Mosquito Populations Research Articles

Optimal Control of Microcephaly Under Vertical Transmission of Zika

The Zika virus, known for its potential to induce neurological conditions such as microcephaly when transmitted vertically from infected mothers to infants, has sparked widespread concerns globally. Motivated by this, we propose an optimal control problem for the prevention of vertical Zika transmission. The novelty of this study lies in its consideration of time-dependent control functions, namely, insecticide spraying and personal protective measures taken to safeguard pregnant women from infected mosquitoes. New results provide a way to minimize the number of infected pregnant women through the implementation of control strategies while simultaneously reducing both the associated costs of control measures and the mosquito population, resulting in a decline in microcephaly cases.

SMART DENGUE CONTROL

This research presents a novel approach to combating dengue by integrating Biological Control methods with Artificial Intelligence (AI). The objective of the study is to reduce the Aedes aegypti mosquito population and decrease dengue transmission through sustainable strategies. A comprehensive research methodology was used, involving extensive literature review, case studies, and data analysis to identify the main factors driving the high incidence of dengue in Brazil. The research applied AI tools to analyze epidemiological, meteorological, and environmental data, allowing for early outbreak predictions and targeted interventions. AI-enhanced surveillance systems were also employed to monitor mosquito populations and identify breeding sites more accurately. These strategies were combined with biological control methods, such as using natural predators and genetically modified mosquitoes, to manage mosquito populations effectively. The study demonstrate that the integration of AI and biological control can significantly improve the efficiency, accuracy, and sustainability of dengue control measures. The study concludes that this data-driven approach, when adapted to local contexts, can reduce reliance on chemical pesticides and offer a more resilient framework for long-term dengue management.

Temporal Activity and Distribution of the Invasive Mosquitoes Aedes albopictus and Aedes japonicus in the Zagreb Area, Croatia

Aedes albopictus and Aedes japonicus are invasive mosquito species that are causing great public concern. Aedes albopictus have successfully spread in Croatia, established in both the coastal and continental parts of the country, while Aedes japonicus is invading temperate climate areas. The invasive Aedes species are particularly attracted to the black plastic water containers and flower vases in cemeteries where they oviposit their eggs. Therefore, monitoring of this species was carried out in 12 cemeteries in Zagreb, using ovitraps with masonite strips as a substrate for oviposition. The monitoring was carried out from 2017 to 2020. The traps were inspected and the substrate was replaced every two weeks. This study showed that these two invasive species were present and very abundant in the cemeteries. In the case of Ae. albopictus, a higher population density and a greater number of occupied cemeteries were detected. This species was identified in all 12 cemeteries. Aedes albopictus was identified as the dominant species at all study sites. The spread of Ae. japonicus increased during 2018 in comparison to the previous year. Although this species was present in approximately 9% of the ovitraps, the observed population remained consistent throughout the course of the study. The findings indicate that cemeteries can be considered as significant public health hotspots, as the invasive Aedes mosquitoes tend to develop and reproduce in such environments. Consequently, the mosquito population of these two invasive species may only be reduced by applying integrated mosquito management measures, focused on the education of citizens.

Identification of Aquatic Habitats of Anopheles Mosquito Using Time-series Analysis of Sentinel-1 data through Google Earth Engine

Abstract. Malaria, a severe disease transmitted by Anopheles mosquitoes, presents a substantial public health concern. Since Anopheles mosquitoes thrive in water-rich environments, accurately mapping surface water is essential for assessing malaria risk and managing mosquito populations. This study seeks to identify areas prone to water accumulation, which create habitats conducive to mosquito breeding. Initially, high-risk months were extracted using precipitation and temperature data. Subsequently, the Sentinel-1 Water Index (SWI) was utilized to analyse seven years of monthly Sentinel-1 time-series images via Google Earth Engine (GEE). To enhance our findings, we integrated monthly surface-water maps using a weighted majority voting strategy. Validation efforts included collecting 520 samples, half of which were water bodies identified through field observations and Google Earth Pro, with masks generated using the Segment Anything Model (SAM) algorithm. Object-based evaluation was employed, treating each water body as a distinct entity. The results revealed an overall accuracy of 96.1% and a kappa coefficient of 92.2% in water body detection, underscoring the method's effectiveness. This method, which outperformed other approaches in the domain and machine learning classifiers, is straightforward to implement, rapid, and does not require training data. Furthermore, while field monitoring may be challenging, the findings of this study could aid health authorities in identifying high-risk areas for disease control and prevention efforts.

Present and future suitability of invasive and urban vectors through an environmentally driven mosquito reproduction number.

Temperature and water availability significantly influence mosquito population dynamics. We have developed a method, integrating experimental data with insights from mosquito and thermal biology, to calculate the basic reproduction number ([Formula: see text]) for urban mosquito species Aedes albopictus and Aedes aegypti. [Formula: see text] represents the number of female mosquitoes produced by one female during her lifespan, indicating suitability for growth. Environmental conditions, including temperature, rainfall and human density, influence [Formula: see text] by altering key mosquito life cycle traits. Validation using data from Spain and Europe confirms the approach's reliability. Our analysis suggests that temperature increases may not uniformly benefit Ae. albopictus proliferation but could boost Ae. aegypti expansion. We suggest using vector [Formula: see text] maps, leveraging climate and environmental data, to predict areas susceptible to invasive mosquito population growth. These maps aid resource allocation for intervention strategies, supporting effective vector surveillance and management efforts.

The effect of climate change and temperature extremes on Aedes albopictus populations: a regional case study for Italy.

The Asian tiger mosquito, Aedes albopictus, has spread widely throughout Italy since its introduction, with significant public health implications. We examine how decadal temperature trends and sub-monthly heatwave events affect its climate-driven geographical distribution and temporal dynamics using a new regional-scale dynamical Aedes model. The model is calibrated using [Formula: see text] years of ovitrap data for Emilia-Romagna and reproduces the vector seasonality and, to a lesser extent, its inter-annual variability. Simulated vector density hotspots overlap with densely populated areas in Rome, Milan, Naples, Foggia, Catania, Palermo, Lecce, Cagliari, Genoa, Turin and large urban centres in Emilia-Romagna. Lower risk is simulated over the Central Apennine mountains and the Alps. At decadal time scale, we simulate a lengthening of the active mosquito season by 0.5-3 weeks per decade, with the vector becoming homodynamic in southern Italy. Depending on the climatic setting, heatwaves can increase or reduce vector populations and, in some locations, can temporarily decrease mosquito populations. Such decreases can be followed by a population rebound and overshoot. Given the model's skill in reproducing key spatio-temporal Ae. albopictus features, there is potential to develop an early warning system to inform control efforts at a national scale.

Toxicity and Sublethal Effect of Chlorantraniliprole on Multiple Generations of Aedes aegypti L. (Diptera: Culicidae)

Due to the quick development of insecticide resistance, it is crucial to optimize management programs by understanding the sublethal effects of effective insecticides like chlorantraniliprole on Aedes aegypti L. populations. Using age-stage and two-sex life tables, we investigated the sublethal impacts of chlorantraniliprole on Ae. aegypti. Larval duration in the progeny of exposed parents was reduced by 0.33–0.42 days, whereas, the longevity of male and female adults was decreased by 1.43–3.05 days. Similarly, the egg-laying capacity of F1 and F2 progeny of the exposed parents was significantly reduced from 27.3% to 41.2%. The mean generation time (T) increased up to 11.8% in exposed populations, and the net reproduction rate (Ro) decreased by 51.50–55.60%. After 24 h of chlorantraniliprole treatment, there was a significant increase in cytochrome P450 activity. Contrarily, the activity of glutathione S-transferase (GST) initially declined but started increasing after 48 h of treatment. This research highlights the importance of chlorantraniliprole in mosquito management, as well as the importance of considering sublethal effects when developing strategies to handle them. Having a thorough understanding of the harmful effects of insecticides on mosquito populations can greatly enhance the effectiveness of insecticide-based interventions, while also minimizing the risk of pest resurgence.

Yeast encapsulation of photosensitive insecticides increases toxicity against mosquito larvae while protecting microorganisms

An important defense against the deadly diseases that mosquitoes transmit is the application of insecticides that reduce mosquito populations. Unfortunately, the evolution and subsequent spread of insecticide resistance has decreased their efficacy. Therefore, new mosquito control strategies are needed. One class of larvicides, known as photosensitive insecticides, or PSIs, kills larvae via light-activated oxidative damage. PSIs are promising larvicides because of their high larvicidal efficacy, rapid photodegradation, inexpensive cost, and mechanism that is dissimilar to other insecticide classes. We explored a novel delivery strategy for increasing both the larvicidal efficiency and environmental biocompatibility of PSIs, known as yeast encapsulation. Using the PSIs, curcumin and methylene blue, we measured the survival of Anopheles gambiae larvae and Escherichia coli following exposure to either non-encapsulated or yeast-encapsulated PSIs and a photoperiod. Yeast encapsulation increased the phototoxicity of both curcumin and methylene blue against mosquito larvae, likely by increasing ingestion. Furthermore, yeast encapsulation protected E. coli from the phototoxicity of yeast-encapsulated curcumin, but not yeast-encapsulated methylene blue. Yeast encapsulation increases the larvicidal efficacy of a PSI while also increasing biocompatibility. Therefore, yeast encapsulation of PSIs is a promising insecticide delivery strategy for mosquito control.

The V410L kdr allele in the VGSC confers higher levels of field resistance to permethrin in urban mosquito populations of Aedes aegypti (L.).

Females of Aedes aegypti transmit emerging arboviruses including Zika, dengue, yellow fever, and chikungunya. Control of these adult mosquitoes heavily relies on synthetic insecticides, including pyrethroids. However, insecticide resistance development in populations poses a significant challenge to vector control, particularly from knockdown resistance (kdr) mutations in the voltage-gated sodium channel (VGSC), the target of pyrethroids. This study investigated the field efficacy of Permanone, a pyrethroid-based insecticide, against Ae. aegypti by assessing the impact of three common kdr mutations (V410L, V1016I, F1534C) on mosquito survival under a real operational mosquito control scenario, by quantifying the pesticide delivered in the field. Field cage tests (FCTs) were conducted while conducting a realistic mosquito control application. Female mosquitoes from six operational areas from Harris County, TX, USA were exposed to Permanone delivered with a handheld sprayer. Permanone deposited near the cages was estimated from aluminum boats placed in the field during FCTs using gas chromatography-mass spectrometry (GC-MS). Mortality rates were recorded, and individual mosquitoes were genotyped for kdr mutations. A probit regression model was used to analyze the factors influencing mosquito survivorship. As the distance from the application source route increased, the amount of Permanone deposited decreased, resulting in higher survivorship frequency of Ae. aegypti females with the triple-resistant kdr genotype (LL/II/CC). The L allele at the 410-site significantly contributed to an increased resistance level when co-occurring with other kdr mutations. This study linked the survival probabilities of mosquitoes with different kdr genotypes, and the amount of pesticide they received in the field. Pesticide quantification, control efficacy results and genotyping allowed us to empirically determine the impact of genotypic resistance on vector control in the field. © 2024 Society of Chemical Industry.

Using Wolbachia Bacteria to Control Mosquito-Borne Disease

This publication is intended for both the general public and mosquito control professionals. It outlines the use of the bacterium Wolbachia pipientis as a tool to control mosquito populations and reduce the spread of mosquito-borne disease. Biting mosquitoes transmit many pathogens that cause deadly diseases in people, our pets, and our livestock. Collectively, malaria, dengue, West Nile, filariasis, and other mosquito-borne diseases result in millions of infections and hundreds of thousands of deaths every year. Effective vaccines for most of these have not been developed or are not yet available to the general public, and disease management is focused on controlling mosquito populations. Insecticides have become less effective over the past fifty years as mosquito populations all over the world have developed resistance. This has driven scientists to explore new options for controlling mosquitoes, including using the bacterium Wolbachia pipientis.

The Physiological Effect Of Zinc Oxide (ZnO) Nanopesticide On Aedes aegypti Larvae

Aedes aegypti is responsible for transmitting various mosquito-borne diseases. Recently, there have been concerns about the negative impacts of the insecticides used in vector control including insecticide resistance development in the mosquito population. These circumstances lead to efforts to develop other strategies for controlling mosquito vectors. As technology in nanoparticles advances, zinc oxide (ZnO) nanoparticles have the potential as the alternative for chemical pesticides for mosquito larvicides due to their optical properties and widespread usage in different industries. The purpose of this study was to determine the toxicity of ZnO nanoparticles towards Ae. aegypti larvae and to examine the physiologies of Ae. aegypti mosquito larvae treated with ZnO nanoparticles at LC50 level. Toxicity bioassays were carried out to determine LC50 and LC90 values. The larvae surface and midgut treated with LC50 ZnO were examined using the Scanning Electron Microscope (FESEM) and Dispersive X-ray spectroscopy (EDX). The LC50 and LC90 concentrations of ZnO nanoparticles after 4 hr of direct UV exposure against Ae. aegypti larvae were 49.141 mg/L and 64.195 mg/L, respectively. After exposure to ZnO nanoparticles, Ae. aegypti larvae showed morphological abnormalities, including distorted and shrunk body parts as well as midgut rupture. Overall, the findings suggest that ZnO nanoparticles have the potential to replace chemical pesticides as a means of reducing the populations of Ae. aegypti mosquitoes.

Exploring new dimensions of immune cell biology in Anopheles gambiae through genetic immunophenotyping.

Mosquito immune cells, or hemocytes, are integral components of the innate immune responses that define vector competence. However, the lack of genetic resources has limited their characterization and our understanding of their functional roles in immune signaling. To overcome these challenges, we engineered transgenic Anopheles gambiae that express fluorescent proteins under the control of candidate hemocyte promoters. Following the characterization of five transgenic constructs through gene expression and microscopy-based approaches, we examine mosquito immune cell populations by leveraging advanced spectral imaging flow cytometry. Our results comprehensively map the composition of mosquito hemocytes, classifying them into twelve distinct populations based on size, granularity, ploidy, phagocytic capacity, and the expression of PPO6, SPARC, and LRIM15 genetic markers. Together, our novel use of morphological properties and genetic markers provides increased resolution into our understanding of mosquito hemocytes, highlighting the complexity and plasticity of these immune cell populations, while providing the foundation for deeper investigations into their roles in immunity and pathogen transmission.

Residual Longevity of Recaptured Sterile Mosquitoes as a Tool to Understand Field Performance and Reveal Quality

Invasive mosquito species, such as Aedes albopictus, pose significant threats to both ecosystems and public health due to their role in transmitting diseases, such as dengue, Zika, and chikungunya. The Sterile Insect Technique (SIT) is a promising vector control strategy aimed at reducing mosquito populations by releasing sterile males to mate with wild females and reduce their reproduction rates. In this study, we employed the captive cohort method, which assesses the remaining longevity of randomly caught released individuals, to assess the longevity and frailty dynamics of sterile and non-sterile Ae. albopictus males. Using a mark–release–recapture approach (MRR), we compared the residual lifespan of sterile and non-sterile released males with that of wild, non-sterile males, aiming to understand the frailty dynamics of released males and, therefore, their quality and field performance. Contrary to expectations, our results revealed that released sterile males showed increased longevity compared to non-sterile males. Further, the marking process did not impact the longevity between lab-kept and marked males, suggesting that the marking process does not adversely affect survival under controlled conditions. These findings underscore the importance of optimizing pre-release and mass-rearing practices to enhance the effectiveness of SIT programs. Our study also demonstrates for the first time the use of the captive cohort method for understanding the biological dynamics of sterile mosquito populations in SIT programs, providing valuable insights for improving vector control strategies.

Ferroptotic cyanobacteria as biocontrol agent of the southern house mosquito Culex quinquefasciatus

Culex quinquefasciatus is a hematophagous mosquito, widely distributed around the world, that plays a crucial role in public and veterinary health. As an efficient vector of etiological agents, it exhibits a marked preference for urban environments and human blood. Despite advances in mosquito-borne disease control, managing mosquito populations remains an economically efficient and safe strategy to reduce the impact of epidemic outbreaks. However, achieving this goal requires ecologically acceptable tools that ensure sustainability and minimize adverse environmental impacts. In the present work, we investigated the effect of a non-toxigenic model cyanobacterium on Cx. quinquefasciatus larvae through regulated cell death. We observed that heat stress treatment of Synechocystis PCC 6803 inducing ferroptosis, results in larval lipid oxidation, leading to their death. This effect can be mitigated by rearing larvae in an environment containing canonical inhibitors of ferroptosis, such as ferrostatin 1, or antioxidants, like glutathione and ascorbic acid. Furthermore, larval cell death induced by ferroptotic cyanobacteria is closely linked to oxidative dysregulation and lipid peroxidation, both hallmarks of ferroptosis. Moreover, while ferroptotic Synechocystis significantly affects larval development, it does not influence oviposition site selection by gravid females.

On the necessity of accounting for age structure in human malaria transmission modeling

Malaria is one of the most common mosquito-borne diseases widespread in tropical and subtropical regions, causing thousands of deaths every year in the world. In a previous paper, we formulated an age-structured model containing three structural variables: (i) the chronological age of human and mosquito populations, (ii) the time since they are infected, and (iii) humans waning immunity (i.e. the progressive loss of protective antibodies after recovery). In the present paper, we expand the analysis of this age-structured model and focus on the derivation of entomological and epidemiological results commonly used in the literature, following the works of Smith and McKenzie. We generalize their results to the age-structured case. In order to quantify the impact of neglecting structuring variables such as chronological age, we assigned values from the literature to our model parameters. While some parameters values are readily accessible from the literature, at least those about the human population, the parameters concerning mosquitoes are less commonly documented and the values of a number of them (e.g. mosquito survival in the presence or in absence of infection) can be discussed extensively. Our analysis, informed by parameter values from the literature, demonstrates that overlooking those structural variables of human and mosquito populations may result in inaccurate epidemiological predictions and suboptimal control strategies. We highlight the epidemiological implications of these findings and emphasize the necessity of considering age structure in future malaria control programs.

A scoping review to determine if adverse human health effects are associated with use of organophosphates for mosquito control.

Organophosphate insecticides are widely used for adult mosquito control. Although proven effective in reducing mosquito populations and limiting arbovirus transmission, public concern exists regarding potential human health effects associated with organophosphate exposure. The aim of this scoping review was to describe any reported human health conditions associated with organophosphates during their use for adult mosquito control in the United States and Canada. Original peer-reviewed articles published in English language journals from 1 January 2000 to 22 May 2024, were obtained by searching from the databases MEDLINE, EMBASE, Agricultural & Environmental Science Collection, CAB Abstracts, and Scopus. The search identified 6,154 screened articles. Following an independent review, 10 studies were identified that described human health conditions associated with organophosphate exposure during adult mosquito control applications. Of the 10 included studies, only two articles were published within the last 11 years (2013 to 22 May 2024). Three types of study design were represented in the included studies: cohort (n = 5), case study (n = 1), and risk assessment (n = 4). The included studies could not determine causality between exposure to adulticides and development of illness or adverse impacts. Exposure to organophosphates did not contribute to an observed increase in metabolic toxicity, hospitalization rates, or self-reported symptoms and exposure. The available and limited evidence indicates that organophosphates can be used safely to control nuisance mosquitoes or mosquitoes that transmit arboviruses. Continued research regarding the human health effects associated with organophosphate applications for adult mosquito control could help evaluate the basis of the public's concerns and inform public health decision-making.

Dengue Dynamics: Modelling Spread and Environmental Interactions

The objective of this study is to analyze the behavior of dengue fever in the city of La Plata during one year, considering temperature as an environmental factor, its influence on the mosquito population and the transmission of the DENV virus (which causes dengue fever, also known as dengue fever). To become aware of the magnitude of the problem in the future, and using the temperature estimated by the global warming trend, we sought to project an increase in average annual temperatures for the coming years, and thus estimate the impact on the spread of dengue fever. The Netlogo simulation tool was used to model the behavior of a mosquito population and the spread of the dengue virus through contact with the human population. Using official data from the National Meteorological Service, a scenario of spread was simulated for the period November 2022-November 2023, and the increase in temperature due to climate change was projected to simulate how it affects the spread of the virus and the mosquito population, maintaining the same trend for 2024, 2025 and 2030. It was concluded that climate change may generate an expansion in both the size of mosquito populations and their annual activity, leading to the appearance of dengue outbreaks outside the identified warmer seasons.

Continuous and Dynamic Circulation of West Nile Virus in Mosquito Populations in Bucharest Area, Romania, 2017-2023.

West Nile virus (WNV) is a mosquito-borne pathogen with a worldwide distribution. Climate change and human activities have driven the expansion of WNV into new territories in Europe during the last two decades. Romania is endemic for WNV circulation since at least 1996 when the presence of lineage 1 was documented during an unprecedented outbreak. Lineage 2 was first identified in this country during a second significant human outbreak in 2010. Its continuous circulation is marked by clade replacement, and even co-circulation of different strains of the same clade was observed until 2016. The present study aims to fill the information gap regarding the WNV strains that were circulating in Romania between 2017 and 2023, providing chiefly viral sequences obtained from mosquito samples collected in the Bucharest metropolitan area, complemented by human and bird viral sequences. WNV was detected mainly in Culex pipiens mosquitoes, the vectors of this virus in the region, but also in the invasive Aedes albopictus mosquito species. Lineage 2 WNV was identified in mosquito samples collected between 2017 and 2023, as well as in human sera from patients in southern and central Romania during the outbreaks of 2017 and 2018. Both 2a and 2b sub-lineages were identified, with evidence of multiple clusters and sub-clusters within sub-lineage 2a, highlighting the complex and dynamic circulation of WNV in Romania, as a consequence of distinct introduction events from neighboring countries followed by in situ evolution.

Density-Dependent Mortality of the Diving Beetle, Rhantus elevatus (Dytiscidae: Coleoptera) Preyed Upon Culex pipiens Larvae: Effects of Prey and Predator Densities.

Diving beetles (Coleoptera: Dytiscidae) are general predators that feed primarily on mosquito larvae and can control their populations, but the evidence for such an assumption remains weak. Rhantus elevatus is an important predator of this group distributed in Egypt with both larval and adult stages preying on immature mosquito. For determine predator effectiveness, it is requisite to identify the functional response (a = rate of attack and Th = time of handling) and searching efficacy (at = area of discovery and m = mutual interference) as both correlate with biocontrol efficacy. This study assessed the density-dependent mortality of Culex pipiens larvae by eliciting functional responses of third-instar and adult predators at prey density ranging from 100 to 500 larvae per arena. By contrast, a searching efficacy for the same predator stages was examined at densities ranging from one to five predators per 500 prey. Predation rates of third-instar and adult of R. elevatus were fitted by a model of Type II response with coefficients were: third-instar (a = 0.208 h-1 and Th = 2413 h) and adult (a = 0.1191 h-1 and Th = 3723 h). The maximum number of mosquitoes which can be devoured by an individual larva and adult of R. elevatus within 24 h was 99.46 and 64.46 prey, respectively. The area of discovery for the larval stage declined more steeply than the adult stage of the predator as their density increased from one to five individuals, indicating more interference estimated for the larval stage. Considering these characteristics, larvae would seem to be the most effective stage against low mosquito populations due to low predation risk compared to that generated at high predator densities in the same arena from intra-specific interference. Eventually, we suggested a ratio of 1:100 (predator per prey) must be considered in biocontrol plans for mosquitoes.

Chromosomal Polymorphism of Malaria Mosquitoes of Karelia and Expansion of Northern Boundaries of Species Areas

Chromosomal variability in peripheral populations of malaria mosquitoes of the genus Anopheles (Diptera, Culicidae) inhabiting the territory of Karelia was studied. The modern northern limits of the ranges of sibling species of malarial mosquitoes An. beklemishevi, An. daciae, An. messeae s. s. and An. maculipennis were established. After 2010, the distribution boundary of malaria mosquitoes shifted northward by 170 km, from the 65th parallel to the Arctic Circle. Inversion heterozygotes XL1, XL2, 2R2, 3R1 and 3R5 were found in peripheral populations of An. beklemishevi. Peripheral populations of An. messeae s. s. were homozygous for inversion of sex chromosome XL1 and differed in the frequencies of autosome inversions from the middle taiga populations. The frequency of heterozygotes for autosomal inversions 2R1, 3R1, and 3L1 increased in populations at the edge of the species area. Chromosomal variability in peripheral populations contributes to the dispersal of malaria mosquitoes in high latitudes under warming climate conditions.