Mapeamento da infestação por Aedes aegypti e Culex spp. adultos em Campinas (SP), Brasil / Mapping of Aedes aegypti and Culex spp. adults in Campinas (SP), Brazil

Introdução: Algumas arboviroses transmitidas por vetores como Aedes aegypti e Culex spp. são consideradas de grande importância epidemiológica, entre estas, destacam-se a dengue, Zika, chikungunya, febre amarela e febre do Nilo ocidental. A transmissão dos arbovírus ocorre enquanto as fêmeas infectadas realizam a hematofagia e as atuais medidas que visam a redução dessas arboviroses na população se dão principalmente com foco na redução da população de mosquitos. Índices de vigilância entomológica fazem parte das rotinas de programas de controle. Estudos recentes têm questionado a eficácia da utilização de índices de formas imaturas do vetor para predição do risco de transmissão de arboviroses e associação com incidência de casos. Isso indica que realizar a vigilância com a forma adulta dos vetores pode ser uma alternativa de maior eficácia. Objetivos: Estimar, predizer e mapear a infestação por Ae. aegypti e o Culex spp. associadas a variáveis de uso e ocupação do solo no município de Campinas/SP no período de verão entre os anos de 2021 a 2023. Material e Métodos: Trata-se de um estudo transversal realizado por meio de coletas mensais de mosquitos adultos realizadas em 200 armadilhas BG MosquititoTM distribuídas aleatoriamente na área urbana de Campinas. Foram realizadas regressões múltiplas em um contexto bayesiano e geoestatístico utilizando a abordagem de aproximações de Laplace aninhadas e integradas e equações diferenciais parciais estocásticas. Foram consideradas como covariáveis o Índice Brasileiro de Privação (IBP) e informações sobre uso e ocupação do solo obtidas de imagens de satélite. Resultados: O melhor modelo de regressão para o número de Ae. aegypti fêmeas encontrou associação positiva com o IBP, uma medida do nível socioeconômico, e árvores. Quanto aos machos, o melhor modelo mostrou associação positiva com cimento e telha de zinco. O melhor modelo para o total de mosquitos Ae. aegypti mostrou associação positiva com o IBP, cimento e árvore e o mesmo ocorreu para Culex spp. Foram elaborados mapas com a predição da quantidade de mosquitos para cada modelo considerando a distribuição das covariáveis presentes na área de estudo. Conclusões: Com esse estudo, foi possível modelar as quantidades de fêmeas, machos e total de Ae. aegypti e total de Culex spp., com base nas informações obtidas com a partir da instalação das armadilhas de adultos, e predizer os níveis de infestação para todos os locais da área de estudo. Variáveis socioeconômicas e de uso e ocupação do solo mostraram-se associadas aos números de mosquitos coletados, com exceção do nível socioeconômico para os machos de Ae. aegypti. Os resultados mostram que a utilização dessas covariáveis nas modelagens foram úteis para melhorar as predições nos locais não amostrados. Nosso estudo mostrou ser possível identificar áreas de maior risco para infestação de forma independente dos limites administrativos da área de estudo, quer sejam bairros ou distritos. Além disso, mostrou ser viável o uso de armadilhas de adultos para realização de vigilância entomológica.

Introduction: Some arboviruses transmitted by vectors such Aedes aegypti and Culex spp. are considered of great epidemiological importance, among which dengue, Zika and chikungunya, yellow fever and West Nile fever stand out. The transmission of arboviruses occurs while infected females are carrying out hematophagy, and current measures aimed at reducing these arboviruses in the population are mainly focused on reducing the mosquito population. Entomological surveillance indices are part of the routines of control programs. Recent studies have questioned the effectiveness of using indices of immature forms of the vector to predict the risk of arbovirus transmission and association with the incidence of cases. This indicates that carrying out surveillance with the adult form of the vectors may be a more effective alternative. Objectives: Estimate, predict and map the infestation of Ae. aegypti and Culex spp. associated with land use and occupation variables in the city of Campinas (SP) in the summer period between 2021 to 2023. Material and Methods: This is a cross-sectional study carried out through monthly collections of adult mosquitoes in 200 BG MosquititoTM traps randomly distributed in the urban area of Campinas. Multiple regressions were performed in a Bayesian and geostatistical context using the approach of nested and integrated Laplace approximations and stochastic partial differential equations. The Brazilian Deprivation Index (IBP) and information on land use and occupation obtained from satellite images were considered as covariates. Results: The best regression model for the number of female Ae. aegypti found a positive association with the IBP, a measure of socioeconomic status, and trees. As for males, the best model considered showed a positive association with cement and zinc tiles. The best model for the total number of Ae. aegypti showed a positive association with IBP, cement and trees, as the same occurred for Culex spp. Conclusions: With this study, it was possible to model the numbers of females, males and total Ae. aegypti and total Culex spp., based on the information obtained from the installation of adult traps, and to predict the infestation levels for all locations in the study area. Socioeconomic and land use and occupation variables were associated with the numbers of mosquitoes collected, with the exception of the socioeconomic level for males of Ae. aegypti. The results show that the use of these covariates in the models was useful to improve predictions in the non-sampled locations. Our study showed that it is possible to identify areas of greater risk for infestation independently of the administrative boundaries of the study area, whether they are neighborhoods, districts. Furthermore, it was shown to be feasible to use adult traps to carry out entomological surveillance.

Mosquitocidal activities of Chenopodium botrys whole plant n-hexane extract against Culex quinquefasciatus / Atividades mosquitocidas do extrato de n-hexano de planta inteira de Chenopodium botrys contra Culex quinquefasciatus

This research aimed to investigate various mosquitocidal activities of Chenopodium botrys whole- plant n-hexane extract against Culex quinquefasciatus. The extract showed remarkable larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus. During the larvicidal and pupicidal activities, the 24-hour lethal concentration (LC50) of extract against 2nd instar larvae, 4th instar larvae and pupae were 324.6, 495.6 and 950.8 ppm, respectively. During the CDC (Centers for Disease Control and Prevention) bottle bioassay for adulticidal activity, the median knockdown times (KDT50) at 1.25% concentration was 123.4 minutes. During the filter paper impregnation bioassay for adulticidal activity, the KDT50 value at 0.138 mg/cm2 concentration was 48.6 minutes. The extract was fractionated into 14 fractions through silica gel column chromatography which were then combined into six fractions on the basis of similar retention factor (Rf) value. These fractions were screened for adulticidal activity by applying CDC bottle bioassay. The fraction obtained through 60:40 to 50:50% n-hexanes-chloroform mobile phase with 0.5 Rf value showed 100% adulticidal activity at 0.2% concentration. During oviposition deterrent activity, the highest concentration (1000 ppm) showed 71.3 ± 4.4% effective repellence and 0.6 ± 0.1 oviposition activity index. During adult emergence inhibition activity, the median emergence inhibition (EI50) value was 312.3 ppm. From the outcome of the present investigation, it is concluded that the n-hexane extract of C. botrys whole- plant possesses strong larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus.(AU)

Esta pesquisa teve como objetivo investigar várias atividades mosquitocidas do extrato n-hexano de planta inteira de Chenopodium botrys contra Culex quinquefasciatus. O extrato mostrou atividades larvicida, pupicida, adulticida, dissuasora de oviposição e inibidora da emergência de adultos contra a Cx. quinquefasciatus. Durante as atividades larvicida e pupicida, a concentração letal de 24 horas (CL50) do extrato contra larvas de 2º estádio, larvas de 4º estádio e pupa foi de 324,6, 495,6 e 950,8 ppm, respectivamente. Durante o bioensaio com frasco do CDC (Centros para Controle e Prevenção de Doenças) para adulticida, o tempo médio de desativação (KDT50) na concentração de 1,25% foi de 123,4 minutos. Durante o bioensaio de impregnação com papel de filtro para a atividade adulticida do extrato, o valor KDT50 na concentração de 0,138 mg / cm2 foi de 48,6 minutos. O extrato foi fracionado em 14 frações através de cromatografia em coluna de gel de sílica que foram então combinadas em seis frações com base em um valor de fator de retenção (Rf) semelhante. Essas frações foram selecionadas quanto à atividade adulticida por meio da aplicação do bioensaio com garrafa do CDC. A fração obtida através da fase móvel de n-hexanos-clorofórmio 60:40% a 50:50% com valor de 0,5 Rf apresentou atividade adulticida de 100% na concentração de 0,2%. Durante a atividade de dissuasão da oviposição, a maior concentração de extrato (1000 ppm) apresentou repelência efetiva de 71,3 ± 4,4% e índice de atividade de oviposição de 0,6 ± 0,1. Durante a atividade de inibição da emergência de adultos, o valor médio de inibição da emergência (EI50) foi de 312,3 ppm. A partir do resultado da presente investigação, conclui-se que o extrato de n-hexano da planta inteira de C. botrys possui fortes atividades larvicida, pupicida, adulticida, dissuasora da oviposição e inibidora da emergência de adultos contra a Cx. quinquefasciatus.(AU)

Mosquitocidal activities of Chenopodium botrys whole plant n-hexane extract against Culex quinquefasciatus / Atividades mosquitocidas do extrato de n-hexano de planta inteira de Chenopodium botrys contra Culex quinquefasciatus

This research aimed to investigate various mosquitocidal activities of Chenopodium botrys whole- plant n-hexane extract against Culex quinquefasciatus. The extract showed remarkable larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus. During the larvicidal and pupicidal activities, the 24-hour lethal concentration (LC50) of extract against 2nd instar larvae, 4th instar larvae and pupae were 324.6, 495.6 and 950.8 ppm, respectively. During the CDC (Centers for Disease Control and Prevention) bottle bioassay for adulticidal activity, the median knockdown times (KDT50) at 1.25% concentration was 123.4 minutes. During the filter paper impregnation bioassay for adulticidal activity, the KDT50 value at 0.138 mg/cm2 concentration was 48.6 minutes. The extract was fractionated into 14 fractions through silica gel column chromatography which were then combined into six fractions on the basis of similar retention factor (Rf) value. These fractions were screened for adulticidal activity by applying CDC bottle bioassay. The fraction obtained through 60:40 to 50:50% n-hexanes-chloroform mobile phase with 0.5 Rf value showed 100% adulticidal activity at 0.2% concentration. During oviposition deterrent activity, the highest concentration (1000 ppm) showed 71.3 ± 4.4% effective repellence and 0.6 ± 0.1 oviposition activity index. During adult emergence inhibition activity, the median emergence inhibition (EI50) value was 312.3 ppm. From the outcome of the present investigation, it is concluded that the n-hexane extract of C. botrys whole- plant possesses strong larvicidal, pupicidal, adulticidal, oviposition deterrent and adult emergence inhibitory activities against Cx. quinquefasciatus.

Esta pesquisa teve como objetivo investigar várias atividades mosquitocidas do extrato n-hexano de planta inteira de Chenopodium botrys contra Culex quinquefasciatus. O extrato mostrou atividades larvicida, pupicida, adulticida, dissuasora de oviposição e inibidora da emergência de adultos contra a Cx. quinquefasciatus. Durante as atividades larvicida e pupicida, a concentração letal de 24 horas (CL50) do extrato contra larvas de 2º estádio, larvas de 4º estádio e pupa foi de 324,6, 495,6 e 950,8 ppm, respectivamente. Durante o bioensaio com frasco do CDC (Centros para Controle e Prevenção de Doenças) para adulticida, o tempo médio de desativação (KDT50) na concentração de 1,25% foi de 123,4 minutos. Durante o bioensaio de impregnação com papel de filtro para a atividade adulticida do extrato, o valor KDT50 na concentração de 0,138 mg / cm2 foi de 48,6 minutos. O extrato foi fracionado em 14 frações através de cromatografia em coluna de gel de sílica que foram então combinadas em seis frações com base em um valor de fator de retenção (Rf) semelhante. Essas frações foram selecionadas quanto à atividade adulticida por meio da aplicação do bioensaio com garrafa do CDC. A fração obtida através da fase móvel de n-hexanos-clorofórmio 60:40% a 50:50% com valor de 0,5 Rf apresentou atividade adulticida de 100% na concentração de 0,2%. Durante a atividade de dissuasão da oviposição, a maior concentração de extrato (1000 ppm) apresentou repelência efetiva de 71,3 ± 4,4% e índice de atividade de oviposição de 0,6 ± 0,1. Durante a atividade de inibição da emergência de adultos, o valor médio de inibição da emergência (EI50) foi de 312,3 ppm. A partir do resultado da presente investigação, conclui-se que o extrato de n-hexano da planta inteira de C. botrys possui fortes atividades larvicida, pupicida, adulticida, dissuasora da oviposição e inibidora da emergência de adultos contra a Cx. quinquefasciatus.

Effects of Peganum harmala L Seed Extract on Culex pipiens (Diptera: Culicidae) / Efeitos do extrato de semente de Peganum harmala L em Culex pipiens (Diptera: Culicidae)

Mosquito-borne diseases result in the loss of life and economy, primarily in subtropical and tropical countries, and the emerging resistance to insecticides is increasing this threat. Botanical insecticides are promising substitutes for synthetic insecticides. This study evaluated the larvicidal and growth index of Culex pipiens of four solvent extracts of Terminalia chebula, Aloe perryi, and Peganum harmala against Cx. pipiens. None of the 12 extracts exhibited larvicidal potential against third instars except the ethyl acetate extract of P. harmala. After 24 h of exposure, the LC50 value was 314.88 ppm, and the LC90 value was 464.19 ppm. At 320 ppm, the hatchability was 25.83%, and it resulted in 100% mortality. In addition, the eggs treated with the EtOAc extract of P. Harmala exhibited a long larval period compared with the control. The larval period continued for 12 days, and the pupal period took three days in the treatment groups. The growth index data also exhibited a decrease (0.00–7.53) in the treated groups compare with 8.5 in the control. The transformation of eggs into adults decreased with increasing concentrations. This paper is the first report on the development and growth index of Cx. pipiens potential using P. harmala seeds.(AU)

As doenças transmitidas por mosquitos resultam na perda de vidas e economia, principalmente em países subtropicais e tropicais, e a resistência emergente aos inseticidas está aumentando essa ameaça. Os inseticidas botânicos são substitutos promissores dos inseticidas sintéticos. Este estudo avaliou o índice larvicida e de crescimento de Culex pipiens de quatro extratos solventes de Terminalia chebula, Aloe perryi e Peganum harmala contra Cx. pipiens. Nenhum dos 12 extratos exibiu potencial larvicida contra o terceiro ínstar, exceto o extrato de acetato de etila de P. harmala. Após 24 horas de exposição, o valor LC50 era 314,88 ppm e o valor LC90 era 464,19 ppm. A 320 ppm, a eclodibilidade foi de 25,83% e resultou em 100% de mortalidade. Além disso, os ovos tratados com o extrato de EtOAc de P. harmala exibiram um longo período larval em comparação com o controle. O período larval continuou por 12 dias, e o período pupal durou três dias nos grupos de tratamento. Os dados do índice de crescimento também exibiram uma diminuição (0,00-7,53) nos grupos tratados em comparação com 8,5 no controle. A transformação de ovos em adultos diminuiu com o aumento das concentrações. Este artigo é o primeiro relatório sobre o índice de desenvolvimento e crescimento de Cx. potencial de pipiens usando sementes de P. harmala.(AU)

Effects of Peganum harmala L Seed Extract on Culex pipiens (Diptera: Culicidae) / Efeitos do extrato de semente de Peganum harmala L em Culex pipiens (Diptera: Culicidae)

Mosquito-borne diseases result in the loss of life and economy, primarily in subtropical and tropical countries, and the emerging resistance to insecticides is increasing this threat. Botanical insecticides are promising substitutes for synthetic insecticides. This study evaluated the larvicidal and growth index of Culex pipiens of four solvent extracts of Terminalia chebula, Aloe perryi, and Peganum harmala against Cx. pipiens. None of the 12 extracts exhibited larvicidal potential against third instars except the ethyl acetate extract of P. harmala. After 24 h of exposure, the LC50 value was 314.88 ppm, and the LC90 value was 464.19 ppm. At 320 ppm, the hatchability was 25.83%, and it resulted in 100% mortality. In addition, the eggs treated with the EtOAc extract of P. Harmala exhibited a long larval period compared with the control. The larval period continued for 12 days, and the pupal period took three days in the treatment groups. The growth index data also exhibited a decrease (0.00–7.53) in the treated groups compare with 8.5 in the control. The transformation of eggs into adults decreased with increasing concentrations. This paper is the first report on the development and growth index of Cx. pipiens potential using P. harmala seeds.

As doenças transmitidas por mosquitos resultam na perda de vidas e economia, principalmente em países subtropicais e tropicais, e a resistência emergente aos inseticidas está aumentando essa ameaça. Os inseticidas botânicos são substitutos promissores dos inseticidas sintéticos. Este estudo avaliou o índice larvicida e de crescimento de Culex pipiens de quatro extratos solventes de Terminalia chebula, Aloe perryi e Peganum harmala contra Cx. pipiens. Nenhum dos 12 extratos exibiu potencial larvicida contra o terceiro ínstar, exceto o extrato de acetato de etila de P. harmala. Após 24 horas de exposição, o valor LC50 era 314,88 ppm e o valor LC90 era 464,19 ppm. A 320 ppm, a eclodibilidade foi de 25,83% e resultou em 100% de mortalidade. Além disso, os ovos tratados com o extrato de EtOAc de P. harmala exibiram um longo período larval em comparação com o controle. O período larval continuou por 12 dias, e o período pupal durou três dias nos grupos de tratamento. Os dados do índice de crescimento também exibiram uma diminuição (0,00-7,53) nos grupos tratados em comparação com 8,5 no controle. A transformação de ovos em adultos diminuiu com o aumento das concentrações. Este artigo é o primeiro relatório sobre o índice de desenvolvimento e crescimento de Cx. potencial de pipiens usando sementes de P. harmala.

Culex quinquefasciatus larvae development arrested when fed on Neochloris aquatica.

Culex quinquefasciatus is a cosmopolitan species widely distributed in the tropical and subtropical areas of the world. Due to its long history of close association with humans, the transmission of arboviruses and parasites have an important role in veterinary and public health. Adult females feed mainly on birds although they can also feed on humans and other mammals. On the other hand, larvae are able to feed on a great diversity of microorganisms, including microalgae, present in natural or artificial breeding sites with a high organic load. These two particularities, mentioned above, are some of the reasons why this mosquito is so successful in the environment. In this work, we report the identification of a microalga found during field sampling in artificial breeding sites, in a group of discarded tires with accumulated rainwater. Surprisingly, only one of them had a bright green culture without mosquito larvae while the other surrounding tires contained a large number of mosquito larvae. We isolated and identified this microorganism as Neochloris aquatica, and it was evaluated as a potential biological control agent against Cx. quinquefasciatus. The oviposition site preference in the presence of the alga by gravid females, and the effects on larval development were analyzed. Additionally, microalga effect on Cx. quinquefasciatus wild type, naturally infected with the endosymbiotic bacterium Wolbachia (w+) and Wolbachia free (w-) laboratory lines was explored. According to our results, even though it is chosen by gravid females to lay their eggs, the microalga had a negative effect on the development of larvae from both populations. Additionally, when the larvae were fed with a culture of alga supplemented with balanced fish food used as control diet, they were not able to reverse its effect, and were unable to complete development until adulthood. Here, N. aquatica is described as a biological agent, and as a potential source of bioactive compounds for the control of mosquito populations important in veterinary and human health.

The External Morphology of the Eggs of Culex (Culex) saltanensis (Diptera: Culicidae) Under Scanning Electron Microscopy.

The aim of the present study was to describe the morphology of the eggs of Culex (Culex) saltanensis Dyar that occurs in the Neotropical region. Eggs of the Cx. (Cux.) saltanensis were collected at the Mata Atlântica FIOCRUZ campus, fixed in 1% osmium tetroxide, prepared for mounting on metal supports, observed under a scanning electron microscope, and described morphologically. The eggs had a coniform shape with a length of approximately 0.5 mm (505-510 µm) and a width in the median portion of 117 µm (113-123 µm). Upper portion is lined with tubers of irregular shape and varying sizes (0.64-1.31 µm), located on a cross-linked matrix forming bands observed under optical microscopy. The micropyle is encased in a necklace of approximately 6.6-µm plates arranged in a flower-like shape. Comparing Cx. (Cux.) saltanensis eggs with several species of different genera, important divergent characteristics can be observed. However, this study points to the need for new descriptions of eggs of species belonging to the same subgenus in order to analyze if there will be differences between them. Culex (Cux.) saltanensis eggs have particular characteristics not observed in eggs of other Culicidae genera.

A survey of tire-breeding mosquitoes (Diptera: Culicidae) in the Dominican Republic: Considerations about a pressing issue. / Estudio de mosquitos (Diptera: Culicidae) que se desarrollan en neumáticos en República Dominicana: consideraciones sobre un problema acuciante

INTRODUCTION: Discarded vehicle tires represent a serious threat both to the environment and to public health as they have the potential to harbor important mosquito (Diptera: Culicidae) vectors. OBJECTIVE: To assess the importance of used vehicle tires as larval habitats for mosquito fauna that colonize these artificial reservoirs in Jarabacoa, Dominican Republic. MATERIALS AND METHODS: Used tires were sampled with pipettes at specialized tire fitting shops and scattered stockpiles of tires between June and August, 2018. RESULTS: We sampled 396 tires; 57 (Container Index=14.4%) were positive for immature stages and contained 2,400 specimens, 11 species, and four genera (Anopheles, Aedes, Culex, and Toxorhynchites). The most abundant species was Aedes albopictus (42.3%) followed by Aedes aegypti (34.3%), and Culex quinquefasciatus (14.0%) while other species (9.4%) were less abundant. The container index varied significantly among the different tire sizes (χ2=13.4; p≤0.05). The highest infestation levels were found in the largest tires. A low positive correlation (r=0.38, n=396; p≤0.001) between the tire size and the prevalence of immature stages was recorded. The presence of organic matter had an overall positive effect on the infestation levels (U=11,430.0; p≤0.001). CONCLUSIONS: These rubber residues, usually located nearby human populations, represent suitable breeding sites for arboviruses vectors such as dengue, chikungunya, Zika, and West Nile.

Introducción. Los neumáticos usados representan una grave amenaza para el medio ambiente y la salud pública, ya que tienen el potencial de albergar mosquitos (Diptera: Culicidae) vectores de enfermedades. Objetivo. Evaluar la importancia de los neumáticos usados como hábitats larvarios de mosquitos que colonizan estos recipientes artificiales en Jarabacoa, República Dominicana. Materiales y métodos. Se muestrearon mediante pipetas neumáticos usados en tiendas de venta y reparación y en vertederos entre junio y agosto de 2018. Resultados. Se muestrearon 396 neumáticos; 57 (índice de contenedor=14,4 %) albergaban estados inmaduros que contenían 2.400 especímenes de 11 especies y cuatro géneros (Anopheles, Aedes, Culex y Toxorhynchites). La especie más abundante fue Aedes albopictus (42,3 %) seguida de Aedes aegypti (34,3 %) y Culex quinquefasciatus (14,0 %), entre otras (9,4 %) de menor abundancia. El índice de contenedor varió significativamente según el tamaño del neumático (χ2=13,4; p≤0,05) y los mayores niveles de infestación se registraron en los neumáticos de mayor tamaño. Se observó una baja correlación positiva (r=0,38; n=396; p≤0,001) entre el tamaño de neumático y la prevalencia de estadios inmaduros. La presencia de materia orgánica tuvo un efecto positivo sobre los niveles de infestación de mosquitos (U=11430,0; p≤0,001). Conclusiones. Estos residuos de caucho, generalmente almacenados cerca de las poblaciones humanas, son propicios para la reproducción de vectores de arbovirus como el dengue, el chikungunya, el Zika y el West Nile.

Spatial and temporal variations on the coexistence of Aedes and Culex larvae in Southern Thailand

This study investigated spatial and temporal variations on the coexistence of Aedes aegypti, Aedes albopictus, and Culex larvae in five subdistricts in Nakhon Si Thammarat, Thailand. We tested two main hypotheses on the spatial and temporal coexistence of mosquito larvae: (1) condition-specific competition and (2) spatial variation among the five subdistricts. We compared the number of positive houses, positive containers, mosquito coexistence during both the wet and dry seasons. The results showed that from a total of 1,072 positive containers collected in both seasons, Ae. albopictus larvae were found in the highest number of containers (745 containers), followed by containers with Ae. aegypti larvae (283 containers) and containers with Culex larvae (254 containers). During the wet season, there were higher numbers of positive houses, positive containers, and containers with only Ae. albopictus larvae than during the dry season. On the other hand, during the dry season when the water containers were very scarce, there were higher numbers of containers with Culex larvae, and containers held more than one type of mosquito larvae. This indicates that both temporal and spatial variations may contribute to the local coexistence of Aedes and Culex mosquito larvae species in Lansaka District areas in Thailand.

Spatial and temporal variations on the coexistence of Aedes and Culex larvae in Southern Thailand

This study investigated spatial and temporal variations on the coexistence of Aedes aegypti, Aedes albopictus, and Culex larvae in five subdistricts in Nakhon Si Thammarat, Thailand. We tested two main hypotheses on the spatial and temporal coexistence of mosquito larvae: (1) condition-specific competition and (2) spatial variation among the five subdistricts. We compared the number of positive houses, positive containers, mosquito coexistence during both the wet and dry seasons. The results showed that from a total of 1,072 positive containers collected in both seasons, Ae. albopictus larvae were found in the highest number of containers (745 containers), followed by containers with Ae. aegypti larvae (283 containers) and containers with Culex larvae (254 containers). During the wet season, there were higher numbers of positive houses, positive containers, and containers with only Ae. albopictus larvae than during the dry season. On the other hand, during the dry season when the water containers were very scarce, there were higher numbers of containers with Culex larvae, and containers held more than one type of mosquito larvae. This indicates that both temporal and spatial variations may contribute to the local coexistence of Aedes and Culex mosquito larvae species in Lansaka District areas in Thailand.(AU)

Seasons and water container types affecting Culex spp. in Southern Thailand

Usually, Culex mosquitoes are responsible for spreading several human diseases such as malaria, Japanese encephalitis, yellow fever, filariasis, and Zika. Lymphatic filariasis and Zika cases are increasing in Thailand with more prevalent in southern Thailand. In this study, our aim is to examine how seasons and water container types affect Culex spp. larvae numbers in Lansaka district, Nakhon Si Thammarat province, southern Thailand. This study was conducted in five sub-districts (Lansaka, Khaokaew, Thadi, Kamlon, and Khunthale) in Lansaka district. In each subdistrict, 120 houses were randomly selected to study the breeding sites of Culex mosquito in dry (March-May, 2018) and wet (October-December, 2018) seasons. Mosquito larvae were collected from indoor, outdoor, natural, artificial, darkcoloured, light-coloured, with lid, and without lid containers. It was observed that in all sub-districts, Culex larvae numbers were higher in dry season compared to wet season. In both seasons, outdoor, without lid, dark-coloured, and artificial containers contained more Culex larvae than inside, with lid, light-coloured, and natural containers, respectively. This study shows that seasons and water container types affect Culex mosquito larvae. Since the larvae numbers are higher in dry season, as well as in outdoor, without lid, dark-coloured, and artificial containers, people should reduce the usage of these containers, especially in the dry season, to prevent Culex borne diseases.

Seasons and water container types affecting Culex spp. in Southern Thailand

Usually, Culex mosquitoes are responsible for spreading several human diseases such as malaria, Japanese encephalitis, yellow fever, filariasis, and Zika. Lymphatic filariasis and Zika cases are increasing in Thailand with more prevalent in southern Thailand. In this study, our aim is to examine how seasons and water container types affect Culex spp. larvae numbers in Lansaka district, Nakhon Si Thammarat province, southern Thailand. This study was conducted in five sub-districts (Lansaka, Khaokaew, Thadi, Kamlon, and Khunthale) in Lansaka district. In each subdistrict, 120 houses were randomly selected to study the breeding sites of Culex mosquito in dry (March-May, 2018) and wet (October-December, 2018) seasons. Mosquito larvae were collected from indoor, outdoor, natural, artificial, darkcoloured, light-coloured, with lid, and without lid containers. It was observed that in all sub-districts, Culex larvae numbers were higher in dry season compared to wet season. In both seasons, outdoor, without lid, dark-coloured, and artificial containers contained more Culex larvae than inside, with lid, light-coloured, and natural containers, respectively. This study shows that seasons and water container types affect Culex mosquito larvae. Since the larvae numbers are higher in dry season, as well as in outdoor, without lid, dark-coloured, and artificial containers, people should reduce the usage of these containers, especially in the dry season, to prevent Culex borne diseases.(AU)

A rural-urban latitudinal study of the distributions of Culex quinquefasciatus and Culex pipiens bioforms in their southernmost sympatric fringe.

Mosquitoes grouped in the complex Culex pipiens L. (Diptera: Culicidae) are important vectors of medical and veterinary diseases. In the South American sympatric region, Cx. pipiens and Culex quinquefasciatus Say coexist and potentially hybridize. To identify key drivers of their geographical distribution, mosquito immatures were collected from flower vases of eight urban/rural cemetery pairs within a 5° latitudinal transect along Buenos Aires Province, Argentina. The specimens were identified by molecular methods and their relative proportion modelled as a function of environmental variables. At the beginning of the warm season, northern and southern cemeteries presented exclusively Cx. quinquefasciatus and Cx. pipiens, respectively, with different proportions of both at mid latitudes. By the end of the summer, Cx. quinquefasciatus was present throughout the study area, exclusively in 11 of the 16 cemeteries both rural and urban, whereas Cx. pipiens was predominant only in the southernmost pair. Mean annual temperature, photoperiod variability and time of the season were key drivers of their distributions. All specimens of Cx. pipiens were identified as form molestus and no hybrids were recognized. The reported distribution patterns and the potential absence of Cx. pipiens f. pipiens and hybrids are discussed, along with their implications in disease transmission.

Transmission potential of African, Asian and American Zika virus strains by Aedes aegypti and Culex quinquefasciatus from Guadeloupe (French West Indies).

Zika virus (ZIKV) is an arbovirus that has dramatically spread in South America and the Caribbean regions since 2015. The majority of vector incrimination studies available for ZIKV showed that Aedes aegypti mosquitoes are important vectors for this virus. However, several reports suggest that Culex quinquefasciatus mosquitoes may be implicated in ZIKV transmission in certain urban settings. In the present study, we evaluated the vector competence for ZIKV of Cx. quinquefasciatus and Ae. aegypti mosquitoes from Guadeloupe using African, American and Asian strains. The results demonstrated that Cx. quinquefasciatus is refractory to ZIKV infection whatever the strain tested at 7, 14 or 21 days post-infection (dpi), while ZIKV transmission was recorded in Ae. aegypti for all the three strains. The African ZIKV strain was better transmitted by Ae. aegypti (∼ 50% mean transmission efficiency) and with a shorter incubation period (7 dpi) when compared to the Asian and American strains (<14% transmission efficiency; incubation period of 14-21 dpi). Taken together, these results suggest that only Ae. aegypti mosquitoes are involved in urban ZIKV transmission in Guadeloupe and highlight a higher infectiousness of the African ZIKV strain in this mosquito species when compared to the Asian and American ones.

The vector ecology of introduced Culex quinquefasciatus populations, and implications for future risk of West Nile virus emergence in the Galápagos archipelago.

Culex quinquefasciatus Say (Diptera: Culicidae), an important vector of West Nile virus (WNV) in the U.S.A., was first detected on the Galápagos Islands (Ecuador) in the 1980s. However, little is known of its ecology, distribution or capacity for arbovirus transmission in the Galápagos. We characterize details of lifecycle (including gonotrophic period), temporal abundance, spatial distribution, vector competence and host-feeding behaviour. Culex quinquefasciatus was detected on five islands of the Galápagos during 2006-2011. A period of 7-14 days was required for egg-adult emergence; water salinity above 5 ppt was demonstrated to hinder larval development. Blood-meal analysis indicated feeding on reptiles, birds and mammals. Assessment of WNV vector competency of Galápagos C. quinquefasciatus showed a median infectious dose of 7.41 log10 plaque-forming units per millilitre and evidence of vertical transmission (minimal filial infection rate of 3.7 per 1000 progeny). The distribution of C. quinquefasciatus across the archipelago could be limited by salt intolerance, and its abundance constrained by high temperatures. Feeding behaviour indicates potential to act as a bridge vector for transmission of pathogens across multiple taxa. Vertical transmission is a potential persistence mechanism for WNV on Galápagos. Together, our results can be used for epidemiological assessments of WNV and target vector control, should this pathogen reach the Galápagos Islands.

Development of an urban molecular xenomonitoring system for lymphatic filariasis in the Recife Metropolitan Region, Brazil.

INTRODUCTION: Molecular xenomonitoring (MX)-pathogen detection in the mosquito rather than human-is a promising tool for lymphatic filariasis (LF) surveillance. In the Recife Metropolitan Region (RMR), the last LF focus in Brazil, Culex quinquefasciatus mosquitoes have been implicated in transmitting Wuchereria bancrofti parasites. This paper presents findings on the ideal mosquito collection method, mosquito dispersion, W. bancrofti infection in mosquitoes and W. bancrofti antigen in humans to aid MX development. METHODS: Experiments occurred within two densely populated urban areas of Olinda, RMR, in July and August 2015. U.S. Centers for Disease Control and Prevention (CDC) light traps were compared to battery-powered aspirators as collection methods, and mosquito dispersion was measured by mosquito mark release recapture (MMRR). Female Cx. quinquefasciatus were tested by PCR for W. bancrofti infection, and study area residents were screened by rapid tests for W. bancrofti antigen. RESULTS: Aspirators caught 2.6 times more total Cx. quinquefasciatus, including 38 times more blood-fed and 5 times more gravid stages, than CDC light traps. They also collected 123 times more Aedes aegypti. Of the 9,644 marked mosquitoes released, only ten (0.01%) were recaptured, nine of which were < 50m (34.8m median, 85.4m maximum) from the release point. Of 9,169 unmarked mosquitoes captured in the MMR, 38.3% were unfed, 48.8% blood-fed, 5.5% semi-gravid, and 7.3% gravid. PCR on 182 pools (1,556 mosquitoes) found no evidence of W. bancrofti infection in Cx. quinquefasciatus. Rapid tests on 110 of 111 eligible residents were all negative for W. bancrofti antigen. CONCLUSIONS: Aspirators were more effective than CDC light traps at capturing Ae. aegypti and all but unfed stages of Cx. quinquefasciatus. Female Cx. quinquefasciatus traveled short (< 86m) distances in this urban area. Lack of evidence for W. bancrofti infection in mosquitoes and antigen in humans in these fine-scale studies does not indicate that LF transmission has ceased in the RMR. A MX surveillance system should consider vector-specific collection methods, mosquito dispersion, and spatial scale but also local context, environmental factors such as sanitation, and host factors such as infection prevalence and treatment history.

Complex Effects of Superior Competitors and Resources on Culex restuans (Diptera: Culicidae) Oviposition.

A growing body of literature on mosquito oviposition behavior supports the hypothesis that females place eggs in habitats that provide best available opportunity for growth, development, and maturation of their offspring. We conducted a field experiment to evaluate Culex oviposition behavior in response to the interspecific competitor Aedes triseriatus (Say) (Diptera: Culicidae) larvae, and resources in the form of quantity of plant detritus, and dissolved nitrogen (TN) and phosphorus (TP) derived from that detritus. We tested a set of specific predictions: 1) As a poorer competitor, Culex will avoid ovipositing in containers with superior interspecific competitors; 2) Culex choose oviposition habitats that contain greater amount of resources for the microbial food of their offspring; 3) Sufficiently high resource abundance can override avoidance of oviposition in containers with interspecific competitors. Culex restuans Theobald (Diptera: Culicidae) was the only species ovipositing, and the oviposition responses changed over time. The effect of resources was more important in driving oviposition decisions at the beginning and end of the experiment. The amount of resources, as manifest by TN and TP concentrations, had differential effects on oviposition. At the beginning females laid more eggs in containers with low detritus, which had the highest TN. After that, females preferred those containers with high detritus, which had low TN and high TP. The effect of competitors was important only during the middle of the experiment. Paradoxically, even as a poorer competitor Cx. restuans preferentially oviposited in containers with late-instar Ae. triseriatus, suggesting that the presence of successful heterospecifics indicates a good quality larval habitat.

[Laboratory susceptibility tests of Aedes aegypti and Culex quinquefasciatus larvae to the entomopathogenic nematode Heterorhabditis bacteriophora].

INTRODUCTION: Aedes aegypti is the vector of dengue, yellow fever, Zika and Chikungunya viruses, and Culex quinquefasciatus is the vector of St. Louis and West Nile encephalitis viruses. OBJECTIVE: To evaluate infectivity of Heterorhabditis bacteriophora N4 in C. quinquefasciatus and A. aegypti larvae under laboratory conditions. MATERIALS AND METHODS: Thirty second-instar larvae of the two mosquito species were exposed each to different doses (0:1, 1:1, 5:1, 15:1, 100:1, 500:1, 750:1 and 1,500:1) of nematode infective juveniles. Four replications per dose were performed. RESULTS: Parasitism varied between 2.5 and 80 % in C. quinquefasciatus, and between 4.2 and 92.5 % in A. aegypti, with significant differences between doses (p<0.0001). DL50 were: 160.8 infective juveniles per larva for C. quinquefasciatus and 113.6 infective juveniles per larva for A. aegypti. In C. quinquefasciatus, 4 to 6 % of the infective juveniles developed to adults and in A. aegypti, 12- 61 %. In A. aegypti the emergence of new infective juveniles occurred with 100:1, 500:1, 750:1 and 1,500:1 infective juveniles per larva, and in C. quinquefasciatus, with 1,500:1 infective juveniles per larva. Melanization of infective juveniles was observed in both mosquito species. CONCLUSION: The susceptibility of these mosquito species to parasitism of an indigenous isolate of H. bacteriophora in the laboratory was demonstrated. Heterorhabditis bacteriophora N4 could be an efficient biological control agent.

Essential oils and their components as an alternative in the control of mosquito vectors of disease.

More than half of the human population is exposed to mosquito-borne infections. Climate change and the emergence of strains resistant to traditionally used insecticides have motivated the search of new agents for mosquito population control. Essential oils have been effective repellents and larvicidal agents.The aim of this work was to review research studies conducted in recent years on the larvicidal activity of essential oils and their components against Aedes, Anopheles and Culex mosquitoes, as well as the latest reports about their possible mechanism of action.

Ensayos de sensibilidad de larvas de Aedes aegypti y Culex quinquefasciatus frente al nematodo Heterorhabditis bacteriophora en condiciones de laboratorio / Laboratory susceptibility tests of Aedes aegypti and Culex quinquefasciatus larvae to the entomopathogenic nematode Heterorhabditis bacteriophora

Resumen Introducción. Aedes aegypti es el vector de los virus del dengue, la fiebre amarilla, el Zika y el chikungunya, y Culex quinquefasciatus, de los virus de la encefalitis de Saint Louis y de la del Oeste del Nilo. Objetivo. Evaluar la capacidad infecciosa de Heterorhabditis bacteriophora N4 en larvas de C. quinquefasciatus y A. aegypti en el laboratorio. Materiales y métodos. Treinta larvas de segundo estadio de cada especie de mosquito se expusieron a diferentes dosis (0:1, 1:1, 5:1, 15:1, 100:1, 500:1, 750:1 y 1.500:1) de ejemplares juveniles infectivos del nematodo. Se hicieron cuatro réplicas por dosis. Resultados. El parasitismo varió entre 2,5 y 80 % en C. quinquefasciatus y entre 4,2 y 92,5 % en A. aegypti, con diferencias significativas entre las dosis (p<0,0001). Las DL50 fueron de 160,8 ejemplares juveniles infectivos por larva de C. quinquefasciatus y 113,6 por larva de A. aegypti; 4 a 6 % de los ejemplares juveniles infectivos llegaron a la fase adulta en C. quinquefasciatus, y 12 a 61 % en A. aegypti. Nuevos ejemplares juveniles infectivos aparecieron a partir de la dosis de 100:1. En A. aegypti aparecieron solo con dosis superiores a esta y, en C. quinquefasciatus, con una dosis de 1500:1. Se observó melanización de los ejemplares juveniles infectivos en las dos especies de mosquitos. Conclusión. Se estableció la sensibilidad de estas especies de mosquitos al parasitismo producido por un aislamiento autóctono de H. bacteriophora en condiciones de laboratorio y su potencial efecto como agente de control biológico.

Abstract Introduction: Aedes aegypti is the vector of dengue, yellow fever, Zika and Chikungunya viruses, and Culex quinquefasciatus is the vector of St. Louis and West Nile encephalitis viruses. Objective: To evaluate infectivity of Heterorhabditis bacteriophora N4 in C. quinquefasciatus and A. aegypti larvae under laboratory conditions. Materials and methods: Thirty second-instar larvae of the two mosquito species were exposed each to different doses (0:1, 1:1, 5:1, 15:1, 100:1, 500:1, 750:1 and 1,500:1) of nematode infective juveniles. Four replications per dose were performed. Results: Parasitism varied between 2.5 and 80 % in C. quinquefasciatus, and between 4.2 and 92.5 % in A. aegypti, with significant differences between doses (p<0.0001). DL50 were: 160.8 infective juveniles per larva for C. quinquefasciatus and 113.6 infective juveniles per larva for A. aegypti. In C. quinquefasciatus, 4 to 6 % of the infective juveniles developed to adults and in A. aegypti, 12- 61 %. In A. aegypti the emergence of new infective juveniles occurred with 100:1, 500:1, 750:1 and 1,500:1 infective juveniles per larva, and in C. quinquefasciatus, with 1,500:1 infective juveniles per larva. Melanization of infective juveniles was observed in both mosquito species. Conclusion: The susceptibility of these mosquito species to parasitism of an indigenous isolate of H. bacteriophora in the laboratory was demonstrated. Heterorhabditis bacteriophora N4 could be an efficient biological control agent.