Mosquito-Borne Diseases

Curing mosquitoes with genetic approaches for malaria control

Malaria remains a persistent global public health challenge because of the limitations of current prevention tools. The use of transgenic mosquitoes incapable of transmitting malaria, in conjunction with existing methods, holds promise for achieving elimination of malaria and preventing its reintroduction. In this context, population modification involves the spread of engineered genetic elements through mosquito populations that render them incapable of malaria transmission. Significant progress has been made in this field over the past decade in revealing promising targets, optimizing genetic tools, and facilitating the transition from the laboratory to successful field deployments, which are subject to regulatory scrutiny. This review summarizes recent advances and ongoing challenges in 'curing' Anopheles vectors of the malaria parasite.

Effect of salinity on the oviposition and growth of Ochlerotatus togoi

Ochlerotatus togoi is a salt-tolerant euryhaline mosquito that lays its eggs in rock pools. Although it is a pest that can transmit flaviviruses and filarial worms to humans, ecological studies have not been previously conducted because of its limited habitat. However, rising sea levels have created a more favorable environment for Oc. togoi, increasing the risk of Oc. togoi-borne diseases. We examined the oviposition and growth rates of Oc. togoi at 0-35 psu to obtain ecological data. It exhibited the highest oviposition preference at 0 psu; however, the hatching rate was highest at 10 psu, the pupation rate was highest at 25 psu, and the emergence rate was highest at 5 psu. Oc. togoi showed the highest rate of growth into adults at 25 psu. The results were assessed using Mann-Whitney U and Kruskal-Wallis H tests (post hoc test: Bonferroni), and a regression equation was generated for the incidence of adult Oc. togoi based on the change in salinity (y = -14.318 + 9.821x; y = adult incidence rate; x = salinity). The oviposition habits and developmental conditions of Oc. togoi were confirmed, and the incidence of Oc. togoi based on changes in sea level and ocean salinity was predicted. The results of this study will be useful for controlling salt-tolerant vectors and responding to vector-borne diseases.

Water and mosquitoes as key components of the infective cycle of Francisella tularensis in Europe: a review

Francisella tularensis is the pathogen of tularemia, a zoonotic disease that have a broad range of hosts. Its epidemiology is related to aquatic environments, particularly in the subspecies holarctica. In this review, we explore the role of water and mosquitoes in the epidemiology of Francisella in Europe. F. tularensis epidemiology has been linked to natural waters, where its persistence has been associated with biofilm and amebas. In Sweden and Finland, the European countries where most human cases have been reported, mosquito bites are a main route of transmission. F. tularensis is present in other European countries, but to date positive mosquitoes have not been found. Biofilm and amebas are potential sources of Francisella for mosquito larvae, however, mosquito vector capacity has not been demonstrated experimentally, with the need to be studied using local species to uncover a potential transmission adaptation. Transstadial, for persistence through life stages, and mechanical transmission, suggesting contaminated media as a source for infection, have been studied experimentally for mosquitoes, but their natural occurrence needs to be evaluated. It is important to clear up the role of different local mosquito species in the epidemiology of F. tularensis and their importance in all areas where tularemia is present.

Aedes albopictus in a recently invaded area in Spain: effects of trap type, locality, and season on mosquito captures

Mosquitoes are primary vectors of pathogens impacting humans, wildlife, and livestock. Among them, the Asian tiger mosquito, Aedes albopictus, stands out as an invasive species with a global distribution, having established populations on every continent except Antarctica. Recent findings incriminate Ae. albopictus in the local transmission of several pathogens causing human diseases, including dengue, chikungunya, and Zika viruses and worm parasites as Dirofilaria. In Spain, the establishment of Ae. albopictus occurred in 2004 and it rapidly expanded, currently reaching southern provinces and creating novel epidemiological scenarios in recently invaded areas. In this study, we conducted captures of Ae. albopictus from May to November 2022 in two provinces, Granada and Malaga, situated near the current edge of the species' expanding range in Spain. The objective was to identify the primary factors influencing their captures in these regions. Mosquitoes were captured using BG-Sentinel traps baited with CO2 and BG-Lure, and miniature CDC-UV traps in five different localities. Our findings underscore the influence of both extrinsic factors, such as locality, and intrinsic factors, including mosquito sex, on the abundance of captured Ae. albopictus. A higher abundance of Ae. albopictus was observed in the Malaga province compared to localities in the Granada province. Furthermore, similar numbers of Ae. albopictus mosquitoes were captured in more urbanized areas of Granada, while the lowest counts were recorded in the less urbanized area. These results were compared to captures of another common species in the area, specifically Culex pipiens. Overall, these results represent the first monitoring of invasive Ae. albopictus in the area and are discussed in the light of the potential importance of the species as a nuisance for humans and vectors of pathogens of public health relevance.

Climate Stressors and Physiological Dysregulations: Mechanistic Connections to Pathologies

This review delves into the complex relationship between environmental factors, their mechanistic cellular and molecular effects, and their significant impact on human health. Climate change is fueled by industrialization and the emission of greenhouse gases and leads to a range of effects, such as the redistribution of disease vectors, higher risks of disease transmission, and shifts in disease patterns. Rising temperatures pose risks to both food supplies and respiratory health. The hypothesis addressed is that environmental stressors including a spectrum of chemical and pathogen exposures as well as physical and psychological influences collectively impact genetics, metabolism, and cellular functions affecting physical and mental health. The objective is to report the mechanistic associations linking environment and health. As environmental stressors intensify, a surge in health conditions, spanning from allergies to neurodegenerative diseases, becomes evident; however, linkage to genetic-altered proteomics is more hidden. Investigations positing that environmental stressors cause mitochondrial dysfunction, metabolic syndrome, and oxidative stress, which affect missense variants and neuro- and immuno-disorders, are reported. These disruptions to homeostasis with dyslipidemia and misfolded and aggregated proteins increase susceptibility to cancers, infections, and autoimmune diseases. Proposed interventions, such as vitamin B supplements and antioxidants, target oxidative stress and may aid mitochondrial respiration and immune balance. The mechanistic interconnections of environmental stressors and disruptions in health need to be unraveled to develop strategies to protect public health.

Mosquito allergy: Immunological aspects and clinical management

Mosquito allergy has been conceived as the cutaneous reactions that appears during and after mosquito biting process; a perception that is supported by several scientific research. Additional data have led to conceive that other manifestations of allergic responses may occur as a cause of the exposure to somatic mosquito allergens. Two main phenotypes of mosquito allergy are identifiable: the cutaneous allergic reactions, induced by salivary allergens, and other manifestations of the allergic responses such as asthma and allergic rhino conjunctivitis that are caused by somatic allergens. The cutaneous reactions have kept the focus of attention of the scientific community. It appears as skin lesions that resembles the phenotype of papular urticaria with a defined natural history of the disease. Although these two phenotypes of mosquito allergy seem to be well differentiated in terms of the allergens that are involved and the routes of exposures, other factors such as geographical distribution, may participate. Mosquitoes have adapted to the host immune response against bites, producing immunomodulatory molecules that counteract such defensive response. The role that the immunomodulatory molecules have on the allergic immune response has not been studied yet and it is still not known if affects all mosquito allergy phenotypes. Only a few studies of allergen specific immunotherapy for cutaneous allergic reactions induced by mosquito bites have been done, and none for respiratory allergic responses. The clinical practice focuses on symptom management and avoiding mosquito bites as much as possible. Avoiding mosquitoes, using different well described methods, is still the best option to limit contact with these insects. The lack of knowledge of mosquito allergy have raised several questions that affects the clinical management of this allergic disease, from its diagnosis, prevention and immunotherapy.

Mosquito-borne diseases in India over the past 50 years and their Global Public Health Implications: A Systematic Review

Mosquito-borne diseases (MBDs) pose a significant public health concern globally, and India, with its unique eco-sociodemographic characteristics, is particularly vulnerable to these diseases. This comprehensive review aims to provide an in-depth overview of MBDs in India, emphasizing their impact and potential implications for global health. The article explores distribution, epidemiology, control or elimination, and economic burden of the prevalent diseases such as malaria, dengue, chikungunya, Japanese encephalitis, and lymphatic filariasis, which collectively contribute to millions of cases annually. It sheds light on their profound effects on morbidity, mortality, and socioeconomic burdens and the potential for international transmission through travel and trade. The challenges and perspectives associated with controlling mosquito populations are highlighted, underscoring the importance of effective public health communication for prevention and early detection. The potential for these diseases to spread beyond national borders is recognized, necessitating a holistic approach to address the challenge. A comprehensive literature search was conducted, covering the past five decades (1972-2022), utilizing databases such as Web of Science, PubMed, and Google Scholar, in addition to in-person library consultations. The literature review analyzed 4,082 articles initially identified through various databases. After screening and eligibility assessment, 252 articles were included for analysis. The review focused on malaria, dengue, chikungunya, Japanese encephalitis, and lymphatic filariasis. The included studies focused on MBDs occurrence in India, while those conducted outside India, lacking statistical analysis, or published before 1970 were excluded. This review provides valuable insights into the status of MBDs in India and underscores the need for concerted efforts to combat these diseases on both national and global scales through consilience.

Does the Presence or a High Titer of Yellow Fever Virus Antibodies Interfere with Pregnancy Outcomes in Women with Zika Virus Infection?

Zika virus (ZIKV) and yellow fever virus (YFV) originated in Africa and expanded to the Americas, where both are co-circulated. It is hypothesized that in areas of high circulation and vaccination coverage against YFV, children of pregnant women have a lower risk of microcephaly. We evaluated the presence and titers of antibodies and outcomes in women who had ZIKV infection during pregnancy. Pregnancy outcomes were classified as severe, moderate, and without any important outcome. An outcome was defined as severe if miscarriage, stillbirth, or microcephaly occurred, and moderate if low birth weight and/or preterm delivery occurred. If none of these events were identified, the pregnancy was defined as having no adverse effects. A sample of 172 pregnant women with an acute ZIKV infection confirmed during pregnancy were collected throughout 2016. About 89% (150 of 169) of them presented immunity against YFV, including 100% (09 of 09) of those who had severe outcomes, 84% (16 of 19) of those who had moderate outcomes, and 89% (125 of 141) of those who had non-outcomes. There was no difference between groups regarding the presence of anti-YFV antibodies (p = 0.65) and YFV titers (p = 0.6). We were unable to demonstrate a protective association between the presence or titers of YFV antibodies and protection against serious adverse outcomes from exposure to ZIKV in utero.

Joint spatial modeling of the risks of co-circulating mosquito-borne diseases in Ceará, Brazil

Mosquito-borne diseases such as dengue and chikungunya have been co-circulating in the Americas, causing great damage to the population. In 2021, for instance, almost 1.5 million cases were reported on the continent, being Brazil the responsible for most of them. Even though they are transmitted by the same mosquito, it remains unclear whether there exists a relationship between both diseases. In this paper, we model the geographic distributions of dengue and chikungunya over the years 2016 to 2021 in the Brazilian state of Ceará. We use a Bayesian hierarchical spatial model for the joint analysis of two arboviruses that includes spatial covariates as well as specific and shared spatial effects that take into account the potential autocorrelation between the two diseases. Our findings allow us to identify areas with high risk of one or both diseases. Only 7% of the areas present high relative risk for both diseases, which suggests a competition between viruses. This study advances the understanding of the geographic patterns and the identification of risk factors of dengue and chikungunya being able to help health decision-making.

A novel Rickettsia species closely related to Rickettsia felis in Anopheles mosquitoes from Yingkou City, Northeast China

Mosquitoes are generally recognized as the most important vector of many zoonotic pathogens. In this study, seven mosquitoes species were identified (Anopheles pullus, Anopheles sinensis, Anopheles lesteri, Anopheles kleini, Ochlerotatus dorsalis, Aedes koreicus and Culex inatomii) in samples collected from Yingkou City, Liaoning Province, Northeastern China. A novel Rickettsia species was detected in Anopheles sinensis (two of 71, 2.82%) and Anopheles pullus (one of 106, 0.94%) mosquitoes. Genetic analysis indicated that the rrs and ompB genes have highest 99.60% and 97.88%-98.14% identities to Rickettsia felis, an emerging human pathogen of global concern mainly harboured by fleas, mosquitoes and booklice. The gltA sequences of these strains have 99.72% of nucleotide similarity with Rickettsia endosymbiont of Medetera jacula. The groEL sequences have 98.37% similarity to both Rickettsia tillamookensis and Rickettsia australis. The htrA sequences have 98.77% similarity to Rickettsia lusitaniae. In the phylogenetic tree based on concatenated nucleotide sequences of rrs, gltA, groEL, ompB and htrA genes, these strains are closely related to R. felis. Herein, we name it 'Candidatus Rickettsia yingkouensis'. Its human pathogenicity to humans and animals is still to be determined.

Recognition of Arboviruses by the Mosquito Immune System

Arthropod-borne viruses (arboviruses) pose a significant threat to both human and animal health worldwide. These viruses are transmitted through the bites of mosquitoes, ticks, sandflies, or biting midges to humans or animals. In humans, arbovirus infection often results in mild flu-like symptoms, but severe disease and death also occur. There are few vaccines available, so control efforts focus on the mosquito population and virus transmission control. One area of research that may enable the development of new strategies to control arbovirus transmission is the field of vector immunology. Arthropod vectors, such as mosquitoes, have coevolved with arboviruses, resulting in a balance of virus replication and vector immune responses. If this balance were disrupted, virus transmission would likely be reduced, either through reduced replication, or even through enhanced replication, resulting in mosquito mortality. The first step in mounting any immune response is to recognize the presence of an invading pathogen. Recent research advances have been made to tease apart the mechanisms of arbovirus detection by mosquitoes. Here, we summarize what is known about arbovirus recognition by the mosquito immune system, try to generate a comprehensive picture, and highlight where there are still gaps in our current understanding.

Multiplex Surveillance Kit Using Sweetened Solid Support to Detect Arboviruses Isothermally in Mosquito Saliva from the Field

Recently reported "displaceable probe" loop amplification (DP-LAMP) architecture has shown to amplify viral RNA from SARS-CoV-2 with little sample processing. The architecture allows signals indicating the presence of target nucleic acids to be spatially separated, and independent in sequence, from the complicated concatemer that LAMP processes create as part of their amplification process. This makes DP-LAMP an attractive molecular strategy to integrate with trap and sampling innovations to detect RNA from arboviruses carried by mosquitoes in the field. These innovations include (a) development of organically produced carbon dioxide with ethylene carbonate as a bait deployable in mosquito trap, avoiding the need for dry ice, propane tanks, or inorganic carbonates and (b) a process that induces mosquitoes to lay virus-infected saliva on a quaternary ammonium-functionalized paper (Q-paper) matrix, where (c) the matrix (i) inactivates the deposited viruses, (ii) releases their RNA, and (iii) captures viral RNA in a form that keeps it stable for days at ambient temperatures. We report this integration here, with a surprisingly simple workflow. DP-LAMP with a reverse transcriptase was found to amplify arboviral RNA directly from Q-paper, without requiring a separate elution step. This capture-amplification-detection architecture can be multiplexed, with the entire system integrated into a device that can support a campaign of surveillance, in the wild outdoors, that reports the prevalence of arboviruses from field-captured mosquitoes.

Mosquito Larvicidal Activity and Cytotoxicity of the Extracts of Aromatic Plants from Malaysia

Despite ongoing control efforts, the mosquito population and diseases vectored by them continue to thrive worldwide, causing major health concerns. There has been growing interest in the use of botanicals as alternatives to insecticides due to their widespread insecticidal properties, biodegradability, and adaptability to ecological conditions. In this study, we investigated the larvicidal activity and cytotoxicity effects of solvent extracts from three aromatic plants-Curcuma longa (turmeric), Ocimum americanum (hoary basil), and Petroselinum crispum (parsley)-against Aedes albopictus. Subsequently, we examined the phytochemical composition of the extracts through gas chromatography-mass spectrometry (GC-MS) analysis. Results revealed that the hexane extracts of O. americanum and P. crispum exhibited the greatest larvicidal activity with the lowest median lethal concentration (LC₅₀) values (<30 µg/mL) at 24 h post-treatment, with the former found to be significantly less toxic towards African monkey kidney (Vero) cells. The GC-MS analysis of the said extract indicated the presence of different classes of metabolites, including phenylpropanoids, very long-chain alkanes, fatty acids and their derivatives, and terpenes, with the most abundant component being methyl eugenol (55.28%), most of which, have been documented for their larvicidal activities. These findings provide valuable insights into the potential use and development of bioinsecticides, particularly from O. americanum.

Assessing the Effectiveness of Qista Baited Traps in Capturing Mosquito Vectors of Diseases in the Camargue Region (France) and Investigating Their Diversity

Nuisance, allergy, and vector role: mosquitoes are responsible for numerous inconveniences. Several strategies have been employed to fight against this confirmed vector. To record the diversity of mosquito vectors in Camargue (France) and assess the effectiveness of the Qista trap, six BAMs were deployed as a belt barrier to protect the Espeyran Castle (Saint-Gilles, Camargue). Prior to evaluating the reduction in the nuisance rate, recovery nets from the traps and human landing catches (HLC) were utilized twice a week in the treated and control areas. Overall, 85,600 mosquitoes were captured, belonging to eleven species, namely Aedes albopictus, Aedes caspius, Aedes detritus, Aedes dorsalis, Aedes rossicus, Aedes vexans, Anopheles maculipennis, Culex pipiens, Culex modestus, Culiseta annulata and Culiseta longiareolata. The six BAM devices trapped 84,461 mosquitoes. The average capture rate per BAM is 76.92 mosquitoes per day. The rate of nuisance has decreased from 4.33 ± 2.88 before the deployment to 1.59 ± 2.77 after BAM implantation. The Qista BAM trap seems to be an excellent tool for reducing the nuisance rate and may help researchers to optimize trapping methods by obtaining more significant sample sizes. It may also allow the updating of the host-seeking mosquito species' reported biodiversity in the south of France.

Evolutionary genomics analysis reveals gene expansion and functional diversity of arylalkylamine N-acetyltransferases in the Culicinae subfamily of mosquitoes

Arylalkylamine N-acetyltransferase (aaNAT), considered a potential new insecticide target, catalyzes the acetylation of arylalkylamine substrates such as serotonin and dopamine and, hence, mediates diverse functions in insects. However, the origin of insect aaNATs (iaaNATs) and the evolutionary process that generates multiple aaNATs in mosquitoes remain largely unknown. Here, we have analyzed the genomes of 33 species to explore and expand our understanding of the molecular evolution of this gene family in detail. We show that aaNAT orthologs are present in Bacteria, Cephalochordata, Chondrichthyes, Cnidaria, Crustacea, Mammalia, Placozoa, and Teleoste, as well as those from a number of insects, but are absent in some species of Annelida, Echinozoa, and Mollusca as well as Arachnida. Particularly, more than 10 aaNATs were detected in the Culicinae subfamily of mosquitoes. Molecular evolutionary analysis of aaNAT/aaNAT-like genes in mosquitoes reveals that tandem duplication events led to gene expansion in the Culicinae subfamily of mosquitoes more than 190 million years ago. Further selection analysis demonstrates that mosquito aaNATs evolved under strongly positive pressures that generated functional diversity following gene duplication events. Overall, this study may provide novel insights into the molecular evolution of the aaNAT family in mosquitoes.

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.

Using Videography to Study the Biomechanics and Behavior of Freely Moving Mosquitoes

Female mosquitoes of most species require a blood meal for egg development. When biting a human host to collect this blood meal, they can spread dangerous diseases such as malaria, yellow fever, or dengue. Researchers use videography to study many aspects of mosquito behavior, including in-flight host-seeking, takeoff, and landing behaviors, as well as probing and blood feeding, and more. Here, we introduce protocols on how to use videography to capture and analyze mosquito movements at high spatial and temporal resolution, in two and three dimensions.

Species Identification of the Major Japanese Encephalitis Vectors within the Culex vishnui Subgroup (Diptera: Culicidae) in Thailand Using Geometric Morphometrics and DNA Barcoding

Japanese encephalitis (JE) is a viral infection of the brain caused by the Japanese encephalitis virus, which spreads globally, particularly in 24 countries of Southeast Asia and the Western Pacific region. In Thailand, the primary vectors of JE are Cx. pseudovishnui, Cx. tritaeniorhynchus, and Cx. vishnui of the Cx. vishnui subgroup. The morphologies of three mosquito species are extremely similar, making identification challenging. Thus, geometric morphometrics (GM) and DNA barcoding were applied for species identification. The results of cross-validation reclassification revealed that the GM technique based on wing shape analysis had relatively high potential for distinguishing Cx. pseudovishnui, Cx. tritaeniorhynchus, and Cx. vishnui (total performance = 88.34% of correctly assigned individuals). While the DNA barcoding yielded excellent results in identifying these Culex species based on the DNA barcode gap (average intraspecific genetic distance = 0.78% ± 0.39% and average interspecific genetic distance = 6.14% ± 0.79%). However, in the absence of the required facilities for DNA barcoding, GM techniques can be employed in conjunction with morphological methods to enhance the reliability of species identification. Based on the results of this study, our approach can help guide efforts to identify members of the Cx. vishnui subgroup, which will be useful for the effective vector control of JE in Thailand.

Mosquito vector diversity and abundance in southern Botswana, in a global context of emerging pathogen transmission

Background

The continued spread of infectious diseases by mosquitoes remains a formidable obstacle to the well-being of the people all over the world. Arboviruses are spread from one vertebrate host to another by vectors through intricate transmission cycles that involve the virus, the vertebrate host, and the vector. It is essential to acquire a better understanding of the current abundance and distribution of major vectors in order to adequately prepare for the possibility of arbovirus outbreaks. This is because the abundance and distribution of these major vectors determines the human populations that are at risk for the diseases that they transmit. The effects of climate change on the amount of mosquitoes and their ability to survive the seasons have had a substantial impact on the spread of diseases that are transmitted by vectors in many different parts of Botswana.

Methods

The purpose was to collect mosquito samples in Gaborone and the neighboring areas in southern Botswana, including border stations. We collected different stages of the mosquito from each place, raised them to maturity, and then identified them. Both morphological and genetic studies were utilized in order to successfully identify the organism. The species of Culex mosquitoes accounted for 88.3% of the 5177 mosquitoes that were collected and identified, whereas the species of Aedes aegypti and Anopheles mosquitoes accounted for 11.5% and 0.2% respectively.

Conclusions

These findings give entomological baseline data that will aid in the study of vectorial patterns and the estimation of future arboviral hazards provided by mosquitoes. Additionally, these findings document the diversity and abundance of mosquito species.

Life barcoded by DNA barcodes

The modern concept of DNA-based barcoding for cataloguing biodiversity was proposed in 2003 by first adopting an approximately 600 bp fragment of the mitochondrial COI gene to compare via nucleotide alignments with known sequences from specimens previously identified by taxonomists. Other standardized regions meeting barcoding criteria then are also evolving as DNA barcodes for fast, reliable and inexpensive assessment of species composition across all forms of life, including animals, plants, fungi, bacteria and other microorganisms. Consequently, global DNA barcoding campaigns have resulted in the formation of many online workbenches and databases, such as BOLD system, as barcode references, and facilitated the development of mini-barcodes and metabarcoding strategies as important extensions of barcode techniques. Here we intend to give an overview of the characteristics and features of these barcode markers and major reference libraries existing for barcoding the planet’s life, as well as to address the limitations and opportunities of DNA barcodes to an increasingly broader community of science and society.

Animal venoms as a source of antiviral peptides active against arboviruses: a systematic review

Arthropod-borne viruses (arboviruses), such as Zika virus (ZIKV), chikungunya virus (CHIKV), dengue virus (DENV), yellow fever virus (YFV), and West Nile virus (WNV), are pathogens of global importance. Therefore, there has been an increasing need for new drugs for the treatment of these viral infections. In this context, antimicrobial peptides (AMPs) obtained from animal venoms stand out as promising compounds because they exhibit strong antiviral activity against emerging arboviral pathogens. Thus, we systematically searched and critically analyzed in vitro and in vivo studies that evaluated the anti-arbovirus effect of peptide derivatives from toxins produced by vertebrates and invertebrates. Thirteen studies that evaluated the antiviral action of 10 peptides against arboviruses were included in this review. The peptides were derived from the venom of scorpions, spiders, wasps, snakes, sea snails, and frogs and were tested against DENV, ZIKV, YFV, WNV, and CHIKV. Despite the high structural variety of the peptides included in this study, their antiviral activity appears to be associated with the presence of positive charges, an excess of basic amino acids (mainly lysine), and a high isoelectric point (above 8). These peptides use different antiviral mechanisms, the most common of which is the inhibition of viral replication, release, entry, or fusion. Moreover, peptides with virucidal and cytoprotective (pre-treatment) effects were also identified. In conclusion, animal-venom-derived peptides stand out as a promising alternative in the search and development of prototype antivirals against arboviruses.

Anti-Microbiota Vaccine Reduces Avian Malaria Infection Within Mosquito Vectors

Animal and human pathogens that are transmitted by arthropods are a global concern, particularly those vectored by mosquitoes (e.g., Plasmodium spp. and dengue virus). Vector microbiota may hold the key to vector-borne pathogen control, as mounting evidence suggests that the contributions of the vector microbiota to vector physiology and pathogen life cycle are so relevant that vectorial capacity cannot be understood without considering microbial communities within the vectors. Anti-tick microbiota vaccines targeting commensal bacteria of the vector microbiota alter vector feeding and modulate the taxonomic and functional profiles of vector microbiome, but their impact on vector-borne pathogen development within the vector has not been tested. In this study, we tested whether anti-microbiota vaccination in birds targeting Enterobacteriaceae within mosquito midguts modulates the mosquito microbiota and disrupt Plasmodium relictum development in its natural vector Culex quinquefasciatus. Domestic canaries (Serinus canaria domestica) were experimentally infected with P. relictum and/or immunized with live vaccines containing different strains of Escherichia coli. Immunization of birds induced E. coli-specific antibodies. The midgut microbial communities of mosquitoes fed on Plasmodium-infected and/or E. coli-immunized birds were different from those of mosquitoes fed on control birds. Notably, mosquito midgut microbiota modulation was associated with a significant decrease in the occurrence of P. relictum oocysts and sporozoites in the midguts and salivary glands of C. quinquefasciatus, respectively. A significant reduction in the number of oocysts was also observed. These findings suggest that anti-microbiota vaccines can be used as a novel tool to control malaria transmission and potentially other vector-borne pathogens.

Mycosynthesis, Characterization, and Mosquitocidal Activity of Silver Nanoparticles Fabricated by Aspergillus niger Strain

Herein, silver nanoparticles (Ag-NPs) were synthesized using an environmentally friendly approach by harnessing the metabolites of Aspergillus niger F2. The successful formation of Ag-NPs was checked by a color change to yellowish-brown, followed by UV-Vis spectroscopy, Fourier transforms infrared (FT-IR), Transmission electron microscopy (TEM), and X-ray diffraction (XRD). Data showed the successful formation of crystalline Ag-NPs with a spherical shape at the maximum surface plasmon resonance of 420 nm with a size range of 3–13 nm. The Ag-NPs showed high toxicity against I, II, III, and IV instar larvae and pupae of Aedes aegypti with LC50 and LC90 values of 12.4–22.9 ppm and 22.4–41.4 ppm, respectively under laboratory conditions. The field assay exhibited the highest reduction in larval density due to treatment with Ag-NPs (10× LC50) with values of 59.6%, 74.7%, and 100% after 24, 48, and 72 h, respectively. The exposure of A. aegypti adults to the vapor of burning Ag-NPs-based coils caused a reduction of unfed individuals with a percentage of 81.6 ± 0.5% compared with the positive control, pyrethrin-based coils (86.1 ± 1.1%). The ovicidal activity of biosynthesized Ag-NPs caused the hatching of the eggs with percentages of 50.1 ± 0.9, 33.5 ± 1.1, 22.9 ± 1.1, and 13.7 ± 1.2% for concentrations of 5, 10, 15, and 20 ppm, whereas Ag-NPs at a concentration of 25 and 30 ppm caused complete egg mortality (100%). The obtained data confirmed the applicability of biosynthesized Ag-NPs to the biocontrol of A. aegypti at low concentrations.

Neuroimaging features of arboviral infections in the Americas

Arboviruses are zoonotic RNA viruses maintained in nature in cycles that involve arthropod vectors. The arboviruses that cause disease in humans are members of the Bunyaviridae, Togaviridae, Flaviviridae, and Reoviridae families. These viral species have geographically and climatically restricted distributions due to particular ecological and vector features. The main emerging arboviruses in the Americas are dengue, zika, yellow fever (Flaviviridae), and chikungunya (Togaviridae). All of these viruses can be transmitted by the Aedes aegypti and Aedes albopictus mosquitoes. Although not commonly, these infections are associated with neurological complications, characterized mainly by hemorrhage, encephalitis, myelitis, acute disseminated encephalomyelitis, Guillain-Barré syndrome, and/or congenital malformations. This review describes the imaging features of the neurological complications of these emerging arbovirus infections.

Periodic Orbits of a Mosquito Suppression Model Based on Sterile Mosquitoes

In this work, we investigate the existence and stability of periodic orbits of a mosquito population suppression model based on sterile mosquitoes. The model switches between two sub-equations as the actual number of sterile mosquitoes in the wild is assumed to take two constant values alternately. Employing the Poincaré map method, we show that the model has at most two T-periodic solutions when the release amount is not sufficient to eradicate the wild mosquitoes, and then obtain some sufficient conditions for the model to admit a unique or exactly two T-periodic solutions. In particular, we observe that the model displays bistability when it admits exactly two T-periodic solutions: the origin and the larger periodic solution are asymptotically stable, and the smaller periodic solution is unstable. Finally, we give two numerical examples to support our lemmas and theorems.

High Prevalence of Rickettsia bellii in Mosquitoes From Eastern China

Mosquitoes are the most important vectors carrying significant numbers of human pathogens. Recent studies implicated that mosquitoes play an important role in circulation and transmission of multiple Rickettsia species. In this study, Rickettsia bellii was identified in four mosquito species (Culex pipiens, C. tritaeniorhynchus, Aedes albopictus, and Anopheles sinensis) collected from three Eastern China provinces during 2019-2020. Rickettsia bellii was detected in 37.50 and 26.32% of the C. pipiens pools from Beijing and Jiangsu province, respectively. In C. tritaeniorhynchus and An. sinensis from Shandong, the infection rate is 20.00 and 6.25%, respectively. Additionally, three Ae. albopictus pools (3/42, 7.14%) from Beijing were also detected positive for R. bellii. Genetic and phylogenetic analysis on 16S, gltA, and groEL genes indicates that sequences from all these strains are highly homologous and closely related to other R. bellii strains. This is the first report that Ae. albopictus and C. tritaeniorhynchus harbor R. bellii. The wide host range and high infection rate in certain areas may dramatically increase the exposure of R. bellii to human and other vertebrates. The role of mosquitoes in transmission of rickettsiosis and its potential risk to public health should be further considered.

Vector microbiota manipulation by host antibodies: the forgotten strategy to develop transmission-blocking vaccines

Human and animal pathogens that are transmitted by arthropods are a global concern, particularly those vectored by ticks (e.g. Borrelia burgdorferi and tick-borne encephalitis virus) and mosquitoes (e.g. malaria and dengue virus). Breaking the circulation of pathogens in permanent foci by controlling vectors using acaricide-based approaches is threatened by the selection of acaricide resistance in vector populations, poor management practices and relaxing of control measures. Alternative strategies that can reduce vector populations and/or vector-mediated transmission are encouraged worldwide. In recent years, it has become clear that arthropod-associated microbiota are involved in many aspects of host physiology and vector competence, prompting research into vector microbiota manipulation. Here, we review how increased knowledge of microbial ecology and vector-host interactions is driving the emergence of new concepts and tools for vector and pathogen control. We focus on the immune functions of host antibodies taken in the blood meal as they can target pathogens and microbiota bacteria within hematophagous arthropods. Anti-microbiota vaccines are presented as a tool to manipulate the vector microbiota and interfere with the development of pathogens within their vectors. Since the importance of some bacterial taxa for colonization of vector-borne pathogens is well known, the disruption of the vector microbiota by host antibodies opens the possibility to develop novel transmission-blocking vaccines.

Laboratory and Greenhouse Performance of Five Commercial Light Traps for Capturing Mosquitoes in China

Mosquito light traps for household use are popular because they are small, cheap, user friendly, and environment friendly. At present, there are many variations and specifications of mosquito traps intended for household use on the market. The light traps claim they are powerful, but research and evaluation are lacking. Key parameters such as capture rates in the laboratory and field of 5 popular mosquito traps were evaluated as intended for household use. This study found that in the laboratory experiments, the capture rate of the mosquito traps selected was between 34.7% and 65.0%. Field tests in greenhouses found that the 5 mosquito traps had high catch rates for Culex quinquefasciatus. The percentage of Cx. quinquefasciatus, Aedes albopictus, Anopheles sinensis, and other flying insects captured was 51.76%, 25.29%, 14.12%, and 8.82%, respectively. There was no significant difference in the capture rate of Ae. albopictus and An. sinensis by the 5 mosquito traps in the greenhouse, but a significant difference in the catch rate of Cx. quinquefasciatus. The analysis showed that the fan speed and design of the air guide of the traps are important factors that affect the mosquito catch rate and that the ultraviolet wavelength (395-400 nm) used by the traps did not impact mosquito catch rates. Therefore, the mosquito traps intended for household use can be improved by adjusting the fan speed and optimizing the air guide.

Isolation and Characterization of Mosquito-Associated Spiroplasma cantharicola from Aedes japonicus Collected in Hokkaido, Japan

Species of the genus Spiroplasma are common within arthropods and plants worldwide. Mosquito-associated Spiroplasma spp. have been reported to show pathogenicity toward mosquitoes, which serve as vectors of several infectious diseases that have detrimental effects on public health. Although Spiroplasma spp. are expected to have potential use as biological vector-control tools, characteristics such as their distribution, host species, and cytopathogenic effects (CPEs) are not well understood. In this study, we isolated a Spiroplasma sp. from a female Aedes japonicus collected in Hokkaido, northern Japan. Phylogenetic analysis based on the 16S rRNA gene sequence indicated our isolate was closely related to S. cantharicola. We screened 103 mosquito pools consisting of 3 genera and 9 species, but only detected S. cantharicola in the first isolation. In an in vitro assay, our isolate grew well at 28 °C, but no propagation was observed at 37 °C. Furthermore, the isolate showed strong CPE on a mosquito-derived cultured cell line (C6/36), and its propagation slightly increased when co-cultured with C6/36 cells. To our knowledge, this is the third report of the isolation of S. cantharicola from mosquitoes and the first case in Asia. Our findings provide epidemiological data on S. cantharicola distribution in the region.

Olfaction in Anopheles mosquitoes

As vectors of disease, mosquitoes are a global threat to human health. The Anopheles mosquito is the deadliest mosquito species as the insect vector of the malaria-causing parasite, which kills hundreds of thousands every year. These mosquitoes are reliant on their sense of smell (olfaction) to guide most of their behaviors, and a better understanding of Anopheles olfaction identifies opportunities for reducing the spread of malaria. This review takes a detailed look at Anopheles olfaction. We explore a range of topics from chemosensory receptors, olfactory neurons, and sensory appendages to behaviors guided by olfaction (including host-seeking, foraging, oviposition, and mating), to vector management strategies that target mosquito olfaction. We identify many research areas that remain to be addressed.

Mosquito Trilogy: Microbiota, Immunity and Pathogens, and Their Implications for the Control of Disease Transmission

In mosquitoes, the interaction between the gut microbiota, the immune system, and the pathogens that these insects transmit to humans and animals is regarded as a key component toward the development of control strategies, aimed at reducing the burden of severe diseases, such as malaria and dengue fever. Indeed, different microorganisms from the mosquito microbiota have been investigated for their ability to affect important traits of the biology of the host insect, related with its survival, development and reproduction. Furthermore, some microorganisms have been shown to modulate the immune response of mosquito females, significantly shaping their vector competence. Here, we will review current knowledge in this field, focusing on i) the complex interaction between the intestinal microbiota and mosquito females defenses, both in the gut and at humoral level; ii) how knowledge on these issues contributes to the development of novel and targeted strategies for the control of mosquito-borne diseases such as the use of paratransgenesis or taking advantage of the relationship between Wolbachia and mosquito hosts. We conclude by providing a brief overview of available knowledge on microbiota-immune system interplay in major insect vectors.

MiR-4448 is involved in deltamethrin resistance by targeting CYP4H31 in Culex pipiens pallens

Background

Culex pipiens (Cx. pipiens) complex, which acts as a vector of viruses and is widespread and abundant worldwide, including West Nile virus, Japanese encephalitis virus, and Sindbis virus, can cause serious vector-borne diseases affecting human health. Unfortunately, mosquitoes have developed deltamethrin resistance because of its long-term overuse, representing a major challenge to mosquito control. Understanding the molecular regulatory mechanisms of resistance is vital to control mosquitoes. MicroRNAs (miRNAs) are short non-coding RNAs that have been demonstrated to be important regulators of gene expression across a wide variety of organisms, which might function in mosquito deltamethrin resistance. In the present study, we aimed to investigate the regulatory functions of miR-4448 and CYP4H31 in the formation of insecticidal resistance in mosquito Culex pipiens pallens.

Methods

We used quantitative real-time reverse transcription PCR to measure miR-4448 and CYP4H31 (encoding a cytochrome P450) expression levels. The regulatory functions of miR-4448 and CYP4H31 were assessed using dual-luciferase reporter assays. Then, oral feeding, RNA interference, and the American Centers for Disease Control and Prevention bottle bioassay were used to determine miR-4448’s association with deltamethrin resistance by targeting CYP4H31in vivo. Cell Counting Kit-8 (CCK-8) was also used to detect the viability of pIB/V5-His-CYP4H31-transfected C6/36 cells after deltamethrin treatment in vitro.

Results

MiR-4448 was downregulated in the deltamethrin-resistant strain (DR strain), whereas CYP4H31 was downregulated in deltamethrin-susceptible strain. CYP4H31 expression was downregulated by miR-4448 recognizing and binding to its 3′ untranslated region. Functional verification experiments showed that miR-4448 overexpression resulted in lower expression of CYP4H31. The mortality of miR-4448 mimic-injected DR strain mosquitoes was higher than that of the controls. CCK-8 assays showed that CYP4H31 decreased cellular resistance to deltamethrin in vitro and the mortality of the DR strain increased when CYP4H31 was knocked down in vivo.

Conclusions

In mosquitoes, miR-4448 participates in deltamethrin resistance by targeting CYP4H31. The results of the present study increase our understanding of deltamethrin resistance mechanisms.

Bioactivities of rose-scented geranium nanoemulsions against the larvae of Anopheles stephensi and their gut bacteria

Anopheles stephensi with three different biotypes is a major vector of malaria in Asia. It breeds in a wide range of habitats. Therefore, safer and more sustainable methods are needed to control its immature stages rather than chemical pesticides. The larvicidal and antibacterial properties of the Pelargonium roseum essential oil (PREO) formulations were investigated against mysorensis and intermediate forms of An. stephensi in laboratory conditions. A series of nanoemulsions containing different amounts of PREO, equivalent to the calculated LC₅₀ values for each An. stephensi form, and various quantities of surfactants and co-surfactants were developed. The physical and morphological properties of the most lethal formulations were also determined. PREO and its major components, i.e. citronellol (21.34%), L-menthone (6.41%), linalool (4.214%), and geraniol (2.19%), showed potent larvicidal activity against the studied mosquitoes. The LC_50/90 values for mysorensis and intermediate forms were computed as 11.44/42.42 ppm and 12.55/47.69 ppm, respectively. The F48/F44 nanoformulations with 94% and 88% lethality for the mysorensis and intermediate forms were designated as optimized formulations. The droplet size, polydispersity index, and zeta-potential for F48/F44 were determined as 172.8/90.95 nm, 0.123/0.183, and -1.08/-2.08 mV, respectively. These results were also confirmed by TEM analysis. Prepared formulations displayed antibacterial activity against larval gut bacteria in the following order of decreasing inhibitory: LC₉₀, optimized nanoemulsions, and LC₅₀. PREO-based formulations were more effective against mysorensis than intermediate. Compared to the crude PREO, the overall larvicidal activity of all nanoformulations boosted by 20% and the optimized formulations by 50%. The sensitivity of insect gut bacteria may be a crucial factor in determining the outcome of the effect of toxins on target insects. The formulations designed in the present study may be a good option as a potent and selective larvicide for An. stephensi.

Green synthesis of silver nanoparticle using Leonotis nepetifolia and their toxicity against vector mosquitoes of Aedes aegypti and Culex quinquefasciatus and agricultural pests of Spodoptera litura and Helicoverpa armigera

Pest insects causing damage to cultivable crops and food products by feeding, fecundity, and parasitizing livestock, also being a nuisance to human health. In consideration with human health, the World Health Organization reports that more than 50% of the world's population is presently at risk from mosquito-borne diseases. Mosquitoes are primary vectors for major dreadful diseases such as yellow fever, malaria, and dengue fever, which infect millions of human beings all over the world and kill millions of peoples every year. The present research work was carried out to evaluate the antifeedant, larvicidal, pupicidal, larval, and pupal duration activity of Leonotis nepetifolia-mediated silver nanoparticles (AgNPs) against Spodoptera litura, Helicoverpa armigera, Aedes aegypti, and Culex quinquefasciatus. Biosynthesized AgNPs were characterized through various techniques such as UV-Vis spectrometer, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential analysis. The AgNPs showed potential antifeedant activity of 78.77% and 82.16% against the larvae of S. litura and H. armigera, respectively. The maximum larval mortality rate (78.49% and 72.70%) and maximum pupal mortality rate (84.66% and 77.44%) were observed against S. litura and H. armigera. Mosquito larvae were tested with biosynthesized AgNPs, and recorded LC₅₀ values were 47.44 ppm and 35.48 ppm on A. aegypti and C. quinquefasciatus, respectively. The histological examinations showed that the acceleration of the nanomaterial caused severe tissue damage in the epithelial and goblet cells in the larval midgut region of S. litura, H. armigera, A. aegypti, and C. quinquefasciatus. Biosynthesis of silver nanoparticles using L. nepetifolia is an ideal eco-friendly approach for the management of insect pests. Graphical abstract.

Field-deployable molecular diagnostic platform for arbovirus detection in Aedes aegypti

BACKGROUND

Surveillance of mosquito infection status is critical for planning and deployment of proper mosquito control initiatives. Point-of-care (POC) detection assays are necessary for monitoring the infection prevalence and geographical range of viruses in mosquito vector populations. We therefore assessed the novel real-time PCR (qPCR) bCUBE (Hyris, London, UK) molecular diagnostic system as a tool for virus detection.

METHODS

Aedes aegypti Rps17 was used to validate and determine correlation coefficient for the novel bCUBE qPCR system to a laboratory standard StepOnePlus real-time PCR system (Applied Biosystems, Waltham, MA, USA). Experimentally infected Ae. aegypti were quantified for Zika (ZIKV) and dengue virus serotype 2 (DENV2) viral genomic RNA. Infection prevalence was compared to plaque assay.

RESULTS

We developed and validated a novel qPCR system for the detection of ZIKV and DENV2 using the real-time qPCR system bCUBE. With bCUBE-based qRT-PCR, viral genomic RNA could be detected in individually infected Ae. aegypti mosquitoes and in pools of 5, 10 or 15 mosquitoes.

CONCLUSIONS

The portable qPCR bCUBE diagnostic system is capable of detecting Zika and dengue virus in mosquitoes and therefore has potential as a practical field-deployable diagnostic test for vector-borne disease surveillance programmes.

Spatial heterogeneity and temporal dynamics of mosquito population density and community structure in Hainan Island, China

BACKGROUND

Mosquitoes are vectors of many tropical diseases. Understanding the ecology of local mosquito vectors, such as species composition, distributions, population dynamics, and species diversity is important for designing the optimal strategy to control the mosquito-borne diseases.

METHODS

Entomological surveillance of adult mosquitoes was conducted in five sites representing different ecological settings across Hainan Island from January to December of 2018 using BG Sentinel (BGS) traps and Centers for Disease Prevention and Control (CDC) light traps. In each site, we selected three areas representing urban, suburban and rural settings. Eighteen trap-days were sampled in each setting at each site, and CDC light traps and BGS traps were setup simultaneously. Mosquito species composition, distribution, population dynamics, and species diversity were analyzed. Mosquito densities were compared between different study sites and between different settings.

RESULTS

Nine species of mosquitoes belonging to four genera were identified. Culex quinquefasciatus (80.8%), Armigeres subalbatus (13.0%) and Anopheles sinensis (3.1%) were the top three species collected by CDC light traps; Cx. quinquefasciatus (91.9%), Ae. albopictus (5.1%), and Ar. subalbatus (2.8%) were the top three species collected by BGS traps. Predominant species varied among study sites. The population dynamics of Ae. albopictus, An. sinensis and Cx. quinquefasciatus showed clear seasonal variation regardless of study sites with a varied peak season for different species. Mosquito abundance of all species showed significant differences among different study sites and among urban, suburban and rural areas. Danzhou had the highest mosquito biodiversity, with an α, β, and Gini-Simpson biodiversity index of 8, 1.13 and 0.42, respectively. BGS traps captured Aedes mosquito at a higher efficiency than CDC light traps, whereas CDC light traps captured significantly more Anopheles and Armigeres mosquitoes than BGS traps.

CONCLUSIONS

Mosquitoes were abundant on Hainan Island with clear seasonality and spatial heterogeneity. Population density, species composition, distribution, and species diversity were strongly affected by the natural environment. Different tools are required for the surveillance of different mosquito species.

Computer-Aided Design, Synthesis, and Antiviral Evaluation of Novel Acrylamides as Potential Inhibitors of E3-E2-E1 Glycoproteins Complex from Chikungunya Virus

Chikungunya virus (CHIKV) causes an infectious disease characterized by inflammation and pain of the musculoskeletal tissues accompanied by swelling in the joints and cartilage damage. Currently, there are no licensed vaccines or chemotherapeutic agents to prevent or treat CHIKV infections. In this context, our research aimed to explore the potential in vitro anti-CHIKV activity of acrylamide derivatives. In silico methods were applied to 132 Michael’s acceptors toward the six most important biological targets from CHIKV. Subsequently, the ten most promising acrylamides were selected and synthesized. From the cytotoxicity MTT assay, we verified that LQM330, 334, and 336 demonstrate high cell viability at 40 µM. Moreover, these derivatives exhibited anti-CHIKV activities, highlighting the compound LQM334 which exhibited an inhibition value of 81%. Thus, docking simulations were performed to suggest a potential CHIKV-target for LQM334. It was observed that the LQM334 has a high affinity towards the E3-E2-E1 glycoproteins complex. Moreover, LQM334 reduced the percentage of CHIKV-positive cells from 74.07 to 0.88%, 48h post-treatment on intracellular flow cytometry staining. In conclusion, all virtual simulations corroborated with experimental results, and LQM334 could be used as a promising anti-CHIKV scaffold for designing new drugs in the future.

Risk factors for death among patients with Chikungunya virus infection during the outbreak in northeast Brazil, 2016-2017

BACKGROUND

Chikungunya virus (CHIKV) infection is a current public health problem. The aim of this study was to investigate risk factors for death among patients with CHIKV infection during a large epidemic in northeast Brazil.

METHODS

This is a cross-sectional study with all registered cases of CHIKV in Ceara, Brazil, during 2016-2017. Data from notification reports were collected, and we have compared non-survivors and survivors.

RESULTS

A total of 182 731 cases were reported, with a mean age of 38±19 years, and the majority was female (62%). There were 383 deaths. Non-survivors were elderly, with a predominance of males, and with a lower educational level. Conditions that were significantly more frequent in the non-survivor group were systemic arterial hypertension, diabetes mellitus and chronic kidney disease (p<0.0001). Independent risk factors for death were advanced age (OR 7.35, p<0.0001), male gender (OR 2.05, p<0.0001), leukopenia (OR 3.18, p<0.0001) and vomiting (OR 2.19, p<0.0001), and comorbidities like hypertension (OR 3.74, p<0.0001), diabetes (OR 3.29, p<0.0001) and chronic kidney disease (OR 3.14, p<0.0001).

CONCLUSION

Advanced age and low educational level were associated with higher risk of mortality in CHIKV. Leukopenia and vomiting were signs of severity, as well as the presence of comorbidities, especially hypertension, diabetes and kidney disease.

Entomological Surveillance for Zika and Dengue Virus in Aedes Mosquitoes: Implications for Vector Control in Thailand

Entomological surveillance for arthropod-borne viruses is vital for monitoring vector-borne diseases and informing vector control programs. In this study, we conducted entomological surveillance in Zika virus endemic areas. In Thailand, it is standard protocol to perform mosquito control within 24 h of a reported dengue case. Aedes females were collected within 72 h of case reports from villages with recent Zika–human cases in Kamphaeng Phet Province, Thailand in 2017 and 2018. Mosquitoes were bisected into head-thorax and abdomen and then screened for Zika (ZIKV) and dengue (DENV) viruses using real-time RT-PCR. ZIKV RNA was detected in three samples from two female Ae. aegypti (1.4%). A partial envelope sequence analysis revealed that the ZIKV sequences were the Asian lineage identical to sequences from ZIKV-infected cases reported in Thailand during 2016 and 2017. Dengue virus-1 (DENV-1) and dengue virus-4 (DENV-4) were found in four Ae. aegypti females (2.8%), and partial capsid sequences were nearly identical with DENV-1 and DENV-4 from Thai human cases reported in 2017. Findings in the current study demonstrate the importance of entomological surveillance programs to public health mosquito-borne disease prevention measures and control.

Identification of Aedes mosquitoes by MALDI-TOF MS biotyping using protein signatures from larval and pupal exuviae

BACKGROUND

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) biotyping is an innovative strategy, applied successfully for the identification of numerous arthropod families including mosquitoes. The effective mosquito identification using this emerging tool was demonstrated possible at different steps of their life-cycle, including eggs, immature and adult stages. Unfortunately, for species identification by MS, the euthanasia of the mosquito specimen is required.

METHODS

To avoid mosquito euthanasia, the present study assessed whether aedine mosquitoes could be identified by MALDI-TOF MS biotyping, using their respective exuviae. In this way, exuviae from the fourth-instar and pupal stages of Aedes albopictus and Aedes aegypti were submitted to MALDI-TOF MS analysis.

RESULTS

Reproducible and specific MS spectra according to aedine species and stage of exuviae were observed which were objectified by cluster analyses, composite correlation index (CCI) tool and principal components analysis (PCA). The query of our reference MS spectra database (DB) upgraded with MS spectra of exuviae from fourth-instar larvae and pupae of both Aedes species revealed that 100% of the samples were correctly classified at the species and stage levels. Among them, 93.8% (135/144) of the MS profiles reached the threshold log score value (LSV > 1.8) for reliable identification.

CONCLUSIONS

The extension of reference MS spectra DB to exuviae from fourth-instar and pupal stages made now possible the identification of mosquitoes throughout their life-cycle at aquatic and aerial stages. The exuviae presenting the advantage to avoid specimen euthanasia, allowing to perform complementary analysis on alive mosquitoes.

Effectiveness of landmark- and semi-landmark-based geometric morphometric to identify four species of Culex mosquitoes in Thailand

Objective:

This research aims to study the effectiveness of landmark- and semi-landmark-based geometric morphometric (LMSL) in the identification of four Culex vectors, namely, C. quinquefasciatus, C. visnui, C. sitiens, and C. whitmorei in Thailand and also compared the potential between LMSL and the landmark-based geometric morphometric method (LM).

Materials and Methods:

The overall size of the wing sample was estimated by the centroid size. Shape variables were computed as principal components of the “partial warp” calculated after generalized procrustes analysis of raw coordinates. Discriminant analysis of the canonical variables performed to explore the shape dissimilarity between Culex species has been shown as a factor map and to calculate the Mahalanobis distance. Size and shape differences based on pairwise Mahalanobis distances were tested using non-parametric methods (1,000 cycles) with Bonferroni correction at a p-value of <0.05.

Results:

A total of 120 individuals were used that were divided into 30 individuals per Culex species. The mean CS of C. sitiens had the largest wings followed by C. visnui, C. quinquefasciatus, and C. whitmorei in LM and LMSM. The patterns of statistical difference in CS of both methods were similar and wing shapes among Culex species were different based on a comparison of pairwise Mahalanobis distances (p < 0.05) in both methods. For the cross-validated reclassification test, LM provided Culex species separation ranging from 54% to 84% and 51% to 93% for LMSM.

Conclusion:

Thus, LMSM is another option to use for the identification in mosquito vectors that have a curved line on the wing specific to the species.