ABSTRACT The Asian tiger mosquito ( Aedes albopictus, Diptera: Culicidae) has spread rapidly in the last 30 years from its native region in Southeast Asia. In Argentina, studies on its potential distribution suggest that this species could be found in temperate zones of the province of Buenos Aires. However, since its initial detection in 1998 Ae. albopictus is bounded to the subtropical province of Misiones. To evaluate the presence and abundance of Ae. albopictus in the Northeast of Argentina, we preliminarily evaluated the presence of this vector by analyzing its presence in tires of 20 cities belonging to the province of Misiones and four cities in Northern Corrientes, and then performed an evaluation of the vector in the towns where the vector was detected. Aedes albopictus was present only in two cities of Misiones: Eldorado and Colonia Aurora. Aedes aegypti and Ae . albopictus accounted for 86% of the individuals collected in the domiciles of both towns. In Colonia Aurora both species were in similar abundances suggesting a co-dominance. The present study extends the austral distribution of Ae. albopictus in Argentina to the city of Colonia Aurora where the highest abundance recorded in Argentina was detected. Nevertheless, the reasons of its bounded distribution in the region are not known.

Se comparó el nivel de oviposición entre ovitrampas ubicadas en viviendas y la vía pública para el monitoreo de Aedes aegypti, y se propone el mejor sitio de instalación en la vía pública en un barrio de la ciudad de Buenos Aires, Argentina. Un total de 60 ovitrampas distribuidas al azar fueron ubicadas en viviendas (n=38) y la vía pública (n=22), se examinaron semanalmente por diez semanas. El índice de Positividad de Ovitrampas (IPO) y el Indice de Densidad de Huevos (IDH) utilizados como indicadores del nivel de oviposición, fueron calculados semanalmente. Las variables ambientales evaluadas en la vía pública fueron el tipo de corredor, la altura de los árboles y altura de las viviendas. Los valores obtenidos de IPO e IDH fueron más altos en las viviendas que en la vía pública, y se observó una correlación positiva entre los índices de infestación en viviendas y la vía pública. En este último ambiente, se halló una asociación positiva entre valores bajos de IPO e IDH y árboles altos, corredor tipo avenida, y viviendas con dos o más plantas, se observó también que los valores altos de dichos índices se asociaron en forma positiva con árboles medianos o bajos, y negativamente con árboles altos, avenida, y viviendas con dos o más plantas. Nuestros resultados sugieren que la sensibilidad de las ovitrampas en monitoreos de A. aegypti en vía pública es menor que en las viviendas, y esta sensibilidad en vía pública aumentaría si se consideran algunas variables ambientales.

The oviposition level between ovitraps placed in human dwellings and on public paved areas for the monitoring of Aedes aegypti was compared,and proposes the best ovitrap installation sites on public paved areas in a neighborhood of Buenos Aires City, Argentina. A total of 60 randomly distributed ovitraps were placed in human dwellings (n=38) and public paved areas (n=22), and examined weekly over a ten-week period. The Ovitrap Positivity Index (OPI) and the Egg Density Index (EDI) were used as indicators of oviposition level. The indexes were calculated on a weekly basis. Environmental variables evaluated for public paved areas were type of corridor, tree height and dwelling height. OPI and EDI values were higher for dwellings than for public paved areas. There was a positive correlation between the infestation indices in dwellings and in public paved areas. In the latter there was a positive association between low OPI and EDI values and tall trees, avenue as type corridor, and dwellings with two stories or more, whereas there was a positive association between high values of these indices and short and medium trees, and a negative association with tall trees, avenue, and dwellings with two stories or more. Our results suggest that the sensitivity of ovitraps in monitoring of A. aegypti in public paved areas is lower than in dwellings, and this sensitivity would increase if considering some environmental variables.

With the objectives of dengue prevention, health promotion, and action-based research, two experiments were conducted in pilot areas of Buenos Aires and Vicente López, Argentina. In each area, community, government, and non-governmental references were identified. The study included an entomological survey (with ovitraps), environmental survey (with field observations, interviews, and workshops), and social survey (using questionnaires, interviews, and meetings). Spaces for dialogue and collaboration were developed with the community, thereby spawning participatory activities and empowerment. Environmental reordering and reduction of mosquito breeding sites were promoted by: incorporation of environmental issues and vector-borne disease prevention into the school curricula; neighborhood workshops; training of environmental agents to transmit information and train peers; and planning community environmental projects. The households were visited, seeking to integrate the residents into their own community environmental diagnosis. There were significant differences between the pilot areas in knowledge and social practices, but not according to socioeconomic status. The schools and health promotion settings proved to be the main community reference for promoting healthy environmental practices.

Con objetivos de prevención de dengue, promoción de la salud e investigación-acción se desarrollaron dos experiencias en zonas piloto de Buenos Aires y Vicente López. En cada zona se identificaron referentes comunitarios, gubernamentales y no gubernamentales. Se realizó un diagnóstico entomológico (mediante ovitrampas), ambiental (con observaciones en terreno, encuestas y talleres), y social (utilizando cuestionarios, entrevistas y reuniones). Se construyeron espacios de diálogo y trabajo conjunto con la comunidad, generando acciones participativas y empoderamiento. Se fomentó el ordenamiento ambiental y la reducción de criaderos de mosquitos a través de incorporación de temas ambientales y prevención de enfermedades vectoriales a los currícula escolares; talleres vecinales de difusión; capacitación de promotoras ambientales para transmitir información y para capacitar a pares; planificación de proyectos ambientales de la comunidad. Se entró en los domicilio, buscando integrar a sus habitantes en el diagnóstico ambiental propio y comunitario. Se registraron diferencias significativas entre conocimientos y prácticas sociales, para ambas zonas piloto, pero no por nivel socioeconómico. Las escuelas y los entornos de promoción de salud resultaron ser los principales referentes comunitarios para fomentar prácticas ambientales saludables.

With the objectives of dengue prevention, health promotion, and action-based research, two experiments were conducted in pilot areas of Buenos Aires and Vicente López, Argentina. In each area, community, government, and non-governmental references were identified. The study included an entomological survey (with ovitraps), environmental survey (with field observations, interviews, and workshops), and social survey (using questionnaires, interviews, and meetings). Spaces for dialogue and collaboration were developed with the community, thereby spawning participatory activities and empowerment. Environmental reordering and reduction of mosquito breeding sites were promoted by: incorporation of environmental issues and vector-borne disease prevention into the school curricula; neighborhood workshops; training of environmental agents to transmit information and train peers; and planning community environmental projects. The households were visited, seeking to integrate the residents into their own community environmental diagnosis. There were significant differences between the pilot areas in knowledge and social practices, but not according to socioeconomic status. The schools and health promotion settings proved to be the main community reference for promoting healthy environmental practices.

Con objetivos de prevención de dengue, promoción de la salud e investigación-acción se desarrollaron dos experiencias en zonas piloto de Buenos Aires y Vicente López. En cada zona se identificaron referentes comunitarios, gubernamentales y no gubernamentales. Se realizó un diagnóstico entomológico (mediante ovitrampas), ambiental (con observaciones en terreno, encuestas y talleres), y social (utilizando cuestionarios, entrevistas y reuniones). Se construyeron espacios de diálogo y trabajo conjunto con la comunidad, generando acciones participativas y empoderamiento. Se fomentó el ordenamiento ambiental y la reducción de criaderos de mosquitos a través de incorporación de temas ambientales y prevención de enfermedades vectoriales a los currícula escolares; talleres vecinales de difusión; capacitación de promotoras ambientales para transmitir información y para capacitar a pares; planificación de proyectos ambientales de la comunidad. Se entró en los domicilio, buscando integrar a sus habitantes en el diagnóstico ambiental propio y comunitario. Se registraron diferencias significativas entre conocimientos y prácticas sociales, para ambas zonas piloto, pero no por nivel socioeconómico. Las escuelas y los entornos de promoción de salud resultaron ser los principales referentes comunitarios para fomentar prácticas ambientales saludables.

The aim of this research was to evaluate the effect of temperature on the development time and survival of Culex (Culex) hepperi Casal and García, 1967. Individuals were reared in the laboratory, from the first larval stage to adult emergence, at five constant temperatures: 15, 20, 25, 30, and 33°C. The total development time was inversely related to temperature between 15 and 25°C. No differences were observed in the development time between sexes and no adults emerged at 33°C. In the larval stages III and IV, the time required for molting to the next stage increased at 30°C. The highest survival was recorded at 20°C. The more developed stages were less resistant to temperatures above and below 20°C. According to the nonlinear model of Briére, the lower and upper development thresholds were 2.6 and 33°C, respectively. Our results suggest that the effect of temperature depends upon the stage of development of C. hepperi.

El objetivo de este trabajo fue analizar el efecto de la temperatura sobre el tiempo de desarrollo y la supervivencia preimaginal de Culex (Culex) hepperi Casal y García, 1967. Los individuos fueron criados en laboratorio, desde el primer estadio larval hasta la emergencia del adulto, a cinco temperaturas constantes: 15, 20, 25, 30 y 33°C. El tiempo total de desarrollo se relacionó de manera inversa con la temperatura entre 15 y 25°C. No se detectaron diferencias entre sexos en el tiempo de desarrollo y ningún individuo alcanzó el estado adulto a 33°C. En los estadios larvales III y IV, el tiempo requerido para mudar al siguiente estadio fue mayor a 30°C. La supervivencia más alta se registró a 20°C. Los estadios más avanzados fueron menos resistentes a las temperaturas por encima y por debajo de los 20°C. De acuerdo con el modelo no lineal de Briére, los umbrales de desarrollo inferior y superior fueron 2.6 y 33°C, respectivamente. Nuestros resultados sugieren que el efecto de la temperatura depende del estadio de desarrollo de C. hepperi.

The object of the present work was to identify the larval habitats of Culex eduardoi and to determine the microenvironmental conditions related to their presence in different artificial freshwater environments (temporary, semi-permanent, irrigation ditches, and drainage ditches) in tillable areas of Chubut Province, Argentina. This report represents the first record of Cx. eduardoi from this Province and extends its range to latitude 45°S. Immature stages of Cx. eduardoi were found in 8 out of 109 (7.3 %) freshwater habitats and were significantly more prevalent in semi-permanent water bodies. Positive sites had significantly larger surface areas and more vegetation cover than negative sites.

We conducted a whole year research on the ecology of Mansonia indubitans and Ma. titillans in Macáes Pond, Costanera Sur Reserve, Buenos Aires, Argentina. The usage of different floating plants by immature instars and their overwintering was analized. The percentage of usage of the available floating macrophytes (Pistia, Limnobium, and Salvinia) by the larvae and pupae was studied. Also, we defined positivity (P+) as the percentage of plants with immature instars for each plant genus on a monthly basis. Ma. immature instars were captured throughout the year and Pistia was the resource most commonly exploited by the mosquitoes. The percentage of fourth-instar larvae and pupae on Pistia roots with respect to total immature instars captured was assessed on a monthly and seasonal basis. The proportion of fourth-instar larvae and pupae from both species of Mansonia on water lettuce roots, showed significant differences between months and seasons. Our results suggest that the populations of Ma. indubitans and Ma. titillans in Macáes Pond, survive during winter mainly as fourth-instar larvae.

Avaliou-se a eficácia de um larvicida, temefós, para controlar Ae. aegypti em um cemitério de Buenos Aires, Argentina. Os criadouros reduziram de 18,4% no primeiro período de estudo (nov de 1998 a maio de 1999, sem temefós) para 2,2% no segundo (nov de 1999 a maio de 2000, duas aplicações), e para 0,05% no terceiro (nov de 2000 a maio de 2001, cinco aplicações). As. ovitrampas com ovos diminuíram de 17% no primeiro período para 5,8% no segundo e para 2,9% no terceiro. Os resultados sugerem que, em Buenos Aires, as populações de Ae. aegypti são altamente susceptíveis ao temefós. É recomendável seu uso para prevenir eventuais epidemias e não para o controle rotineiro.

The efficacy of a larvicide, temephos, for controlling Ae. aegypti was evaluated in a cemetery in Buenos Aires, Argentina. Breeding sites decreased from 18.4% in the first study period (Nov 1998 to May 1999, without temephos) to 2.2% in the second period (Nov 1999 to May 2000, two applications), and to 0.05% in the third one (Nov 2000 to May 2001, five applications). Ovitraps with eggs decreased from 17% in the first period to 5.8% in the second period, and to 2.9% in the third one. Results suggest that, in Buenos Aires, Ae. aegypti populations are highly susceptible to temephos. It is recommended to limit the use of temephos to prevent potential epidemics rather than for routine control.

Se evaluó la eficacia de un larvicida, temefós, para controlar Ae. aegypti en un cementerio de Buenos Aires, Argentina. Los criaderos descendieron de 18,4% en el primer periodo de estudio (Nov 1998 a May 1999, sin temefos) a 2,2% en el segundo (Nov 1999 a May 2000, dos aplicaciones), y a 0,05% en el tercero (Nov 2000 a May 2001, cinco aplicaciones). Las ovitrampas con huevos disminuyeron de 17% en el primer periodo a 5,8% en el segundo, y a 2,9% en el tercero. Los resultados sugieren que, en Buenos Aires, las poblaciones de Ae. aegypti son altamente susceptibles al temefós. Es recomendable limitar su uso para prevenir eventuales epidemias y no para el control rutinario.

Avaliou-se a eficácia de um larvicida, temefós, para controlar Ae. aegypti em um cemitério de Buenos Aires, Argentina. Os criadouros reduziram de 18,4% no primeiro período de estudo (nov de 1998 a maio de 1999, sem temefós) para 2,2% no segundo (nov de 1999 a maio de 2000, duas aplicações), e para 0,05% no terceiro (nov de 2000 a maio de 2001, cinco aplicações). As. ovitrampas com ovos diminuíram de 17% no primeiro período para 5,8% no segundo e para 2,9% no terceiro. Os resultados sugerem que, em Buenos Aires, as populações de Ae. aegypti são altamente susceptíveis ao temefós. É recomendável seu uso para prevenir eventuais epidemias e não para o controle rotineiro.

The efficacy of a larvicide, temephos, for controlling Ae. aegypti was evaluated in a cemetery in Buenos Aires, Argentina. Breeding sites decreased from 18.4% in the first study period (Nov 1998 to May 1999, without temephos) to 2.2% in the second period (Nov 1999 to May 2000, two applications), and to 0.05% in the third one (Nov 2000 to May 2001, five applications). Ovitraps with eggs decreased from 17% in the first period to 5.8% in the second period, and to 2.9% in the third one. Results suggest that, in Buenos Aires, Ae. aegypti populations are highly susceptible to temephos. It is recommended to limit the use of temephos to prevent potential epidemics rather than for routine control.

Se evaluó la eficacia de un larvicida, temefós, para controlar Ae. aegypti en un cementerio de Buenos Aires, Argentina. Los criaderos descendieron de 18,4% en el primer periodo de estudio (Nov 1998 a May 1999, sin temefos) a 2,2% en el segundo (Nov 1999 a May 2000, dos aplicaciones), y a 0,05% en el tercero (Nov 2000 a May 2001, cinco aplicaciones). Las ovitrampas con huevos disminuyeron de 17% en el primer periodo a 5,8% en el segundo, y a 2,9% en el tercero. Los resultados sugieren que, en Buenos Aires, las poblaciones de Ae. aegypti son altamente susceptibles al temefós. Es recomendable limitar su uso para prevenir eventuales epidemias y no para el control rutinario.

Cases of dengue detected in Buenos Aires City between 1999 and 2000 confirmed the possibility of epidemic outbreaks. The activity of its vector Aedes aegypi was monitored to study the spatial and temporal risk of dengue transmission. Adult oviposition activity of Aedes aegypti showed an heterogeneous spatio-temporal distribution pattern. It was detected between October and May. The vector was detected from spring to fall in the Northern, Western and Southern areas of the city (periphery) and only in summer in the Eastern part (downtown-river). The proportion of infested sites differed between the three periods but the infested areas coincided spatially. Although a spatial and temporal heterogeneity exists, the pattern repeated itself during the three periods suggesting stable dynamics. The not infested areas presented the highest population and employees densities while the areas infested during the three periods the lowest. This might represent an attenuation of the risk, because higher densities do not coincide with higher infestation. From the point of view of the vector the risk of transmission would concentrate between January and March and occupy 50% of the city surface in the periphery.

Los casos de dengue detectados en la Ciudad de Buenos Aires entre 1999 y 2000 confirmaron la posibilidad de brotes epidémicos. Para estudiar el riesgo de transmisión de dengue espacial y temporalmente se midió la actividad de su vector, el mosquito Aedes aegypti. La actividad de ovipostura del vector mostró un patrón de distribución heterogéneo en el tiempo y el espacio. Ocurrió entre octubre y mayo. En las áreas del Norte, Oeste y Sur de la ciudad (periferia) el vector fue detectado entre la primavera y el otoño en tanto que en las áreas del Este (microcentro-río) sólo en el verano. La proporción de sitios infestados varió entre los 3 períodos de estudio, pero las zonas infestadas coincidieron espacialmente. Aunque se observó variación anual y espacial de la infestación, el patrón se repitió durante los 3 años de estudio sugiriendo una dinámica estable. Las áreas de la ciudad no infestadas presentaron las mayores densidades de población y de empleados, mientras que las infestadas durante los 3 períodos presentaron las menores densidades. Esto podría representar una atenuación del riesgo, ya que no coincide la mayor densidad de habitantes con la mayor infestación. El riesgo de transmisión desde el punto de vista del vector se concentraría entre enero y marzo y ocuparía el 50% de la superficie de la ciudad en la periferia.

In Buenos Aires, the most crowded city of Argentina, there is a potential risk of dengue virus transmission by the mosquito Aedes aegypti during late summer. The temporal patterns of oviposition activity and abundance of breeding sites of this vector were studied in two cemeteries of the city. Between September 1998 and August 1999, we examined 142 ovitraps weekly and a total of 18,010 water-filled containers. Both study areas showed remarkable differences in the percentages of positive ovitraps (19% vs 8%) and breeding sites (18% vs 1%), but similar temporal abundance patterns. The percentage of breeding sites was higher in summer and autumn than in spring and winter, and the percentage of positive ovitraps was higher in summer than in the other three seasons. Immatures were recorded from the first week of October to the second week of July, and oviposition activity from the third week of October until the end of April. In both cemeteries and with both methodologies the highest infestation levels were registered in March (ovitraps: 41.8% and 20.6%, breeding sites: 39.2% and 3.4%). These highest abundances took place after several months with mean temperatures above 20ºC and accumulated rainfalls above 150 mm. A sharp decline in oviposition activity was observed when monthly mean temperature decreased to 16.5ºC, and no eggs were found below 14.8ºC. Seasonal fluctuation of Ae. aegypti abundances in mid-latitudes like Buenos Aires would allow reduction of the egg mosquito population through the elimination of containers during the coldest months, which are free of adults.

Until early 1998 the presence of Aedes albopictus had never been detected in Argentina. During April of the same year, few individuals of this species were recorded in 33 breeding sites found in 25 out of 161 inspected houses in the city of Eldorado, Province of Misiones. The homogeneous spatial distribution of the proliferation foci suggests the existence of a generalized infestation in this locality during the study period.

La presencia de Aedes albopictus en Argentina no había sido detectada hasta comienzos de 1998. En abril de ese mismo año se registraron 33 criaderos, con pocos ejemplares en cada uno, en 25 de las 161 viviendas inspeccionadas en la ciudad de Eldorado, Provincia de Misiones. La distribución espacial homogénea de los focos de proliferación detectados durante el período de estudio sugiere la existencia de una infestación generalizada en esta localidad.

Until early 1998 the presence of Aedes albopictus had never been detected in Argentina. During April of the same year, few individuals of this species were recorded in 33 breeding sites found in 25 out of 161 inspected houses in the city of Eldorado, Province of Misiones. The homogeneous spatial distribution of the proliferation foci suggests the existence of a generalized infestation in this locality during the study period.

La presencia de Aedes albopictus en Argentina no había sido detectada hasta comienzos de 1998. En abril de ese mismo año se registraron 33 criaderos, con pocos ejemplares en cada uno, en 25 de las 161 viviendas inspeccionadas en la ciudad de Eldorado, Provincia de Misiones. La distribución espacial homogénea de los focos de proliferación detectados durante el período de estudio sugiere la existencia de una infestación generalizada en esta localidad.

The immature stages of Ochlerotatus albifasciatus develop in temporary pools. The present study aims at evaluating the seasonal dynamics of the aquatic stages of this mosquito, also analyzing the relationship among their presence and breeding success to some relevant climatic and environmental variables in the ephemeral rain pools of an urban park. Nineteen cohorts of O. albifasciatus that developed synchronously after rain events were recorded in all seasons. The proportions of mosquito-positive pools were significantly higher during the fall-winter period than in the spring-summer months (p < 0.001). The presence of this mosquito species was positively related to the amount of rain (p < 0.001), whereas negatively correlated to air temperature (p < 0.05) within a 5.2 to 29.7ºC range. The distribution of the number of cohorts per pool throughout the year was grouped (variance/mean: 3.96), indicating that these habitats were not equally suitable as breeding sites. The immature stages of O. albifasciatus were detected in pools belonging to all of the categories of surface area, depth, duration, vegetation cover, and insolation. However, the proportion of pools where immature mosquitoes were detected was positively and significantly related to surface, depth, duration, and vegetation cover. On the other hand, the proportion of mosquito-positive pools was higher at an intermediate insolation degree. Our results suggest that although preimaginal stages were present in all seasons, high temperatures may be unfavorable to larval development, and substrate vegetation may regulate water temperature. The positive relationship between the proportion of mosquito-positive pools and pool size and duration might reflect a strategy of O. albifasciatus to accomplish immature development.

Cemeteries are ideal urban areas to study the importance of different types of containers as breeding sites of Aedes aegypti (L.). In the present study, the suitability of plastic, glass, ceramic and metal containers was evaluated in four patches within a cemetery of Buenos Aires City, Argentina. Between October 1998 and May 2000, we found 215 breeding sites of Ae. aegypti out of 13,022 water-filled containers examined. In two patches containing microenvironments sheltered from the sun, the use of the different types of containers was proportional to the offer (correlation coefficient = 0.99, P < 0.05 in both cases). In the remaining patches, plastic and metal containers were the most and less frequent breeding sites, respectively (P < 0.001 in both cases). The number of immatures per breeding site (median = 4.5) did not show significant differences among the four types of containers examined (H3, 215 = 1.216, P = 0.749). Differences found in patches from a same cemetery suggest that different microenvironmental conditions affect the suitability of each type of container for Ae. aegypti breeding. Plastic containers appeared as key breeding sites that should be removed to reduce the Ae. aegypti population in the study area.