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1.
PLoS One ; 15(3): e0221838, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32160192

RESUMO

Larval mosquitoes are aquatic omnivorous scavengers which scrape food from submerged surfaces and collect suspended food particles with their mouth brushes. The composition of diets that have been used in insectaries varies widely though necessarily provides sufficient nutrition to allow colonies to be maintained. Issues such as cost, availability and experience influence which diet is selected. One component of larval diets, essential fatty acids, appears to be necessary for normal flight though deficiencies may not be evident in laboratory cages and are likely more important when mosquitoes are reared for release into the field in e.g. mark-release-recapture and genetic control activities. In this study, four diets were compared for rearing Anopheles gambiae and Aedes aegypti, all of which provide these essential fatty acids. Two diets were custom formulations specifically designed for mosquitoes (Damiens) and two were commercially available fish foods: Doctors Foster and Smith Koi Staple Diet and TetraMin Plus Flakes. Development rate, survival, dry weight and adult longevity of mosquitoes reared with these four diets were measured. The method of presentation of one diet, Koi pellets, was additionally fed in two forms, pellets or a slurry, to determine any effect of food presentation on survival and development rate. While various criteria might be selected to choose 'the best' food, the readily-available Koi pellets resulted in development rates and adult longevity equal to the other diets, high survival to the adult stage and, additionally, this is available at low cost.


Assuntos
Aedes/crescimento & desenvolvimento , Anopheles/crescimento & desenvolvimento , Dieta/métodos , Larva/crescimento & desenvolvimento , Animais , Peso Corporal , Dieta/economia , Ácidos Graxos Essenciais , Feminino , Alimentos/economia , Abrigo para Animais/economia , Longevidade , Masculino , Taxa de Sobrevida , Temperatura , Água
2.
Ecotoxicol Environ Saf ; 195: 110451, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32199214

RESUMO

Application of synthetic pesticides over decades to control insects, pests, and disease vectors has resulted in negative impacts on environment and health. The current study assessed the toxicological effects of 12 botanicals obtained from 4 different red seaweeds against the dengue vector mosquito Aedes aegypti L. (Diptera: Culicidae). Four species of red seaweeds, namely Laurencia karachiana, Gracilaria foliifera, Jania rubens, Asparagopsis taxiformis, were collected from Karachi coast and extracted with hexane, dichloromethane and methanol. The efficiency of these extracts was determined by using a dose-response bioassay method against 4th instar larvae of Ae. aegypti. Separate investigations on the toxicity and IGI effects were done. Comparative studies showed that the hexane extracts induced more toxic effects. Based on the LC50 values, obtained after 24 h of treatments, hexane extract of J. rubens (HJ) exhibited toxic effects with LC50 32 µg/mL, (equivalent to GHS category 3), followed by G. foliifera (HG) (LC50 76.8 µg/mL). HJ also showed prominent neurotoxic effects within 1-6 h. Comparatively, higher morphological abnormalities and growth inhibiting (IGI) effects were obtained in the dichloromethane and methanol extracts treated larvae, after 48-96 h, resulting in the formation of immature life forms such as larvi-pupae and pupi-adult. Presumptive growth inhibiting effects were also noted. These included formation of albino and black pupae, deformities in the internal structure of the treated larvae and the chitin synthesis related effects such as 'inhibiting effect on adult emergence'. Finding revealed that red seaweeds, harvested from the Arabian Sea, have potentials to affect Ae. aegypti survival and thus can be utilized as green pesticides.


Assuntos
Aedes , Inseticidas , Mosquitos Vetores , Rodófitas , Alga Marinha , Aedes/crescimento & desenvolvimento , Animais , Dengue/transmissão , Larva , Dose Letal Mediana , Extratos Vegetais , Pupa
3.
PLoS Negl Trop Dis ; 14(3): e0008130, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32130209

RESUMO

BACKGROUND: Yellow fever, dengue, chikungunya and Zika viruses are responsible for considerable morbidity and mortality in humans. Aedes aegypti and Aedes albopictus are the most important mosquito vectors involved in their transmission. Accurate identification of these species is essential for the implementation of control programs to limit arbovirus transmission, during suspected detections at ports of first entry, to delimit incursions or during presence/absence surveillance programs in regions vulnerable to invasion. We developed and evaluated simple and rapid colorimetric isothermal tests to detect these two mosquito species based on loop-mediated isothermal amplification (LAMP) targeting the ribosomal RNA internal transcribed spacer 1 (ITS1). METHODOLOGY/PRINCIPAL FINDINGS: Samples were prepared by homogenizing and heating at 99 oC for 10 min before an aliquot was added to the LAMP reaction. After 40 min incubation at 65 oC, a colour change indicated a positive result. The tests were 100% sensitive and species-specific, and demonstrated a limit of detection comparable with PCR-based detection (TaqMan chemistry). The LAMP assays were able to detect target species for various life stages tested (adult, 1st instar larva, 4th instar larva and pupa), and body components, such as legs, wings and pupal exuviae. Importantly, the LAMP assays could detect Ae. aegypti DNA in mosquitoes stored in Biogents Sentinel traps deployed in the field for 14 d. A single 1st instar Ae. aegypti larva could also be detected in a pool of 1,000 non-target 1st instar Aedes notoscriptus, thus expediting processing of ovitrap collections obtained during presence/absence surveys. A simple syringe-sponge protocol facilitated the concentration and collection of larvae from the ovitrap water post-hatch. CONCLUSIONS/SIGNIFICANCE: We describe the development of LAMP assays for species identification and demonstrate their direct application for surveillance in different field contexts. The LAMP assays described herein are useful adjuncts to laboratory diagnostic testing or could be employed as standalone tests. Their speed, ease-of-use, low cost and need for minimal equipment and training make the LAMP assays ideal for adoption in low-resource settings without the need to access diagnostic laboratory services.


Assuntos
Aedes/classificação , Aedes/crescimento & desenvolvimento , Colorimetria/métodos , Entomologia/métodos , Técnicas de Diagnóstico Molecular/métodos , Mosquitos Vetores/classificação , Mosquitos Vetores/crescimento & desenvolvimento , Técnicas de Amplificação de Ácido Nucleico/métodos , Aedes/genética , Animais , DNA Espaçador Ribossômico/genética , Feminino , Mosquitos Vetores/genética , Sensibilidade e Especificidade
4.
PLoS Negl Trop Dis ; 14(3): e0007753, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32176693

RESUMO

BACKGROUND: Resistance to pyrethroid insecticides in Aedes aegypti has become widespread after almost two decades of the frequent use of these pesticides to reduce arbovirus transmission. Despite this resistance, pyrethroids continue to be used because they are relatively inexpensive and have low human toxicity. Resistance management has been proposed as a way to retain the use of pyrethroids in natural populations. A key component of resistance management is the assumption that negative fitness is associated with resistance alleles such that resistance alleles will decline in frequency when the insecticides are removed. At least three studies in Ae. aegypti have demonstrated a decrease in pyrethroid resistance once the insecticide has been removed. METHODS/PRINCIPAL FINDINGS: The present study aims to evaluate variation in the loss of pyrethroid resistance among newly established laboratory populations of Ae. aegypti from Mexico. Eight field collections were maintained for up to eight generations, and we recorded changes in the frequencies of the mutations at the V1,016I locus and at the F1,534C locus in the voltage-gated sodium channel gene (VGSC). I1,016 and C1,534 confer resistance. We also examined resistance ratios (RR) with type 1 and 2 pyrethroids. CONCLUSIONS/SIGNIFICANCE: We demonstrate that, in general, the frequency of the Ae. aegypti pyrethroid-resistance alleles I1,016 and C1,534 decline when they are freed from pyrethroid pressure in the laboratory. However, the pattern of decline is strain dependent. In agreement with earlier studies, the RR was positively correlated with the frequencies of the resistance allele I1,016 and showed significant protection against permethrin, and deltamethrin, whereas F1,534C showed protection against permethrin but not against deltamethrin.


Assuntos
Aedes/efeitos dos fármacos , Aedes/crescimento & desenvolvimento , Resistência a Inseticidas , Inseticidas/farmacologia , Mutação , Piretrinas/farmacologia , Canais de Sódio Disparados por Voltagem/genética , Animais , Feminino , Frequência do Gene , Aptidão Genética , México , Seleção Genética , Canais de Sódio Disparados por Voltagem/metabolismo
5.
PLoS Negl Trop Dis ; 14(2): e0007948, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32012156

RESUMO

Aedes cadherin (AaeCad, AAEL024535) has been characterized as a receptor for Bacillus thuringiensis subsp. israelensis (Bti) Cry11A toxins. However, its role in development is still unknown. In this study, we modified the cadherin gene using ZFN and TALEN. Even though we obtained heterozygous deletions, no homozygous mutants were viable. Because ZFN and TALEN have lower off-targets than CRISPR/Cas9, we conclude the cadherin gene is essential for Aedes development. In contrast, in lepidopteran insects loss of a homologous cadherin does not appear to be lethal, since homozygous mutants are viable. To analyze the role of AaeCad in vivo, we tagged this protein with EGFP using CRISPR-Cas9-mediated homologous recombination and obtained a homozygous AaeCad-EGFP line. Addition of Aedes Rad51 mRNA enhanced the rate of recombination. We then examined AaeCad protein expression in most tissues and protein dynamics during mosquito development. We observe that AaeCad is expressed in larval and adult midgut-specific manner and its expression pattern changed during the mosquito development. Confocal images showed AaeCad has high expression in larval caecae and posterior midgut, and also in adult midgut. Expression of AaeCad is observed primarily in the apical membranes of epithelial cells, and not in cell-cell junctions. The expression pattern observed suggests AaeCad does not appear to play a role in these junctions. However, we cannot exclude its role beyond cell-cell adhesion in the midgut. We also observed that Cry11A bound to the apical side of larval gastric caecae and posterior midgut cells exactly where AaeCad-EGFP was expressed. Their co-localization suggests that AaeCad is indeed a receptor for the Cry11A toxin. Using this mosquito line we also observed that low doses of Cry11A toxin caused the cells to slough off membranes, which likely represents a defense mechanism, to limit cell damage from Cry11A toxin pores formed in the cell membrane.


Assuntos
Aedes/metabolismo , Proteínas de Bactérias/metabolismo , Endotoxinas/metabolismo , Proteínas Hemolisinas/metabolismo , Proteínas de Insetos/metabolismo , Larva/crescimento & desenvolvimento , Aedes/genética , Aedes/crescimento & desenvolvimento , Animais , Proteínas de Bactérias/genética , Caderinas/metabolismo , Sistema Digestório/crescimento & desenvolvimento , Sistema Digestório/metabolismo , Endotoxinas/genética , Proteínas Hemolisinas/genética , Proteínas de Insetos/genética , Larva/genética , Larva/metabolismo , Ligação Proteica
6.
PLoS Pathog ; 16(1): e1008288, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31961911

RESUMO

Insects rely on the innate immune system for defense against pathogens, some aspects of which are under hormonal control. Here we provide direct experimental evidence showing that the juvenile hormone-binding protein (mJHBP) of Aedes aegypti is required for the regulation of innate immune responses and the development of mosquito blood cells (hemocytes). Using an mJHBP-deficient mosquito line generated by means of CRISPR-Cas9 gene editing technology we uncovered a mutant phenotype characterized by immunosuppression at the humoral and cellular levels, which profoundly affected susceptibility to bacterial infection. Bacteria-challenged mosquitoes exhibited significantly higher levels of septicemia and mortality relative to the wild type (WT) strain, delayed expression of antimicrobial peptides (AMPs), severe developmental dysregulation of embryonic and larval hemocytes (reduction in the total number of hemocytes) and increased differentiation of the granulocyte lineage. Interestingly, injection of recombinant wild type mJHBP protein into adult females three-days before infection was sufficient to restore normal immune function. Similarly, injection of mJHBP into fourth-instar larvae fully restored normal larval/pupal hemocyte populations in emerging adults. More importantly, the recovery of normal immuno-activation and hemocyte development requires the capability of mJHBP to bind JH III. These results strongly suggest that JH III functions in mosquito immunity and hemocyte development in a manner that is perhaps independent of canonical JH signaling, given the lack of developmental and reproductive abnormalities. Because of the prominent role of hemocytes as regulators of mosquito immunity, this novel discovery may have broader implications for the understanding of vector endocrinology, hemocyte development, vector competence and disease transmission.


Assuntos
Aedes/crescimento & desenvolvimento , Aedes/imunologia , Proteínas de Transporte/imunologia , Proteínas de Insetos/imunologia , Aedes/genética , Aedes/microbiologia , Animais , Proteínas de Transporte/genética , Feminino , Hemócitos/imunologia , Hemócitos/microbiologia , Imunidade Inata , Proteínas de Insetos/genética , Hormônios Juvenis/imunologia , Larva/genética , Larva/crescimento & desenvolvimento , Larva/imunologia , Larva/microbiologia , Masculino , Serratia marcescens/fisiologia
7.
J Ethnopharmacol ; 248: 112333, 2020 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-31654797

RESUMO

ETHNOPHARMACOLOGICAL RELEVANCE: The use of Hazomalania voyronii, popularly known as hazomalana, to repel mosquitoes and resist against insect attacks is handed down from generation to generation in Madagascar. In the present study, we investigated the ability of the essential oils (EOs) obtained from the stem wood, fresh and dry bark of H. voyronii to keep important mosquito vectors (Aedes aegypti and Culex quinquefasciatus) away, as well as their toxicity on three insect species of agricultural and public health importance (Cx. quinquefasciatus, Musca domestica and Spodoptera littoralis). MATERIALS AND METHODS: Hydrodistillation was used to obtain EOs from stem wood, fresh and dry bark. The chemical compositions were achieved by gas chromatography-mass spectrometry (GC-MS). Toxicity assays using stem wood and bark EOs were performed on larvae of Cx. quinquefasciatus and S. littoralis, and adults of M. domestica by WHO and topical application methods, respectively. Mosquito repellent activity of the most effective EO, i.e. the bark one, was determined on human volunteers by arm-in-cage tests, and results were compared with that of the commercial repellent N,N-ddiethyl-m-toluamide (DEET). RESULTS: The H. voyronii EOs were characterized by oxygenated monoterpenes with perilla aldehyde (30.9-47.9%) and 1,8-cineole (19.7-33.2%) as the main constituents. The fresh and dry bark EOs were the most active on Cx. quinquefasciatus and S. littoralis larvae, respectively, with LC50/LD50 of 65.5  mg L-1, and 50.5  µg larva-1; the EOs from wood and fresh bark displayed the highest toxicity on M. domestica (LD50 values 60.8 and 65.8 µg adult-1, respectively). Repellence assay revealed an almost complete protection (>80%) from both mosquito species for 30 min when pure fresh bark EO was applied on the volunteers' arm, while DEET 10% repelled >80% of the mosquitoes up to 120 min from application. CONCLUSION: The traditional use of the bark EO to repel insects has been demonstrated although an extended-release formulation based on H. voyronii EOs is needed to increase the repellent effect over time. A wide spectrum of insecticidal activity has been provided as well, suggesting a possible use of H. voyronii EOs in the fabrication of green repellents and insecticides useful to control mosquito vectors and agricultural pests.


Assuntos
Aedes/efeitos dos fármacos , Culex/efeitos dos fármacos , Hernandiaceae , Moscas Domésticas/efeitos dos fármacos , Repelentes de Insetos/farmacologia , Controle de Mosquitos , Óleos Voláteis/farmacologia , Casca de Planta , Óleos Vegetais/farmacologia , Spodoptera/efeitos dos fármacos , Madeira , Aedes/crescimento & desenvolvimento , Animais , Culex/embriologia , DEET/farmacologia , Hernandiaceae/química , Moscas Domésticas/crescimento & desenvolvimento , Humanos , Repelentes de Insetos/isolamento & purificação , Larva/efeitos dos fármacos , Larva/crescimento & desenvolvimento , Óleos Voláteis/isolamento & purificação , Casca de Planta/química , Óleos Vegetais/isolamento & purificação , Spodoptera/embriologia , Fatores de Tempo , Madeira/química
8.
BMC Public Health ; 19(1): 1729, 2019 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-31870343

RESUMO

BACKGROUND: Aedes aegypti-borne diseases are becoming major public health problems in tropical and sub-tropical regions. While socioeconomic status has been associated with larval mosquito abundance, the drivers or possible factors mediating this association, such as environmental factors, are yet to be identified. We examined possible associations between proximity to houses and roads and immature mosquito abundance, and assessed whether these factors and mosquito prevention measures mediated any association between household environmental factors and immature mosquito abundance. METHODS: We conducted two cross-sectional household container surveys in February-March and November-December, 2017, in urban and rural areas of Quetzaltenango, Guatemala. We used principal components analysis to identify factors from 12 variables to represent the household environment. One factor which included number of rooms in house, electricity, running water, garbage service, cable, television, telephone, latrine, well, and sewer system, was termed "environmental capital." Environmental capital scores ranged from 0 to 5.5. Risk factors analyzed included environmental capital, and distance from nearest house/structure, paved road, and highway. We used Poisson regression to determine associations between distance to nearest house/structure, roads, and highways, and measures of immature mosquito abundance (total larvae, total pupae, and positive containers). Using cubic spline generalized additive models, we assessed non-linear associations between environmental capital and immature mosquito abundance. We then examined whether fumigation, cleaning containers, and distance from the nearest house, road, and highway mediated the relationship between environmental capital and larvae and pupae abundance. RESULTS: We completed 508 household surveys in February-March, and we revisited 469 households in November-December. Proximity to paved roads and other houses/structures was positively associated with larvae and pupae abundance and mediated the associations between environmental capital and total numbers of larvae/pupae (p ≤ 0.01). Distance to highways was not associated with larval/pupal abundance (p ≥ 0.48). Households with the lowest and highest environmental capital had fewer larvae/pupae than households in the middle range (p < 0.01). CONCLUSIONS: We found evidence that proximity to other houses and paved roads was associated with greater abundance of larvae and pupae. Understanding risk factors such as these can allow for improved targeting of surveillance and vector control measures in areas considered at higher risk for arbovirus transmission.


Assuntos
Aedes/crescimento & desenvolvimento , Planejamento Ambiental/estatística & dados numéricos , Habitação , Larva , Pupa , Animais , Estudos Transversais , Guatemala , Humanos , Fatores de Risco , Inquéritos e Questionários
9.
Artigo em Inglês | MEDLINE | ID: mdl-31861276

RESUMO

: Numerous urban villages (UVs) with substandard living conditions that cause people to live there with vulnerability to health impacts, including vector-borne diseases such as dengue fever (DF), are major environmental and public health concerns in highly urbanized regions, especially in developing countries. It is necessary to explore the relationship between UVs and vector for effectively dealing with these problems. In this study, land-use types, including UVs, normal construction land (NCL), unused land (UL), vegetation, and water, were retrieved from the high-resolution remotely sensed imagery in the central area of Guangzhou in 2017. The vector density from May to October in 2017, including Aedes. albopictus (Ae. albopictus)'s Breteau index (BI), standard space index (SSI), and adult density index (ADI) were obtained from the vector surveillance system implemented by the Guangzhou Center for Disease Control and Prevention (CDC). Furthermore, the spatial and temporal patterns of vector monitoring sites and vector density were analyzed on a fine scale, and then the Geodetector tool was further employed to explore the relationships between vector density and land-use types. The monitoring sites were mainly located in NCL (55.70%-56.44%) and UV (13.14%-13.92%). Among the total monitoring sites of BI (79), SSI (312), and ADI (326), the random sites accounted for about 88.61%, 97.12%, and 98.47%, respectively. The density of Ae. albopictus was temporally related to rainfall and temperature and was obviously differentiated among different land-use types. Meanwhile, the grids with higher density, which were mostly concentrated in the Pearl River fork zone that collects a large number of UVs, showed that the density of Ae. albopictus was spatially associated with the UVs. Next, the results of the Geodetector illustrated that UVs posed great impact on the density of Ae. albopictus across the central region of Guangzhou. We suggest that the number of monitoring sites in the UVs should be appropriately increased to strengthen the current vector surveillance system in Guangzhou. This study will provide targeted guidance for local authorities, making more effective control and prevention measures on the DF epidemics.


Assuntos
Aedes/fisiologia , Distribuição Animal , Dengue/epidemiologia , Monitoramento Epidemiológico , Mosquitos Vetores/fisiologia , Aedes/crescimento & desenvolvimento , Animais , China/epidemiologia , Larva/fisiologia , Mosquitos Vetores/crescimento & desenvolvimento , Densidade Demográfica , Urbanização
10.
PLoS Negl Trop Dis ; 13(12): e0007985, 2019 12.
Artigo em Inglês | MEDLINE | ID: mdl-31887138

RESUMO

INTRODUCTION: Dengue is the most important mosquito-borne diseases worldwide but was considered scarce in West-Central Africa. During the last decade, dengue outbreaks have increasingly been reported in urban foci in this region suggesting major epidemiological changes. However, in Central Africa where both vectors, Aedes aegypti and Aedes albopictus are well established, the role of each species in dengue transmission remains poorly investigated. METHODOLOGY/PRINCIPAL FINDINGS: Field-collected strains of Ae. aegypti and Ae. albopictus from different ecological settings in Central Africa were experimentally challenged with dengue 2 virus (DENV-2). Mosquitoes were analysed at 14- and 21-days post-infection. Analysis provide evidence that both Ae. aegypti and Ae. albopictus in Central Africa were able to transmit dengue virus with Ae. aegypti exhibiting a higher transmission rate. Unexpectedly, two Ae. aegypti populations from Bénoué and Maroua, in northern Cameroon, were not able to transmit DENV-2. CONCLUSIONS/SIGNIFICANCE: We conclude that both Ae. aegypti and Ae. albopictus are susceptible to DENV-2 and may intervene as active dengue vectors. These findings highlight the urgent need to plan a vector surveillance program and control methods against dengue vectors in Central Africa in order to prevent future outbreaks.


Assuntos
Aedes/crescimento & desenvolvimento , Aedes/virologia , Vírus da Dengue/crescimento & desenvolvimento , Dengue/epidemiologia , Dengue/transmissão , Transmissão de Doença Infecciosa , Tropismo Viral , África Central/epidemiologia , Animais , Feminino , Humanos , Mosquitos Vetores/crescimento & desenvolvimento , Mosquitos Vetores/virologia , Medição de Risco
11.
Parasit Vectors ; 12(1): 524, 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31694685

RESUMO

BACKGROUND: Aedes koreicus was detected in northern Italy for the first time in 2011, and it is now well established in several areas as a new invasive mosquito species. Data regarding the influence of temperature on mosquito survival and development are not available yet for this species. METHODS: We experimentally investigated the influence of different constant rearing temperatures (between 4 and 33 °C) on the survival rates and developmental times of different life stages of Ae. koreicus under laboratory conditions. The resulting data were subsequently used to inform a mathematical model reproducing the Ae. koreicus life-cycle calibrated to counts of adult females captured in the field in the autonomous province of Trento (northern Italy) between 2016 and 2018. RESULTS: We found that temperatures above 28 °C are not optimal for the survival of pupae and adults, whereas temperate conditions of 23-28 °C seem to be very favorable, explaining the recent success of Ae. koreicus at establishing into new specific areas. Our results indicate that Ae. koreicus is less adapted to local climatic conditions compared to Ae. albopictus, another invasive species which has been invading the area for the last three decades. Warmer seasons, which are more likely to occur in the future because of climate change, might extend the breeding time and therefore increase the abundance of Ae. koreicus in the study region. CONCLUSIONS: Our findings provide, to our knowledge, the first evidence on how temperature influences the bionomics and dynamics of Ae. koreicus and highlight the need for further studies on the phenology of this species in temperate areas of Europe.


Assuntos
Aedes/crescimento & desenvolvimento , Aedes/efeitos da radiação , Espécies Introduzidas , Dinâmica Populacional , Temperatura , Animais , Ecologia , Feminino , Itália , Modelos Teóricos , Análise de Sobrevida
12.
Parasit Vectors ; 12(1): 552, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31752961

RESUMO

BACKGROUND: The Asian tiger mosquito, Aedes albopictus, is one of the 100 worst invasive species in the world and the vector for several arboviruses including dengue, Zika and chikungunya viruses. Understanding the population spatial genetic structure, migration, and gene flow of vector species is critical to effectively preventing and controlling vector-borne diseases. Little is known about the population structure and genetic differentiation of native Ae. albopictus in China. The aim of this study was to examine the patterns of the spatial genetic structures of native Ae. albopictus populations, and their relationship to dengue incidence, on a large geographical scale. METHODS: During 2016-2018, adult female Ae. albopictus mosquitoes were collected by human landing catch (HLC) or human-bait sweep-net collections in 34 localities across China. Thirteen microsatellite markers were used to examine the patterns of genetic diversity, population structure, and gene flow among native Ae. albopictus populations. The correlation between population genetic indices and dengue incidence was also examined. RESULTS: A total of 153 distinct alleles were identified at the 13 microsatellite loci in the tested populations. All loci were polymorphic, with the number of distinct alleles ranging from eight to sixteen. Genetic parameters such as PIC, heterozygosity, allelic richness and fixation index (FST) revealed highly polymorphic markers, high genetic diversity, and low population genetic differentiation. In addition, Bayesian analysis of population structure showed two distinct genetic groups in southern-western and eastern-central-northern China. The Mantel test indicated a positive correlation between genetic distance and geographical distance (R2 = 0.245, P = 0.01). STRUCTURE analysis, PCoA and GLS interpolation analysis indicated that Ae. albopictus populations in China were regionally clustered. Gene flow and relatedness estimates were generally high between populations. We observed no correlation between population genetic indices of microsatellite loci in Ae. albopictus populations and dengue incidence. CONCLUSION: Strong gene flow probably assisted by human activities inhibited population differentiation and promoted genetic diversity among populations of Ae. albopictus. This may represent a potential risk of rapid spread of mosquito-borne diseases. The spatial genetic structure, coupled with the association between genetic indices and dengue incidence, may have important implications for understanding the epidemiology, prevention, and control of vector-borne diseases.


Assuntos
Aedes/classificação , Aedes/crescimento & desenvolvimento , Distribuição Animal , Variação Genética , Genótipo , Mosquitos Vetores/classificação , Mosquitos Vetores/crescimento & desenvolvimento , Animais , China , Dengue/epidemiologia , Fluxo Gênico , Genética Populacional , Incidência , Repetições de Microssatélites , Análise Espacial
13.
J Am Mosq Control Assoc ; 35(3): 192-199, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31647707

RESUMO

The chemical control of the mosquito Aedes aegypti is a great challenge worldwide, since several populations of this species are already resistant to traditional insecticides, such as temephos. In Brazil, alternative larvicides, such as Bacillus thuringiensis israelensis (Bti) and pyriproxyfen, have been used more recently. In this study we evaluated the persistence of pyriproxyfen (Sumilarv 0.5%G), 2 commercial formulations of Bti (Vectobac WDG and Vectobac G), and temephos (Fersol 1G) under field and simulated field conditions with treatments exposed to sun and shadow. In the field tests, the 2 formulations of Bti presented less persistence in the 8th wk of evaluation (46% and 37% positivity) compared with temephos (3.6% and 6.8% positivity) and Sumilarv (6.6% and 3.8% positivity) in containers exposed to the sun and shadow, respectively. In the simulated field trial, temephos and the 2 formulations of Bti presented high persistence (100% mortality at 8th wk) when applied in the water box and in deposits placed in the shade. In containers exposed to the sun, the persistence of these products was lower (>80% mortality by temephos after 4 wk, Bti formulations for 3 wk, and Sumilarv for 6 wk). Based on these data, however, Sumilarv presented better performance in the containers exposed to the sun than the 2 formulations of Bti (Vectobac G and Vectobac WDG), which were affected by the sun.


Assuntos
Aedes , Bacillus thuringiensis/química , Inseticidas , Controle de Mosquitos , Piridinas , Temefós , Aedes/crescimento & desenvolvimento , Animais , Brasil , Larva/crescimento & desenvolvimento
14.
J Am Mosq Control Assoc ; 35(3): 210-213, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31647708

RESUMO

A survey was carried out in 51 households within a suburban area of Merida, Yucatan, Mexico, for 5 consecutive days. Adult collections were performed using Prokopack aspirators (indoors) and human-landing mosquito catches (HLC) outdoors, and larval sites (artificial containers) were revised for larvae collection. A total of 259 Aedes albopictus were collected, 246 from artificial larval sites, 8 by indoor aspiration, and 5 by HLC. This is the first record of Ae. albopictus in Merida, Yucatan, Mexico.


Assuntos
Aedes , Distribuição Animal , Aedes/crescimento & desenvolvimento , Animais , Feminino , Larva/crescimento & desenvolvimento , México , Controle de Mosquitos
15.
J Am Mosq Control Assoc ; 35(3): 233-237, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31647710

RESUMO

South Texas is recognized as a potential area for the emergence and re-emergence of mosquito-borne diseases due to recent circulation of Zika, chikungunya, and dengue viruses. During 2017, high Aedes aegypti abundance found in the city of Brownsville, TX, in combination with the previous year's local transmission of Zika virus, triggered the activation of the Texas Department of State Health Services Emergency Mosquito Control Contingency Contract. A contract with the Clarke Environmental and Mosquito Control was a response to control Ae. aegypti, using a ground-based wide-area larvicide spray (WALS™) containing Bacillus thuringiensis israelensis. The WALS application was evaluated through a field-based bioassay and by comparing surveillance data pre- and post-WALS application. The WALS application bioassay demonstrated that the larvicide was effective up to 60 m into the target properties. Additionally, the number of Ae. aegypti captured in traps decreased in the WALS intervention areas compared with the untreated control areas, with an estimated 29% control.


Assuntos
Aedes , Bacillus thuringiensis/química , Controle de Mosquitos/métodos , Aedes/efeitos dos fármacos , Aedes/crescimento & desenvolvimento , Animais , Larva/efeitos dos fármacos , Texas
16.
PLoS Negl Trop Dis ; 13(10): e0007783, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31589616

RESUMO

The case-fatality rate of yellow fever virus (YFV) is one of the highest among arthropod-borne viruses (arboviruses). Although historically, the Asia-Pacific region has remained free of YFV, the risk of introduction has never been higher due to the increasing influx of people from endemic regions and the recent outbreaks in Africa and South America. Singapore is a global hub for trade and tourism and therefore at high risk for YFV introduction. Effective control of the main domestic mosquito vector Aedes aegypti in Singapore has failed to prevent re-emergence of dengue, chikungunya and Zika viruses in the last two decades, raising suspicions that peridomestic mosquito species untargeted by domestic vector control measures may contribute to arbovirus transmission. Here, we provide empirical evidence that the peridomestic mosquito Aedes malayensis found in Singapore can transmit YFV. Our laboratory mosquito colony recently derived from wild Ae. malayensis in Singapore was experimentally competent for YFV to a similar level as Ae. aegypti controls. In addition, we captured Ae. malayensis females in one human-baited trap during three days of collection, providing preliminary evidence that host-vector contact may occur in field conditions. Finally, we detected Ae. malayensis eggs in traps deployed in high-rise building areas of Singapore. We conclude that Ae. malayensis is a competent vector of YFV and re-emphasize that vector control methods should be extended to target peridomestic vector species.


Assuntos
Aedes/virologia , Mosquitos Vetores/virologia , Febre Amarela/virologia , Vírus da Febre Amarela/fisiologia , Aedes/crescimento & desenvolvimento , Animais , Feminino , Interações Hospedeiro-Patógeno/fisiologia , Humanos , Mosquitos Vetores/fisiologia , Saliva/virologia , Singapura/epidemiologia , Febre Amarela/epidemiologia , Febre Amarela/transmissão
17.
Proc Natl Acad Sci U S A ; 116(43): 21501-21507, 2019 10 22.
Artigo em Inglês | MEDLINE | ID: mdl-31570611

RESUMO

The yellow fever mosquito, Aedes aegypti, vectors human pathogens. Juvenile hormones (JH) control almost every aspect of an insect's life, and JH analogs are currently used to control mosquito larvae. Since RNA interference does not work efficiently during the larval stages of this insect, JH regulation of larval development and mode of action of JH analogs are not well studied. To overcome this limitation, we used a multiple single guide RNA-based CRISPR/Cas9 genome-editing method to knockout the methoprene-tolerant (Met) gene coding for a JH receptor. The Met knockout larvae exhibited a black larval phenotype during the L3 (third instar larvae) and L4 (fourth instar larvae) stages and died before pupation. However, Met knockout did not affect embryonic development or the L1 and L2 stages. Microscopy studies revealed the precocious synthesis of a dark pupal cuticle during the L3 and L4 stages. Gene expression analysis showed that Krüppel homolog 1, a key transcription factor in JH action, was down-regulated, but genes coding for proteins involved in melanization, pupal and adult cuticle synthesis, and blood meal digestion in adults were up-regulated in L4 Met mutants. These data suggest that, during the L3 and L4 stages, Met mediates JH suppression of pupal/adult genes involved in the synthesis and melanization of the cuticle and blood meal digestion. These results help to advance our knowledge of JH regulation of larval development and the mode of action of JH analogs in Ae. aegypti.


Assuntos
Aedes/genética , Proteínas de Transporte/genética , Proteínas de Insetos/genética , Hormônios Juvenis/metabolismo , Metoprene/metabolismo , Aedes/crescimento & desenvolvimento , Aedes/metabolismo , Animais , Proteínas de Transporte/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Técnicas de Inativação de Genes , Proteínas de Insetos/metabolismo , Larva/genética , Larva/crescimento & desenvolvimento , Larva/metabolismo , Mosquitos Vetores/genética , Mosquitos Vetores/crescimento & desenvolvimento , Mosquitos Vetores/metabolismo , Pupa/genética , Pupa/crescimento & desenvolvimento , Pupa/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
18.
PLoS Genet ; 15(10): e1008443, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31661489

RESUMO

Arthropod-specific juvenile hormones control numerous essential functions in development and reproduction. In the dengue-fever mosquito Aedes aegypti, in addition to its role in immature stages, juvenile hormone III (JH) governs post-eclosion (PE) development in adult females, a phase required for competence acquisition for blood feeding and subsequent egg maturation. During PE, JH through its receptor Methoprene-tolerant (Met) regulate the expression of many genes, causing either activation or repression. Met-mediated gene repression is indirect, requiring involvement of intermediate repressors. Hairy, which functions downstream of Met in the JH gene-repression hierarchy, is one such factor. Krüppel-homolog 1, a zinc-finger transcriptional factor, is directly regulated by Met and has been implicated in both activation and repression of JH-regulated genes. However, the interaction between Hairy and Kr-h1 in the JH-repression hierarchy is not well understood. Our RNAseq-based transcriptomic analysis of the Kr-h1-depleted mosquito fat body revealed that 92% of Kr-h1 repressed genes are also repressed by Met, supporting the existence of a hierarchy between Met and Kr-h1 as previously demonstrated in various insects. Notably, 130 genes are co-repressed by both Kr-h1 and Hairy, indicating regulatory complexity of the JH-mediated PE gene repression. A mosquito Kr-h1 binding site in genes co-regulated by this factor and Hairy was identified computationally. Moreover, this was validated using electrophoretic mobility shift assays. A complete phenocopy of the effect of Met RNAi depletion on target genes could only be observed after Kr-h1 and Hairy double RNAi knockdown, suggesting a synergistic action between these two factors in target gene repression. This was confirmed using a cell-culture-based luciferase reporter assay. Taken together, our results indicate that Hairy and Kr-h1 not only function as intermediate downstream factors, but also act together in a synergistic fashion in the JH/Met gene repression hierarchy.


Assuntos
Aedes/genética , Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Proteínas de Insetos/metabolismo , Hormônios Juvenis/metabolismo , Fatores de Transcrição Kruppel-Like/metabolismo , Proteínas Repressoras/metabolismo , Aedes/crescimento & desenvolvimento , Animais , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Corpo Adiposo/metabolismo , Feminino , Perfilação da Expressão Gênica , Técnicas de Silenciamento de Genes , Proteínas de Insetos/genética , Fatores de Transcrição Kruppel-Like/genética , Interferência de RNA , RNA-Seq , Proteínas Repressoras/genética
19.
Parasite ; 26: 57, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31535969

RESUMO

The mass production of mosquitoes is becoming more wide-spread due to the increased application of the sterile insect technique (SIT) and other genetic control programmes. Due to the variable availability and high cost of the bovine liver powder (BLP) constituent of many current larval diets, there is an urgent demand for new ingredients in order to support sustainable and efficient mosquito production while reducing rearing cost, without affecting the quality of the insects produced. Two black soldier fly (BSF) powder-based diet formulations (50% tuna meal, 35% BSF powder, 15% brewer's yeast and 50% tuna meal + 50% BSF powder) were tested for their suitability to support the development of Aedes aegypti and Ae. albopictus mosquitoes in mass-rearing conditions. Overall, the results indicate that the use of the BSF powder did not negatively impact the development and quality of the produced insects in terms of time to pupation, adult production and male flight ability. Furthermore, depending on the species and diet formulations, there were improvements in some parameters such as female body size, egg production, egg hatch rate and male longevity. BSF powder is a valuable ingredient that can effectively replace costly BLP for the mass production of high quality Ae. aegypti and Ae. albopictus mosquitoes. Both diet formulations can be used for Ae. aegypti showing high plasticity to nutrition sources. However, for Ae. albopictus we recommend the combination including brewer's yeast.


Assuntos
Aedes/crescimento & desenvolvimento , Ração Animal/análise , Pós/administração & dosagem , Simuliidae/química , Animais , Feminino , Larva/crescimento & desenvolvimento , Pós/química
20.
PLoS Negl Trop Dis ; 13(9): e0007775, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31553724

RESUMO

INTRODUCTION: The widespread emergence of resistance to insecticides used to control adult Aedes mosquitoes has made traditional control strategies inadequate for the reduction of various vector populations. Therefore, complementary vector control methods, such as the Sterile Insect Technique, are needed to enhance existing efforts. The technique relies on the rearing and release of large numbers of sterile males, and the development of efficient and standardized mass-rearing procedures and tools is essential for its application against medically important mosquitoes. METHODS: In the effort to reduce the cost of the rearing process, a prototype low-cost plexiglass mass-rearing cage has been developed and tested for egg production and egg hatch rate in comparison to the current Food and Agriculture Organization/International Atomic Energy Agency (FAO/IAEA) stainless-steel cage. Additionally, an adult-index was validated and used as a proxy to estimate the mosquito survival rates by counting the number of male and female mosquitoes that were resting within each of the 6 squares at a given point of time each day in the cage. RESULTS: The study has shown that the prototype mass-rearing cage is cheap and is as efficient as the FAO/IAEA stainless-steel cage in terms of egg production, with even better overall egg hatch rate. The mean numbers of eggs per cage, after seven cycles of blood feeding and egg collection, were 969,789 ± 138,101 and 779,970 ± 123,042, corresponding to 81 ± 11 and 65 ± 10 eggs per female over her lifespan, in the prototype and the stainless-steel-mass-rearing cages, respectively. The longevity of adult male and female mosquitoes was not affected by cage type and, the adult-index could be considered as an appropriate proxy for survival. Moreover, the mass-rearing cage prototype is easy to handle and transport and improves economic and logistic efficiency. CONCLUSION: The low-cost mass-rearing prototype cage can be recommended to produce Ae. aegypti in the context of rear and release techniques. The proposed adult-index can be used as a quick proxy of mosquito survival rates in mass-rearing settings.


Assuntos
Aedes/fisiologia , Abrigo para Animais/economia , Aedes/crescimento & desenvolvimento , Criação de Animais Domésticos/instrumentação , Criação de Animais Domésticos/métodos , Animais , Feminino , Abrigo para Animais/normas , Masculino , Mosquitos Vetores
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