Biological control is one of the methods available for control of Aedes aegypti populations. We used experimental microcosms to evaluate the effects of actual predation and predation risk by dragonfly larvae (Odonata) on larval development, adult longevity, and adult size of Ae. aegypti. We used six treatments: control, removal, variable density cues (Cues VD), fixed density cues (Cues FD), variable density predator (Predator VD), and fixed density predator (Predator FD) (n = 5 each). Predator treatments received one dragonfly larva. Cue treatments were composed of crushed Ae. aegypti larvae released into the microcosm. For the FD treatments, we maintained a larval density of 200 individuals. The average mortality of Ae. aegypti larvae in the Predator VD treatment was used as the standard mortality for the other treatments. Mosquitoes from the Predator VD and Cues VD treatments developed faster, and adults were larger and had greater longevity compared to all other treatments, likely due to the higher food availability from larval density reduction. High larval density negatively affected larval developmental time, adult size, and longevity. Males were less sensitive to density-dependent effects. Results from this study suggest that the presence of predators may lead to the emergence of adult mosquitoes with greater fitness, causing an overall positive effect on Ae. aegypti population growth rates.
Justificativa e Objetivos: Artrópodes são de longe os animais mais comuns na Terra em indivíduos totais e táxons descritos. No Brasil, a importância dos acidentes por animais peçonhentos, nos quais se incluem acidentes por artrópodes peçonhentos, pode ser expressa pelos mais de 100 mil casos e cerca de 200 óbitos registrados ao ano. Os serviços públicos de saúde têm aumentado as notificações deste tipo de acidente nos estados da região sul do Brasil, principalmente os ocorridos na zona rural. Este acréscimo decorre das modificações do ambiente natural pelo desmatamento e pelos diferentes usos do solo pelo homem. O objetivo deste estudo foi descrever a ocorrência de acidentes com artrópodes peçonhentos e o perfil social dos acidentes associados no município de São Miguel do Oeste, no período de 2007 a 2016. Métodos: Trata-se de um transversal e retrospectivo, com dados obtidos nas fichas de notificação e investigação individual do Sistema de Informação de Agravos de Notificação (Sinan). Resultados: A predominância dos acidentes envolveu pessoas do sexo masculino para lonomismo e outras lagartas venenosas e do sexo feminino para loxoscelismo, ocorreram mais frequentemente no ambiente urbano e envolveram a faixa etária entre 20 a 59 anos, afetando a população economicamente ativa. Conclusões: O estudo contribui para a compreensão dos determinantes para a ocorrência de animais peçonhentos em uma região de fronteira e fornece embasamento para as políticas públicas de promoção da saúde e de prevenção de agravos. PALAVRAS-CHAVE: Animais venenosos. Promoção de saúde. Saúde pública.
The mosquito Aedes aegypti L. (Diptera: Culicidae) is a vector of arboviral diseases such as dengue fever. Currently, the main approach to mosquito control is the application of synthetic insecticides, which can lead to negative environmental impacts and insecticide resistance in mosquito populations. As such, there has been increased interest in developing alternative methods for control of vector populations such as utilizing plant compounds that act as larvicides. The aim of this work is to evaluate the effectiveness of Eucalyptus sp. (Myrtaceae) essential oils for control of Ae. aegypti larvae. The essential oils of seven Eucalyptus species and hybrids were extracted by hydrodistillation and analyzed by gas chromatography coupled to mass spectrometry. The essential oils were further diluted in water with acetone (0.40%) at the following concentrations: 100, 50, 25, and 10 lg ml À1 . Mortality trials were conducted in plastic containers with a solution of ultrapure water and 200 ll of diluted oil for a total volume of 50 ml per treatment. The experiments for each Eucalyptus species/hybrid and concentration were performed in triplicate, using a control containing only water and acetone. Twenty larvae were added to each container and mortality was recorded at 1, 2, 4, and 24 h. The Eucalyptus essential oils showed larvicidal activity in most of the evaluated concentrations, mainly at 50 and 100 lg ml À1 . Eucalyptus benthamii Maiden & Cambage and the hybrid Urograndis displayed the highest larvicidal potential (100% at 24 h) in the 100 lg ml À1 treatment. Larval mortality of Ae. aegypti showed a positive correlation with the compounds c-, o-cymol, o-cymene, terpineol, 3-dodecylfuran-2,5-dione, a-pinene, globulol, and ledol. The most abundant compounds identified in the essential oils were 1,8-cineole and a-pinene. These results highlight the potential of using Eucalyptus essential oils for the isolation of natural larvicidal products.
The establishment of an invasive species depends on reproductive success and dispersion capability in the new environment. One of the striking examples of invasion in urban environments is the mosquito Aedes aegypti Linnaeus, 1762 (Culicidae). The success of this species is primarily attributed to its ability to colonize urban environments, and some of the important adaptive strategies associated with this ability is the preference for humans as a blood source and intense occupation of residential (indoor) environments. This study evaluated the effects of location (indoor vs. outdoor) and water nutrient level (% organic matter) on the oviposition preference of A. aegypti in an urban environment. We used oviposition choice experiments to evaluate mosquito oviposition in containers holding 1:1 vs 1:0 ratios of water: organic matter placed indoors and outdoors. Eggs were sampled once per week for nine weeks. Our results revealed a strong oviposition preference for outdoor containers, with a significant preference for containers with higher concentrations of organic matter during the fifth to ninth weeks. However, mosquitoes occupying indoor environments did not prefer to lay eggs in containers with lower levels of organic matter. A better understanding of the preferences of A. aegypti regarding the nutrient level and location of oviposition containers can increase our understanding of the behavioral factors allowing mosquitoes to utilize anthropogenic environments.
O objetivo deste trabalho foi avaliar o efeito do uso de larvas predadoras da ordem Odonata (família Libellulidae) associado ao BTI na redução larval de mosquitos. Foi testada a hipótese de que na presença de larvas de predadores haveria aumento na mortalidade de larvas de A. aegypti causada pelo efeito sinergético do BTI juntamente com o predador. Larvas de A. aegypti e libélulas (Odonata: Libellulidae) foram oriundas de colônia laboratorial e coletas em campo, respectivamente. Os microcosmos contituiam-se de recipientes com capacidade para 300mL contendo 100mL de água com densidades de 100, 200, e 300 larvas de A. aegypti e uma larva do predador. Os tratamentos, BTI e BTI + Predador receberam 0,01ppm de BTI. O controle recebeu apenas as larvas de A. aegypti. Os resultados mostraram um efeito significativo do tratamento BTI + Predador apenas na menor densidade, elucidando o aparecimento de um efeito sinergético. Para as densidades de 200 e 300 larvas este efeito não foi observado. O aumento da densidade larval aumentou a taxa de predação, enquanto o efeito do BTI sobre a mortalidade diminuiu. Nossos resultados mostram que o efeito sinergético existe, mas que fatores dependentes da densidade podem ocultar tal efeito.
Aedes aegypti has overcome all kinds of mosquito control attempts over the last century. Strategies for population control resorts to the use of synthetic insecticides, which can lead to problems like human intoxication and environmental contamination. The effects of Bacillus thuringiensis var. israelensis (Bti), Ilex paraguariensis (yerba mate), and Ilex theezans (caúna herb) extracts against A. aegypti larvae were evaluated. The bioassays were conducted under controlled laboratory conditions of temperature (27 ± 3°C) and photoperiod (12 h). Hydroalcoholic extract of the leaves of I. theezans displayed better residual effect compared to the aqueous extract of I. paraguariensis fruits. The strongest residual effect of I. theezans was probably due to the presence of certain chemicals in its leaves, such as coumarins, hemolytic saponins, and cyanogenic glucosides, which were absent in I. paraguariensis. The results herein contributed to the prospection of natural insecticides and opened the possibility for subsequent studies on the use of plant extracts in field situations in a short-time scale.
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