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      Factores ecológicos asociados con la presencia de larvas de Aedes aegypti en zonas de alta infestación del municipio Playa, Ciudad de La Habana, Cuba Translated title: Ecological factors linked to the presence of Aedes aegypti larvae in highly infested areas of Playa, a municipality belonging to Ciudad de La Habana, Cuba

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          Abstract

          OBJETIVOS: Identificar los factores ecológicos locales que pudieron incidir en la mayor infestación vectorial con Aedes aegypti observada en cuatro áreas de salud urbanas de Ciudad de La Habana, Cuba, así como los tipos de depósitos con mayor número de larvas. MÉTODOS: Estudio descriptivo en cuatro áreas de salud (Docente, 28 de Enero, 26 de Julio y 1.° de Enero) del municipio Playa, Ciudad de La Habana, Cuba, seleccionadas por la presencia reiterada del vector del dengue en el año 2003. Entre abril de 2004 y marzo de 2005 se inspeccionaron todos los locales de las manzanas seleccionadas. Se caracterizaron los depósitos existentes con agua (tipo, cantidad y ubicación) y los factores ecológicos observados (existencia de patio y de sombra, forma en que estaban tapados los tanques, presencia de materia orgánica en ellos e higiene de la vivienda). Se contaron las larvas y pupas de mosquitos de cada depósito mediante filtración. La identificación taxonómica de las pupas se realizó con microscopio estereoscópico. RESULTADOS: Los depósitos en que se encontraron larvas y pupas de A. aegypti con mayor frecuencia en todas las áreas fueron los tanques bajos y los pequeños depósitos artificiales. En tres de las áreas estudiadas la mayor cantidad de pupas se encontró en los tanques bajos (88,6%, 100% y 56,6%), de los cuales 90,9% se encontraban destapados o tapados solo parcialmente, mientras que en el área restante los pequeños depósitos artificiales fueron los más frecuentes (85,7%). Se encontró correlación entre el número de depósitos infestados en las viviendas con la presencia de patio (ji2 = 29,59; P = 0,0001), de sombra parcial (ji2 = 4,108; P = 0,0001), de vegetación (ji2 = 43,59; P = 0,0001) y de árboles (ji2 = 101,459; P = 0,0001), así como con la mala higiene (c² = 53,76; P = 0,0001). CONCLUSIÓN: Los depósitos artificiales, especialmente los tanques bajos y los recipientes pequeños, son las criaderos más frecuentes de A. aegypti, por lo que constituyen un factor de riesgo de infestación con ese vector. Los tanques destapados con materia orgánica y situados a la sombra y en el exterior fueron los más peligrosos en ese sentido.

          Translated abstract

          OBJECTIVES: To identify local ecological factors that might have had an impact on the higher infestation rates by the vector mosquito Aedes aegypti seen in four urban health districts of Ciudad de La Habana, Cuba, and to determine the type of containers with the highest number of larvae. METHODS: This is a descriptive study that was carried out in four health areas (Docente, 28 de Enero, 26 de Julio, and 1.º de Enero) within Playa, a municipality belonging to Ciudad de La Habana, Cuba. These areas were chosen because of the persistent presence of the dengue vector throughout 2003. All buildings on the selected blocks were inspected between April 2004 and March 2005, and note was taken of existing water deposits (type, number, and location) and of surrounding ecological factors (existence of a patio and shade, the way tanks were covered, the presence of organic matter inside them, and the overall cleanliness of the dwelling). Using filtration, the mosquito larvae and pupae in each deposit were counted. Pupae were typified as to their taxonomic species under a stereoscopic microscope. RESULTS: The types of deposits where larvae and pupae of A. aegypti were most often found in all areas were low tanks and small artificial containers. In three of the study areas the greatest numbers of pupae were found in low tanks (88.6%, 100%, and 56.6%), 90.9% of which were uncovered or only partially covered. On the other hand, in the fourth study area small artificial deposits were the most commonly infested (85.7%). A correlation was noted between the number of deposits in infested houses and the presence of a patio (chi2 = 29.59; P = 0.0001), partial shade (chi2 = 4.108; P = 0.0001), shrubbery (chi2 = 43.59; P = 0.0001) and trees (chi2 = 101.459; P = 0.0001), as well as poor hygiene (chi2 = 53.76; P = 0.0001). CONCLUSIONS: Artificial deposits, especially low tanks and small containers, are the most frequent breeding sites for A. aegypti and are therefore risk factors for infestation with this vector species. Uncovered tanks containing organic matter and located in the shade on the outside of homes were found to present the highest risk in this respect.

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          Most cited references 29

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          Pupal survey: an epidemiologically significant surveillance method for Aedes aegypti: an example using data from Trinidad.

          This report documents the results of a country-wide pupal survey of Aedes aegypti (L.) conducted in Trinidad. The survey was designed to identify the important Ae. aegypti-producing containers, importance being a function of a container's abundance and its productivity. Results are summarized on a country-wide basis and by county: urban versus rural comparisons are also made. Numerically, the most common water-filled containers positive for the larvae or pupae of Ae. aegypti (foci) were outdoor drums, water storage tanks and buckets, laundry tubs, discarded tires, and small miscellaneous containers such as drink bottles and cans. The island-wide average number of foci per hectare was 287 and ranged between 65 and 499. The average standing crop per container of Ae. aegypti pupae was 9.5 and ranged 12-fold, the most and least productive being the flower pot (> 30) and the small indoor vase ( 90% of all Ae. aegypti pupae: the remaining seven types were responsible for 80% of Ae. aegypti production in the country. In our survey, the traditional Stegomyia indices used to document the density of Ae. aegypti and predict the threat of dengue transmission, the House, Container, and Breteau indices, were seen to have virtually no correspondence with the actual number of pupae per hectare or per person. We conclude that pupal survey is more appropriate for assessing risk and directing control operations.
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            The Premise Condition Index: a tool for streamlining surveys of Aedes aegypti.

            Premise inspections and treatment of the larval habitats of container-breeding Aedes aegypti are extremely labor intensive. Since this means of control is the only one available in relation to dengue fever, this report presents an effective approach for streamlining premise surveys in north Queensland, Australia. From a survey of 877 premises in Townsville, Charters Towers, and Mingela/Ravenswood in 1990, occupier and premise variables were collected to examine any relationships with the presence of Ae. aegypti. Statistical modeling of these parameters using multiple and simple Poisson regression indicated that for both adjusted and unadjusted models respectively, the degree of shade and tidiness of the yard had strong correlations with both the proportion of positive premises and the numbers of infested containers therein. Condition of the house was also a significant variable in the unadjusted model. On this basis, the Premise Condition Index is proposed as a rapid assessment tool that can increase efficiency of detecting positive premises and containers by 270-370%. Although habitat selection by Aedes varies throughout the world, this approach could be used as a model for control of vectors of both dengue and yellow fever.
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              Evaluation of a sampling methodology for rapid assessment of Aedes aegypti infestation levels in Iquitos, Peru.

              An epidemic of dengue during 2001 in Northwestern Peru reemphasized the need for efficient, accurate, and economical vector surveillance. Between November 1998 and January 1999, we carried out extensive entomological surveys in two neighborhoods of approximately 600 contiguous houses located in the Amazonian city of Iquitos, providing a unique opportunity to evaluate the Aedes aegypti (L.) rapid assessment survey strategy. Based on Pan American Health Organization recommendations, this strategy is used by the Peruvian Ministry of Health (MOH). In our analysis all household locations, including closed and unoccupied houses, were georeferenced and displayed in a geographic information system, which facilitated simulations of MOH surveys based on hypothetical systematic sampling transects. Larval, pupal, and adult mosquito indices were calculated for each simulation (n = 10) and compared with the indices calculated from the complete data set (n = 4). The range of indices calculated from simulations was moderately high, but included actual indices. For example, simulation ranges for house indices (HI, percentage of infested houses from complete survey) were 38-56% (45%), 36-42% (38%), 21-34% (30%), and 13-33% (27%) in four surveys. HI, Breteau index, pupae per hectare, adult index, and adults per hectare were more robust entomological indicators (coefficient of variation [CV]/mean = 0.1-2.9) than the container index, pupae per person, pupae per house, adults per person, and adults per house (CV/mean >20). Our results demonstrate that the MOH's Ae. aegypti risk assessment program provides reasonable estimates of indices based on samples from every house. However, it is critical that future studies investigate the association of these indices with rates of virus transmission to determine whether sampling variability will negatively impact the application of indices in a public health context.
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                Author and article information

                Journal
                rpsp
                Revista Panamericana de Salud Pública
                Rev Panam Salud Publica
                Organización Panamericana de la Salud (Washington, Washington, United States )
                1020-4989
                1680-5348
                June 2006
                : 19
                : 6
                : 379-384
                Affiliations
                La Habana orgnameInstituto de Medicina Tropical Pedro Kourí orgdiv1Centro Colaborador OPS/OMS para el Estudio del Dengue y su Vector orgdiv2Departamento de Control de Vectores Cuba
                Matanzas orgnameCentro Provincial de Higiene y Epidemiología orgdiv1Departamento de Control de Vectores Cuba
                Article
                S1020-49892006000600003 S1020-4989(06)01900603
                10.1590/s1020-49892006000600003

                This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

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