Letteratura scientifica selezionata sul tema "Asian tiger mosquito"

The Asian tiger mosquito, Aedes albopictus (Stegomya albopicta) originating from south-east Asia, has spread primarily by the trade of used tyres to the United States, Europe, Latin America and Africa [1]. In Italy, the mosquito species was first detected in Genoa in 1990 and has since spread to several parts of the country, including border areas with Switzerland [2]. In 2000, an active monitoring system was established in southern Switzerland. The first tiger mosquito was detected in the canton of Ticino in 2003 [3]. Monitoring was gradually intensified due to growing mosquito densities in northern Italy. As the long-distance migration of Ae. albopictus depends on passive transport, the monitoring system consisted of strategically positioned oviposition traps along main traffic axes, including parking lots within industrial complexes, border crossings and shopping centres. In 2007, this monitoring system consisted of over 70 checkpoints with a total of 300 traps. Bi-weekly control visits to all traps were conducted between April and November 2007. As soon as eggs were detected, the surrounding vegetation within a perimeter of about 100 metres was sprayed with permethrin against adult mosquitoes. Stagnant water was treated with Bacillus thuringiensis and in some cases with diflubenzuron to control the larval stages.

The Asian tiger mosquito, Aedes albopictus, is an invasive mosquito species that is considered a potential vector of about 22 arboviruses, among which dengue, chikungunya and Zika. Here we report the first record of Aedes albopictus in the territory of the Republic of Kosovo. The first finding, in July 2020, was driven by a photo of an adult mosquito published by a citizen in social media. The subsequent field investigation in July 2020 confirmed the presence of adult mosquitoes by human landing catch and collection of eggs in ovitraps at the village Zhur. Monitoring was performed for 7 weeks with ovitraps and BG-Sentinel adult traps at 36 sampling stations from 7 localities, in the Southern part of Kosovo, on the border with Albania. Fifty-two out of 81 ovitrap samples resulted positive for the presence of Ae. albopictus. A total of 2,711 eggs are collected in 22 out 36 stations and a total of 78 adults from 4 out 4 stations with BG Sentinel trap and 15 adults with handled electric aspirator. Our finding shows that the tiger mosquito is expanding its geographical range in the Balkans, southeastern Europe.

AbstractAedes albopictus is an invasive mosquito species spreading throughout Europe and its presence in North Macedonia was recorded in 2016. Following the first detection in September 2018, we conducted a two-week mosquito monitoring by ovitraps in order to determine if there were established populations of Aedes albopictus in Skopje, the capital of North Macedonia. Ninety-four Ae. albopictus eggs (0 to 18 eggs per ovitrap per week) were collected from 7 (14%) ovitraps in 3 (30%) municipalities. Thirty-eight eggs (40.4%) successfully hatched and the adult mosquitoes were identified by morphology and PCR. No other potentially invasive species were identified during the monitoring period. Ae. albopictus distribution is expanding and poses a risk for an Aedes-borne disease transmission in North Macedonia. The available data highlight the need for a regular monitoring for tiger mosquitoes to plan adequate control measures.

Abstract Effective suppression of container-inhabiting Asian Tiger [Aedes albopictus (Skuse)] (Diptera: Culicidae) and yellow fever [Aedes aegypti (L.)] (Diptera: Culicidae) mosquitoes presents one of the most intractable problems for modern mosquito control. Traditional tools often fail to control populations of these mosquito species, and are prohibitively expensive or have negative environmental impacts. Novel approaches and tools are urgently needed for integrated container-inhabiting mosquito management programs. One of the most promising techniques is autodissemination. We present the results of a long-term large-scale study conducted in a temperate urbanized environment representing typical Ae. albopictus habitats. Three treatment sites with autodissemination stations and three nearby reference sites were monitored for eggs, immature, and adult mosquitoes over a period of 3 yr from 2014 to 2016. Elevated larval and pupal mortality of 12–19% on average was the most notable outcome in sentinel cups of the treatment sites. The number of eggs in the treatment sites was significantly reduced in 2014, but not in 2015 or 2016. Adult populations remained similar in treatment and reference sites throughout the study. The impact of autodissemination on mosquito populations was lower than reported by previous investigations. Technical and logistical problems associated with wider coverage and working in multiple urban neighborhoods contributed to reduced efficacy. Incorporating autodissemination with routine mosquito control operations and commercializing this methodology for general public use will require further research on combining this tool with other novel or conventional technologies.

The population dynamics of mosquitoes in temperate regions are not as well understood as those in tropical and subtropical regions, despite concerns that vector-borne diseases may be prevalent in future climates. Aedes albopictus, a vector mosquito in temperate regions, undergoes egg diapause while overwintering. To assess the prevalence of mosquito-borne diseases in the future, this study aimed to simulate and predict mosquito population dynamics under estimated future climatic conditions. In this study, we tailored the physiology-based climate-driven mosquito population (PCMP) model for temperate mosquitoes to incorporate egg diapauses for overwintering. We also investigated how the incorporation of the effect of rainfall on larval carrying capacity (into a model) changes the population dynamics of this species under future climate conditions. The PCMP model was constructed to simulate mosquito population dynamics, and the parameters of egg diapause and rainfall effects were estimated for each model to fit the observed data in Tokyo. We applied the global climate model data to the PCMP model and observed an increase in the mosquito population under future climate conditions. By applying the PCMP models (with or without the rainfall effect on the carrying capacity of the A. albopictus), our projections indicated that mosquito population dynamics in the future could experience changes in the patterns of their active season and population abundance. According to our results, the peak population number simulated using the highest CO2 emission scenario, while incorporating the rainfall effect on the carrying capacity, was approximately 1.35 times larger than that predicted using the model that did not consider the rainfall effect. This implies that the inclusion of rainfall effects on mosquito population dynamics has a major impact on the risk assessments of mosquito-borne diseases in the future.

Abstract To reduce the population of the Asian tiger mosquito Aedes albopictus (Skuse, 1894) (Diptera: Culicidae), a mosquito control campaign was organized by five Slovenian municipalities in 2020. The campaign focused on the application of Aquatain AMFTM in public water containers. The main objective of our study was to test the efficacy of the agent by directly testing the water drains for mosquito larvae and monitoring the density of the mosquito population. The drains were inspected before and after the application of the product from May to September. A water sample was taken from the drains using a dipper. For mosquito monitoring, the number of mosquito eggs and adult mosquitoes was counted from June to October. Up to two weeks after the application of the product, we observed the lethal effect of Aquatain on mosquito larvae, pupae and adult mosquitoes. After rainfall, the product was washed away and the live mosquitoes were sampled in the inspected water drains. The average number of eggs collected per site was twice as high in the area without mosquito control as in the threated locations. Nevertheless, we assessed the mosquito control campaign as partially successful, as mosquito abundance was still high in the locations with mosquito control. However, we believe that this is a good starting point and that mosquito control should be continued in the future together with the citizen education campaign.

Abstract The use of semiochemicals as repellents and attractants has been proposed to complement insecticides used for the control of vector mosquito populations. In several studies, the optical purities of the molecules tested have been described as having little or no effect on repellent activity. However, these observations seem difficult to explain because of the chirality effect of molecules on the olfactory system of insects and humans. Thus, the purpose of this study is to assess the effects of chirality on the repellent properties of 4-alcoxycoumarins against Aedes albopictus Skuse, mosquito vector of arboviruses. We report here that the racemic (R/S)-4-sec-butoxycoumarin had the highest repellent effect (Repellent Index = 49.9%) followed by (R) enantiomer (Repellent Index = 24.2%) for the dose of 5 mg/mL. Contrary, no significant repellent activity was recorded for S-(+)-4-sec-butoxycoumarin. This experiment demonstrates the close relationship between the molecules’ optical purities and the behavioral response of mosquitoes.

The overall theme that drove my research was the concern for public health and its possible compromise due to the colonization of large areas of the United States by the disease-vectoring Aedes albopictus. The main objective is to determine the elements that make an environment conducive to Aedes albopictus populations. Specifically, the objective of this research is to identify the socio-economic impact of Aedes albopictus on residents in the Hampton Roads area in southeast Virginia and determine if there is an identifiable environment in which A. albopictus could be found. Data were collected at the Census block group level (demographic variables) and at the single household level (survey and physical-cultural variables). The variables were then correlated (Pearson) and the results were analyzed. Only variables that were less than (.1) significance were examined. The following physical-cultural variables were found to be associated with the reduction of A. albopictus activity: having a sea breeze, being near an oceanfront, cutting the grass frequently, and keeping the overall neatness of a property high. Secondary variables that are related to the decrease in A. albopictus populations are sunny yards, yards with no containers that can hold water, and yards that contain coniferous trees versus deciduous trees. The primary socio-economic variables that can signify an environment with high A. albopictus activity are: lower house value and median rent value, lower levels of education, and a lower median income level. Other demographic variables that help determine the size of an A. albopictus population are (in order of significance): ethnicity (white or black), poverty/unemployed, owner/renter occupied, and the year a house was built. These secondary variables increase A. albopictus numbers if the following trends exist: high percent of persons in poverty and unemployed, higher percent of renter occupied homes, and older houses.
Master of Science

Understanding the factors that make non-native species successful invaders is an important step towards mitigating spread. At the same time, species invasions can serve as natural experiments to test range-limit theory. Range-limit theory postulates declines in local abundance (abundant center model) and genetic diversity (central-peripheral hypothesis) towards range edges because of underlying environmental gradients. Such declines constrain adaptation to marginal habitats via gene swamping. However, broader evolutionary theory predicts intermediate rates of immigration into range-edge populations can relieve genetic drift and improve adaptive potential. I tested hypotheses generated from theory while illuminating aspects affecting of the invasion of the Asian tiger mosquito (Aedes albopictus Skuse) into the US. Using reciprocal distribution modeling, I found US populations occupied significantly different climate and habitat than in their native range (SE Asia). Most inconsistencies were found in the northern US range, where Ae. albopictus has recently crept northward, providing an opportunity to test range-limit theory as the range reaches its limit. Because of its limited natural dispersal ability, rapid spread after the 1985 US introduction pointed to human-aided dispersal. I tested the current role of human-aided versus natural dispersal using a landscape genetics framework, and found that natural dispersal dominated current patterns. Some distant localities were highly genetically similar, indicating potential human-aided transport in limited cases. Asymmetric gene flow from core to edge localities supported the abundant center model, but uniformly high genetic diversity contrasted with the central-marginal hypothesis. I detected a significant signature of local adaptation by overwintering diapause-induced eggs in multiple field sites using reciprocal transplants. Surprisingly, most genotypes from throughout the range produced large offspring when overwintered at the range edge. Relative offspring mass between home and away winters peaked at an intermediate immigration rate. These results show that rapid adaptation has occurred in US populations of Ae. albopictus and highlight the potential for further spread. Genetic admixture from multiple introductions may explain high genetic diversity throughout the US range and contribute to high offspring size for all genotypes overwintered at the range edge. Finally, my work highlights the need for a better understanding of contemporary ecological and evolutionary processes leading to range-limits (or expansion) to more accurately reflect processes occurring in a human-dominated world.
Ph.D.
Doctorate
Biology
Sciences
Conservation Biology; Ecology and Organismal Biology

Mosquito-borne diseases, including arboviral diseases such as Dengue, Chikungunya and Zika, have increased their world-wide incidence in the past 50 years and currently account for about 17% of all infectious diseases globally. Urbanization, globalization, increased international mobility and the widespread distribution of the main arboviral vectors, the mosquitoes Aedes aegypti and Aedes albopictus are all factors that have contributed to the (re)-emergence of arboviral diseases. Effective therapies and vaccines are limited for most arboviruses. Accordingly, vector control is the primary way to prevent transmission of arboviruses to humans. A deep understanding of the interaction and co-evolution between viruses and mosquito vectors is expected to aid in the development of novel transmission control strategies. The capacity of mosquitoes to support viral replication and transmission is called vector competence and is a dynamic and variable trait affected by many factors, suggesting an “arms race” between mosquitoes and viruses. The main arboviral vector in Europe is the invasive species Ae. albopictus, which has increasingly received attention from the scientific community due to its quick worldwide spread from south East Asia in the past 50 years. Nonretroviral RNA endogenous viral elements (nrEVEs) with similarities to the non-retroviral RNA viruses of the Flaviviridae and Rhabdoviridae family have been found with high frequency in Ae. albopictus mosquitoes. These viral integrations often interact with the most-recently characterized of the three RNA interference (RNAi) pathways: the PIWI-interacting RNA (piRNA) pathway. Most, but not all, nrEVEs in the genome of Ae. albopictus map next to transposable elements (TEs) fragments in piRNA clusters and produce piRNAs, small molecules that associate with Argonaute proteins of the PIWI clade to silence TEs based on sequence complementarity to piRNAs. In addition to its canonical role in preserving genome integrity, the piRNA pathway has antiviral activity in Aedes spp. mosquitoes. Despite the abundance of nrEVEs the biology, functional role, and patterns of integration in wild mosquito populations are still relatively unexplored. nrEVEs could be expressed and influence the phenotype of mosquitoes acting as a form of host antiviral immunity. A difficulty in studying the Ae. albopictus genome was the absence of a high-quality reference genome. During my PhD, I focused my attention on Ae. albopictus to primarily improve knowledge of its genome. I contributed to the sequencing, assembly, and annotation of a new reference genome for Ae. albopictus based on long-reads sequencing technologies; I coordinated an international consortium to annotate and characterize genomic features and their expression and produce a physical map of the genome. The availability of this new assembly allowed me to ask more specific questions on the landscape of viral integrations. A newly developed bioinformatic pipeline was combined with molecular biology techniques to identify viral sequences integrated into the genomes of wild-collected mosquitoes from different geographical locations. I also used the new genome assembly to reconstruct and identify RNA viruses in mosquito small-RNA sequencing data. I correlated the viruses identified in the mosquitoes with their population-specific nrEVE landscape, under the hypothesis that the pattern of nrEVEs is shaped by exposure to viruses. Lastly, I applied the CRISPR-Cas9 genome editing technology on Ae. albopictus embryos to modify a viral integration and a piRNA cluster and test the hypothesis that viral integrations have a role as immunity effectors against cognate viral infections. Overall, results gained through my PhD activities will enhance our understanding on the genome structure of Ae. albopictus and the importance of repetitive elements like viral integrations in the context of its biology.
Mosquito-borne diseases, including arboviral diseases such as Dengue, Chikungunya and Zika, have increased their world-wide incidence in the past 50 years and currently account for about 17% of all infectious diseases globally. Urbanization, globalization, increased international mobility and the widespread distribution of the main arboviral vectors, the mosquitoes Aedes aegypti and Aedes albopictus are all factors that have contributed to the (re)-emergence of arboviral diseases. Effective therapies and vaccines are limited for most arboviruses. Accordingly, vector control is the primary way to prevent transmission of arboviruses to humans. A deep understanding of the interaction and co-evolution between viruses and mosquito vectors is expected to aid in the development of novel transmission control strategies. The capacity of mosquitoes to support viral replication and transmission is called vector competence and is a dynamic and variable trait affected by many factors, suggesting an “arms race” between mosquitoes and viruses. The main arboviral vector in Europe is the invasive species Ae. albopictus, which has increasingly received attention from the scientific community due to its quick worldwide spread from south East Asia in the past 50 years. Nonretroviral RNA endogenous viral elements (nrEVEs) with similarities to the non-retroviral RNA viruses of the Flaviviridae and Rhabdoviridae family have been found with high frequency in Ae. albopictus mosquitoes. These viral integrations often interact with the most-recently characterized of the three RNA interference (RNAi) pathways: the PIWI-interacting RNA (piRNA) pathway. Most, but not all, nrEVEs in the genome of Ae. albopictus map next to transposable elements (TEs) fragments in piRNA clusters and produce piRNAs, small molecules that associate with Argonaute proteins of the PIWI clade to silence TEs based on sequence complementarity to piRNAs. In addition to its canonical role in preserving genome integrity, the piRNA pathway has antiviral activity in Aedes spp. mosquitoes. Despite the abundance of nrEVEs the biology, functional role, and patterns of integration in wild mosquito populations are still relatively unexplored. nrEVEs could be expressed and influence the phenotype of mosquitoes acting as a form of host antiviral immunity. A difficulty in studying the Ae. albopictus genome was the absence of a high-quality reference genome. During my PhD, I focused my attention on Ae. albopictus to primarily improve knowledge of its genome. I contributed to the sequencing, assembly, and annotation of a new reference genome for Ae. albopictus based on long-reads sequencing technologies; I coordinated an international consortium to annotate and characterize genomic features and their expression and produce a physical map of the genome. The availability of this new assembly allowed me to ask more specific questions on the landscape of viral integrations. A newly developed bioinformatic pipeline was combined with molecular biology techniques to identify viral sequences integrated into the genomes of wild-collected mosquitoes from different geographical locations. I also used the new genome assembly to reconstruct and identify RNA viruses in mosquito small-RNA sequencing data. I correlated the viruses identified in the mosquitoes with their population-specific nrEVE landscape, under the hypothesis that the pattern of nrEVEs is shaped by exposure to viruses. Lastly, I applied the CRISPR-Cas9 genome editing technology on Ae. albopictus embryos to modify a viral integration and a piRNA cluster and test the hypothesis that viral integrations have a role as immunity effectors against cognate viral infections. Overall, results gained through my PhD activities will enhance our understanding on the genome structure of Ae. albopictus and the importance of repetitive elements like viral integrations in the context of its biology.

Le moustique tigre Aedes albopictus est considéré comme une espèce particulièrement menaçante pour la santé publique en raison de son caractère invasif et de sa capacité à transmettre des arbovirus comme le virus de la dengue ou du chikungunya. Face à un manque de prophylaxie efficace et disponible pour tous, le contrôle des populations de moustiques reste la principale solution pour faire face à ce problème. Pour mieux comprendre la biologie des vecteurs, l’étude des interactions hôte-microorganismes est devenu un enjeu majeur. Si les interactions moustiques-bactéries ont intensivement été étudiées, les autres microorganismes restent encore à ce jour négligés. Chez le moustique tigre le membre dominant le microbiote eucaryote est une grégarine appartenant au phylum des Apicomplexa, Ascogregarina taiwanensis. Pourtant, ce microorganisme reste encore aujourd’hui relativement méconnu. Pour combler ces lacunes, nos travaux ont visé à déchiffrer les interactions entre le moustique tigre et As. taiwanensis en alliant des approches écologiques, expérimentales et moléculaires. Nous avons d’abord étudié sa prévalence et son abondance au sein de différentes populations de moustique tigre à l’échelle mondiale. Nous avons montré que ce parasite colonisait fortement les populations natives de moustique tigre mais était à l’inverse peu prévalent au sein des populations récemment introduites. Nous avons notamment montré que le parasite était peu résistant aux conditions de transport du moustique lors de son introduction passive largement liée aux activités humaines. Nous nous sommes pas la suite intéressés à la transmission verticale du parasite et nos résultats ont suggéré que pour maximiser sa transmission ce dernier pourrait favoriser l’ovogénèse et modifier le comportement de ponte des femelles infectées afin de maximiser sa transmission. En couplant ces expériences avec des analyses de transcriptomique, nous avons ainsi observé qu’As. taiwanensis impacterait en particulier l’ovogénèse de son hôte via la détoxication de métabolites du sang et une meilleure conversion des acides aminées qu’il contient. Enfin, afin de confirmer le rôle des gènes impliqués dans ces interactions nous avons réalisé une étude méthodologique visant à étudier l’efficacité d’approches d’interférence ARN chez le moustique tigre. Nos travaux amènent notamment à mieux comprendre comment les activités humaines peuvent influencer les interactions hôtes-microorganismes mais également à comprendre et repenser la complexité des interactions entre le moustique et ce parasite bien souvent ignoré
The Asian tiger mosquito, Aedes albopictus, is considered a threatening species to public health due to its invasive nature and its ability to transmit arboviruses such as the dengue or Chikungunya . Due to the lack of effective and widely available prophylaxis, controlling mosquito populations remains the main solution to address this issue. To provide a better understanding of vector biology, the study of host-microbe interactions arose as a powerful tool. While mosquito-bacteria interactions have been extensively studied, other microorganisms remain largely neglected to this day. In the Asian tiger mosquito Aedes albopictus, the dominant member of the eukaryotic microbiota is a gregarine belonging to the phylum Apicomplexa, Ascogregarina taiwanensis. However, this microorganism remains relatively unknown. To fill these knowledge gaps, our research aimed to decipher the interactions between the Asian tiger mosquito and As. taiwanensis by combining ecological, experimental, and molecular approaches. First, we studied its prevalence and abundance in various mosquito populations worldwide. We showed that this parasite heavily colonizes native mosquito populations but is less prevalent in recently introduced populations. Notably, we demonstrated that the parasite was sensitive to the transport conditions of mosquitoes during their passive introduction, largely linked to human activities. We then focused on the vertical transmission of the parasite, and our results suggested that the parasite might promote oogenesis and alter the egg-laying behavior of infected females to enhance its own spread. By coupling these experiments with transcriptomic analyses, we observed that As. taiwanensis particularly affects the oogenesis of its host through the detoxification of blood metabolites and a more efficient conversion of the amino acids. Finally, to confirm the role of genes involved in these interactions, we conducted a methodological study to assess the effectiveness of RNA interference approaches in the Asian tiger mosquito. Our work revealed how human activities can influence host-microorganism interactions, as well as the complexity of interactions between mosquitoes and this often-overlooked parasite