Determinants of Aedes mosquito density as an indicator of arbovirus transmission risk in three sites affected by co-circulation of globally spreading arboviruses in Colombia, Ecuador and Argentina.

BACKGROUND: The global impact of Zika virus in Latin America has drawn renewed attention to circulating mosquito-borne viruses in this region, such as dengue and chikungunya. Our objective was to assess socio-ecological factors associated with Aedes mosquito vector density as a measure of arbovirus transmission risk in three cities of potentially recent Zika virus introduction: Ibagué, Colombia; Manta, Ecuador; and Posadas, Argentina, in order to inform disease mitigation strategies. METHODS: We sampled Aedes mosquito populations in a total of 1086 households, using indoor and peridomestic mosquito collection methods, including light traps, resting traps, traps equipped with chemical attractant and aspirators. For each sampled household, we collected socio-economic data using structured questionnaires and data on microenvironmental conditions using iButton data loggers. RESULTS: A total of 3230 female Aedes mosquitoes were collected, of which 99.8% were Aedes aegypti and 0.2% were Aedes albopictus. Mean female Aedes mosquito density per household was 1.71 (standard deviation: 2.84). We used mixed-effects generalized linear Poisson regression analyses to identify predictors of Aedes density, using month, neighborhood and country as random-effects variables. Across study sites, the number of household occupants [incidence rate ratio (IRR): 1.08, 95% confidence interval (CI): 1.01-1.14], presence of entry points for mosquitoes into the household (IRR: 1.51, 95% CI: 1.30-1.76) and presence of decorative vegetation (IRR: 1.52, 95% CI: 1.22-1.88) were associated with higher Aedes density; while being in the highest wealth tertile of household wealth (IRR: 0.78, 95% CI: 0.66-0.92), knowledge of how arboviruses are transmitted (IRR: 0.94, 95% CI: 0.89-1.00) and regular emptying of water containers by occupants (IRR: 0.79, 95% CI: 0.67-0.92) were associated with lower Aedes density. CONCLUSIONS: Our study addresses the complexities of arbovirus vectors of global significance at the interface between human and mosquito populations. Our results point to several predictors of Aedes mosquito vector density in countries with co-circulation of multiple Aedes-borne viruses, and point to modifiable risk factors that may be useful for disease prevention and control.

Uso de membrana de drenaje para evitar acumulación de agua y posibles criaderos de Aedes aegypti (Linnaeus 1762) (Diptera: Culicidae) en neumáticos desechables / Use of a drainage membrane to prevent accumulation of water and the creation of potential breeding sites for Aedes aegypti (Linnaeus 1762) (Diptera: Culicidae) in disposable pneumatic tires

Introducción: los neumáticos presentan características que los hacen un criadero efectivo recurrente para el desarrollo de los estadios juveniles de Aedes aegypti, principal vector dengue en la región Objetivo: evaluar la utilidad de una membrana, como sistema de drenaje, en neumáticos desechables para evitar la acumulación de agua que propicie el desarrollo de estadíos pre-adulto de Ae. aegypti. Métodos: el trabajo se realizó en el Laboratorio de Entomología Médica en Posadas, Misiones, Argentina de abril a mayo de 2012. Se seleccionaron 8 neumáticos en desuso con características similares. Con los 8 neumáticos se establecieron dos subgrupos: horizontal (NH) y vertical (NV) identificados con los números del 1 al 4. En cada neumático se vertieron 1 500 ml de agua. Se utilizó una membrana no tejido de Ballerina ® CIF paño absorbente en los depósitos identificados con los números de 1 a 3 de ambos subgrupos. Como controles se consideraron los neumáticos restantes identificados con los números 4, las cuales se dejaron sin membrana de drenaje. El registro del volumen de agua se realizó, cada 24 horas, en los primeros 5 días de experiencia y cada 48 horas a partir del 6to día excepto el control que se registró cada 24 horas durante el experimento. Se utilizó un análisis de varianza no paramétrico para comparar los valores de volumen de agua en cada posición. Resultados: los neumáticos 1, 2, 3 de las posiciones NH y NV mostraron diferencias estadísticamente significativas, en cuanto al contenido de agua con sus correspondientes controles. No se observaron diferencias estadísticas relacionadas con el contenido de agua en los neumáticos colocados en las posiciones vertical y horizontal. El volumen de agua eliminado por evaporación espontánea en los neumáticos controles fue de 4,16 ml cada 24 horas sin diferencias significativas entre ellos, quedando un volumen de 1495,84 ml, apto para el desarrollo de los estadios acuáticos de los mosquitos...

Introduction: due to their characteristics, pneumatic tires may be effective recurrent breeding sites for the development of juvenile stages of Aedes aegypti, the main dengue vector in the region. Objective: evaluate the usefulness of a membrane as a drainage system in disposable pneumatic tires to prevent accumulation of water and the consequent development of preadult stages of Aedes aegypti. Methods: the study was conducted at the Medical Entomology Laboratory in Posadas, Misiones, Argentina from April to May 2012. Eight discarded pneumatic tires of similar characteristics were selected. The 8 tires were divided into two subgroups: horizontal (HP) and vertical (VP), and numbered from 1 to 4 for identification. 1 500 ml of water were poured into each tire. A non-woven BallerinaTM CIF absorbent cloth was placed in containers 1 to 3 of each subgroup. Drainage membranes were not placed in the remaining tires, identified with the number 4, which were used as controls. Water volume was gauged every 24 hours during the first 5 days of the study, and every 48 hours from the 6th day onwards, except for the control, which was checked every 24 hours throughout the experiment. Non-parametric analysis of variance was performed to compare water volume values in each position. Results: pneumatic tires 1, 2 and 3 of positions HP and VP showed statistically significant differences in water content with respect to their respective controls. No statistical difference was found between the water content in pneumatic tires placed in vertical and horizontal positions. The volume of water eliminated by spontaneous evaporation in control pneumatic tires was 4.16 ml every 24 hours with no significant differences between them. A total 1 495.84 ml remained, sufficient for the development of aquatic stages of mosquito development...

Uso de membrana de drenaje para evitar acumulación de agua y posibles criaderos de Aedes aegypti (Linnaeus 1762) (Diptera: Culicidae) en neumáticos desechables / Use of a drainage membrane to prevent accumulation of water and the creation of potential breeding sites for Aedes aegypti (Linnaeus 1762) (Diptera: Culicidae) in disposable pneumatic tires

IINTRODUCCIÓN: los neumáticos presentan características que los hacen un criadero efectivo recurrente para el desarrollo de los estadios juveniles de Aedes aegypti, principal vector dengue en la región OBJETIVO: evaluar la utilidad de una membrana, como sistema de drenaje, en neumáticos desechables para evitar la acumulación de agua que propicie el desarrollo de estadíos pre-adulto de Ae. aegypti. MÉTODOS: el trabajo se realizó en el Laboratorio de Entomología Médica en Posadas, Misiones, Argentina de abril a mayo de 2012. Se seleccionaron 8 neumáticos en desuso con características similares. Con los 8 neumáticos se establecieron dos subgrupos: horizontal (NH) y vertical (NV) identificados con los números del 1 al 4. En cada neumático se vertieron 1 500 ml de agua. Se utilizó una membrana no tejido de Ballerina ® CIF paño absorbente en los depósitos identificados con los números de 1 a 3 de ambos subgrupos. Como controles se consideraron los neumáticos restantes identificados con los números 4, las cuales se dejaron sin membrana de drenaje. El registro del volumen de agua se realizó, cada 24 horas, en los primeros 5 días de experiencia y cada 48 horas a partir del 6to día excepto el control que se registró cada 24 horas durante el experimento. Se utilizó un análisis de varianza no paramétrico para comparar los valores de volumen de agua en cada posición. RESULTADOS: los neumáticos 1, 2, 3 de las posiciones NH y NV mostraron diferencias estadísticamente significativas, en cuanto al contenido de agua con sus correspondientes controles. No se observaron diferencias estadísticas relacionadas con el contenido de agua en los neumáticos colocados en las posiciones vertical y horizontal. El volumen de agua eliminado por evaporación espontánea en los neumáticos controles fue de 4,16 ml cada 24 horas sin diferencias significativas entre ellos, quedando un volumen de 1495,84 ml, apto para el desarrollo de los estadios acuáticos de los mosquitos. CONCLUSIONES: el uso de la membrana absorbente en los neumáticos desechables, resultó ser un método eficaz de drenaje de agua, lo que contribuye a evitar posibles criaderos de Ae. aegypti.

INTRODUCTION: due to their characteristics, pneumatic tires may be effective recurrent breeding sites for the development of juvenile stages of Aedes aegypti, the main dengue vector in the region. OBJECTIVE: evaluate the usefulness of a membrane as a drainage system in disposable pneumatic tires to prevent accumulation of water and the consequent development of preadult stages of Aedes aegypti. METHODS: the study was conducted at the Medical Entomology Laboratory in Posadas, Misiones, Argentina from April to May 2012. Eight discarded pneumatic tires of similar characteristics were selected. The 8 tires were divided into two subgroups: horizontal (HP) and vertical (VP), and numbered from 1 to 4 for identification. 1 500 ml of water were poured into each tire. A non-woven BallerinaTM CIF absorbent cloth was placed in containers 1 to 3 of each subgroup. Drainage membranes were not placed in the remaining tires, identified with the number 4, which were used as controls. Water volume was gauged every 24 hours during the first 5 days of the study, and every 48 hours from the 6th day onwards, except for the control, which was checked every 24 hours throughout the experiment. Non-parametric analysis of variance was performed to compare water volume values in each position. RESULTS: pneumatic tires 1, 2 and 3 of positions HP and VP showed statistically significant differences in water content with respect to their respective controls. No statistical difference was found between the water content in pneumatic tires placed in vertical and horizontal positions. The volume of water eliminated by spontaneous evaporation in control pneumatic tires was 4.16 ml every 24 hours with no significant differences between them. A total 1 495.84 ml remained, sufficient for the development of aquatic stages of mosquito development. CONCLUSIONS: the use of absorbent membranes in disposable pneumatic tires proved to be an effective water drainage method, contributing to prevent the creation of Aedes aegypti breeding sites.