Study of oviposition behavior of aedes aegypti in two neighborhoods under the influence of semi-arid climate in the municipality of salinas, state of Minas Gerais, Brazil

The mosquito Aedes aegypti (Diptera: Culicidae) is the main vector of human arborvirus in Brazil.Oviposition behavior is important for the survival and dispersal of A. aegypti. The objective of this studywas to evaluate the oviposition behavior and its relationship to meteorological factors. Twenty ovitrapswere installed in two neighborhoods in the urban area of the city of Salinas, MG, southeastern Brazil.The traps were inspected weekly for the presence of eggs in the water and on the paddle. Simultaneously,regional weather data were analyzed. The results showed the Ovitrap Positivity Index (OPI) variedgreatly, from 0 to 90 percent, between the weeks and boroughs sampled, demonstrating the vector’s greatpopulation fluctuation. Among the analyzed climatic factors, rainfall strongly influenced oviposition,followed by relative air humidity. The number of eggs found on the paddle was significantly higher thanin the water (p<0.05). However, a significant increase of eggs in the water was noticed when the relativehumidity dropped below 40 percent. This seems to be an important behavior to maintain the population inperiods of drought. Through the low number of eggs (<30) found in 56 percent of positive traps, we concludedthat skip-oviposition behavior occurred, contributing to the prevalence of mosquitoes during thesampled period. It is concluded that the occurrence of water oviposition may be higher than described inthe literature, and should be studied due to its evolutionary and epidemiological importance...

O mosquito Aedes aegypti é o principal vetor de arborvírus humanos no Brasil. O comportamentode oviposição é importante para a sobrevivência e dispersão do A. aegypti. O objetivo deste trabalho foi avaliar estes comportamentos e sua relação com fatores climáticos. Instalaram-se vintearmadilhas ovitrampa em dois bairros de Salinas-MG. Todas foram inspecionadas semanalmentepara contagem e identificação dos ovos presentes na água e na palheta. Paralelamente, analisaram-sedados meteorológicos da região. Os resultados mostraram que o Índice de Positividade deOvitrampa (IPO) variou muito (0 por cento a 90 por cento) entre as semanas/bairros amostrados, o que demonstraa grande flutuabilidade populacional do vetor. Dentre os fatores climáticos analisados, o que maisintensamente influenciou a oviposição foi a precipitação, seguida da umidade relativa. O númerode ovos encontrados na palheta foi significativamente maior que na água (p<0,05). Entretanto,observou-se aumento significativo de ovos na água quando a umidade relativa esteve abaixo de 40 por cento.Este parece ser um dado importante para a manutenção das populações em períodos de seca. O baixonúmero de ovos (<30) encontrados em 56 por cento das armadilhas positivas demonstrou a ocorrência docomportamento de skip-oviposition que pareceu contribuir para a prevalência do mosquito em todoo período amostrado. Concluiu-se que a ocorrência de oviposição na água pode ser maior do que odescrito na literatura e deve ser investigada em virtude de sua importância evolutiva e epidemiológica...

Estudio entomológico en un caso de dengue introducido en Camagüey / Entomological study of a case of dengue introduced into Camagüey

Los crecientes brotes de dengue complejiza la ya deteriorada situación epidemiológica mundial, lo cual se favorece por la presencia de macrofactores condicionantes para la transmisión. Objetivo: evaluar los resultados entomológicos durante el control de un caso de dengue introducido en Camagüey en julio de 2010. Métodos: se realizó un estudio descriptivo longitudinal retrospectivo, para referir las principales acciones entomológicas, así como su efectividad en el control del evento epidemiológico. Resultados: los valores de los índices aédicos estuvieron por encima de lo permisible en los tres primeros ciclos de trabajo, con altos valores del Indice Breteau en comparación con el Indice Casa, por lo que hubo dispersión de la especie. El control de calidad municipal aportó las mayores colectas, con una proporción de una muestra larval/20,3 viviendas inspeccionadas y una muestra de adulto/426,5 viviendas inspeccionadas. Se destacan tanques bajos, cisternas y toneles con la mayor presencia del vector, siendo el 52,63 % permanentes, útiles y no modificables según criterio de la población. De haber ejecutado la población el autofocal familiar, se pudo evitar el 89,47 % de los depósitos positivos. Dos manzanas repitieron en dos ocasiones y otras dos tres veces. Conclusiones: las experiencias acumuladas en el tratamiento focal y adulticida, demostraron ser eficaces en el control antivectorial ante la notificación del caso dengue introducido, lo que junto al apoyo de la extrasectorialidad, resultó ser clave en el enfrentamiento exitoso del evento en el menor tiempo posible.

The growing outbreaks of dengue complicate the deteriorated epidemiologic worldwide situation, which is favored by the presence of determining macrofactors for transmission. Objective: to evaluate the entomological results during the control of a dengue’s case introduced into Camagüey in July 2010. Methods: a descriptive longitudinal retrospective study was performed, in order to refer the main entomological actions, as well as its effectiveness in the control of the epidemiologic event. Results: values of Aedes´index were beyond of what is permissible in the first three cycles of work, with high values of Breteau rate compared to House rate that is why there was species´ dispersion. The municipal quality control contributed to greater collections, with a proportion of a larval sample/20,3 inspected houses and adult's sample/426,5 inspected houses. Low tanks, cisterns and barrels with the vector stands out, being the 52,63 % permanent, useful and no modifiable according to the population's opinion. If the population were carried out family inspection, 89,47 % of positive water tanks could be avoided. Two blocks repeated in two occasions and another two or three times. Conclusions: gained experiences in the focal treatment, proved to be efficacious in the anti-vectorial control in the faced of the notification of a case of dengue introduced, which together with extrasectorial support, it turned out to be key in the successful confrontation of the event in the short possible time.