Search Results (173)

Rift Valley fever (RVF) is a climate-sensitive mosquito-borne zoonosis long regarded as a rural, pastoral disease, yet accelerating tropical urbanization and intensifying climate variability may be reshaping its epidemiology at the urban–peri-urban interface. This narrative review examines how global climate change and urban-specific climatic conditions jointly shape RVF virus (RVFV) vector habitats, transmission, and burden in tropical and subtropical cities, synthesizing 51 of 412 English-language records identified by a structured, non-systematic search of PubMed, Scopus, Web of Science, and Google Scholar (2009–2026) and selected for relevance to urban and peri-urban RVF. This research draws on human, livestock, and vector evidence from Sub-Saharan Africa, the Arabian Peninsula, and Indian Ocean islands across epidemic and inter-epidemic periods. The synthesis indicates that impervious surfaces, poor drainage, and open water storage can recreate the water-retaining function of rural dambos, sustaining a year-round larval habitat, and that Culex quinquefasciatus dominance together with peri-urban cattle may form an amplification bridge to humans. Direct evidence remains scarce, anchored by a single peri-urban serosurvey and limited urban slaughterhouse entomology. Critical gaps include urban primary-vector ecology, infection-rate data, urban-heat effects, city-specific exposure studies, and coupled climate–urban burden models. We conclude that RVF is a plausible emerging urban threat warranting proactive inter-epidemic surveillance and integration of RVF into urban planning and One Health systems. Full article

The chikungunya virus (CHIKV) is an emerging alphavirus transmitted primarily by Aedes mosquitoes. This narrative review synthesised evidence from 56 mosquito-based records (34 field surveillance records and 22 laboratory vector competence records) published from January 2020 to June 2026. Aedes aegypti was the most frequently detected species, confirmed as CHIKV-positive in 22 of the 29 field studies that examined it, followed by Aedes albopictus (positive in nine of 12). Both species demonstrated consistent laboratory competence. Descriptive laboratory analysis showed mean infection, dissemination, and transmission values of approximately 76%, 77%, and 37% for Ae. aegypti, and 79%, 80%, and 47% for Ae. albopictus, respectively; these values are descriptive summaries across heterogeneous laboratory protocols and inconsistently reported genotypes. East/Central/South African–Indian Ocean Lineage of the chikungunya virus (ECSA-IOL) showed the highest mean transmission efficiency among genotype groups. In addition, CHIKV RNA was also detected in Culex quinquefasciatus, Psorophora spp., Wyeomyia spp., and other culicids in field studies, but laboratory evidence does not support these species as confirmed competent vectors. Other Aedes species, including Aedes vittatus, Aedes polynesiensis, Aedes koreicus, and Aedes japonicus, may have regional relevance but require further validation. Key evidence gaps include incomplete genotype reporting, limited virus isolation from positive mosquito pools, and inconsistent transmission metrics. Future preparedness for CHIKV emergence and spread requires integrated surveillance combining field detection, virus isolation, genomic sequencing, and standardised vector competence assays within an integrated surveillance framework. Full article

Assessing mosquito vector competence for emerging arboviruses, including the underlying determinants of infection, is a foundational line of investigation towards understanding arbovirus transmission dynamics and vector–virus interactions. We developed a novel quantitative immune gene array that measures the relative expression of 22 immune genes with functional representation across five major immune pathways using quantitative reverse-transcriptase polymerase chain reaction. Homologous primers were developed for Culex tarsalis, Cx. quinquefasciatus, and Ae. aegypti mosquitoes. As an initial pilot test for this array, Cx. tarsalis and Ae. aegypti mosquitoes were orally challenged with Rift Valley fever virus (RVFV) MP12 strain. Midguts, legs/wings, and salivary glands were harvested at 3 and 7 days post-challenge. Differential gene expression was measured against Rpl32 as a housekeeping gene. This assay was sensitive enough to generate results for single mosquito midgut and salivary gland tissues, providing an initial snapshot of the types of gene expression patterns that can be observed for two mosquito species infected with MP12. This new tool will be broadly applicable for assessing mosquito immune profiles for arbovirus infection across major immune genes in five key pathways, as well as generating comparable results across mosquito and arbovirus systems. Full article

Mosquito control programs rely on larvicides such as S-methoprene to suppress vector populations and prevent mosquito-borne diseases including West Nile virus (WNV). Resistance surveillance is essential for maintaining the long-term effectiveness of larvicide active ingredients and is typically conducted using cup bioassays to evaluate larval susceptibility. Disposable Styrofoam cups are commonly used for these assays because they minimize adsorption of S-methoprene under standard testing conditions. However, recent restrictions on expanded polystyrene products in California necessitated the identification and evaluation of suitable replacement cup materials for larval resistance bioassays. Four alternative cup materials, high-density polyethylene (HDPE), polyethylene terephthalate (PET), polypropylene (PP), and paper cups, were compared to Styrofoam cups. Cup bioassays were conducted using a laboratory colony of Culex quinquefasciatus exposed to S-methoprene concentrations of 1–40 ppb. Emergence inhibition data were analyzed using probit regression to estimate the concentrations causing 50% and 90% emergence inhibition (LC₅₀ and LC₉₀, respectively) for each cup type. Cup material significantly affected concentration-response relationships. HDPE and paper cups produced significantly higher LC₅₀ and LC₉₀ estimates than Styrofoam, whereas PET and PP produced responses more comparable to the Styrofoam reference. Concentration-response slopes were similar among cup materials, indicating that cup material primarily shifted the concentration required to achieve a given level of emergence inhibition. These findings demonstrate that cup material can significantly influence estimated S-methoprene LC values. Replacement assay cups should therefore be validated before implementation in larval resistance monitoring programs. Full article

In Singapore, indoor space spraying, such as ultra-low-volume (ULV) treatment, is used to control adult mosquitoes during vector-borne disease outbreaks. This study assessed the efficacy of Mirakn^® GX, a pyrethroid-based insecticide formulation combining d,d-trans-cyphenothrin with desiccated carbon dioxide as a propellant. The implications of these findings for operational use will be discussed. Mirakn^® GX was evaluated against confined field and laboratory strains of Aedes aegypti, Ae. albopictus and Culex quinquefasciatus under semi-field conditions, following World Health Organization (WHO) guidelines. This study was conducted within an occupied residential apartment unit. An additional evaluation focusing on Ae. aegypti, designed to mimic operational practice, was performed using a reduced exposure duration of 10 min. At an application rate of 1 g/m³ with 60 min exposure, 100% knockdown and 99.79–100% mortality were observed across all three mosquito species. A shortened 10 min exposure also resulted in complete knockdown and mortality in both laboratory and field strains of Ae. aegypti, supporting operational feasibility. Under semi-field conditions, the insecticide formulation showed good penetration into enclosed spaces, indicating its potential use for scenarios where timely management of indoor adult mosquitoes is required, including during outbreaks to kill infected mosquitoes. Full article

Background/Objectives: Mosquitoes, including Culex quinquefasciatus and Aedes aegypti, are important vectors of dengue fever, Zika virus, West Nile virus, Japanese encephalitis virus, Eastern equine encephalitis virus, etc. Biological control has always been urgent in mosquito prevention due to resistance developing to synthetic insecticides and environmental toxicity by insecticides. Methods: The leaf essential oil of Mosla. chinensis was isolated, and major components were identified via GC-MS, followed by olfactory behavior assays to evaluate its repellent activity against C. quinquefasciatus. Additionally, the odorant-binding protein 1 and odorant-binding protein 2 (CquiOBP1-2) genes were prokaryotically expressed, and their fluorescence competitive binding activities with the active components of essential oils were examined. Results: The bioassays indicated this essential oil greatly repels C. quinquefasciatus, which will significantly protect people against vector-borne diseases. In the fluorescence competitive binding experiments, the CquiOBP1-2 proteins exhibit great binding capacities to volatile components, including Citronellal, Citronellol, Geraniol, Limonene and Isopulegol. Furthermore, the behavioral experimental results also indicate that the mixture of these five ligand compounds has an obvious repellent effect on mosquitoes, highlighting that they may be applied as potential mosquito repellent agents. Moreover, molecular docking and site-directed mutation analysis further confirm Phe123 and Gln77 are both key amino acid residues of CquiOBP1-2 proteins involved in the olfactory recognition of repellent ligand compounds from M. chinensis essential oil. Conclusions: The behavioral experimental verification and the exploration of olfactory molecular mechanisms are helpful to promote the biological control of plant essential oils in mosquito pests. Full article

Mosquito-borne diseases pose a significant public health concern globally; however, data on mosquito population dynamics in Taipei, Taiwan are limited and outdated. Updated information on species composition and seasonal abundance is crucial for enhancing vector surveillance and informing effective control strategies. In this study, to investigate the seasonal dynamics of mosquito populations in Taipei, Taiwan, adult females were collected biweekly from June 2023 to May 2025 using CDC light traps baited with ultraviolet light and dry ice. Species identification was performed based on morphological characteristics, and morphologically challenging Culex mosquito species were further confirmed using cytochrome c oxidase I barcoding. Mosquito surveillance from June 2023 to May 2025 yielded 1926 females representing 31 species. Of these, Culex quinquefasciatus, Culex pipiens molestus, Aedes albopictus, and Culex tritaeniorhynchus accounted for over 90% of all specimens. These dominant species exhibited distinct seasonal patterns: Cx. quinquefasciatus occurred year-round, Cx. pipiens molestus predominated during winter and spring, while Ae. albopictus and Cx. tritaeniorhynchus populations peaked in summer. Furthermore, spatial heterogeneity in both mosquito abundance and species composition was noted among the study sites. Monitoring the composition and seasonal dynamics of mosquito species is essential for understanding the epidemiology of mosquito-borne pathogens. These insights can inform more effective and targeted vector control strategies for reducing disease transmission. Such ecological insights can also support One Health approaches by linking human, animal, and environmental factors that influence the transmission of mosquito-borne diseases. Full article

Urban coastal wetlands constitute important ecological interfaces where human activities, wildlife, and arthropod vectors interact, potentially increasing the risk of pathogen transmission. In the city of Veracruz, Mexico, several interdunal lagoons have been incorporated into urban areas and are intensively used for recreational activities; however, information on their mosquito fauna remains limited. This study aimed to characterize mosquito species composition, abundance, and diversity in three urban recreational interdunal lagoons in Veracruz. Adult mosquitoes were collected weekly during the rainy season (June–September) 2023 using CDC light traps. Specimens were identified based on morphological characters using standard taxonomic keys, including genitalia dissections for male specimens when necessary. Species richness, sampling completeness, and community structure were evaluated using non-parametric richness estimators, diversity indices, species accumulation curves, and similarity analyses. A total of 1465 adult mosquitoes belonging to 11 species and five genera were collected. Mosquito assemblages were characterized by low species richness and a marked dominance of Culex panocossa and Culex quinquefasciatus across all lagoons. Diversity indices were low, and species composition showed a high degree of similarity among sites. Notably, Uranotaenia apicalis was recorded for the first time in the state of Veracruz, expanding its known geographical distribution. These findings indicate that urban interdunal lagoons support simplified mosquito communities dominated by disturbance-tolerant species, highlighting their potential epidemiological relevance and the need for targeted vector surveillance in urban coastal environments. Full article

Attractive toxic sugar baits (ATSB) exploit mosquito sugar-feeding as a control strategy, but their use has been hindered by non-target (pollinator) exposure, environmental degradation, and the difficulties of selectively administering toxicants to mosquitoes. We developed and evaluated a perforated bag-based ATSB system incorporating 200–300 microperforations (<0.25 mm in diameter) to selectively deliver toxicants in sugar water to mosquitoes while physically excluding non-target pollinators (i.e., butterflies and honey bees). In laboratory assays, the perforated bag design supported high mosquito feeding success (87%) and rapid mortality (100% within 24 h) when combined with propylene glycol or dinotefuran, without deterring feeding behavior. Butterflies and honey bees were unable to access sugar solutions through the perforated bag, demonstrating selectivity toward mosquitoes due to differences in mouthpart morphology compared to non-targets. Semi-field trials showed that integrating perforated ATSB system into passive traps did not reduce capture rates of gravid Culex quinquefasciatus or host-seeking Aedes aegypti, while inducing near complete mosquito mortality (>90%) following capture. Our results indicate that perforated bag-based ATSB systems incorporated into passive traps can target mosquitoes across multiple physiological states while minimizing the non-target risk. This platform provides promising and environmentally responsible integration of ATSB deployment into mosquito surveillance and control programs. Full article

Haiti is a Caribbean country of about 11 million people with a high burden of mosquito-transmitted disease and limited vector control, thereby making effective operational mosquito control of high importance. Previous studies have examined vector-borne disease burden and insecticide resistance markers in Haitian Aedes and Anopheles mosquitoes, but not Culex species. In this study, we examined collections of Culex quinquefasciatus from 12 locations in northern and southern Haiti for the presence of markers of insecticide resistance (using a variety of target-site mutations and biochemical assays) and pathogens (using a deep-sequencing microbiome workflow). The metagenomic analysis identified Wolbachia, Rhabdoviridae, and Plasmodium infections in all sample pools at relatively high levels, along with less frequent detections of other potential pathogens. Insecticide resistance marker examination identified variable frequencies of knockdown resistance and acetylcholinesterase resistance mutations, as well as variation in resistance-associated enzymatic activities in these populations. These findings indicate that insecticide resistance to pyrethroid and organophosphate insecticides is likely. Although there was variation among Culex mosquito populations and no clear activity pattern, enzymatic activity was significantly higher at the southern sites than at the northern sites. Similar findings in Cx. quinquefasciatus populations in other locations in the Americas strongly suggest that vector control with pyrethroid and organophosphate adulticides may be of limited efficacy. Full article

New insecticides for indoor residual spraying (IRS) are being developed to manage resistance. Chlorfenapyr (Sylando^® 240SC), a pro-insecticide, is metabolized by active mosquitoes into the toxic metabolite tralopyril. This mode of action requires adapted “free flying” bioassays (because chlorfenapyr is converted to its toxic metabolite tralopyril when mosquitoes are metabolically active). A miniature-experimental hut (MEH) assay was developed within the Ifakara Ambient Chamber Test (I-ACT) with a rabbit as a host to measure residual efficacy under controlled conditions. Sylando^® 240SC was compared with SumiShield^® 50WG (clothianidin) for 12-month residual efficacy against malaria and arbovirus vectors. Residual activity was assessed on mud, wood and concrete with two huts per substrate treated with Sylando^® 240SC, one with SumiShield^® 50WG, and one with untreated control. Five replicates of 20 mosquitoes per strain (malaria vectors: pyrethroid-susceptible Anopheles gambiae and -resistant An. arabiensis and An. funestus; culicines Aedes aegypti and Culex quinquefasciatus) were exposed overnight at one-week post spraying and monthly thereafter. Multivariable mixed-effect logistic regression with binomial errors and log link function assessed non-inferiority with a 7% margin on mosquito mortality as the primary outcome for malaria vectors. Both products induced delayed mortality, with higher effects on malaria vectors than culicines. Across all substrates and malaria species combined over the full 12 months of observation, Sylando^® 240SC was non-inferior to SumiShield^® 50WG on mortality measured at 72 h (76% vs. 67%, OR = 0.86, 95% CI: 0.77–0.97) and 168 h (89% vs. 82%, OR = 0.74, 95% CI: 0.63–0.87). Sylando^® 240SC performed comparably to SumiShield^® 50WG, supporting its use as an IRS additional option. The new I-ACT mini-experimental-hut assay provides a practical tool for evaluating pro-insecticides. The importance of free-flight evaluation methods for pro-insecticides is discussed. Full article

Mosquitoes are key vectors of numerous infectious diseases, making the study of their behavior essential for effective control strategies. This study investigates the color preferences of Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus during foraging, using an ink-based staining method to assess feeding behavior under varying light intensities (0, 130 and 1600 lx). At 0 lx, no consistent visual preferences emerged, confirming reliance on olfactory cues only. Under dusk-like illumination (130 lx), diurnal Aedes exhibited a tendency to approach red stimuli (probably perceived as grey) over darker targets, with Ae. albopictus females and males showing significant preference for red over green responses, indicating early salience of red contrasts. At high illumination (1600 lx), Aedes shifted preference toward black, especially in males, reflecting dominance of achromatic contrast and camouflage considerations. In contrast, crepuscular Cx. quinquefasciatus showed strong attraction to black at dusk-like light in both sexes; at high illumination, females’ preferences shifted from black to red, whereas males maintained or reverted to black preference across assays. These divergent patterns align with differences in photoreceptor sensitivity, contrast processing, and ecological niches governing host- and swarm-seeking. Identifying how dusk-like versus bright light modulates color-driven behavior provides insights for designing trap colors and illumination regimes optimized for specific mosquito species and sexes, thereby enhancing targeted vector-control strategies. Full article

The reliance on synthetic repellents such as N,N-diethyl-meta-toluamide (DEET) has raised health and environmental concerns, prompting the search for safer, plant-based alternatives. Catnip (Nepeta cataria L.), a rich source of iridoid monoterpenes, particularly nepetalactones, known for strong insect-repellent activity. However, their efficient extraction and molecular mechanisms in insect inhibition remains challenging. This study examined the chemical composition, protein–ligand interactions, and safety profiles of nepetalactones in comparison with DEET, with particular focus on mosquito odorant-binding proteins (OBPs) from Anopheles gambiae (AgamOBP), Culex quinquefasciatus (CquiOBP), and Aedes aegypti (AaegOBP). GC–MS/MS analysis identified nepetalactone isomers as the predominant constituents in catnip extracts obtained via steam distillation and olive oil extraction from dried leaves. Molecular docking results indicated that cis,cis-, cis,trans-, and nepetalactone isomers exhibited higher binding affinities toward the target OBPs than DEET. Furthermore, molecular dynamics simulations confirmed that all nepetalactone–OBP complexes exhibited stable conformations characterized by low average RMSD values and persistent hydrogen bond formation. Notably, cis,trans-NL–AaegOBP, NL–AaegOBP, and cis,cis-NL–AgamOBP complexes displayed lower binding free energies (ΔG_MM-PBSA) compared to DEET. These findings suggest that nepetalactones stabilize OBP–ligand interactions while inducing subtle conformational flexibility, potentially disrupting mosquito odorant recognition in a manner distinct from DEET. ADMET predictions indicated that nepetalactones exhibit favorable absorption, distribution, and safety profiles with reduced predicted toxicity compared to DEET. Collectively, these results establish nepetalactones as promising candidates for the development of effective, safe, and sustainable plant-based repellents. Full article

Arthropod-borne viruses (arboviruses) such as dengue, chikungunya, Zika, and yellow fever pose significant global health risks, with mosquitoes from the Aedes genus as the primary vectors responsible for human transmission. The Republic of the Marshall Islands (RMI), particularly the urbanized areas of Kwajalein and Majuro atolls, has experienced multiple outbreaks of dengue, Zika, and chikungunya with substantial health and economic impacts. Vector control remains the most effective method for reducing disease risk, but comprehensive data on local mosquito vector composition, distribution, and abundance are needed to guide new, effective control efforts. From 2022 to 2024, we conducted a longitudinal baseline assessment of mosquito abundance and species composition on Ebeye and nearby islets in Kwajalein Atoll, RMI, using BG-Sentinel traps and ovitraps. Aedes aegypti was the most prevalent species, accounting for 58% of all adult females collected across study locations, with higher relative abundances on Ebeye than on northern islets (4.7 vs. 2.3 per trap/night). Aedes albopictus was more abundant on northern islets (0.7 vs. 3.2 per trap/night), and Culex quinquefasciatus showed similar abundances (1.2 vs. 1.7 per trap/night). Rainfall and anthropogenic factors, including water storage practices and housing density, influenced mosquito abundance. These findings provide multi-seasonal baseline data to support targeted vector control strategies in RMI. Full article