Replication is the key barrier during the dual-host adaptation of mosquito-borne flaviviruses.

Mosquito-borne flaviviruses (MBFs) adapt to a dual-host transmission circle between mosquitoes and vertebrates. Dual-host affiliated insect-specific flaviviruses (dISFs), discovered from mosquitoes, are phylogenetically similar to MBFs but do not infect vertebrates. Thus, dISF­MBF chimeras could be an ideal model to study the dual-host adaptation of MBFs. Using the pseudoinfectious reporter virus particle and reverse genetics systems, we found dISFs entered vertebrate cells as efficiently as the MBFs but failed to initiate replication. Exchange of the untranslational regions (UTRs) of Donggang virus (DONV), a dISF, with those from Zika virus (ZIKV) rescued DONV replication in vertebrate cells, and critical secondary RNA structures were further mapped. Essential UTR-binding host factors were screened for ZIKV replication in vertebrate cells, displaying different binding patterns. Therefore, our data demonstrate a post-entry cross-species transmission mechanism of MBFs, while UTR-host interaction is critical for dual-host adaptation.

Wuchereria bancrofti Lymphatic Filariasis, Barrancabermeja, Colombia, 2023.

We describe a recent case of lymphatic filariasis in Colombia caused by Wuchereria bancrofti nematodes. Our study combines clinical-epidemiologic findings with phylogenetic data. Resurgence of lymphatic filariasis may be linked to increasing urbanization trends and migration from previously endemic regions. Fieldwork can be a beneficial tool for screening and containing transmission.

Mosquitoes as Vectors of Mycobacterium ulcerans Based on Analysis of Notifications of Alphavirus Infection and Buruli Ulcer, Victoria, Australia.

Alphavirus infections are transmitted by mosquitoes, but the mode of transmission for Mycobacterium ulcerans, which causes Buruli ulcer, is contested. Using notification data for Victoria, Australia, during 2017-2022, adjusted for incubation period, we show close alignment between alphavirus and Buruli ulcer seasons, supporting the hypothesis of mosquito transmission of M. ulcerans.

Detection of Invasive Anopheles stephensi Mosquitoes through Molecular Surveillance, Ghana.

The invasive Anopheles stephensi mosquito has rapidly expanded in range in Africa over the past decade. Consistent with World Health Organization guidelines, routine entomologic surveillance of malaria vectors in Accra, Ghana, now includes morphologic and molecular surveillance of An. stephensi mosquitoes. We report detection of An. stephensi mosquitoes in Ghana.

Molecular Epidemiology of Mayaro Virus among Febrile Patients, Roraima State, Brazil, 2018-2021.

We detected Mayaro virus (MAYV) in 3.4% (28/822) of febrile patients tested during 2018-2021 from Roraima State, Brazil. We also isolated MAYV strains and confirmed that these cases were caused by genotype D. Improved surveillance is needed to better determine the burden of MAYV in the Amazon Region.

Case Series of Jamestown Canyon Virus Infections with Neurologic Outcomes, Canada, 2011-2016.

Jamestown Canyon virus (JCV) is a mosquitoborne orthobunyavirus in the California serogroup that circulates throughout Canada and the United States. Most JCV exposures result in asymptomatic infection or a mild febrile illness, but JCV can also cause neurologic diseases, such as meningitis and encephalitis. We describe a case series of confirmed JCV-mediated neuroinvasive disease among persons from the provinces of British Columbia, Alberta, Quebec, and Nova Scotia, Canada, during 2011-2016. We highlight the case definitions, epidemiology, unique features and clinical manifestations, disease seasonality, and outcomes for those cases. Two of the patients (from Quebec and Nova Scotia) might have acquired JCV infections during travel to the northeastern region of the United States. This case series collectively demonstrates JCV's wide distribution and indicates the need for increased awareness of JCV as the underlying cause of meningitis/meningoencephalitis during mosquito season.

Molecular Epidemiology of Western Equine Encephalitis Virus, South America, 2023-2024.

Western equine encephalitis virus (WEEV) is a mosquitoborne virus that reemerged in December 2023 in Argentina and Uruguay, causing a major outbreak. We investigated the outbreak using epidemiologic, entomological, and genomic analyses, focusing on WEEV circulation near the Argentina‒Uruguay border in Rio Grande do Sul state, Brazil. During November 2023‒April 2024, the outbreak in Argentina and Uruguay resulted in 217 human cases, 12 of which were fatal, and 2,548 equine cases. We determined cases on the basis of laboratory and clinical epidemiologic criteria. We characterized 3 fatal equine cases caused by a novel WEEV lineage identified through a nearly complete coding sequence analysis, which we propose as lineage C. Our findings highlight the importance of continued surveillance and equine vaccination to control future WEEV outbreaks in South America.

Tips and tools to obtain and assess mosquito viromes.

Due to their vectorial capacity, mosquitoes (Diptera: Culicidae) receive special attention from health authorities and entomologists. These cosmopolitan insects are responsible for the transmission of many viral diseases, such as dengue and yellow fever, causing huge impacts on human health and justifying the intensification of research focused on mosquito-borne diseases. In this context, the study of the virome of mosquitoes can contribute to anticipate the emergence and/or the reemergence of infectious diseases. The assessment of mosquito viromes also contributes to the surveillance of a wide variety of viruses found in these insects, allowing the early detection of pathogens with public health importance. However, the study of mosquito viromes can be challenging due to the number and complexities of steps involved in this type of research. Therefore, this article aims to describe, in a straightforward and simplified way, the steps necessary for obtention and assessment of mosquito viromes. In brief, this article explores: the capture and preservation of specimens; sampling strategies; treatment of samples before DNA/RNA extraction; extraction methodologies; enrichment and purification processes; sequencing choices; and bioinformatics analysis.

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.

Using image segmentation models to analyse high-resolution earth observation data: new tools to monitor disease risks in changing environments.

BACKGROUND: In the near future, the incidence of mosquito-borne diseases may expand to new sites due to changes in temperature and rainfall patterns caused by climate change. Therefore, there is a need to use recent technological advances to improve vector surveillance methodologies. Unoccupied Aerial Vehicles (UAVs), often called drones, have been used to collect high-resolution imagery to map detailed information on mosquito habitats and direct control measures to specific areas. Supervised classification approaches have been largely used to automatically detect vector habitats. However, manual data labelling for model training limits their use for rapid responses. Open-source foundation models such as the Meta AI Segment Anything Model (SAM) can facilitate the manual digitalization of high-resolution images. This pre-trained model can assist in extracting features of interest in a diverse range of images. Here, we evaluated the performance of SAM through the Samgeo package, a Python-based wrapper for geospatial data, as it has not been applied to analyse remote sensing images for epidemiological studies. RESULTS: We tested the identification of two land cover classes of interest: water bodies and human settlements, using different UAV acquired imagery across five malaria-endemic areas in Africa, South America, and Southeast Asia. We employed manually placed point prompts and text prompts associated with specific classes of interest to guide the image segmentation and assessed the performance in the different geographic contexts. An average Dice coefficient value of 0.67 was obtained for buildings segmentation and 0.73 for water bodies using point prompts. Regarding the use of text prompts, the highest Dice coefficient value reached 0.72 for buildings and 0.70 for water bodies. Nevertheless, the performance was closely dependent on each object, landscape characteristics and selected words, resulting in varying performance. CONCLUSIONS: Recent models such as SAM can potentially assist manual digitalization of imagery by vector control programs, quickly identifying key features when surveying an area of interest. However, accurate segmentation still requires user-provided manual prompts and corrections to obtain precise segmentation. Further evaluations are necessary, especially for applications in rural areas.

Determinants of intended prevention behaviour against mosquitoes and mosquito-borne viruses in the Netherlands and Spain using the MosquitoWise survey: cross-sectional study.

BACKGROUND: Recently, Europe has seen an emergence of mosquito-borne viruses (MBVs). Understanding citizens' perceptions of and behaviours towards mosquitoes and MBVs is crucial to reduce disease risk. We investigated and compared perceptions, knowledge, and determinants of citizens' behavioural intentions related to mosquitoes and MBVs in the Netherlands and Spain, to help improve public health interventions. METHODS: Using the validated MosquitoWise survey, data was collected through participant panels in Spain (N = 475) and the Netherlands (N = 438). Health Belief Model scores measuring behavioural intent, knowledge, and information scores were calculated. Confidence Interval-Based Estimation of Relevance was used, together with potential for change indexes, to identify promising determinants for improving prevention measure use. RESULTS: Spanish participants' responses showed slightly higher intent to use prevention measures compared to those of Dutch participants (29.1 and 28.2, respectively, p 0.03). Most participants in Spain (92.2%) and the Netherlands (91.8%) indicated they used at least one prevention measure, but differences were observed in which types they used. More Spanish participants indicated to have received information on mosquitoes and MBVs compared to Dutch participants. Spanish participants preferred health professional information sources, while Dutch participants favoured government websites. Determinants for intent to use prevention measures included "Knowledge", "Reminders to Use Prevention Measures", and "Information" in the Netherlands and Spain. Determinants for repellent use included "Perceived Benefits" and "Cues to Action", with "Perceived Benefits" having a high potential for behavioural change in both countries. "Self-Efficacy" and "Knowledge" were determinants in both countries for breeding site removal. CONCLUSION: This study found differences in knowledge between the Netherlands and Spain but similarities in determinants for intent to use prevention measures, intent to use repellents and intent to remove mosquito breeding sites. Identified determinants can be the focus for future public health interventions to reduce MBV risks.

Structural and mechanistic insights into the complexes formed by Wolbachia cytoplasmic incompatibility factors.

Wolbachia bacteria, inherited through the female germ line, infect a large fraction of arthropod species. Many Wolbachia strains manipulate host reproduction, most commonly through cytoplasmic incompatibility (CI). CI, a conditional male sterility, results when Wolbachia-infected male insects mate with uninfected females; viability is restored if the female is similarly infected (called "rescue"). CI is used to help control mosquito-borne viruses such as dengue and Zika, but its mechanisms remain unknown. The coexpressed CI factors CifA and CifB form stable complexes in vitro, but the timing and function of this interaction in the insect are unresolved. CifA expression in the female germ line is sufficient for rescue. We report high-resolution structures of a CI-factor complex, CinA-CinB, which utilizes a unique binding mode between the CinA rescue factor and the CinB nuclease; the structures were validated by biochemical and yeast growth analyses. Importantly, transgenic expression in Drosophila of a nonbinding CinA mutant, designed based on the CinA-CinB structure, suggests CinA expressed in females must bind CinB imported by sperm in order to rescue embryonic viability. Binding between cognate factors is conserved in an enzymatically distinct CI system, CidA-CidB, suggesting universal features in Wolbachia CI induction and rescue.

History of research on Aedes albopictus (Diptera: Culicidae) in Europe: approaching the world's most invasive mosquito species from a bibliometric perspective.

The Asian tiger mosquito, Aedes albopictus (Skuse), is an invasive species native to Southeast Asia. This insect, which is an important vector of arbovirus such as dengue, Zika, and chikungunya, has spread rapidly to several parts of the world over the last few decades. This study employed a bibliometric approach to explore, for the first time, Ae. albopictus research activity and output in Europe. We used the Web of Science Core Collection data source to characterize the current scientific research. A total of 903 publications from 1973 to 2022 were retrieved. We also provided a comprehensive analysis by year of publication; distribution by most productive European countries, institutions, and authors; collaboration networks; research topics; most productive journals; and most cited publications. Results showed a notable increase in the number of studies after the chikungunya virus outbreak in Northeast Italy in 2007. More than 60% of these publications across the entire European continent originated from France and Italy. Research output related to 'population and community ecology' topics was significantly high. The most common type of collaboration was national, which occurred between institutions in the same European country. By providing an overview of Ae. albopictus research in Europe, this work contributes to upcoming debates, decision-making, planning on research and development, and public health strategies on the continent and worldwide.

Integrating wing morphometrics and mitochondrial DNA analysis to assess the filaria vector Mansonia uniformis (Diptera: Culicidae) populations in Thailand.

Mansonia uniformis (Diptera: Culicidae) is recognized as a vector of Brugia malayi and has been reported to transmit Wuchereria bancrofti, both causing lymphatic filariasis in humans. This study employed geometric morphometrics (GM) to investigate wing shape variation and analyzed genetic diversity through cytochrome c oxidase subunit 1 (COI) gene analyses in Ma. uniformis populations across Thailand. Wing GM analyses indicated significant differences in wing shape based on Mahalanobis distances among nearly all population pairs (p < 0.05), with no significant correlation between wing shape and geographic distance (r = 0.210, p > 0.05). Genetic analyses identified 63 haplotypes and 49 polymorphic sites, with the overall population exhibiting a nucleotide diversity of 0.006 (± 0.001) and a haplotype diversity of 0.912 (± 0.017). Deviations from neutrality, as indicated by Tajima's D and Fu's FS tests for the overall Ma. uniformis populations in Thailand, were statistically significant and negative, suggesting population expansion (both p < 0.05). Analysis of molecular variance revealed no significant genetic structure when all populations were categorized based on collection sites and geographic regions. However, significant differences in FST values were observed between some populations. These findings enhance our understanding of the geographical and genetic factors influencing Ma. uniformis populations, which are crucial for developing effective control strategies in Thailand.

Effectiveness of structured Behavior Change Communication methods in control of mosquito-borne diseases: A quasi-experimental study.

Background: Behavior Change Communication (BCC) is evidence-based, theoretically supported and utilizes all opportunities for communication. Evidence reports BCC as a relevant tool for averting and controlling many forms of public health challenges. Through schools, many countries have shown health improvements via students and the community's exposure to behavior change messages. The study was planned with an aim of evaluating the effectiveness of mosquito-borne disease control measures implementation through BCC to adolescent school students in a Cantonment area, in North India. Methods: The present study was undertaken as a quasi-experimental study from April 2019 to March 2020. Of the 334 students enrolled in the school as per eligibility criteria, 315 were available during the initial assessment, and 288 were available throughout the study. For the evaluation of effectiveness of the BCC at household level, 200 households (100 intervention and 100 control) were selected. Students' knowledge about mosquito-borne diseases was the primary outcome measure. The difference in proportions was tested using the chi-square test. The difference in proportions for paired samples was tested using Mc Nemar's test. Results: Proportion of students who gave correct responses significantly increased after intervention in post-test as compared to pre-test for most of the knowledge-related questions. The proportion of households with the availability of mosquito nets and self-reported use of mosquito nets was significantly high in intervention group as compared to control group post-intervention. Conclusion: BCC in the form of different intervention programs to adolescent school children was effective in improving the knowledge and attitude toward mosquito-borne diseases and also ensured less mosquito-genic environment in households.

Reemergence of Dengue Virus Serotype 3, Brazil, 2023.

We characterized 3 autochthonous dengue virus serotype 3 cases and 1 imported case from 2 states in the North and South Regions of Brazil, 15 years after Brazil's last outbreak involving this serotype. We also identified a new Asian lineage recently introduced into the Americas, raising concerns about future outbreaks.

Reemergence of Cosmopolitan Genotype Dengue Virus Serotype 2, Southern Vietnam.

We performed phylogenetic analysis on dengue virus serotype 2 Cosmopolitan genotype in Ho Chi Minh City, Vietnam. We document virus emergence, probable routes of introduction, and timeline of events. Our findings highlight the need for continuous, systematic genomic surveillance to manage outbreaks and forecast future epidemics.

Insulin reduces the transmission potential of chikungunya virus and activates the toll pathway in Aedes aegypti mosquitoes.

Chikungunya virus (CHIKV) is an alphavirus that has re-emerged globally over the last two decades and has the potential to become endemic in the United States due to the presence of competent mosquito vectors, Aedes aegypti and Aedes albopictus. CHIK disease is characterised by fever, rash, and joint pain, and causes chronic debilitating joint pain and swelling in >50% of infected individuals. Given the disease severity caused by CHIKV and the global presence of vectors to facilitate its spread, strategies to reduce viral transmission are desperately needed; however, the human biological factors driving CHIKV transmission are poorly understood. Towards that end, we have previously shown that mosquitoes fed on alphavirus-infected obese mice have reduced infection and transmission rates compared to those fed on infected lean mice despite similar viremia in lean and obese mice. One of the many host factors that increase in obese hosts is insulin, which was previously shown to impact the infection of mosquitoes by several flaviviruses. However, insulin's impact on alphavirus infection of live mosquitoes is unknown and whether insulin influences mosquito-borne virus transmission has not been tested. To test this, we exposed A. aegypti mosquitoes to bloodmeals with CHIKV in the presence or absence of physiologically relevant levels of insulin and found that insulin significantly lowered both infection and transmission rates. RNA sequencing analysis on mosquito midguts isolated at 1-day-post-infectious-bloodmeal (dpbm) showed enrichment in genes in the Toll immune pathway in the presence of insulin, which was validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). We then sought to determine if the Toll pathway plays a role in CHIKV infection of Ae. aegypti mosquitoes; therefore, we knocked down Myd88, a critical immune adaptor molecule for the Toll pathway, in live mosquitoes, and found increased CHIKV infection compared to the mock knockdown control group. Overall, these data demonstrate that insulin reduces CHIKV transmission by Ae. aegypti and activates the Toll pathway in mosquitoes, suggesting that conditions resulting in higher serum insulin concentrations may reduce alphavirus transmission. Finally, these studies suggest that strategies to activate insulin or Toll signalling in mosquitoes may be an effective control strategy against medically relevant alphaviruses.

A meta-analysis reveals that dragonflies and damselflies can provide effective biological control of mosquitoes.

Dragonfly/damselfly naiads have the potential to control mosquitoes, and indirectly the diseases they carry, due to their extensive predation on mosquito larvae. Experimental studies have measured the effectiveness of individual dragonfly/damselfly naiads in controlling mosquitoes by introducing them to mosquito larvae and counting the number of larvae eaten in a given time period (i.e. predation success). Without a quantitative synthesis, however, such individual measures are unable to provide a generalized estimation about the effectiveness of dragonflies/damselflies as biological mosquito control agents. To achieve this, we assembled a database containing 485 effect sizes across 31 studies on predation successes of 47 species of commonly found dragonfly/damselfly naiads on nine species of mosquito larvae belonging to Aedes, Anopheles and Culex. These studies covered 14 countries across Asia, Africa and South and North America, where mosquitoes are the vectors of Chikungunya, Dengue, Japanese encephalitis, Lymphatic filariasis, Malaria, Rift Valley fever, West Nile fever, Yellow fever and Zika. Using this database, we conducted a meta-analysis to estimate the average predation success per day by a single individual dragonfly/damselfly naiad on these mosquito larvae as a generalized measure of the effectiveness of dragonflies/damselflies for mosquito control. We also built an interaction network for predator-dragonflies/damselflies and prey-mosquitoes and the diseases they vector to understand the functioning of this important predator-prey network. Our results showed that mosquito larvae were significantly reduced through predation by dragonfly/damselfly naiads. Within experimental containers, a single individual dragonfly/damselfly naiad can eat on average 40 (95% confidence intervals [CIs] = 20, 60) mosquito larvae per day, equivalent to a reduction of the mosquito larval population by 45% (95% CIs = 30%, 59%) per day. The average predation success did not significantly vary among Aedes, Anopheles and Culex mosquitoes or among the four (I-IV) mosquito larval stages. These results provide strong evidence that dragonflies/damselflies can be effective biological control agents of mosquitoes, and environmental planning to promote them could lower the risk of spreading mosquito-borne diseases in an environmentally friendly and cost-effective manner.

Predictive modelling of Ross River virus using climate data in the Darling Downs.

Ross River virus (RRV) is the most common mosquito-borne infection in Australia. RRV disease is characterised by joint pain and lethargy, placing a substantial burden on individual patients, the healthcare system and economy. This burden is compounded by a lack of effective treatment or vaccine for the disease. The complex RRV disease ecology cycle includes a number of reservoirs and vectors that inhabit a range of environments and climates across Australia. Climate is known to influence humans, animals and the environment and has previously been shown to be useful to RRV prediction models. We developed a negative binomial regression model to predict monthly RRV case numbers and outbreaks in the Darling Downs region of Queensland, Australia. Human RRV notifications and climate data for the period July 2001 - June 2014 were used for model training. Model predictions were tested using data for July 2014 - June 2019. The final model was moderately effective at predicting RRV case numbers (Pearson's r = 0.427) and RRV outbreaks (accuracy = 65%, sensitivity = 59%, specificity = 73%). Our findings show that readily available climate data can provide timely prediction of RRV outbreaks.