Mosquito Ecology Research Articles

Mosquito (Diptera: Culicidae) Larval Ecology in Rubber Plantations and Rural Villages in Dabou (Côte d'Ivoire).

In Côte d'Ivoire, rubber cultivation has more than doubled since 2010. These mass agricultural areas require a large workforce with little information on how this environment might impact risk of mosquito-borne diseases. The objective of this study was to assess the larval ecology of mosquitoes in rubber areas of Dabou, Côte d'Ivoire. From January to June 2017, an entomological survey was conducted of mature (MP) and immature (IP) rubber plantations, as well as in villages surrounded by rubber plantations (SV) and remote from rubber plantations (RV). The number and type of potential and positive breeding sites were recorded, and mosquito larval densities and diversity were estimated. Seven genera divided into 31 species including major vector such as Anopheles gambiae s.l. and Aedes aegypti were identified. A total of 1,660 waterbodies were identified with a larvae positivity rate of 63.1%. A majority of waterbodies were identified in SV (N = 875, 53.4% positivity rate), followed by MP (N = 422, 81.8% positivity rate), IP (N = 194, 72.2% positivity rate) and least in RV (N = 169, 57.4% positivity rate). The most important breeding sites for disease vectors were leaf axils in IP (N = 108, 77.1%), latex collection cups in MP (N = 332, 96.2%) and the containers abandoned in the SV (N = 242, 51.8%) as well as in the RV (N = 59, 60.8%). All these results allow us to affirm that the cultivation of rubber trees has an impact on the larval ecology by increasing the number of available sites and favoring a high larval density and diversity.

Lizards Are Important Hosts for Zoonotic Flavivirus Vectors, Subgenus Culex, in the Southern USA

Host association is among the most important factors that drive the transmission dynamics of mosquito-vectored pathogens. Competent vectors that feed exclusively upon non-competent hosts will not transmit pathogens, and highly competent hosts that are not bitten by competent vectors will not contribute to pathogen amplification. Therefore, characterizing the blood-feeding ecology of vector mosquitoes is critical to understanding how zoonotic pathogens amplify within ecosystems and spillover to humans and domesticated animals. In North America, mosquito species of the subgenus Culex are considered the most important vectors of zoonotic Flaviviruses, particularly West Nile virus (WNV), St. Louis encephalitis virus (SLEV), and western equine encephalitis virus. Many species of the Culex subgenus Culex are thought to feed predominantly upon birds and mammals, a behavior that facilitates the amplification and spillover of these zoonotic pathogens. Much of our understanding of the host associations of Culex vectors is based on research conducted in the 1960s and 1970s that used serological methods to infer host group(s). Here we reevaluate host associations of six Culex species from the southern US (Florida and Arizona) using DNA barcoding-based blood meal analysis. Our results demonstrate that reptiles, particularly lizards, constitute an important, and previously underappreciated, group of vertebrate hosts for several subgenus Culex mosquitoes. In Florida, >25% of Culex nigripalpus blood meals were derived from lizards (mainly Anolis spp.), and reptile host use generally increased from north to south with ~10%, ~25% and ~60% of Cx. nigripalpus blood meals derived from reptiles in northern, central, and southern Florida, respectively. In southern Arizona, lizards (mainly Sceloporus spp. and Urosaurus ornatus) constituted 40-45% of blood meals of Culex tarsalis, Culex thriambus, and Culex stigmatosoma. Other species of the subgenus Culex, including Culex quinquefasciatus, were not found to feed upon reptiles at the same sites, suggesting host association variation within Culex subgenus Culex. Whether or not lizards contribute to or dilute amplification of zoonotic Flaviviruses depends upon host competency of the lizard species bitten for WNV and SLEV. To date, very few studies have evaluated host competence of lizards for these viruses, so their roles in transmission cycles of zoonotic Flaviviruses remains obscure.

Larval ecology of Aedes mosquitoes and risk of arbovirus transmission at the port of San-pedro (Côte d’ivoire)

Mosquitoes of the genera Aedes are vectors of arboviruses. Through trade at the entry points, they spread to new areas where they can cause arbovirus epidemics. The lack of vaccine and treatment for most arboviruses makes vector control the only means of prevention. This study aimed to determine the level of infestation of Aedes mosquitoes and the risk of arbovirus by describing their larval ecology. All water containers found in activity and residential areas of the port of San Pedro were inspected for immature mosquitoes once a month from March to July 2018. Out of 227 identified potential breeding sites, 102 (44.93%) contained Aedes larvae. Abandoned containers constituted 53.92% of the sites colonized by Aedes and represented 73.43% of productivity. Sites associated with turbid water, organic debris, and those with vegetation around were more preferred by Aedes for oviposition. The house (20.80%), Breteau (27.20%) and Container (44.93%) Indices indicated a high level of entomological risk on the WHO density scale for both the activity area and the residential area. This study shows that Aedes uses more anthropogenic sites preferably abandoned containers and that its presence constitutes a risk of transmission of arboviruses in the port of San Pedro.

Functional conservation of Anopheline linalool receptors through 100 million years of evolution.

Insects rely on olfactory receptors to detect and respond to diverse environmental chemical cues. Detection of semiochemicals by these receptors modulates insect behavior and has a direct impact on species fitness. Volatile organic compounds (VOCs) are released by animals and plants and can provide contextual cues that a blood meal host or nectar source is present. One such VOC is linalool, an enantiomeric monoterpene, that is emitted from plants and bacteria species. This compound exists in nature as one of two possible stereoisomers, (R)-(-)-linalool or (S)-(+)-linalool. In this study, we use a heterologous expression system to demonstrate differential responsiveness of a pair of Anopheline odorant receptors (Ors) to enantiomers of linalool. The mosquitoes Anopheles gambiae and Anopheles stephensi encode single copies of Or29 and Or53, which are expressed in the labella of An. gambiae. (S)-(+)-linalool activates Or29 orthologs with a higher potency than (R)-(-)-linalool, while the converse is observed for Or53 orthologs. The conservation of these receptors across a broad range of Anopheline species suggests they may function in the discrimination of linalool stereoisomers, thereby influencing the chemical ecology of mosquitoes. One potential application of this knowledge would be in the design of novel attractants or repellents to be used in integrated pest management practices.

The Impact of Deforestation, Urbanization, and Changing Land Use Patterns on the Ecology of Mosquito and Tick-Borne Diseases in Central America.

Simple SummaryCentral America is a region that possesses distinct ecological and socioeconomic characteristics, making it increasingly vulnerable to vector-borne diseases. The emergence and resurgence of these diseases has been linked to environmental changes driven by human activities, particularly land use changes associated with deforestation, forest degradation, and urbanization. However, the effects of these environmental modifications on the transmission dynamics and the increase of infection risks are not well understood in Central America where information is limited and scattered. In this article, we review and analyze the current knowledge and potential impacts of deforestation and urbanization on the risk and transmission dynamics of the most relevant mosquito-borne and tick-borne diseases in Central America. Disease events, such as the recent Zika and dengue epidemics, and the uneven progress towards regional malaria elimination highlight the need to increase awareness regarding the complex ecological interactions and environmental changes taking place in this region and how this information could be used to improve prevention and control strategies.Central America is a unique geographical region that connects North and South America, enclosed by the Caribbean Sea to the East, and the Pacific Ocean to the West. This region, encompassing Belize, Costa Rica, Guatemala, El Salvador, Honduras, Panama, and Nicaragua, is highly vulnerable to the emergence or resurgence of mosquito-borne and tick-borne diseases due to a combination of key ecological and socioeconomic determinants acting together, often in a synergistic fashion. Of particular interest are the effects of land use changes, such as deforestation-driven urbanization and forest degradation, on the incidence and prevalence of these diseases, which are not well understood. In recent years, parts of Central America have experienced social and economic improvements; however, the region still faces major challenges in developing effective strategies and significant investments in public health infrastructure to prevent and control these diseases. In this article, we review the current knowledge and potential impacts of deforestation, urbanization, and other land use changes on mosquito-borne and tick-borne disease transmission in Central America and how these anthropogenic drivers could affect the risk for disease emergence and resurgence in the region. These issues are addressed in the context of other interconnected environmental and social challenges.

Bionomy of Mosquitoes in Bamboo Internodes in an Atlantic Forest Remnant of the State of Rio De Janeiro, Brazil.

Living bamboo stalks are one of the most specialized habitats for mosquito oviposition and immature development. Most of the mosquito species that breed in these habitats are sylvatic, and some are of importance for public health as possible vectors of pathogens. Perforated internodes are a very specialized environment due to the difficulty of access. Furthermore, due to their relatively simple fauna, they represent a valuable model for ecological studies that may be applicable to more complex environments. This study aims to assess the mosquito bionomics of species raised in bamboo internodes. Therefore, the diversity of mosquito species and the influence of abiotic variables (pH and temperature) on the distribution of mosquitoes that breed in this habitat were analyzed. The study area is a fragment of Atlantic Forest within the Association of da Armada (ATA) in Nova Iguaçu, state of Rio de Janeiro, Brazil. Immature mosquitoes were sampled with suction tubes (mouth aspirators) between August 2017 and July 2018. A total of 3,170 larvae were collected in 5 bamboo plants, each with 8 stalks perforated. Of these, 688 larvae reached the adult stage, representing 10 genera and 19 species. The most common species were Culex neglectus (43%), Trichoprosopon digitatum (22%), Culex iridescens (8%), Sabethes identicus (7%), and Orthopodomyia albicosta (7%). The richness of the immatures collected in the ATA was 19 species, with a diversity of 1.10 and Shannon evenness of 0.57. A diverse composition of Culicidae in bamboo stalks was found, although dominance was low.

The impact of mating and sugar feeding on blood-feeding physiology and behavior in the arbovirus vector mosquito Aedes aegypti.

Aedes aegypti mosquitoes are globally distributed vectors of viruses that impact the health of hundreds of millions of people annually. Mating and blood feeding represent fundamental aspects of mosquito life history that carry important implications for vectorial capacity and for control strategies. Females transmit pathogens to vertebrate hosts and obtain essential nutrients for eggs during blood feeding. Further, because host-seeking Ae. aegypti females mate with males swarming near hosts, biological crosstalk between these behaviors could be important. Although mating influences nutritional intake in other insects, prior studies examining mating effects on mosquito blood feeding have yielded conflicting results. To resolve these discrepancies, we examined blood-feeding physiology and behavior in virgin and mated females and in virgins injected with male accessory gland extracts (MAG), which induce post-mating changes in female behavior. We controlled adult nutritional status prior to blood feeding by using water- and sugar-fed controls. Our data show that neither mating nor injection with MAG affect Ae. aegypti blood intake, digestion, or feeding avidity for an initial blood meal. However, sugar feeding, a common supplement in laboratory settings but relatively rare in nature, significantly affected all aspects of feeding and may have contributed to conflicting results among previous studies. Further, mating, MAG injection, and sugar intake induced declines in subsequent feedings after an initial blood meal, correlating with egg production and laying. Taking our evaluation to the field, virgin and mated mosquitoes collected in Colombia were equally likely to contain blood at the time of collection. Mating, MAG, and sugar feeding impact a mosquito's estimated ability to transmit pathogens through both direct and indirect effects on multiple aspects of mosquito biology. Our results highlight the need to consider natural mosquito ecology, including diet, when assessing their physiology and behavior in the laboratory.

Ecological characterization of mosquitoes (Diptera: Culicidae) in areas of the Mato Grosso Pantanal, Mato Grosso State, Brazil

Bimonthly diurnal and nocturnal captures were conducted in four different sampling sites of the Mato Grosso Pantanal region over 24 consecutive months between March 2009 and January 2011. The goal of performing these collections was to elucidate aspects of the biology and ecology of mosquitoes in this region since little to nothing is known about these aspects for many species. A total of 17,532 specimens were captured, comprising two subfamilies, nine genera, and 44 species. The main species of culicids found in the Mato Grosso Pantanal had strong ecological compatibility with well-preserved environments and with some of the specific habitats found in at least one of the four selected collection sampling sites. Anopheles darlingi, An. albitarsis, and An. triannulatus are well-suited to environments with large water bodies and greater anthropic activity. Culex nigripalpus and Cx. quinquefasciatus prefer environments with bush fragments and pronounced human action and movement. Culex declarator and Psorophora albigenu, the most eclectic, prefer wild areas and with some anthropic activity. Mansonia titillans is associated with environments offering a wide variety of natural breeding areas that enable its development, in particular natural swamp areas covered with macrophytes, which is one of the natural components of the Pantanal biome. The effect of the flooding season on the population density of anophelines is especially advantageous, with an explosion in the number of individuals in periods of widespread flooding. The region’s environmental dynamics are regulated by flooding cycles with alternating periods of flooding and drought, which are the main factors governing the ecology of the local fauna and flora. Flooding periods contribute to raising culicid species’ richness and diversity, while the droughts result in a more even distribution of specimens within species. The flooding season of the Pantanal occurs between November and May and coincides with the greatest abundance of culicid species. During this period, the human population of the region has greater contact with mosquito vectors carrying pathogens, including arboviruses, which previous studies have confirmed via seropositivity in the region’s equines and birds.

Fine-scale estimation of key life-history parameters of malaria vectors: implications for next-generation vector control technologies

BackgroundMosquito control has the potential to significantly reduce malaria burden on a region, but to influence public health policy must also show cost-effectiveness. Gaps in our knowledge of mosquito population dynamics mean that mathematical modelling of vector control interventions have typically made simplifying assumptions about key aspects of mosquito ecology. Often, these assumptions can distort the predicted efficacy of vector control, particularly next-generation tools such as gene drive, which are highly sensitive to local mosquito dynamics.MethodsWe developed a discrete-time stochastic mathematical model of mosquito population dynamics to explore the fine-scale behaviour of egg-laying and larval density dependence on parameter estimation. The model was fitted to longitudinal mosquito population count data using particle Markov chain Monte Carlo methods.ResultsBy modelling fine-scale behaviour of egg-laying under varying density dependence scenarios we refine our life history parameter estimates, and in particular we see how model assumptions affect population growth rate (Rm), a crucial determinate of vector control efficacy.ConclusionsSubsequent application of these new parameter estimates to gene drive models show how the understanding and implementation of fine-scale processes, when deriving parameter estimates, may have a profound influence on successful vector control. The consequences of this may be of crucial interest when devising future public health policy.Graphical abstract

Eave and swarm collections prove effective for biased captures of male Anopheles gambiae mosquitoes in Uganda

BackgroundTraditional malaria vector sampling techniques bias collections towards female mosquitoes. Comprehensive understanding of vector dynamics requires balanced vector sampling of both males and females. Male mosquito sampling is also necessary for population size estimations by male-based mark-release-recapture (MRR) studies and for developing innovations in mosquito control, such as the male-targeted sterile insect technique and other genetic modification approaches. This study evaluated a range of collection methods which show promise in providing a more equal, or even male-biased, sex representation in the sample.ResultsSwarms were found at all study sites and were more abundant and larger at the peak of the wet season. Swarm sampling caught the most males, but when man/hour effort was factored in, sampling of eaves by aspiration was the more efficient method and also provided a representative sample of females. Grass-roofed houses were the most productive for eave collections. Overall few mosquitoes were caught with artificial resting traps (clay pots and buckets), although these sampling methods performed better at the start of the wet season than at its peak, possibly because of changes in mosquito ecology and an increased availability of natural resting sites later in the season. Aspiration of bushes was more productive at the peak of the wet season than at the start.ConclusionsThe results of this study demonstrate that eave aspiration was an efficient and useful male mosquito collection method at the study sites and a potentially powerful aid for swarm location and MRR studies. The methods evaluated may together deliver more sex-balanced mosquito captures and can be used in various combinations depending on the aims and ecological parameters of a given study.Graphical

Blood-feeding ecology of mosquitoes in two zoological gardens in the United Kingdom

BackgroundZoological gardens contain unique configurations of exotic and endemic animals and plants that create a diverse range of developing sites and potential sources of blood meals for local mosquitoes. This may imply unusual interspecific pathogen transmission risks involving zoo vertebrates, like avian malaria to captive penguins. Understanding mosquito ecology and host feeding patterns is necessary to improve mosquito control and disease prevention measures in these environments.MethodsMosquito sampling took place in Chester Zoo for 3 years (2017, 2018, and 2019) and for 1 year in Flamingo Land (2017) using different trapping methods. Blood-fed mosquitoes were identified and their blood meal was amplified by PCR, sequenced, and blasted for host species identification.ResultsIn total, 640 blood-fed mosquitoes were collected [Culex pipiens (n = 497), Culiseta annulata (n = 81), Anopheles maculipennis s.l. (n = 7), An. claviger (n = 1), and unidentifiable (n = 55)]. Successful identification of the host species was achieved from 159 blood-fed mosquitoes. Mosquitoes fed on birds (n = 74), non-human mammals (n = 20), and humans (n = 71). There were mixed blood meals from two hosts (n = 6). The proportions of blood-fed mosquitoes varied across sampling seasons and sites within the zoos. The use of resting traps and aspiration of vegetation were more efficient techniques for capturing blood-fed mosquitoes than traps for host-seeking or gravid mosquitoes. By relating the locations of zoo vertebrates to where fed mosquitoes were trapped, the minimum travelling distances were calculated (13.7 to 366.7 m). Temperature, precipitation, relative humidity, proximity to zoo vertebrate exhibits, and vegetation level were found to be significantly associated with the proportion of captured blood-fed mosquitoes by generalized linear modelling.ConclusionsMosquito feeding behaviour in zoos is mainly influenced by time, location (sampling area), temperature, and host availability, which highlights the value of mosquito monitoring in complex settings to plan control strategies and potentially reduce inherent disease transmission risks for humans and threatened zoo vertebrates.Graphical

Mosquito-Associated Viruses and Their Related Mosquitoes in West Africa.

Mosquito-associated viruses (MAVs), including mosquito-specific viruses (MSVs) and mosquito-borne (arbo)viruses (MBVs), are an increasing public, veterinary, and global health concern, and West Africa is projected to be the next front for arboviral diseases. As in-depth knowledge of the ecologies of both western African MAVs and related mosquitoes is still limited, we review available and comprehensive data on their diversity, abundance, and distribution. Data on MAVs’ occurrence and related mosquitoes were extracted from peer-reviewed publications. Data on MSVs, and mosquito and vertebrate host ranges are sparse. However, more data are available on MBVs (i.e., dengue, yellow fever, chikungunya, Zika, and Rift Valley fever viruses), detected in wild and domestic animals, and humans, with infections more concentrated in urban areas and areas affected by strong anthropogenic changes. Aedes aegypti, Culex quinquefasciatus, and Aedes albopictus are incriminated as key arbovirus vectors. These findings outline MAV, related mosquitoes, key knowledge gaps, and future research areas. Additionally, these data highlight the need to increase our understanding of MAVs and their impact on host mosquito ecology, to improve our knowledge of arbovirus transmission, and to develop specific strategies and capacities for arboviral disease surveillance, diagnostic, prevention, control, and outbreak responses in West Africa.

Buzzing Homes: Using Citizen Science Data to Explore the Effects of Urbanization on Indoor Mosquito Communities.

Simple SummaryMany mosquito species can transmit pathogens and may pose a risk to human health. With increasing urbanization and alteration of natural habitats, the composition of mosquito communities is changing, with some species thriving particularly well in and adjacent to human settlements. In the present study, indoor mosquito collections submitted to the citizen science project ‘Mückenatlas’ were used to investigate the composition, abundance, and diversity of species of different urbanization levels, and to detect preferences for less or more urbanized areas. We found that species richness and diversity decreases with increasing urbanization, and some important vector species are captured most frequently in densely urbanized regions. Our results highlight the importance of long-term mosquito monitoring to learn how these vectors respond to habitat change caused by humans. Only with sufficient knowledge about the ecology of mosquitoes can we assess risks, plan counter strategies, and take action.Urbanization has been associated with a loss of overall biodiversity and a simultaneous increase in the abundance of a few species that thrive in urban habitats, such as highly adaptable mosquito vectors. To better understand how mosquito communities differ between levels of urbanization, we analyzed mosquito samples from inside private homes submitted to the citizen science project ‘Mückenatlas’. Applying two urbanization indicators based on soil sealing and human population density, we compared species composition and diversity at, and preferences towards, different urbanization levels. Species composition between groups of lowest and highest levels of urbanization differed significantly, which was presumably caused by reduced species richness and the dominance of synanthropic mosquito species in urban areas. The genus Anopheles was frequently submitted from areas with a low degree of urbanization, Aedes with a moderate degree, and Culex and Culiseta with a high degree of urbanization. Making use of citizen science data, this first study of indoor mosquito diversity in Germany demonstrated a simplification of communities with increasing urbanization. The dominance of vector-competent species in urban areas poses a potential risk of epidemics of mosquito-borne diseases that can only be contained by a permanent monitoring of mosquitoes and by acquiring a deeper knowledge about how anthropogenic activities affect vector ecology.

Larval habitat diversity and Anopheles mosquito species distribution in different ecological zones in Ghana

BackgroundUnderstanding the ecology of larval malaria and lymphatic filariasis mosquitoes in a changing environment is important in developing effective control tools or programmes. This study characterized the breeding habitats of Anopheles mosquitoes in rural communities in different ecological zones in Ghana during the dry and rainy seasons.MethodsThe spatio-temporal distribution, species composition, and abundance of larval Anopheles mosquitoes in breeding habitats were studied in five locations in three ecological zones of Ghana. These were Anyakpor (coastal savannah area), Duase (forest area), and Libga, Pagaza, and Kpalsogu (Sahel savannah area). Larvae were collected using standard dippers and were raised in the insectary for identification.ResultsOut of a total of 7984 mosquito larvae collected, 2152 (27.26%) were anophelines and were more abundant in the rainy season (70.82%) than in the dry season (29.18%). The anophelines comprised 2128 (98.88%) An. gambiae s.l., 16 (0.74%) An. rufipes, and 8 (0.37%) An. pharoensis. In the coastal savannah and forest zones, dug-out wells were the most productive habitat during the dry (1.59 larvae/dip and 1.47 larvae/dip) and rainy seasons (11.28 larvae/dip and 2.05 larvae/dip). Swamps and furrows were the most productive habitats in the Sahel savannah zone during the dry (0.25 larvae/dip) and rainy (2.14 larvae/dip) seasons, respectively. Anopheles coluzzii was the most abundant sibling species in all the ecological zones. Anopheles melas and An. arabiensis were encountered only in the coastal savannah and the Sahel savannah areas, respectively. Larval habitat types influenced the presence of larvae as well as larval density (p < 0.001). The land-use type affected the presence of Anopheles larvae (p = 0.001), while vegetation cover influenced larval density (p < 0.05).ConclusionThe most productive habitats were dug-out wells in the coastal savannah and forest zones, and furrows from irrigated canals in the Sahel savannah zone. Anopheles coluzzii was the predominant vector species in all the ecological zones. The abundance of Anopheles breeding habitats and larvae were influenced by anthropogenic activities. Encouraging people whose activities create the larval habitats to become involved in larval source management such as habitat manipulation to stop mosquito breeding will be important for malaria and lymphatic filariasis control.

Mosquito survey reveals the first record of Aedes (Diptera: Culicidae) species in urban area, Annaba district, Northeastern Algeria

The diversity, distribution and ecology of mosquitoes, especially arbovirus vectors are important indices for arthropod-borne diseases control. The mosquito larvae were collected in different habitats in four sites of Annaba district, Algeria, during the period of March 2018 to February 2019 and the properties of larval habitats were recorded for each site. The systematic study revealed the presence of 8 species belonging to 4 genera; including Culex pipiens (Linnaeus, 1758), Culex modestus (Ficalbi, 1889), Culex theileri (Theobald, 1903), Culiseta longiareolata (Macquart, 1838), Anopheles labranchiae (Falleroni, 1926), Anopheles claviger (Meigen, 1804), Aedes aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse, 1894). Among the species, C. pipiens presented the highest species abundance (RA %) (55.23%) followed by C. longiareolata (20.21%). The Aedes species are recorded for the first time in the study urban area. Variation of diversity in different sites depends on the type of breeding habitat. These results provided important information on species diversity, distribution and factors associated with breeding habitats. They could be used for the mosquito control and to prevent the spread of mosquito-borne diseases to the population of the region.

Anopheles ecology, genetics and malaria transmission in northern Cambodia

In the Greater Mekong Subregion, malaria cases have significantly decreased but little is known about the vectors or mechanisms responsible for residual malaria transmission. We analysed a total of 3920 Anopheles mosquitoes collected during the rainy and dry seasons from four ecological settings in Cambodia (villages, forested areas near villages, rubber tree plantations and forest sites). Using odor-baited traps, 81% of the total samples across all sites were collected in cow baited traps, although 67% of the samples attracted by human baited traps were collected in forest sites. Overall, 20% of collected Anopheles were active during the day, with increased day biting during the dry season. 3131 samples were identified morphologically as 14 different species, and a subset was also identified by DNA amplicon sequencing allowing determination of 29 Anopheles species. The investigation of well characterized insecticide mutations (ace-1, kdr, and rdl genes) indicated that individuals carried mutations associated with response to all the different classes of insecticides. There also appeared to be a non-random association between mosquito species and insecticide resistance with Anopheles peditaeniatus exhibiting nearly fixed mutations. Molecular screening for Plasmodium sp. presence indicated that 3.6% of collected Anopheles were positive, most for P. vivax followed by P. falciparum. These results highlight some of the key mechanisms driving residual human malaria transmission in Cambodia, and illustrate the importance of diverse collection methods, sites and seasons to avoid bias and better characterize Anopheles mosquito ecology in Southeast Asia.

CONTROL OF ADULT AND LARVAL AEDES ALBOPICTUS WITH ATTRACTIVE TOXIC SUGAR BAITS (ACTIVE INGREDIENT: CINNAMON-SESAME OIL) IN NORTHEASTERN FLORIDA

Because traditional methods of mosquito control using insecticides has produced resistance, new methods that are environmentally friendly, sustainable and cost effective have been sought. One method, attractive toxic sugar baits (ATSB), uses the biological requirements, ecology, and behavior of mosquitoes to attract and kill them. In this study, the efficacy of a new ATSB active ingredient, microencapsulated cinnamon oil-plus-sesame oil, was tested in the laboratory and field against Aedes albopictus (Skuse) and the effect on non-target organisms was evaluated. The average mortality among groups of 20 third instar larvae after exposure to microencapsulated cinnamon-sesame oil ATSB in the laboratory for 48 h was high. Mortality at 10% and 1% ATSB concentration was 95.8% and 90.0% respectively and began to drop off (to 65%) at 0.1%. After application of the ATSB in the field, on day 11 of the study, the adult Ae. albopictus populations at the experimental site dropped significantly compared to pre-treatment levels and to the untreated control population. The differences between the control and the treated sites remained significant until the end of the study period on day 28. If used in accordance with label instructions and applied on non-flowering green vegetation, the potential impact on non-target populations was negligible with the exception of non-biting midges (Chironomidae). The synergistic effect of the attracting and killing adult mosquitoes as well as wash-off into part of the breeding sites with larvicidal cinnamon oil-plus-sesame oil product likely explains the high mortality of this ATSB formulation.

Anthropogenic landscape decreases mosquito biodiversity and drives malaria vector proliferation in the Amazon rainforest.

Inter-relationships among mosquito vectors, Plasmodium parasites, human ecology, and biotic and abiotic factors, drive malaria risk. Specifically, rural landscapes shaped by human activities have a great potential to increase the abundance of malaria vectors, putting many vulnerable people at risk. Understanding at which point the abundance of vectors increases in the landscape can help to design policies and interventions for effective and sustainable control. Using a dataset of adult female mosquitoes collected at 79 sites in malaria endemic areas in the Brazilian Amazon, this study aimed to (1) verify the association among forest cover percentage (PLAND), forest edge density (ED), and variation in mosquito diversity; and to (2) test the hypothesis of an association between landscape structure (i.e., PLAND and ED) and Nyssorhynchus darlingi (Root) dominance. Mosquito collections were performed employing human landing catch (HLC) (peridomestic habitat) and Shannon trap combined with HLC (forest fringe habitat). Nyssorhynchus darlingi abundance was used as the response variable in a generalized linear mixed model, and the Shannon diversity index (H’) of the Culicidae community, PLAND, and the distance house-water drainage were used as predictors. Three ED categories were also used as random effects. A path analysis was used to understand comparative strengths of direct and indirect relationships among Amazon vegetation classes, Culicidae community, and Ny. darlingi abundance. Our results demonstrate that Ny. darlingi is negatively affected by H´ and PLAND of peridomestic habitat, and that increasing these variables (one-unit value at β0 = 768) leads to a decrease of 226 (P < 0.001) and 533 (P = 0.003) individuals, respectively. At the forest fringe, a similar result was found for H’ (β1 = -218; P < 0.001) and PLAND (β1 = -337; P = 0.04). Anthropogenic changes in the Amazon vegetation classes decreased mosquito biodiversity, leading to increased Ny. darlingi abundance. Changes in landscape structure, specifically decreases in PLAND and increases in ED, led to Ny. darlingi becoming the dominant species, increasing malaria risk. Ecological mechanisms involving changes in landscape and mosquito species composition can help to understand changes in the epidemiology of malaria.

Natural Basis for the Proliferation of Malaria Vectors in Northern Benin (West Africa)

Background: Malaria transmission is based on four essential elements: the vector, the parasite, humans and the environment. However, of the four elements, the environment is not sufficiently exploited. Methods: In the research presence carried out in 6 localities in North Benin, we used a microscopic vision of the health geographer, focusing on certain components of geography, entomology and meteorology to show what to show spatial disparities in malaria transmission using Arcgis 10.4, Global Mapper and SPSS 21.0 for regression and correlation analysis. Results: The results of our research show that the slopes are unstable. Also, the lower the altitude, the lower the water kinetics and consequently a lot of water stagnation favourable for the development of mosquito breeding sites. The explanatory power of the regression model means that 54.3% of the variation in positive mosquito breeding is explained by human population density. Conclusions: Benin must make significant progress in the elimination of malaria using a new effort to understand the ecology of vector mosquitoes based on spatial disparities in the fight against malaria.

Sindbis Virus Infection in Non-Blood-Fed Hibernating Culex pipiens Mosquitoes in Sweden.

A crucial, but unresolved question concerning mosquito-borne virus transmission is how these viruses can remain endemic in regions where the transmission is halted for long periods of time, due to mosquito inactivity in, e.g., winter. In northern Europe, Sindbis virus (SINV) (genus alphavirus, Togaviridae) is transmitted among birds by Culex mosquitoes during the summer, with occasional symptomatic infections occurring in humans. In winter 2018–19, we sampled hibernating Culex spp females in a SINV endemic region in Sweden and assessed them individually for SINV infection status, blood-feeding status, and species. The results showed that 35 out of the 767 collected mosquitoes were infected by SINV, i.e., an infection rate of 4.6%. The vast majority of the collected mosquitoes had not previously blood-fed (98.4%) and were of the species Cx. pipiens (99.5%). This is the first study of SINV overwintering, and it concludes that SINV can be commonly found in the hibernating Cx. pipiens population in an endemic region in Sweden, and that these mosquitoes become infected through other means besides blood-feeding. Further studies on mosquito ecology and viral interactions are needed to elucidate the mechanisms of the persistence of these viruses over winter.