Breeding sites of Aedes aegypti in metropolitan vacant lots in Greater Vitória, State of Espírito Santo, Brazil

INTRODUCTION: This study aimed to evaluate the presence of Aedes aegypti in breeding sites located in vacant lots (VLs) and determine the effectiveness of VL cleaning to reduce insect foci. METHODS: Two types of VLs were sampled, the experimental VL, which was cleaned monthly, and the control VL, which was not cleaned. RESULTS: Monthly cleaning of VLs reduced the abundance of immature forms of A. aegypti. CONCLUSIONS: Strategies for combating this vector should include regular cleaning of VLs and educating the public regarding the risks of discarding waste in inappropriate areas.

Aedes aegypti and Aedes albopictus (Diptera: Culicidae): coexistence and susceptibility to temephos, in municipalities with occurrence of dengue and differentiated characteristics of urbanization

INTRODUCTION: The aim of the present study was to verify the coexistence between Aedes aegypti and Aedes albopictus populations in municipalities of the States of Paraná and Santa Catarina with different urbanization profiles where dengue occurs and evaluate their susceptibility to the organophosphate temephos. METHODS: The number of eggs per ovitrap were counted and incubated for hatching to identify the species. Data analysis of the populations was conducted to determine randomness and aggregation, using the variance-to-mean ratio (index of dispersion). Susceptibility to temephos was evaluated by estimation of the resistance ratios RR50 and RR95. Aedes aegypti samples were compared with the population Rockefeller and Aedes albopictus samples were compared with a population from the State of Santa Catarina and with the Rockefeller population. RESULTS: Coexistence between Aedes aegypti and Aedes albopictus and the aggregation of their eggs were observed at all the sites analyzed in the State of Paraná. CONCLUSIONS: All the Aedes aegypti populations from the State of Parana showed alteration in susceptibility status to the organophosphate temephos, revealing incipient resistance. Similarly, all the Aedes albopictus populations (States of Paraná and Santa Catarina) presented survival when exposed to the organophosphate temephos.

Comportamento de formas imaturas de Aedes aegypti, no litoral do Estado de São Paulo

INTRODUÇÃO: Em região de alta incidência de dengue, no litoral do Estado de São Paulo, selecionaram-se 9 áreas, com objetivo de avaliar o comportamento de formas imaturas de Aedes aegypti. MÉTODOS: As 9 áreas foram agrupadas em 4 estratos, diferenciados pelo uso e ocupação do solo. Foram coletadas larvas e pupas numa amostra de cerca de 500 imóveis em cada área. RESULTADOS: Apesar do pneu e lona apresentarem as maiores taxas de positividade para Aedes aegypti, o ralo, juntamente com outros recipientes fixos nas edificações foram altamente predominantes entre os recipientes positivos (32 a 76% dos recipientes positivos). As áreas coletivas de prédios e os imóveis não residenciais de grande porte apresentaram as maiores taxas de positividade para Aedes aegypti enquanto os apartamentos, as menores. Os níveis de infestação foram maiores na área residencial com predominância de prédios de apartamentos, onde 76% dos criadouros detectados foram recipientes fixos nas edificações. CONCLUSÕES: Esses conhecimentos são importantes subsídios para a estratégia de controle, pois reforçam a necessidade de atenção especial para determinados tipos de imóveis, bem como da adequação da norma técnica de ralo de água pluvial e da melhoria de manutenção das edificações. Além disso, são necessárias observações sistemáticas que permitam acompanhar a dinâmica de ocupação de diferentes imóveis e recipientes por Aedes aegypti e a incorporação desses conhecimentos nas ações de controle do vetor na região.

Variation in Aedes aegypti (Linnaeus) (Diptera, Culicidae) infestation in artificial containers in Caxias, state of Maranhão, Brazil

INTRODUCTION: Dengue is a serious public health problem worldwide, with cases reported annually in tropical and subtropical regions. Aedes aegypti (Linnaeus, 1762), the main vector of dengue, is a domiciliary species with high dispersal and survival capacities and can use various artificial containers as breeding sites. We assessed potential container breeding sites of A. aegypti in the municipality of Caxias, Maranhão, Brazil. METHODS: In the initial phase, we analyzed 900 properties in 3 neighborhoods during the dry and rainy seasons (August-October 2005 and February-April 2006, respectively). During the second sampling period, September 2006-August 2007, we used 5 assessment cycles for 300 properties in a single neighborhood. RESULTS: During the dry and rainy seasons, water-storage containers comprised 55.7% (n = 1,970) and 48.5% (n = 1,836) of the total containers inspected, and showed the highest productivity of immature A. aegypti; we found 23.7 and 106.1 individuals/container, respectively, in peridomicile sites. In intradomicile sites, water-storage containers were also the most important breeding sites with 86.4% (n = 973) and 85.6% (n = 900) of all containers and a mean of 7.9 and 108.3 individuals/container in the dry and rainy seaso-October 2006 (1,342). The highest number of positives (70) was recorded in May, mostly (94%) in storage containers. CONCLUSIONS: Storage containers are the principal and most productive A. aegypti breeding sites and are a major contributing factor to the maintenance of this vector in Caxias.

Identification of dengue viruses in naturally infected Aedes aegypti females captured with BioGents (BG)-Sentinel traps in Manaus, Amazonas, Brazil

IntroductionIn Manaus, the first autochthonous cases of dengue fever were registered in 1998. Since then, dengue cases were diagnosed by the isolation of viruses 1, 2, 3, and 4.MethodsOne hundred eighty-seven mosquitoes were collected with BioGents (BG)-Sentinel traps in 15 urban residential areas in the Northern Zone of Manaus and processed by molecular tests.ResultsInfections with dengue viruses 1, 2, 3, and 4 and a case of co-infection with dengue viruses 2 and 3 were identified.ConclusionsThese findings corroborate the detection of dengue in clinical samples and reinforce the need for epidemiological surveillance by the Health authorities.

Bioactivity of plant extracts on the larval and pupal stages of Aedes aegypti (Diptera, Culicidea)

Introduction Aedes aegypti is responsible for the transmission of the dengue and yellow fever viruses. This study evaluated the effects of extracts from Cnidosculos phyllacanthus, Ricinus communis, and Coutarea hexandra on the developmental periods of A.aegypti larvae and pupae. Crude extracts of C. phyllacanthus and C. hexandra and oil from R. communis and C. phyllacanthus were used. Methods Bioassays of the larvicidal and pupicidal effects of these products at different concentrations and times of exposure were evaluated. The lethal and sublethal effects were determined using different concentrations in larvicidal tests. Mortality data were evaluated by Probit analysis to determine the LC50 and LC90 values. Results The vegetable oils from C. phyllacanthus and R. communis demonstrated greater efficiency for larval control with an LC50=0.28µl/mL and an LC90=1.48µl/mL and LC50=0.029µl/mL and a LC90=0.26µl/mL, respectively. In pupal tests toxic effects for all insects were verified after exposure to the products at significant LC50 and LC90 values for 24 and 48h. The effects of sublethal concentrations of C. phyllacanthus (oil) were more effective on the insects. Conclusions The vegetables oils from C. phyllacanthus and R. communis demonstrated greater potential from the control of different developmental periods in the life cycle of this insect.

Evaluation of two sweeping methods for estimating the number of immature Aedes aegypti (Diptera: Culicidae) in large containers

Introduction Here, we evaluated sweeping methods used to estimate the number of immature Aedes aegypti in large containers. Methods III/IV instars and pupae at a 9:1 ratio were placed in three types of containers with, each one with three different water levels. Two sweeping methods were tested: water-surface sweeping and five-sweep netting. The data were analyzed using linear regression. Results The five-sweep netting technique was more suitable for drums and water-tanks, while the water-surface sweeping method provided the best results for swimming pools. Conclusions Both sweeping methods are useful tools in epidemiological surveillance programs for the control of Aedes aegypti.

Impact of insecticide resistance on the field control of Aedes aegypti in the State of São Paulo

IntroductionThe need to control dengue transmission by means of insecticides has led to the development of resistance to most of the products used worldwide against mosquitoes. In the State of São Paulo, the Superintendência de Controle de Endemias(SUCEN) has annually monitored the susceptibility of Aedes aegypti to insecticides since 1996; since 1999, surveys were conducted in collaboration with the National Network of Laboratories (MoReNAa Network) and were coordinated by the Ministry of Health. In this study, in addition to the biological characterization of insecticide resistance in the laboratory, the impact of resistance on field control was evaluated for vector populations that showed resistance in laboratory assays.MethodsField efficacy tests with larvicides and adulticides were performed over a 13-year period, using World Health Organization protocols.ResultsData from the field tests showed a reduction in the residual effect of temephos on populations with a resistance ratio of 3. For adults, field control was less effective in populations characterized as resistant in laboratory qualitative assays, and this was confirmed using qualitative assays and field evaluation.ConclusionsOur results indicated that management of resistance development needs to be adopted when insect populations show reduced susceptibility. The use of insecticides is a self-limiting tool that needs to be applied cautiously, and dengue control requires more sustainable strategies.

Effects of piperonyl butoxide on the toxicity of the organophosphate temephos and the role of esterases in the insecticide resistance of Aedes aegypti

IntroductionThe effects of piperonyl butoxide (PBO) on the toxicity of the organophosphate temephos (TE) and the role of esterases in the resistance of Aedes aegypti to this insecticide were evaluated.MethodsA. aegypti L4 larvae susceptible and resistant to TE were pre-treated with PBO solutions in acetone at concentrations of 0.125, 0.25, 0.5, 1, and 2% for 24h and subsequently exposed to a diagnostic concentration of 0.02mg/L aqueous TE solution. The esterase activity of the larvae extracts pre-treated with varying PBO concentrations and exposed to TE for three time periods was determined.ResultsAt concentrations of 0.25, 0.5, 1, and 2%, PBO showed a significant synergistic effect with TE toxicity. High levels of esterase activity were associated with the survival of A. aegypti L4 larvae exposed to TE only.ConclusionsThe results of the biochemical assays suggest that PBO has a significant inhibitory effect on the total esterase activity in A. aegypti larvae.

Natural transovarial transmission of dengue virus 4 in Aedes aegypti from Cuiabá, State of Mato Grosso, Brazil

INTRODUCTION: Dengue is the most prevalent arboviral disease in tropical areas. In Mato Grosso, outbreaks are reported every year, but studies on dengue in this state are scarce. METHODS: Natural transovarial infection of Aedes aegypti by a flavivirus was investigated in the Jardim Industriário neighborhood of Cuiabá, Mato Grosso. Eggs were collected with ovitraps during the dry, intermediate, and rainy seasons of 2012. After the eggs hatched and the larvae developed to adulthood, mosquitoes (n = 758) were identified and allocated to pools of 1-10 specimens according to the collection location, sex, and climatic period. After RNA extraction, multiplex semi-nested RT-PCR was performed to detect the four dengue virus (DENV) serotypes, yellow fever virus, West Nile virus and Saint Louis encephalitis virus. RESULTS: DENV-4 was the only flavivirus detected, and it was found in 8/50 pools (16.0%). Three of the positive pools contained females, and five contained males. Their nucleotide sequences presented 96-100% similarity with DENV-4 genotype II strains from Manaus, Amazonas. The minimum infection rate was 10.5 per 1000 specimens, and the maximum likelihood estimator of the infection rate was 11.6 (95% confidence interval: 4.8; 23.3). CONCLUSIONS: This study provides the first evidence of natural transovarial infection by DENV-4 in Ae. Aegypti in Mato Grosso, suggesting that this type of infection might serve as a mechanism of virus maintenance during interepidemic periods in Cuiabá, a city where dengue epidemics are reported every year. These results emphasize the need for efficient vector population control measures to prevent arbovirus outbreaks in the state.

Phenotypic and genotypic profile of pyrethroid resistance in populations of the mosquito Aedes aegypti from Goiânia, Central West Brazil

ABSTRACTINTRODUCTION:The mosquito Aedes aegypti has evolved resistance to pyrethroid insecticides. The present study evaluated Ae. aegypti from Goiânia for the resistant phenotype and for mutations associated with resistance.METHODS:Insecticide dose-response bioassays were conducted on mosquitoes descended from field-collected eggs, and polymerase chain reaction (PCR) was used to genotype 90 individuals at sites implicated in pyrethroid resistance.RESULTS:All mosquito populations displayed high levels of resistance to deltamethrin, as well as high frequencies of the 1016Ile kdr and 1534Cys kdrmutations.CONCLUSIONS:Aedes aegypti populations in the Goiânia area are highly resistant to deltamethrin, presumably due to high frequencies of kdr(knockdown-resistance) mutations.

Aedes aegypti eggs oviposited on water surface collected from field ovitraps in Nova Iguaçu City, Brazil

ABSTRACT INTRODUCTION: Aedes aegypti eggs can be collected from the water surface. METHODS: Aedes aegypti oviposition from 97 field ovitraps was studied. RESULTS: Of the 16,016 eggs collected, 11,439 were obtained from paddles in ovitraps and 4,577 from water. Further, 89 (91.8%) traps contained eggs on water and 22 (22.7%) traps contained eggs only on water. CONCLUSIONS: In field traps, Aedes aegypti females usually oviposit some eggs on water surface suggesting that they might also oviposit on water of some natural breeding, and this possibility needs to be investigated. Eggs oviposited on water need to be considered for collecting trap data.

Screening of plants found in the State of Amazonas, Brazil for activity against Aedes aegypti larvae

Ethanol, methanol and water extracts representing mostly native plant species found in the Amazon region were prepared, respectively, by maceration, continuous liquid-solid extraction and infusion, followed by evaporation and freeze-drying. The freeze-dried extracts were tested for lethality toward Aedes aegypti larvae at test concentrations of 500 mg / mL. In general, methanol extracts exhibited the greatest larvicidal activity. The following 7 methanol extracts of (the parts of) the indicated plant species were the most active, resulting in 100% mortality in A. aegypti larvae: Tapura amazonica Poepp. (root), Piper aduncum L. (leaf and root), P. tuberculatum Jacq. (leaf, fruit and branch). and Simaba polyphylla (Cavalcante) W.W. Thomas (branch).

Efeitos da temperatura no ciclo de vida, exigências térmicas e estimativas do número de gerações anuais de Aedes aegypti (Diptera, Culicidae)

O trabalho teve por objetivo avaliar o efeito da temperatura sobre o ciclo de vida de Aedes aegypti (Linnaeus, 1762), determinar as exigências térmicas para o desenvolvimento e estimar o número de gerações anuais do inseto em campo. O ciclo de vida das populações de A. aegypti foi estudado nas temperaturas de 18, 22, 26, 28, 32 e 34 ± 2ºC e fotofase de 12 horas, determinando-se ainda os limites térmicos inferiores de desenvolvimento (Tb) e as constantes térmicas (K) e estimado o número de gerações anuais do inseto em laboratório e em campo. A temperatura favorável ao desenvolvimento de A. aegypti encontra-se entre 22ºC e 32ºC, e para a longevidade e fecundidade dos adultos entre 22ºC e 28ºC. As Tb, K de ovo a adulto, e o número de gerações anuais em campo foram de 11,33; 8,99 e 13,61ºC, 192,3; 213,2 e 116,5 graus-dias, e 23; 24,6 e 30,3 gerações para as populações de A. aegypti de Boqueirão (07º29'27''S, 36º08'09''W), Campina Grande (07º13'32''S, 35º54'15''W) e Remígio (06º58'1''S, 35º47'29''W), respectivamente.