The anti-immune dengue subgenomic flaviviral RNA is present in vesicles in mosquito saliva and is associated with increased infectivity.

Mosquito transmission of dengue viruses to humans starts with infection of skin resident cells at the biting site. There is great interest in identifying transmission-enhancing factors in mosquito saliva in order to counteract them. Here we report the discovery of high levels of the anti-immune subgenomic flaviviral RNA (sfRNA) in dengue virus 2-infected mosquito saliva. We established that sfRNA is present in saliva using three different methods: northern blot, RT-qPCR and RNA sequencing. We next show that salivary sfRNA is protected in detergent-sensitive compartments, likely extracellular vesicles. In support of this hypothesis, we visualized viral RNAs in vesicles in mosquito saliva and noted a marked enrichment of signal from 3'UTR sequences, which is consistent with the presence of sfRNA. Furthermore, we show that incubation with mosquito saliva containing higher sfRNA levels results in higher virus infectivity in a human hepatoma cell line and human primary dermal fibroblasts. Transfection of 3'UTR RNA prior to DENV2 infection inhibited type I and III interferon induction and signaling, and enhanced viral replication. Therefore, we posit that sfRNA present in salivary extracellular vesicles is delivered to cells at the biting site to inhibit innate immunity and enhance dengue virus transmission.

[Evaluating an Information, Education and Communication (IEC) strategy which was adopted for Aedes aegypti control in La Dorada, Colombia]. / Evaluación preliminar de la Estrategia de Información, Comunicación y Educación para el control del Aedes aegypti, en La Dorada, Colombia.

OBJECTIVE: Estimating the impact of the Information, Education and Communication strategy on Aedes aegypti infestation in homes in La Dorada, Colombia. METHODS: A cross-sectional study was carried out during June and July 2008 in La Dorada; 228 houses were chosen and vector presence was measured in two ways: immature forms were captured by the rapid sweeping method in water tanks and adults were captured by active collection. A survey simultaneously measured exposure to the strategy. EPI Info 2000 was used for analysing the database so created. Prevalence ratios and 95 % confidence intervals were calculated. RESULTS: A relationship was found between being a housewife and not having larvae present in the home. No immature forms were found in houses where somebody washed the water tank at least once a week. There were also no larvae in homes where people had knowledge about larvae and dengue transmission. The presence of adult forms was found in houses having more than one water tank. Almost 80 % of the interviewees acquired knowledge about dengue transmission through the strategy. CONCLUSIONS: Although all strategy components had not been implemented, several factors were found which might have a protective effect (i.e. being related to vector absence). The study showed that the strategy achieved only partial success in La Dorada.

Evaluación preliminar de la Estrategia de Información, Comunicación y Educación para el control del Aedes aegypti, en La Dorada, Colombia / Evaluating an Information, Education and Communication (IEC) strategy which was adopted for Aedes aegypti control in La Dorada, Colombia

Objetivo Estimar el impacto de la estrategia de Información, Educación y Comunicación sobre la infestación de Aedes aegypti en viviendas de La Dorada. Métodos Estudio transversal adelantado entre junio y julio de 2008 en La Dorada, Colombia. Se seleccionaron 228 viviendas donde se midió presencia del vector a través del método rapid sweeping para formas inmaduras en tanques y de captura activa para adultos. Simultáneamente, una encuesta midió la exposición a la estrategia. La base de datos se analizó en EPI info 2000. Se calcularon Razones de Prevalencia e intervalos de confianza al 95 por ciento. Resultados Las viviendas que no tenían larvas se caracterizaban por tener mujeres cabeza de familia o moradores con conocimiento acerca de las larvas y la forma de transmisión del dengue. Aquellas viviendas donde se lavaba el tanque de agua al menos una vez por semana, carecían de formas inmaduras. La presencia de mosquitos adultos era más frecuente en las casas que tenían más de un tanque. Cerca del 80 por ciento de los encuestados adquirieron el conocimiento de transmisión del dengue a través de la estrategia. Conclusiones Si bien la estrategia no ha sido aplicada en todos sus componentes, se encontraron factores que podrían tener un efecto protectivo al estar relacionados con ausencia del vector. El estudio revela solo un éxito parcial de la estrategia en La Dorada.

Objective Estimating the impact of the Information, Education and Communication strategy on Aedes aegypti infestation in homes in La Dorada, Colombia. Methods A cross-sectional study was carried out during June and July 2008 in La Dorada; 228 houses were chosen and vector presence was measured in two ways: immature forms were captured by the rapid sweeping method in water tanks and adults were captured by active collection. A survey simultaneously measured exposure to the strategy. EPI Info 2000 was used for analysing the database so created. Prevalence ratios and 95 percent confidence intervals were calculated. Results A relationship was found between being a housewife and not having larvae present in the home. No immature forms were found in houses where somebody washed the water tank at least once a week. There were also no larvae in homes where people had knowledge about larvae and dengue transmission. The presence of adult forms was found in houses having more than one water tank. Almost 80 percent of the interviewees acquired knowledge about dengue transmission through the strategy. Conclusions Although all strategy components had not been implemented, several factors were found which might have a protective effect (i.e. being related to vector absence). The study showed that the strategy achieved only partial success in La Dorada.