinensis, Citrus reticulata, Aegle marmelos, and Ocimum tenuiflorum were the common species thus identified. The willingness to cultivate and supply aromatic plants with mosquito repellent ability varied between 88% and 60%. The Chi-squared test indicated a significant association between gender and willingness to cultivate and supply these plants. Men had a higher willingness (82%). Persons formally educated up to elementary school level had the highest willingness (85%). The willingness from households with many non-income-generating members was 100%. The random forest model developed in this study identifies farmers' willingness to cultivate and supply aromatic plants with mosquito repellent properties. It was trained using an upsampling strategy. Our findings aid in understanding the scenarios involved with introducing, cultivating, and supplying aromatic plants.

Northern and Central Chile still free of emerging flaviviruses in mosquitoes (Diptera: Culicidae)

Geographic isolation and strict control limits in border areas have kept Chile free from various pathogens, including Flavivirus. However, the scenario is changing mainly due to climate change, the reintroduction of more aggressive mosquitoes, and the great wave of migration of people from endemic countries in recent years. Hence, it is necessary to surveillance mosquitoes to anticipate a possible outbreak in the population and take action to control it. This study aimed to investigate the presence of Flavivirus RNA by molecular tools with consensus primers in mosquitoes collected in the extreme north and central Chile. From 2019 to 2021, a prospective study was carried out in localities of Northern and part of Central Chile. Larvae, pupae, and adults of mosquitoes were collected in rural and urban sites in each locality. The collected samples were pooled by species and geographical location and tested using RT-PCR and RT-qPCR to determine presence of Flavivirus. 3085 specimens were collected, the most abundant specie Culex quinquefasciatus in the North and Aedes (Ochlerotatus) albifasciatus in the Center of Chile. Both genera are associated with Flavivirus transmission. However, PCR and RT-PCR did not detect Flavivirus RNA in the mosquitoes studied. These negative results indicate we are still a free Flavivirus country, which is reaffirmed by the non-existence of endemic human cases. Despite this, routine surveillance of mosquitoes and the pathogens they carry is highly recommended to evaluate each area-specific risk of vector-borne transmission.

The chaperone BiP promotes dengue virus replication and mosquito vitellogenesis in Aedes aegypti

Binding immunoglobulin protein (BiP, also known as GRP78), a chaperone and master regulator of the unfolded protein response (UPR) pathway, plays an essential role in several flavivirus infections, but its functional role in regulating dengue virus replication in the mosquito remains largely unknown. We here demonstrated the interaction between a dengue virus serotype 2 (DENV2) and BiP in Aedes aegypti and report the discovery of a novel functional role of BiP in mosquito vitellogenesis. Silencing Ae. aegypti BiP (AaBiP) expression resulted in the significant inhibition of DENV2 viral genome replication, viral protein production, and infectious viral particle biogenesis. Co-immunoprecipitation assays showed that the DENV2 non-structural protein 1 (NS1) interacts with the AaBiP protein, and silencing AaBiP expression led to enhanced DENV2 NS1 aggregation, indicating that AaBiP plays a role in viral protein stability. A kinetic study focusing on pulse treatment of MG132, a proteasome inhibitor, in AaBiP-silenced mosquitoes showed that DENV2 NS1 was drastically elevated, which further suggests that AaBiP-mediated viral protein degradation is mediated by proteasomal machinery. Silencing of AaBiP also resulted in a reduction in mosquito fertility and fecundity. Depletion of AaBiP inhibited mosquito vitellogenesis due to the reduction of vitellogenin mRNA and elevated aggregation of vitellogenin protein post blood meal, further suppressing ovary development and fecundity. Overall, our results suggest that AaBiP is a dual-function protein with roles in both the regulation of dengue virus replication and mosquito reproduction. Our findings will be useful in the establishment of more efficient strategies for vector-borne disease control.

The Others: A Systematic Review of the Lesser-Known Arboviruses of the Insular Caribbean

The Caribbean enjoys a long-standing eminence as a popular tourist destination; however, over the years it has also amassed the sobriquet "arbovirus hotspot". As the planet warms and vectors expand their habitats, a cognizant working knowledge of the lesser-known arboviruses and the factors that influence their emergence and resurgence becomes essential. The extant literature on Caribbean arboviruses is spread across decades of published literature and is quite often difficult to access, and, in some cases, is obsolete. Here, we look at the lesser-known arboviruses of the insular Caribbean and examine some of the drivers for their emergence and resurgence. We searched the scientific literature databases PubMed and Google Scholar for peer-reviewed literature as well as scholarly reports. We included articles and reports that describe works resulting in serological evidence of the presence of arboviruses and/or arbovirus isolations in the insular Caribbean. Studies without serological evidence and/or arbovirus isolations as well as those including dengue, chikungunya, Zika, and yellow fever were excluded. Of the 545 articles identified, 122 met the inclusion criteria. A total of 42 arboviruses were identified in the literature. These arboviruses and the drivers that affect their emergence/resurgence are discussed.

Mosquito-Borne Diseases and Their Control Strategies: An Overview Focused on Green Synthesized Plant-Based Metallic Nanoparticles

Mosquitoes act as vectors of pathogens that cause most life-threatening diseases, such as malaria, Dengue, Chikungunya, Yellow fever, Zika, West Nile, Lymphatic filariasis, etc. To reduce the transmission of these mosquito-borne diseases in humans, several chemical, biological, mechanical, and pharmaceutical methods of control are used. However, these different strategies are facing important and timely challenges that include the rapid spread of highly invasive mosquitoes worldwide, the development of resistance in several mosquito species, and the recent outbreaks of novel arthropod-borne viruses (e.g., Dengue, Rift Valley fever, tick-borne encephalitis, West Nile, yellow fever, etc.). Therefore, the development of novel and effective methods of control is urgently needed to manage mosquito vectors. Adapting the principles of nanobiotechnology to mosquito vector control is one of the current approaches. As a single-step, eco-friendly, and biodegradable method that does not require the use of toxic chemicals, the green synthesis of nanoparticles using active toxic agents from plant extracts available since ancient times exhibits antagonistic responses and broad-spectrum target-specific activities against different species of vector mosquitoes. In this article, the current state of knowledge on the different mosquito control strategies in general, and on repellent and mosquitocidal plant-mediated synthesis of nanoparticles in particular, has been reviewed. By doing so, this review may open new doors for research on mosquito-borne diseases.

MosChito rafts as effective and eco-friendly tool for the delivery of a Bacillus thuringiensis-based insecticide to Aedes albopictus larvae

Adult mosquito females, through their bites, are responsible for the transmission of different zoonotic pathogens. Although adult control represents a pillar for the prevention of disease spread, larval control is also crucial. Herein we characterized the effectiveness of a suitable tool, named "MosChito raft", for the aquatic delivery of a Bacillus thuringiensis var. israelensis (Bti) formulate, a bioinsecticide active by ingestion against mosquito larvae. MosChito raft is a floating tool composed by chitosan cross-linked with genipin in which a Bti-based formulate and an attractant have been included. MosChito rafts (i) resulted attractive for the larvae of the Asian tiger mosquito Aedes albopictus, (ii) induced larval mortality within a few hours of exposure and, more importantly, (iii) protected the Bti-based formulate, whose insecticidal activity was maintained for more than one month in comparison to the few days residual activity of the commercial product. The delivery method was effective in both laboratory and semi-field conditions, demonstrating that MosChito rafts may represent an original, eco-based and user-friendly solution for larval control in domestic and peri-domestic aquatic habitats such as saucers and artificial containers in residential or urban environments.

Evaluating the Mating Competency of Genetically Modified Male Mosquitoes in Laboratory Conditions

Efforts to eradicate mosquito-borne diseases have increased the demand for genetic control strategies, many of which involve the release of genetically modified (GM) mosquito males into natural populations. The first hurdle for GM males is to compete with their wild-type counterparts for access to females. Here, we introduce an eye color-based mating assay, in which both Lvp wild-type and kynurenine 3-monooxygenase (kmo)-null males compete for access to kmo-null females, and therefore the eye color phenotype (black or white) of the progeny is dependent on the parental mating pair. A series of tests addressed that male mating competitiveness between the two strains can significantly be influenced by adult density, light intensity, and mating duration. Interestingly, the mating competitiveness of males was not correlated with body size, which was negatively influenced by a high larval density. Lastly, this eye color-associated assay was applied to characterize GM mosquitoes in their mating competitiveness, establishing this method as a fast and precise way of benchmarking this fitness parameter for laboratory-raised males.

Laboratory and semi-field evaluation on OmniPrene™ G against Aedes, Anopheles and Culex mosquitoes

With the current existing, emerging, and resurging mosquito species and mosquito-borne diseases, and very low availability of mosquito control products, exploration of novel active ingredients and innovative formulations based on available active ingredients are crucial to ensure the sustainable mosquito control interventions. The larviciding by applying biorational mosquito larvicides with microbial and insect growth regulator origins is a routine practice in most areas. The current paper evaluated an innovated granular S-methoprene formulation, namely OmniPrene™ in the laboratory bioassays, as well as outdoor microcosms at 2.8, 5.6 and 11.2 kg/ha with 30.5 cm water depth, and at 2.8 kg/ha with shallow water (15.25 cm) against Aedes aegypti, Anopheles hermsi and Culex quinquefasciatus. Over 90% efficacy was achieved against Aedes and Anopheles for at least 49 days, and against Culex for up to 42 days at 2.8, 5.6 and 11.2 kg/ha when water depth was 30.5 cm. The control levels were further elevated when water depth was 15.25 cm, where over 90% control was observed for 63 days against Aedes and Anopheles, but 56 days against Culex. The high initial and residual efficacy were attributable to the unique diatomaceous earth carrier granules and proprietary binding process. With well documented bioactivity and safety of S-methoprene, demonstrated performance of the OmniPrene G, plus the unique feature of the formulation to render vegetation penetration, even coverage, and other advantages of dry granules, it would be reasonable to recommend this product as one of the routine larvicidal tools in a wide variety of habitats against mosquito species of public health importance while complying with the local regulations.

Potent Bioactivity of Endophytic Fungi Isolated from Moringa oleifera Leaves

Plant species are known to harbor large number of endophytes, which stays in plant tissues as symbionts. These endophytes secrete large array of bioactive compounds that have potency against certain diseases with no side effects. We have collected leaf samples of the Moringa oleifera plant from the Pakistan Forest Institute, Khyber Pakhtunkhwa, Pakistan for the isolation of beneficial endophytes. The strains isolated from the leaves of M. oleifera were coded with MOL and tested for antimicrobial, antifungal, germicidal, phytotoxic, insecticidal, cytotoxic, and anti-inflammatory activities. The isolates, MOL1, MOL16, MOL19, and MOL21, possessed antibacterial activity against Staphylococcus aureus, whereas MOL7 inhibited 55% of the growth of Escherichia coli. MOL3 inhibited the growth of E. coli, S. aureus, and Pseudomonas aeruginosa. The strains, MOL1 and MOL7, showed antifungal activity against Candida albicans and Saccharomyces cerevisiae, while the strains, MOL11 and MOL17, showed activity against Verticillium chlamydosporium. The isolates, MOL3, MOL7, MOL9, MOL15, MOL17, MOL18, and MOL19, inhibited the growth of Lemna minor (duckweed) at 100 μg/ml. MOL2 exhibited strong activity in the brine shrimp assay, while MOL1, MOL2, MOL5, MOL6, MOL12, MOL17, MOL19, and MOL20 showed insecticidal, and MOL3 demonstrated larvicidal and antileishmanial activity. The isolated potent endophytes were identified as Aspergillus, Penicillium, Fusarium, Tricoderma, Rhizoctonia, Mucor, Alternaria, Pestalotiopsis, Acremonium, and Cladosporium through morphological and microscopic characteristics of the colonies.

Malayan kraits (Bungarus candidus) show affinity to anthropogenic structures in a human dominated landscape

Animal movement can impact human–wildlife conflict by influencing encounter and detection rates. We assess the movement and space use of the highly venomous and medically important Malayan krait (Bungarus candidus) on a suburban university campus. We radio-tracked 14 kraits for an average of 114 days (min: 19, max: 218), during which we located individuals an average of 106 times (min: 21, max: 229) each. Most individuals displayed some level of attraction to buildings (n = 10) and natural areas (n = 12); we identified a similar unambiguous pattern of attraction to buildings and natural areas at the population level (of our sample). Snakes remained in shelter sites for long durations (max: 94 days) and revisited sites on average every 15.45 days. Over 50% of locations were within human settlements and 37.1% were associated with buildings. We found generally seasonal patterns of activity, with higher activity in wet seasons, and lower activity in the hot season. These results show frequent proximity between Malayan kraits and humans at the university; thereby, suggesting a near constant potential for human-wildlife conflict. Despite the fact that no snakebites from this species occurred at the university during our study period, substantial education and awareness training should be considered to ensure continued coexistence on campus.

Defining Virus-Carrier Networks that Shape the Composition of the Mosquito Core Virome of a Local Ecosystem

Mosquitoes are the most important vectors of emerging infectious diseases. During the past decade, our understanding of the diversity of viruses they carry has greatly expanded. Most of these viruses are considered mosquito-specific, but there is increasing evidence that these viruses may affect the vector competence of mosquitoes. Metagenomics approaches have focused on specific mosquito species for the identification of what is called the core virome. Despite the fact that, in most ecosystems, multiple species may participate in virus emergence and circulation, there is a lack of understanding of the virus-carrier/host network for both vector-borne and mosquito-specific viruses. Here, we studied the core virome of mosquitoes in a diverse local ecosystem that had 24 different mosquito species. The analysis of the viromes of these 24 mosquito species resulted in the identification of 34 viruses, which included 15 novel viruses, as determined according to the species demarcation criteria of the respective virus families. Most of the mosquito species had never been analysed previously, and a comparison of the individual viromes of the 24 mosquito species revealed novel relationships among mosquito species and virus families. Groups of related viruses and mosquito species from multiple genera formed a complex web in the local ecosystem. Furthermore, analyses of the virome of mixed-species pools of mosquitoes from representative traps of the local ecosystem showed almost complete overlap with the individual-species viromes identified in the study. Quantitative analysis of viruses’ relative abundance revealed a linear relationship to the abundance of the respective carrier/host mosquito species, supporting the theory of a stable core virome in the most abundant species of the local ecosystem. Finally, our study highlights the importance of using a holistic approach to investigating mosquito viromes relationships in rich and diverse ecosystems.

Overview of paratransgenesis as a strategy to control pathogen transmission by insect vectors

This article presents an overview of paratransgenesis as a strategy to control pathogen transmission by insect vectors. It first briefly summarises some of the disease-causing pathogens vectored by insects and emphasises the need for innovative control methods to counter the threat of resistance by both the vector insect to pesticides and the pathogens to therapeutic drugs. Subsequently, the state of art of paratransgenesis is described, which is a particularly ingenious method currently under development in many important vector insects that could provide an additional powerful tool for use in integrated pest control programmes. The requirements and recent advances of the paratransgenesis technique are detailed and an overview is given of the microorganisms selected for genetic modification, the effector molecules to be expressed and the environmental spread of the transgenic bacteria into wild insect populations. The results of experimental models of paratransgenesis developed with triatomines, mosquitoes, sandflies and tsetse flies are analysed. Finally, the regulatory and safety rules to be satisfied for the successful environmental release of the genetically engineered organisms produced in paratransgenesis are considered.

Transmission-Blocking Strategies Against Malaria Parasites During Their Mosquito Stages

Malaria is still the most widespread parasitic disease and causes the most infections globally. Owing to improvements in sanitary conditions and various intervention measures, including the use of antimalarial drugs, the malaria epidemic in many regions of the world has improved significantly in the past 10 years. However, people living in certain underdeveloped areas are still under threat. Even in some well-controlled areas, the decline in malaria infection rates has stagnated or the rates have rebounded because of the emergence and spread of drug-resistant malaria parasites. Thus, new malaria control methods must be developed. As the spread of the Plasmodium parasite is dependent on the part of its life cycle that occurs in mosquitoes, to eliminate the possibility of malaria infections, transmission-blocking strategies against the mosquito stage should be the first choice. In fact, after the gametocyte enters the mosquito body, it undergoes a series of transformation processes over a short period, thus providing numerous potential blocking targets. Many research groups have carried out studies based on targeting the blocking of transmission during the mosquito phase and have achieved excellent results. Meanwhile, the direct killing of mosquitoes could also significantly reduce the probability of malaria infections. Microorganisms that display complex interactions with Plasmodium, such as Wolbachia and gut flora, have shown observable transmission-blocking potential. These could be used as a biological control strategy and play an important part in blocking the transmission of malaria.

Release of Sterile Mosquitoes with Drones in Urban and Rural Environments under the European Drone Regulation

In recent years, several countries have developed the use of sterile insect techniques (SIT) to fight against mosquitoes that transmit diseases. From a technical and economic point of view, the use of drones in the aerial release of sterile mosquitoes leads to important improvements in aerial coverage and savings in operational costs due to the requirement of fewer release sites and field staff. However, these operations are under the European drone regulation, one of the most advanced in the world. The main contribution and novelty of this paper with respect to previous work is the analysis of the SIT application with drones under the European risk-based regulation in two scenarios: urban and rural areas. The specific operations risk assessment (SORA) methodology has been applied to assess the risk of drone operations in these scenarios. The paper presents the operational requirements for aerial release of mosquitoes with drones along with the regulatory considerations that must be applied. Finally, an overview of the conditions in operation that could relax risks and mitigation measures is also discussed.

Hyssopus Essential Oil: An Update of Its Phytochemistry, Biological Activities, and Safety Profile

The genus Hyssopus is widespread in central Asia, East Mediterranean, and Mongolian areas. It has six main species which are used as herbal remedies, such as Hyssopus officinalis which is used as a condiment and flavoring agent in food industry. The other five species are H. ambiguus, H. cuspidatus, H. latilabiatus, H. macranthus, and H. seravschanicus. Its species are used in the treatment of various ailments such as cold, cough, loss of appetite, fungal infection, and spasmodic condition. Its constituents especially essential oils are popularly used as an additive in beverages, foods, and cosmetics. The volatile constituents are used for aroma in the food industry, cosmetic industry, and household products. The important active constituents in its essential oils are β-pinene, pinocamphone, isopinocamphone, and other terpenoids. Hyssopus genus is also bundled with other secondary metabolites including flavonoids luteolin, quercetin, apigenin, and their glucosides, as well as phenolic compounds including ferulic, p-hydroxy-benzoic acid, protocatechuic acid, chlorogenic, and caffeic acid. Combinedly, the extracts of Hyssopus are reported to have potential antiviral and antifungal activities proven using in vitro studies, whereas in vivo investigations have reported the crucial role of Hyssopus extracts in plasma membrane relaxation, cytotoxic, and sedative effects. This plant is believed to be relatively safe at levels commonly used in foods; nevertheless, more studies are needed to determine the safety profile.

Predators as Control Agents of Mosquito Larvae in Micro-Reservoirs (Review)

The article reviews predators that are able to control populations of mosquito larvae (Culicidae) in phytotelmata and their anthropogenic analogs. The spectrum of mosquito larva consumers in micro-reservoirs is listed. It includes flatworms, crustaceans, arachnids, insects, vertebrates, and carnivorous plants. The biology and practical use of the two most effective biological control agents, predatory mosquitoes Toxorhynchites and copepods, are considered in more detail. Prospects of invertebrate predators as controlling agents for the mosquito larvae in micro-reservoirs in temperate climate zones are briefly discussed.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1134/S1995082922010138.

Drug targeting of aminoacyl-tRNA synthetases in Anopheles species and Aedes aegypti that cause malaria and dengue

BACKGROUND

Mosquito-borne diseases have a devastating impact on human civilization. A few species of Anopheles mosquitoes are responsible for malaria transmission, and while there has been a reduction in malaria-related deaths worldwide, growing insecticide resistance is a cause for concern. Aedes mosquitoes are known vectors of viral infections, including dengue, yellow fever, chikungunya, and Zika. Aminoacyl-tRNA synthetases (aaRSs) are key players in protein synthesis and are potent anti-infective drug targets. The structure-function activity relationship of aaRSs in mosquitoes (in particular, Anopheles and Aedes spp.) remains unexplored.

METHODS

We employed computational techniques to identify aaRSs from five different mosquito species (Anopheles culicifacies, Anopheles stephensi, Anopheles gambiae, Anopheles minimus, and Aedes aegypti). The VectorBase database ( https://vectorbase.org/vectorbase/app ) and web-based tools were utilized to predict the subcellular localizations (TargetP-2.0, UniProt, DeepLoc-1.0), physicochemical characteristics (ProtParam), and domain arrangements (PfAM, InterPro) of the aaRSs. Structural models for prolyl (PRS)-, and phenylalanyl (FRS)-tRNA synthetases-were generated using the I-TASSER and Phyre protein modeling servers.

RESULTS

Among the vector species, a total of 37 (An. gambiae), 37 (An. culicifacies), 37 (An. stephensi), 37 (An. minimus), and 35 (Ae. aegypti) different aaRSs were characterized within their respective mosquito genomes. Sequence identity amongst the aaRSs from the four Anopheles spp. was > 80% and in Ae. aegypti was > 50%.

CONCLUSIONS

Structural analysis of two important aminoacyl-tRNA synthetases [prolyl (PRS) and phenylanalyl (FRS)] of Anopheles spp. suggests structural and sequence similarity with potential antimalarial inhibitor [halofuginone (HF) and bicyclic azetidine (BRD1369)] binding sites. This suggests the potential for repurposing of these inhibitors against the studied Anopheles spp. and Ae. aegypti.

Metarhizium anisopliae blastospores are highly virulent to adult Aedes aegypti, an important arbovirus vector

BACKGROUND

The use of entomopathogenic fungi (EPF) for the control of adult mosquitoes is a promising alternative to synthetic insecticides. Previous studies have only evaluated conidiospores against adult mosquitoes. However, blastospores, which are highly virulent against mosquito larvae and pupae, could also be effective against adults.

METHODS

Metarhizium anisopliae (ESALQ 818 and LEF 2000) blastospores and conidia were first tested against adult Aedes aegypti by spraying insects with spore suspensions. Blastospores were then tested using an indirect contact bioassay, exposing mosquitoes to fungus-impregnated cloths. Virulence when using blastospores suspended in 20% sunflower oil was also investigated.

RESULTS

Female mosquitoes sprayed with blastospores or conidia at a concentration of 108 propagules ml-1 were highly susceptible to both types of spores, resulting in 100% mortality within 7 days. However, significant differences in virulence of the isolates and propagules became apparent at 107 spores ml-1, with ESALQ 818 blastospores being more virulent than LEF 2000 blastospores. ESALQ 818 blastospores were highly virulent when mosquitoes were exposed to black cotton cloths impregnated with blastospores shortly after preparing the suspensions, but virulence declined rapidly 12 h post-application. The addition of vegetable oil to blastospores helped maintain virulence for up to 48 h.

CONCLUSION

The results showed that blastospores were more virulent to adult female Ae. aegypti than conidia when sprayed onto the insects or applied to black cloths. Vegetable oil helped maintain blastospore virulence. The results show that blastospores have potential for use in integrated vector management, although new formulations and drying techniques need to be investigated.

Fungi of entomopathogenic potential in Chytridiomycota and Blastocladiomycota, and in fungal allies of the Oomycota and Microsporidia

The relationship between entomopathogenic fungi and their insect hosts is a classic example of the co-evolutionary arms race between pathogen and target host. The present review describes the entomopathogenic potential of Chytridiomycota and Blastocladiomycota fungi, and two groups of fungal allies: Oomycota and Microsporidia. The Oomycota (water moulds) are considered as a model biological control agent of mosquito larvae. Due to their shared ecological and morphological similarities, they had long been considered a part of the fungal kingdom; however, phylogenetic studies have since placed this group within the Straminipila. The Microsporidia are parasites of economically-important insects, including grasshoppers, lady beetles, bumblebees, colorado potato beetles and honeybees. They have been found to display some fungal characteristics, and phylogenetic studies suggest that they are related to fungi, either as a basal branch or sister group. The Blastocladiomycota and Chytridiomycota, named the lower fungi, historically were described together; however, molecular phylogenetic and ultrastructural research has classified them in their own phylum. They are considered parasites of ants, and of the larval stages of black flies, mosquitoes and scale insects.

Skin bacterial volatiles: propelling the future of vector control

The skin microbiota plays an essential role in the protection against pathogens. It is our skin microbiota that makes us smell different from each other, rendering us more or less attractive to mosquitoes. Mosquitoes exploit skin bacterial odours to locate their hosts and are vectors of pathogens that can cause severe diseases such as malaria and dengue fever. A novel solution for long-lasting protection against insect vectors of disease could be attained by manipulating the bacterial commensals on human skin. The current options for protection against biting insects usually require topical application of repellents that evaporate within hours. We discuss possible routes for the use of commensal bacteria to create a microbial-based repellent.

A DNA barcode reference library of Portuguese mosquitoes

Mosquitoes are important biological vectors of pathogens and species identification in all life stages is the first step for effective monitoring and control of mosquito-borne diseases. Molecular methods for species identification have been developed over the last years to overcome the limitations of the taxonomic identification based on morphology. DNA barcoding, using a fragment of the mitochondrial cytochrome oxidase I (COI) gene, can be used for species identification but a reliable and comprehensive reference database of verified sequences is required. In this study, we aimed to generate a DNA barcode reference library for the identification of mosquito species from Portuguese mosquito fauna, including most relevant vector species. Mosquitoes captured under the National Vector Surveillance Program (REVIVE) were processed for DNA extraction, COI gene fragment amplification and sequencing. Nighty-eight barcode sequences were obtained, representing 26 species and 6 genera. Sequences were submitted to GenBank and BOLD and were used for validation of phenetic classification. Barcode Index Number (BIN) assignment and Automatic Barcode Gap Discovery (ABGD) were used and clustered COI sequences into twenty-five molecular operational taxonomic units (MOTUs). This is the first comprehensive study that combines morphological and molecular identification of most mosquito species present in Portugal aiming to offer a reliable framework for mosquito species identification.

Self-Assembled Chromogenic Polymeric Nanoparticle-Laden Nanocarrier as a Signal Carrier for Derivative Binary Responsive Virus Detection

In the current biosensor, the signal generation is limited to single virus detection in the reaction chamber. An adaptive strategy is required to enable the recognition of multiple viruses for diagnostics and surveillance. In this work, a nanocarrier is deployed to bring specific signal amplification into the biosensor, depending on the target viruses. The nanocarrier is designed using pH-sensitive polymeric nanoparticle-laden nanocarriers (PNLNs) prepared by sequential nanoprecipitation. The nanoprecipitation of two chromogens, phenolphthalein (PP) and thymolphthalein (TP), is investigated in three different solvent systems in which PNLNs demonstrate a high loading of the chromogen up to 59.75% in dimethylformamide (DMF)/dimethyl sulfoxide (DMSO)/ethanol attributing to the coprecipitation degree of the chromogens and the polymer. The PP-encapsulated PNLNs (PP@PNLNs) and TP-encapsulated PNLNs (TP@PNLNs) are conjugated to antibodies specific to target viruses, influenza virus A subtype H1N1 (IV/A/H1N1) and H3N2 (IV/A/H3N2), respectively. After the addition of anti-IV/A antibody-conjugated magnetic nanoparticles (MNPs) and magnetic separation, the enriched PNLNs/virus/MNPs sandwich structure is treated in an alkaline solution. It demonstrates a synergy reaction in which the degradation of the polymeric boundary and the pH-induced colorimetric development of the chromogen occurred. The derivative binary biosensor shows feasible detection on IV/A with excellent specificities of PP@PNLNs on IV/A/H1N1 and TP@PNLNs on IV/A/H3N2 with LODs of 27.56 and 28.38 fg mL^-1, respectively. It intrigues the distinguished analytical signal in human serum with a variance coefficient of 25.8% and a recovery of 93.6-110.6% for one-step subtype influenza virus detection.

Bacillus thuringiensis Cry4Ba Insecticidal ToxinExploits Leu615 in Its C-Terminal Domain to Interact with a Target Receptor-Aedes aegypti Membrane-Bound Alkaline Phosphatase

In addition to the receptor-binding domain (DII), the C-terminal domain (DIII) of three-domain Cry insecticidal δ-endotoxins from Bacillus thuringiensis has been implicated in target insect specificity, yet its precise mechanistic role remains unclear. Here, the 21 kDa high-purity isolated DIII fragment derived from the Cry4Ba mosquito-specific toxin was achieved via optimized preparative FPLC, allowing direct rendering analyses for binding characteristics toward its target receptor—Aedes aegypti membrane-bound alkaline phosphatase (Aa-mALP). Binding analysis via dotblotting revealed that the Cry4Ba-DIII truncate was capable of specific binding to nitrocellulose-bound Aa-mALP, with a binding signal comparable to its 65 kDa Cry4Ba-R203Q full-length toxin. Further determination of binding affinity via sandwich ELISA revealed that Cry4Ba-DIII exhibited a rather weak binding to Aa-mALP with a dissociation constant (K_d) of ≈1.1 × 10⁻⁷ M as compared with the full-length toxin. Intermolecular docking between the Cry4Ba-R203Q active toxin and Aa-mALP suggested that four Cry4Ba-DIII residues, i.e., Glu⁵²², Asn⁵⁵², Asn⁵⁷⁶, and Leu⁶¹⁵, are potentially involved in such toxin–receptor interactions. Ala substitutions of each residue (E522A, N552A, N576A and L615A) revealed that only the L615A mutant displayed a drastic decrease in biotoxicity against A. aegypti larvae. Additional binding analysis revealed that the L615A-impaired toxin also exhibited a reduction in binding capability to the surface-immobilized Aa-mALP receptor, while two bio-inactive DII-mutant toxins, Y332A and F364A, which almost entirely lost their biotoxicity, apparently retained a higher degree of binding activity. Altogether, our data disclose a functional importance of the C-terminal domain of Cry4Ba for serving as a potential receptor-binding moiety in which DIII-Leu⁶¹⁵ could conceivably be exploited for the binding to Aa-mALP, highlighting its contribution to toxin interactions with such a target receptor in mediating larval toxicity.

Unraveling mosquito metabolism with mass spectrometry-based metabolomics

Nearly half a million people die annually due to mosquito-borne diseases. Despite aggressive mosquito population-control efforts, current strategies are limited in their ability to control these vectors. A better understanding of mosquito metabolism through modern approaches can contribute to the discovery of novel metabolic targets and/or regulators and lead to the development of better mosquito-control strategies. Currently, cutting-edge technologies such as gas or liquid chromatography-mass spectrometry-based metabolomics are considered 'mature technologies' in many life-science disciplines but are still an emerging area of research in medical entomology. This review primarily discusses recent developments and progress in the application of mass spectrometry-based metabolomics to answer multiple biological questions related to mosquito metabolism.

Effects of Kathon, a Chemical Used Widely as a Microbicide, on the Survival of Two Species of Mosquitoes

In recent decades, demands for novel insecticides against mosquitoes are soaring, yet candidate chemicals with desirable properties are limited. Kathon is a broad-spectrum isothiazolinone microbicide, but other applications remain uncharacterized. First, we treated larvae of Culex quinquefasciatus and Aedes albopictus, two major mosquito vectors of human viral diseases, with Kathon at 15 mg/L (a concentration considered safe in cosmetic and body care products), and at lower concentrations, and found that Kathon treatment resulted in high mortality of larvae. Second, sublethal concentration of Kathon can cause significantly prolonged larval development of C. quinquefasciatus. Third, we explored the effects of two constituents of Kathon, chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT), on the survival of larvae, and found that CMIT was the major toxic component. Further, we explored the mechanisms of action of Kathon against insect cells and found that Kathon reduces cell viability and adenosine triphosphate production but promotes the release of lactate dehydrogenase in Drosophila melanogaster S2 cells. Our results indicate that Kathon is highly toxic to mosquito larvae, and we highlight its potential in the development of new larvicides for mosquito control.

A knockout screen of genes expressed specifically in Ae. aegypti pupae reveals a critical role for stretchin in mosquito flight

Aedes aegypti is a critical vector for transmitting Zika, dengue, chikungunya, and yellow fever viruses to humans. Genetic strategies to limit mosquito survival based upon sex distortion or disruption of development may be valuable new tools to control Ae. aegypti populations. We identified six genes with expression limited to pupal development; osi8 and osi11 (Osiris protein family), CPRs and CPF (cuticle protein family), and stretchin (a muscle protein). Heritable CRISPR/Cas9-mediated gene knockout of these genes did not reveal any defects in pupal development. However, stretchin-null mutations (strn^Δ35/Δ41) resulted in flightless mosquitoes with an abnormal open wing posture. The inability of adult strn^Δ35/Δ41 mosquitoes to fly restricted their escape from aquatic rearing media following eclosion, and substantially reduced adult survival rates. Transgenic strains which contain the EGFP marker gene under the control of strn regulatory regions (0.8 kb, 1.4 kb, and 2.2 kb upstream, respectively), revealed the gene expression pattern of strn in muscle-like tissues in the thorax during late morphogenesis from L₄ larvae to young adults. We demonstrated that Ae. aegypti pupae-specific strn is critical for adult mosquito flight capability and a key late-acting lethal target for mosquito-borne disease control.