Effect of the type and number of washes in the efficacy of long lasting insecticidal nets for Aedes aegypti control in Girardot, Colombia.

INTRODUCTION: The use of long lasting insecticidal materials has shown promising results in the control of Aedes aegypti. OBJECTIVE: To evaluate the efficacy of long-lasting insecticidal nets (PermaNet®) for Aedes aegypti control after three washing treatments in the city of Girardot, Colombia. MATERIALS AND METHODS: Standard bioassays were conducted with the nets following the World Health Organization protocols using wild A. aegypti after three washing treatments: (1) Detergent powder, (2) detergent powder and bleach, and (3) bar soap, until completing 20 washes. RESULTS: The type and number of wash treatments had a significant effect on net efficacy. Greater effects in the insecticide bioavailability were seen for the bar soap treatment. After six washes, mortality decreased by 50% (25/50), vs 66% (33/50) for the detergent powder and 84% (42/50) for the detergent powder and bleach treatments. Regarding the number of washes, the bar soap treatment reduced the efficacy to 68% after only three washes. CONCLUSION: The effectiveness of long-lasting insecticidal nets (PermaNet 2.0) for A. aegypti control varied in relation to the treatment and number of washes. The bar soap treatment resulted in the greatest reduction of mortality. Further studies on insecticidal reductions are needed under local conditions.

Efecto del tipo y del número de lavados en la eficacia de mosquiteros tratados con deltametrina de larga duración para el control de Aedes aegypti en Girardot, Colombia / Effect of the type and number of washes in the efficacy of long lasting insecticidal nets for Aedes aegypti control in Girardot, Colombia

Resumen Introducción. El uso de mosquiteros tratados con insecticida en fórmulas de larga duración ha demostrado resultados prometedores en el control de Aedes aegypti. Objetivo. Evaluar la eficacia de mosquiteros impregnados con deltametrina en una fórmula de larga duración para el control de A. aegypti en Girardot, Colombia, después de tres lavados. Materiales y métodos. Se hicieron bioensayos de eficacia de los mosquiteros contra A. aegypti silvestres después de utilizar los siguientes tres productos de lavado, siguiendo la metodología de la Organización Mundial de la Salud: detergente en polvo, detergente en polvo y blanqueador, y jabón de barra, todos utilizados hasta en 20 lavados. Resultados. El tipo de producto de lavado y el número de lavados afectaron significativamente la eficacia de los mosquiteros impregnados con deltametrina. El lavado con jabón de barra presentó el mayor efecto, pues en tan solo seis lavados la mortalidad bajó a 50 % (25/50), en contraste con 66 % (33/50 de mortalidad después del lavado con detergente en polvo y de 84 % (42/50) después del lavado con detergente y blanqueador. En cuanto al número de lavados, el jabón en barra también causó una mayor reducción de la eficacia: a 68 % con solo tres lavados. Conclusión. La eficacia de los mosquiteros impregnados con deltametrina de larga duración en el control de A. aegypti varió con el tipo de producto de lavado y el número de lavados, siendo el jabón en barra el que redujo su eficacia en mayor medida. Se requieren nuevos estudios para establecer la disminución en la concentración del insecticida entre lavados.

Abstract Introduction: The use of long lasting insecticidal materials has shown promising results in the control of Aedes aegypti. Objective: To evaluate the efficacy of long-lasting insecticidal nets (PermaNet®) for Aedes aegypti control after three washing treatments in the city of Girardot, Colombia. Materials and methods: Standard bioassays were conducted with the nets following the World Health Organization protocols using wild A. aegypti after three washing treatments: (1) Detergent powder, (2)detergent powder and bleach, and (3) bar soap, until completing 20 washes. Results: The type and number of wash treatments had a significant effect on net efficacy. Greater effects in the insecticide bioavailability were seen for the bar soap treatment. After six washes, mortality decreased by 50% (25/50), vs 66% (33/50) for the detergent powder and 84% (42/50) for the detergent powder and bleach treatments. Regarding the number of washes, the bar soap treatment reduced the efficacy to 68% after only three washes. Conclusion: The effectiveness of long-lasting insecticidal nets (PermaNet 2.0) for A. aegypti control varied in relation to the treatment and number of washes. The bar soap treatment resulted in the greatest reduction of mortality. Further studies on insecticidal reductions are needed under local conditions.

[Estimation of Aedes aegypti (L.) (Diptera: Culicidae) productivity in households and public spaces in a dengue endemic city in Colombia]. / Productividad de Aedes aegypti (L.) (Diptera: Culicidae) en viviendas y espacios públicos en una ciudad end éndemica para dengue en Colombia.

INTRODUCTION: Aedes aegypti is a vector for the dengue virus in Colombia. Its productivity can be estimated using pupal counts. OBJECTIVE: To determine Ae. aegypti productivity in households and public spaces in Girardot (Colombia) during both wet and dry seasons. MATERIALS AND METHODS: The amount of Ae. aegypti pupae was evaluated in 20 randomly selected clusters in Girardot, each consisting of 100 households and public spaces. Inspections were performed during the rainy (February-May, 2011), and dry (August-September, 2011) seasons. House, container, Breteau, person and hectare pupae indices were estimated. RESULTS: During the rainy season households contributed 94% to the total number of pupae (n=7,098) while only 6% (n=482) were found in public spaces. In the dry season, 98% (n=9,138) of pupae were found in households and 2% (n=223), in public spaces. Low water-storage tanks and tanks for washing purposes provided >87% of pupae in households, whereas jars, tires and sinks contained most pupae in public spaces. High pupal densities were observed in public spaces during the rainy season and in streets and schools in the dry season. There were no significant differences in the index per person (rainy season=1.0; dry season=1.3) or per hectare (rainy season=0.96, dry season=0.45) between seasons. CONCLUSIONS: High Ae. aegypti pupal densities were found inside households in low water-storage tanks and tanks for washing purposes during both the dry and rainy seasons. Public spaces provided more aquatic habitats during the rainy season. Vector control strategies targeting these containers could allow a more rational use of resources and increase efficiency.

Productividad de Aedes aegypti (L.) (Diptera: Culicidae) en viviendas y espacios públicos en una ciudad end éndemica para dengue en Colombia / Estimation of Aedes aegypti (L.) (Diptera: Culicidae) productivity in households and public spaces in a dengue endemic city in Colombia

Introducción. Aedes aegypti es el vector del dengue en Colombia y su presencia se puede estimar mediante el conteo de pupas. Objetivo. Determinar la productividad de Ae. aegypti en viviendas y espacios públicos de Girardot (Colombia), en época de lluvias y de sequía. Materiales y métodos. Se evaluó la productividad de pupas de Ae. aegypti en 20 conglomerados seleccionados aleatoriamente en Girardot, cada uno compuesto de 100 viviendas y sus espacios públicos. Se hizo una inspección en época de lluvias (febrero a mayo de 2011) y, otra, en época de sequía (agosto a septiembre de 2011). Se estimaron los índices de pupas en viviendas y en recipientes, así como el índice de Breteau, y los índices por persona y por hectárea. Resultados. En época de lluvias, las viviendas aportaron el 94 % de las pupas (n=7.098) y, los espacios públicos, el 6 % (n=482), y en época de sequía, el 98 % (n=9.138) y el 2 % (n=223), respectivamente. Las albercas y tanques bajos (>20 litros) aportaron más del 87 % de las pupas en viviendas; los tarros, llantas y sumideros en espacios públicos fueron más productivos (=20 litros). No se encontraron diferencias significativas en el índice de pupas por persona (lluvias=1,0; sequía=1,3), ni por hectárea (lluvias=0,96, sequía=0,45) (p>0,05). Los espacios públicos con más pupas en época de lluvias, fueron las zonas verdes y los lotes abandonados, y en época de sequía, los colegios y las calles. Conclusiones. La productividad de pupas de Ae. aegypti en las albercas y tanques bajos de las viviendas fue elevada tanto en la época de sequía como en la de lluvias, en tanto que los espacios públicos contribuyeron con más sitios de cría durante la época de lluvias. Las estrategias de control vectorial focalizadas en las pupas, permitirían un uso más racional y eficaz de los recursos.

Introduction: Aedes aegypti is a vector for the dengue virus in Colombia. Its productivity can be estimated using pupal counts. Objective: To determine Ae. aegypti productivity in households and public spaces in Girardot (Colombia) during both wet and dry seasons. Materials and methods: The amount of Ae. aegypti pupae was evaluated in 20 randomly selected clusters in Girardot, each consisting of 100 households and public spaces. Inspections were performed during the rainy (February-May, 2011), and dry (August-September, 2011) seasons. House, container, Breteau, person and hectare pupae indices were estimated. Results: During the rainy season households contributed 94% to the total number of pupae (n=7,098) while only 6% (n=482) were found in public spaces. In the dry season, 98% (n=9,138) of pupae were found in households and 2% (n=223), in public spaces. Low water-storage tanks and tanks for washing purposes provided >87% of pupae in households, whereas jars, tires and sinks contained most pupae in public spaces. High pupal densities were observed in public spaces during the rainy season and in streets and schools in the dry season. There were no significant differences in the index per person (rainy season=1.0; dry season=1.3) or per hectare (rainy season=0.96, dry season=0.45) between seasons. Conclusions: High Ae. aegypti pupal densities were found inside households in low water-storage tanks and tanks for washing purposes during both the dry and rainy seasons. Public spaces provided more aquatic habitats during the rainy season. Vector control strategies targeting these containers could allow a more rational use of resources and increase efficiency.

Effectiveness and feasibility of long-lasting insecticide-treated curtains and water container covers for dengue vector control in Colombia: a cluster randomised trial.

BACKGROUND: Long-lasting insecticide-treated net (LLIN) window and door curtains alone or in combination with LLIN water container covers were analysed regarding effectiveness in reducing dengue vector density, and feasibility of the intervention. METHODS: A cluster randomised trial was conducted in an urban area of Colombia comparing 10 randomly selected control and 10 intervention clusters. In control clusters, routine vector control activities were performed. The intervention delivered first, LLIN curtains (from July to August 2013) and secondly, water container covers (from October to March 2014). Cross-sectional entomological surveys were carried out at baseline (February 2013 to June 2013), 9 weeks after the first intervention (August to October 2013), and 4-6 weeks after the second intervention (March to April 2014). RESULTS: Curtains were installed in 922 households and water container covers in 303 households. The Breteau index (BI) fell from 14 to 6 in the intervention group and from 8 to 5 in the control group. The additional intervention with LLIN covers for water containers showed a significant reduction in pupae per person index (PPI) (p=0.01). In the intervention group, the PPI index showed a clear decline of 71% compared with 25% in the control group. Costs were high but options for cost savings were identified. CONCLUSIONS: Short term impact evaluation indicates that the intervention package can reduce dengue vector density but sustained effect will depend on multiple factors.