Transcriptome comparison of dengue-susceptible and -resistant field derived strains of Colombian Aedes aegypti using RNA-sequencing

BACKGROUND Forty percent of the world's population live in areas where they are at risk from dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. Dengue viruses are transmitted primarily by the mosquito Aedes aegypti. In Cali, Colombia, approximately 30% of field collected Ae. aegypti are naturally refractory to all four dengue serotypes. OBJECTIVES Use RNA-sequencing to identify those genes that determine refractoriness in feral mosquitoes to dengue. This information can be used in gene editing strategies to reduce dengue transmission. METHODS We employed a full factorial design, analyzing differential gene expression across time (24, 36 and 48 h post bloodmeal), feeding treatment (blood or blood + dengue-2) and strain (susceptible or refractory). Sequences were aligned to the reference Ae. aegypti genome for identification, assembled to visualize transcript structure, and analyzed for dynamic gene expression changes. A variety of clustering techniques was used to identify the differentially expressed genes. FINDINGS We identified a subset of genes that likely assist dengue entry and replication in susceptible mosquitoes and contribute to vector competence. MAIN CONCLUSIONS The differential expression of specific genes by refractory and susceptible mosquitoes could determine the phenotype, and may be used to in gene editing strategies to reduce dengue transmission.

Costos de un programa de control del vector Aedes aegypti en municipios de Colombia: el caso de Girón y Guadalajara de Buga, 2016 / Costs of an Aedes aegypti vector control program in municipalities in Colombia: a case study in Girón and Guadalajara de Buga, 2016 / Custos de um programa de controle ao vetor Aedes aegypti em municípios da Colômbia: o caso de Girón e Guadalajara de Buga, 2016

Resumen: El objetivo de este estudio fue cuantificar los costos de los programas de control de enfermedades transmitidas por vectores a nivel local en Colombia (2016). Para ello, fue realizado un análisis de costos desde la perspectiva del hacedor de política en los municipios de Girón y Guadalajara de Buga, específicamente para el programa de control del Aedes aegypti, principal vector trasmisor del dengue, Zika y chikungunya. Este análisis implicó la cuantificación de todos los costos requeridos para cada una de las estrategias de prevención y control de enfermedades transmitidas por vectores. Los costos fueron clasificados en recurrentes y de capital, además, con fines comparativos se obtuvo el costo por caso y a nivel per cápita. El costo total estimado de los programas fue de USD 146.651 en el municipio de Girón y USD 97.936 en el municipio de Guadalajara de Buga; a nivel per cápita el costo fue de USD 0,88 en Girón y en Guadalajara de Buga fue de USD 0,99. En general, las estrategias predominantes en costos fueron el control químico de vectores adultos, con un 26% del total de los costos en Girón y un 47% en Guadalajara de Buga, esta fue intensiva en costos recurrentes, con un costo de personal 40% del total de costos para esta estrategia en Girón y un 66% de costos operacionales en Guadalajara de Buga.

Abstract: The aim of this study was to measure the costs of vector-borne disease control programs at the local level in Colombia (2016). A cost analysis was performed for this purpose from the policymaker's perspective in the municipalities (counties) of Girón and Guadalajara de Buga, specifically for the Aedes aegypti control program, the principal mosquito vector of dengue, Zika, and chikungunya. The analysis involved the quantification of all the costs required for each of the prevention and control strategies in vector-borne diseases. The costs were classified as operating and capital costs, and for purposes of comparison the costs were also calculated per case and per capita. The programs' total estimated costs were USD 146,651 in Girón and USD 97,936 in Guadalajara de Buga. Per capita cost was USD 0.88 in Girón and USD 0.99 in Guadalajara de Buga. In general, the predominant cost strategies were chemical spraying of adult mosquitos, accounting for 26% of the total costs in Girón and 47% in Guadalajara de Buga, with personnel representing 40% of the total costs for this strategy in Girón and 66% of the operating costs in Guadalajara de Buga.

Resumo: O objetivo deste estudo foi quantificar os custos dos programas de controle de doenças transmitidas por vetores ao nível local na Colômbia em (2016). Para isso, foi realizada uma análise de custos desde a perspectiva do criador de políticas nos municípios de Girón e Guadalajara de Buga, especificamente para o programa de controle do Aedes aegypti, principal vector transmissor da dengue, Zika e chikungunya. Esta análise implicou a quantificação de todos os custos requeridos para cada uma das estratégias de prevenção e controle de doenças transmitidas por vetores. Os custos foram classificados em recorrentes e do capital, ademais, para fins comparativos foi obtido o custo por caso e nível per capita. O custo total estimado dos programas foi de USD 146.651 no Município de Girón e USD 97.936 no Município de Guadalajara de Buga; ao nível per capita o custo foi de USD 0,88 em Girón e em Guadalajara de Buga foi de USD 0,99. Em geral, as estratégias predominantes em custos foram o controle químico de vetores adultos, com um 26% do total dos custos em Girón e um 47% em Guadalajara de Buga, essa foi intensiva em custos recorrentes, com um custo de pessoal de um 40% do total de custos para esta estratégia em Girón e um 66% de custos operacionais em Guadalajara de Buga.

Changing paradigms in Aedes control: considering the spatial heterogeneity of dengue transmission / Cambio de paradigma en el control de Aedes: consideración de la heterogeneidad espacial de la transmisión del dengue

ABSTRACT Current dengue vector control strategies, focusing on reactive implementation of insecticide-based interventions in response to clinically apparent disease manifestations, tend to be inefficient, short-lived, and unsustainable within the worldwide epidemiological scenario of virus epidemic recrudescence. As a result of a series of expert meetings and deliberations, a paradigm shift is occurring and a new strategy, using risk stratification at the city level in order to concentrate proactive, sustained efforts in areas at high risk for transmission, has emerged. In this article, the authors 1) outline this targeted, proactive intervention strategy, within the context of dengue epidemiology, the dynamics of its transmission, and current Aedes control strategies, and 2) provide support from published literature for the need to empirically test its impact on dengue transmission as well as on the size of disease outbreaks. As chikungunya and Zika viruses continue to expand their range, the need for a science-based, proactive approach for control of urban Aedes spp. mosquitoes will become a central focus of integrated disease management planning.

RESUMEN Las estrategias actuales de control de vectores del dengue, centradas en la ejecución reactiva de intervenciones con insecticidas en respuesta a la aparición de cuadros clínicos evidentes de la enfermedad, suelen ser ineficientes, de duración limitada e insostenibles en el contexto epidemiológico mundial, caracterizado por la recrudescencia de las epidemias virales. Como resultado de una serie de reuniones y deliberaciones entre expertos, está en proceso un cambio de paradigma y ha surgido una nueva estrategia, que consiste en estratificar el riesgo de cada ciudad para concentrar y mantener los esfuerzos proactivos donde hay un alto riesgo de transmisión. En este artículo, los autores 1) describen esta estrategia de intervención específica y proactiva dentro del contexto de las características epidemiológicas del dengue, la dinámica de su transmisión y las estrategias actuales de control de Aedes y 2) fundamentan con fuentes bibliográficas la necesidad de demostrar empíricamente las repercusiones de esta estrategia sobre la transmisión del dengue y el tamaño de los brotes. Dado que los virus del chikunguña y el Zika siguen ampliando su alcance, uno de los objetivos primordiales de la planificación de la atención integrada de estas enfermedades estará determinado por la necesidad de adoptar un enfoque científico y proactivo del control urbano de los mosquitos del género Aedes.

Spatial modeling of cutaneous leishmaniasis in the Andean region of Colombia

The objective of this research was to identify environmental risk factors for cutaneous leishmaniasis (CL) in Colombia and map high-risk municipalities. The study area was the Colombian Andean region, comprising 715 rural and urban municipalities. We used 10 years of CL surveillance: 2000-2009. We used spatial-temporal analysis - conditional autoregressive Poisson random effects modelling - in a Bayesian framework to model the dependence of municipality-level incidence on land use, climate, elevation and population density. Bivariable spatial analysis identified rainforests, forests and secondary vegetation, temperature, and annual precipitation as positively associated with CL incidence. By contrast, livestock agroecosystems and temperature seasonality were negatively associated. Multivariable analysis identified land use - rainforests and agro-livestock - and climate - temperature, rainfall and temperature seasonality - as best predictors of CL. We conclude that climate and land use can be used to identify areas at high risk of CL and that this approach is potentially applicable elsewhere in Latin America.

Difusión masiva de reportes situacionales sobre dengue: efectos de la intervención en Guadalajara de Buga, Colombia / Mass communication of dengue surveillance data: effect of an intervention in Guadalajara de Buga, Colombia

Introducción. La retroalimentación a las comunidades de la situación de dengue en su localidad, podría ser útil para mantener la motivación para su participación en el control del dengue y disminuir los índices entomológicos de Aedes . Objetivos. Evaluar la cobertura y el alcance de una intervención basada en la difusión masiva de reportes situacionales sobre el dengue y su efecto en la presencia de criaderos intradomiciliarios de Aedes spp. en Guadalajara de Buga, Colombia. Materiales y métodos. Se llevó a cabo un estudio observacional de corte transversal en 1.426 viviendas, para establecer la presencia de criaderos intradomiciliarios y caracterizar la exposición a la intervención. El efecto de la intervención se evaluó en un estudio de casos y controles. Los casos obedecieron al total de viviendas con criaderos positivos y, entre las viviendas sin criaderos positivos ubicadas en la misma manzana del caso, se seleccionaron aleatoriamente cuatro controles por caso. Resultados. El índice de viviendas positivas fue de 2,5 %. La cobertura fue del 59,4 % y el alcance del 22,3 %. El contacto con la intervención no se asoció con la ausencia de criaderos intradomiciliarios positivos. La presencia de matas con agua o floreros se asoció con criaderos positivos (p=0,01) y el uso de anjeos se consideró como factor protector (p=0,02). Conclusiones. Aunque la cobertura de la intervención fue adecuada, no se observó que tuviera efecto sobre la ausencia de criaderos intradomiciliarios positivos. Por lo tanto, se requiere la evaluación de la intervención en términos de su fidelidad, diseño y proceso de implementación.

Introduction: Maintaining communities abreast of their local dengue situation could help to keep them motivated to participate in dengue control and to decrease Aedes entomological indexes. Objectives: To evaluate the coverage and reach of an intervention based on mass-media communication of dengue surveillance reports and its effect on the presence of intra-domiciliary breeding sites for Aedes in Guadalajara de Buga, Colombia. Materials and methods: An observational cross-sectional study was conducted in 1,426 households to identify the intra-domiciliary breeding sites and to characterize the intervention exposure. To evaluate the effect of the intervention, a case-control study was performed. All households with positive breeding sites were considered as cases. Four controls per case were randomly selected among the non-positive breeding site households located on the same block of the case. Results: The positive house index was 2.5%; coverage was 59.4% and reach was 22.3%. There was no association between the intervention and the presence of intra-domiciliary breeding sites. The presence of water plants and flower pots were associated to positive breeding sites (p=0.01) and the use of screens was associated to the absence of breeding sites (p=0.02). Conclusions: Although intervention coverage was adequate, the lack of association between the intervention and the absence of positive breeding sites requires assessing its fidelity, factors related to the design, and the implementation process.

Description of Lutzomyia (Helcocyrtomyia) tolimensis, a new species of phlebotomine sandfly (Diptera: Psychodidae) from Colombia

A description is presented of Lutzomyia tolimensis sp. nov., a new species of the subgenus Helcocyrtomyia, series sanguinaria. It was collected in dwellings, peridomestic environment and in nearby forest patches located in the foothills of the Andean Central Cordillera, where in 2004-2006 occurred the largest epidemic ever recorded of leishmaniasis in Colombia. The male of this species is differentiated from other members of the series sanguinaria based on the following combination of characters: (i) base of coxite with 0-3 subequal setae, (ii) spines of gonostyle organized in positions 2.1.2, (iii) spines inserted on distal half of gonostyle and (iv) relationship of alar indices. The female is recognized principally by the following characters: (i) palpomere V longer than III, (ii) length of labro-epipharynx and (iii) relationship of the alar indices.

Comparison of the efficacy of long-lasting insecticidal nets PermaNet® 2.0 and Olyset® against Anopheles albimanus under laboratory conditions

Insecticide-treated nets provide a reduction in human-vector contact through physical barrier, mortality and/or repellent effects that protect both users and non-users, thereby protecting the wider community from vector-borne diseases like malaria. Long-lasting insecticide-treated nets (LLINs) are the best alternative. This study evaluated the bioefficacy of LLINs PermaNet® 2.0 and Olyset® under laboratory conditions with Anopheles albimanus. The laboratory strain was evaluated for insecticide susceptibility with selected insecticides used for malarial control. Regeneration time and wash resistance were evaluated with the standard bioassay cone technique following WHO guidelines. Heat assistance was used for Olyset® nets; the nets were exposed to four different temperatures to speed the regeneration process. The regeneration study of PermaNet® 2.0 showed that efficacy was fully recovered by 24 h after one and three washes and wash resistance persisted for 15 washes. Regeneration of Olyset® nets was not observed for nets washed three times, even with the different temperature exposures for up to seven days. Thus, for Olyset® the wash resistance evaluation could not proceed. Differences in response between the two LLINs may be associated with differences in manufacturing procedures and species response to the evaluated LLINs. PermaNet® 2.0 showed higher and continuous efficacy against An. albimanus.

Evaluation of community-based strategies for Aedes aegypti control inside houses

Introduction: Dengue viruses transmitted principally by the urban mosquito Aedes aegypti, cause one of the major public health problems confronting tropical cities. Insecticide spraying has been the mainstay of mosquito control; however, its continuous use has selected for resistance. Other important methods of control involve community participation. Objective: This study evaluated two control methods for Ae. aegypti that can be used by the community: Lethal ovitraps (LOs) and Bacillus thuringiensis var israeliensis (Bti) briquettes. Materials and methods: The project study was carried out in four similar neighborhoods within a representative district in the city of Cali, Colombia. Three interventions (LO, Bti, LO+Bti plus education and one control (education only) area were evaluated for efficacy in post-intervention entomological surveys. Additionally, entomological indices were also compared to results from a pre-intervention survey carried out on a sample of city blocks in the same neighborhoods. Relative vector abundance in relation to weather conditions using the same entomological sampling methods was compared. Results: The interventions did not achieve significant differences in vector abundance among the treatments. However, the interventions achieved a significant reduction in entomological indices compared with those observed during the pre-intervention survey: House index 15.1% vs. 8.5%, mean pupae per house 1.15 vs. 0.073, and Adult index 56.3% vs. 34.8% (p<0.05). Conclusions: The lack of significant differences among the interventions, and between treated and control blocks suggested that educational activities together with periodic visits to the houses produced similar reductions of immature and adult Aedes aegypti.

Introducción. Los virus del dengue transmitidos principalmente por el mosquito urbano Aedes aegypti, causan uno de los mayores problemas de salud pública que confrontan las ciudades tropicales. La aplicación de insecticidas ha sido la base para el control de mosquitos; sin embargo, su continuo uso ha servido para seleccionar individuos resistentes en las poblaciones de mosquitos. Otro método importante para el control involucra la participación comunitaria. Objetivo. Este estudio evaluó dos métodos de control para Ae. aegypti que podrían ser usados por la comunidad: las ovitrampas letales (OL) y las briquetas de Bacillus thuringiensis var israeliensis (Bti). Materiales y métodos. El estudio se llevó a cabo en cuatro barrios similares de la Comuna 16 de Cali, Colombia. Se evaluaron tres intervenciones (OL, Bti, OL y Bti) más educación y un área control (sólo educación) para medir la eficacia de la vigilancia entomológica posterior a la intervención. Además, los índices entomológicos se compararon con los resultados de una vigilancia antes de la intervención llevada a cabo en bloques de casas seleccionadas aleatoriamente en los mismos barrios. La abundancia relativa del vector en relación con las condiciones climáticas se comparó usando los mismos métodos del muestreo entomológico. Resultados. Las intervenciones no produjeron diferencias significativas entre los tratamientos en la abundancia del vector. Sin embargo, las intervenciones lograron una reducción significativa de los índices entomológicos comparados con los observados en la vigilancia antes de la intervención: índice de casa, de 15,1% a 8,5%; promedio de pupas por casa, de 1,15 a 0,073, e índice de adultos, de 56,3% a 34,8% (p<0,05). Conclusiones. La ausencia de diferencias significativas entre las intervenciones y el bloque control sugiere que las actividades educacionales junto con las visitas periódicas a las casas producen reducciones similares de los estadios inmaduros y adultos de Ae. aegypti.

Evaluación del triflumuron y la mezcla de Bacillus thuringiensis más B. sphaericus para control de formas inmaduras de Aedes aegypti y Culex quinquefasciatus en sumideros en Cali, Colombia / Evaluation of the triflumuron and the mixture of Bacillus thuringiensis plus B Bacillus sphaericus for control of the immature stages of Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) in catch basins

Introducción. En Cali los sumideros son uno de los principales criaderos de Aedes aegypti y Culex quinquefasciatus que son controlados por la Secretaría de Salud Municipal utilizando el insecticida triflumurón desde 1999. Se sospecha falla al tratamiento. Objetivos. Evaluar la eficacia del Starycide® (Triflumuron) y VectoMax® (mezcla bacteriana de Bacillus thuringiensis var. israelensis + B. sphaericus) en el control de Ae. aegypti y Cx. quinquefasciatus en los sumideros y determinar el efecto residual de una única aplicación deVectoMax®, en épocas de alta y baja pluviosidad.Materiales y métodos. La eficacia de los productos fue medida en 60 sumideros de una zona residencial de Cali por un período de 90 días. La media de individuos inmaduros (larvas y pupas de Ae. aegypti y Cx. quinquefasciatus) fueron obtenidas quincenalmente de 40sumideros intervenidos (20 con Triflumuron y 20 con VectoMax®) y 20 sin tratamiento (grupo testigo). El efecto residual de la mezcla bacteriana se evaluó quincenalmente en 10 sumideros en cada temporada climática evaluada. Resultados. Los sumideros tratados con VectoMax® presentaron diferencias en el promediode estadios inmaduros en ambas especies frente al testigo (p<0,01). En contraste, el tratamiento con triflumuron sólo presentó diferencias en los estadios inmaduros de Ae. aegypti con respecto al testigo (p<0,001). El efecto residual del VectoMax® fue mayor en la época de baja pluviosidad con respecto al testigo (p<0,001). Conclusión. La mezcla bacteriana fue el tratamiento más eficaz en el control de ambasespecies durante el período evaluado (15 días).