RESUMO

In the Americas, as in much of the rest of the world, the dengue virus vector Aedes aegypti is found in close association with human habitations, often leading to high population densities of mosquitoes in urban settings. In the Peruvian Amazon, this vector has been expanding to rural communities over the last 10-15 years, but to date, the population genetic structure of Ae. aegypti in this region has not been characterized. To investigate the relationship between Ae. aegypti gene flow and human transportation networks, we characterized mosquito population structure using a panel of 8 microsatellite markers and linked results to various potential mechanisms for long-distance dispersal. Adult and immature Ae. aegypti (>20 individuals per site) were collected from Iquitos city and from six neighboring riverine communities, i.e., Nauta, Indiana, Mazan, Barrio Florida, Tamshiaco, and Aucayo. FST statistics indicate significant, but low to moderate differentiation for the majority of study site pairs. Population structure of Ae. aegypti is not correlated with the geographic distance between towns, suggesting that human transportation networks provide a reasonable explanation for the high levels of population mixing. Our results indicate that Ae. aegypti gene flow among sub-populations is greatest between locations with heavy boat traffic, such as Iquitos-Tamshiaco and Iquitos-Indiana-Mazan, and lowest between locations with little or no boat/road traffic between them such as Barrio Florida-Iquitos. Bayesian clustering analysis showed ancestral admixture among three genetic clusters; no single cluster was exclusive to any site. Our results are consistent with the hypothesis that human transportation networks, particularly riverways, are responsible for the geographic spread of Ae. aegypti in the Peruvian Amazon. Our findings are applicable to other regions of the world characterized by networks of urban islands connected by fluvial transport routes.

Assuntos

RESUMO

In the wake of the Zika epidemic, there has been intensified interest in the surveillance and control of the arbovirus vectors Aedes aegypti and Aedes albopictus, yet many existing surveillance systems could benefit from improvements. Vector control programs are often directed by national governments, but are carried out at the local level, resulting in the discounting of spatial heterogeneities in ecology and epidemiology. Furthermore, entomological and epidemiological data are often collected by separate governmental entities, which can slow vector control responses to outbreaks. Colombia has adopted several approaches to address these issues. First, a web-based, georeferenced Aedes surveillance system called SIVIEN AEDES was developed to allow field entomologists to record vector abundance and insecticide resistance data. Second, autocidal gravid oviposition (AGO) traps are deployed as an alternative way to measure vector abundance. Third, data collected by SIVIEN AEDES are used to develop mathematical models predicting Ae. aegypti abundance down to a city block, thus allowing public health authorities to target interventions to specific neighborhoods within cities. Finally, insecticide resistance is monitored through bioassays and molecular testing in 15 high-priority cities, providing a comprehensive basis to inform decisions about insecticide use in different regions. The next step will be to synchronize SIVIEN AEDES data together with epidemiological and climatic data to improve the understanding of the drivers of local variations in arbovirus transmission dynamics. By integrating these surveillance data, health authorities will be better equipped to develop tailored and timely solutions to control and prevent Aedes-borne arbovirus outbreaks.

Tras la epidemia del Zika, se ha intensificado el interés en vigilar y controlar los vectores de arbovirus Aedes aegypti y Aedes albopictus. Aun así, muchos de los sistemas existentes de vigilancia necesitan mejorar. En general son los gobiernos nacionales los que dirigen los programas de control de vectores, aunque estos programas se llevan a cabo a nivel local, por lo que no se tiene en cuenta la heterogeneidad del lugar en cuanto a las características ecológicas y epidemiológicas. Además, normalmente los datos entomológicos y epidemiológicos son recopilados por entidades gubernamentales distintas, lo que puede ralentizar el control de vectores durante un brote. Colombia ha puesto en marcha varias iniciativas para abordar estas cuestiones. La primera es un sistema en línea de geolocación del mosquito Aedes, llamado SIVIEN AEDES, para que los entomólogos de campo puedan registrar la abundancia de los mosquitos vectores y recoger datos sobre la resistencia a los insecticidas. La segunda es la implantación de ovitrampas autocidales para hembras grávidas (AGO, por su sigla en inglés), que son una manera alternativa de medir la abundancia de vectores. La tercera iniciativa es utilizar los datos recogidos por el sistema SIVIEN AEDES para elaborar modelos matemáticos que predigan la abundancia del A. aegypti hasta incluso en una cuadra de ciudad, de manera que las autoridades de salud pública puedan dirigir las intervenciones a vecindarios específicos dentro de las ciudades. Por último, Colombia está vigilando en quince ciudades prioritarias la resistencia a los insecticidas mediante ensayos biológicos y análisis moleculares, de esta forma se genera una base de datos exhaustiva sobre la que fundamentar las decisiones acerca del uso de insecticidas en las diferentes regiones. El paso siguiente será sincronizar los datos recopilados por el sistema SIVIEN AEDES con datos epidemiológicos y climáticos para poder entender mejor cómo se originan las variaciones locales en la dinámica de transmisión de los arbovirus. Al integrar estos datos de vigilancia, las autoridades sanitarias estarán mejor equipadas para encontrar soluciones oportunas y adecuadas para la situación específica, a fin de controlar y prevenir los brotes de arbovirus transmitidos por el Aedes.

Depois da epidemia de zika, intensificou-se o interesse na vigilância e controle dos vetores arbovirais Aedes aegypti e Aedes albopictus, mas muitos dos sistemas de vigilância existentes poderiam ser aprimorados. Muitos programas de controle de vetores são dirigidos pelos governos nacionais, mas implementados no âmbito local, o que leva à desconsideração de heterogeneidades espaciais em aspectos ecológicos e epidemiológicos. Além disso, é comum que dados entomológicos e epidemiológicos sejam coletados por agências governamentais separadas, o que pode desacelerar o controle de vetores em resposta aos surtos. A Colômbia adotou vários enfoques para abordar esses problemas. Primeiro, um sistema de vigilância de Aedes georreferenciado e baseado na Internet, chamado SIVIEN AEDES, foi desenvolvido para permitir aos entomólogos de campo registrar a abundância de vetores e a resistência aos inseticidas. Segundo, ovitrampas letais para fêmeas grávidas estão sendo mobilizadas como maneira alternativa de medir a abundância vetorial. Terceiro, os dados coletados pelo SIVIEN AEDES estão sendo utilizados para desenvolver modelos matemáticos para prever a abundância do Ae. aegypti até o nível de quadra/quarteirão, permitindo assim às autoridades de saúde pública direcionar intervenções para bairros específicos em cada município. Finalmente, a resistência aos inseticidas é monitorada através de ensaios biológicos e testes moleculares em 15 cidades de alta prioridade, o que proporciona uma base abrangente para subsidiar decisões sobre o uso de inseticida em diferentes regiões. O próximo passo será sincronizar os dados do SIVIEN AEDES com dados epidemiológicos e climáticos para melhorar a compreensão dos fatores que impulsionam variações locais na dinâmica da transmissão arboviral. Ao integrar esses dados de vigilância, as autoridades de saúde estarão mais bem equipadas para desenvolver soluções personalizadas e oportunas para controlar e prevenir os surtos de arbovírus transmitidos por mosquitos do gênero Aedes.

RESUMO

[ABSTRACT]. In the wake of the Zika epidemic, there has been intensified interest in the surveillance and control of the arbovirus vectors Aedes aegypti and Aedes albopictus, yet many existing surveillance systems could benefit from improvements. Vector control programs are often directed by national governments, but are carried out at the local level, resulting in the discounting of spatial heterogeneities in ecology and epidemiology. Furthermore, entomological and epidemiological data are often collected by separate governmental entities, which can slow vector control responses to outbreaks. Colombia has adopted several approaches to address these issues. First, a web-based, georeferenced Aedes surveillance system called SIVIEN AEDES was developed to allow field entomologists to record vector abundance and insecticide resistance data. Second, autocidal gravid oviposition (AGO) traps are deployed as an alternative way to measure vector abundance. Third, data collected by SIVIEN AEDES are used to develop mathematical models predicting Ae. aegypti abundance down to a city block, thus allowing public health authorities to target interventions to specific neighborhoods within cities. Finally, insecticide resistance is monitored through bioassays and molecular testing in 15 high-priority cities, providing a comprehensive basis to inform decisions about insecticide use in different regions. The next step will be to synchronize SIVIEN AEDES data together with epidemiological and climatic data to improve the understanding of the drivers of local variations in arbovirus transmission dynamics. By integrating these surveillance data, health authorities will be better equipped to develop tailored and timely solutions to control and prevent Aedes-borne arbovirus outbreaks.

[RESUMEN]. Tras la epidemia del Zika, se ha intensificado el interés en vigilar y controlar los vectores de arbovirus Aedes aegypti y Aedes albopictus. Aun así, muchos de los sistemas existentes de vigilancia necesitan mejorar. En general son los gobiernos nacionales los que dirigen los programas de control de vectores, aunque estos programas se llevan a cabo a nivel local, por lo que no se tiene en cuenta la heterogeneidad del lugar en cuanto a las características ecológicas y epidemiológicas. Además, normalmente los datos entomológicos y epidemiológicos son recopilados por entidades gubernamentales distintas, lo que puede ralentizar el control de vectores durante un brote. Colombia ha puesto en marcha varias iniciativas para abordar estas cuestiones. La primera es un sistema en línea de geolocación del mosquito Aedes, llamado SIVIEN AEDES, para que los entomólogos de campo puedan registrar la abundancia de los mosquitos vectores y recoger datos sobre la resistencia a los insecticidas. La segunda es la implantación de ovitrampas autocidales para hembras grávidas (AGO, por su sigla en inglés), que son una manera alternativa de medir la abundancia de vectores. La tercera iniciativa es utilizar los datos recogidos por el sistema SIVIEN AEDES para elaborar modelos matemáticos que predigan la abundancia del A. aegypti hasta incluso en una cuadra de ciudad, de manera que las autoridades de salud pública puedan dirigir las intervenciones a vecindarios específicos dentro de las ciudades. Por último, Colombia está vigilando en quince ciudades prioritarias la resistencia a los insecticidas mediante ensayos biológicos y análisis moleculares, de esta forma se genera una base de datos exhaustiva sobre la que fundamentar las decisiones acerca del uso de insecticidas en las diferentes regiones. El paso siguiente será sincronizar los datos recopilados por el sistema SIVIEN AEDES con datos epidemiológicos y climáticos para poder entender mejor cómo se originan las variaciones locales en la dinámica de transmisión de los arbovirus. Al integrar estos datos de vigilancia, las autoridades sanitarias estarán mejor equipadas para encontrar soluciones oportunas y adecuadas para la situación específica, a fin de controlar y prevenir los brotes de arbovirus transmitidos por el Aedes.

[RESUMO]. Depois da epidemia de zika, intensificou-se o interesse na vigilância e controle dos vetores arbovirais Aedes aegypti e Aedes albopictus, mas muitos dos sistemas de vigilância existentes poderiam ser aprimorados. Muitos programas de controle de vetores são dirigidos pelos governos nacionais, mas implementados no âmbito local, o que leva à desconsideração de heterogeneidades espaciais em aspectos ecológicos e epidemiológicos. Além disso, é comum que dados entomológicos e epidemiológicos sejam coletados por agências governamentais separadas, o que pode desacelerar o controle de vetores em resposta aos surtos. A Colômbia adotou vários enfoques para abordar esses problemas. Primeiro, um sistema de vigilância de Aedes georreferenciado e baseado na Internet, chamado SIVIEN AEDES, foi desenvolvido para permitir aos entomólogos de campo registrar a abundância de vetores e a resistência aos inseticidas. Segundo, ovitrampas letais para fêmeas grávidas estão sendo mobilizadas como maneira alternativa de medir a abundância vetorial. Terceiro, os dados coletados pelo SIVIEN AEDES estão sendo utilizados para desenvolver modelos matemáticos para prever a abundância do Ae. aegypti até o nível de quadra/quarteirão, permitindo assim às autoridades de saúde pública direcionar intervenções para bairros específicos em cada município. Finalmente, a resistência aos inseticidas é monitorada através de ensaios biológicos e testes moleculares em 15 cidades de alta prioridade, o que proporciona uma base abrangente para subsidiar decisões sobre o uso de inseticida em diferentes regiões. O próximo passo será sincronizar os dados do SIVIEN AEDES com dados epidemiológicos e climáticos para melhorar a compreensão dos fatores que impulsionam variações locais na dinâmica da transmissão arboviral. Ao integrar esses dados de vigilância, as autoridades de saúde estarão mais bem equipadas para desenvolver soluções personalizadas e oportunas para controlar e prevenir os surtos de arbovírus transmitidos por mosquitos do gênero Aedes.

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RESUMO

BACKGROUND: Zika virus (ZIKV) became a global human health concern owing to its rapid spread worldwide and its association with congenital and neurological disorders. The current epidemiological profile of arboviruses in Brazil is characterized by widespread co-circulation of Dengue virus, Chikungunya virus, and ZIKV throughout the country. These viruses cause acute diseases frequently with overlapping symptoms, which could result in an inaccurate diagnosis based solely on clinical and epidemiological grounds. Here we conducted a screening for ZIKV RNA in serum samples from patients across Brazil with suspected ZIKV infection. METHODS: Using RT-qPCR, we investigated ZIKV RNA in 3001 serum samples. Samples were passively acquired through a private laboratory network, between December 2015 and August 2016, from 27 Brazilian Federative Units. We performed descriptive statistics on demographic variables including sex, age, and geographic location. RESULTS: ZIKV was detected in 11.4% (95%CI = 10.3-12.6%) of the sera. ZIKV RNA was detected in sera collected throughout the country, but during the analyzed period, RNA was more frequently detected in samples from the Southeast, Midwest, and North regions (3.9 to 5.8 times higher) when compared to the Northeast and South regions. CONCLUSIONS: These data reinforce the importance of laboratory diagnosis, surveillance systems, and further epidemiological studies to understand the dynamics of outbreaks and diseases associated with ZIKV and other arboviruses.

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RESUMO

Dengue vector Aedes aegypti L. is invading peri-urban and rural areas throughout Latin America. Our previous research in the Peruvian Amazon has shown that river boats are heavily infested with immature and adult Ae. aegypti mosquitoes, likely playing a major role in their long-distance dispersal and successful invasion. However, the presence of immature mosquitoes provides no information about the timing of oviposition, and whether it took place in the boats. Here, we used baited ovitraps deployed on river boats to test the hypothesis that Ae. aegypti oviposition occurs during boat travel. We deployed 360 ovitraps on 60 different barges during August and October of 2013, and February 2014 (with 20 barges sampled during each month). We found that Ae. aegypti mosquitoes in 22 individual ovitraps from 15 of the 60 barges (premise index 25%) across all sampling dates. Further, the distribution of Ae. aegypti egg abundance was highly aggregated: 2.6% of traps (N=7) were responsible for 71.8% of eggs found, and 1.5% of traps (N=4) were responsible for all (100%) of the larvae found. Similarly, 5% of boats were responsible for the 71.47% of eggs. Our results provide strong evidence that Ae. aegypti oviposition commonly occurs during boat travel. Baited ovitraps could represent a cost-effective means of monitoring and controlling mosquito populations on boats.

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BACKGROUND AND OBJECTIVES: The dramatic range expansion of the dengue vector Aedes aegypti is associated with various anthropogenic transport activities, but little is known about the underlying mechanisms driving this geographic expansion. We longitudinally characterized infestation of different vehicle types (cars, boats, etc.) to estimate the frequency and intensity of mosquito introductions into novel locations (propagule pressure). METHODS: Exhaustive adult and immature Ae. aegypti collections were performed on six different vehicle types at five ports and two bus/ taxi departure points in the Amazonian city of Iquitos, Peru during 2013. Aquatic vehicles included 32 large and 33 medium-sized barges, 53 water taxis, and 41 speed boats. Terrestrial vehicles sampled included 40 buses and 30 taxis traveling on the only highway in the region. Ae. aegypti adult infestation rates and immature indices were analyzed by vehicle type, location within vehicles, and sampling date. RESULTS: Large barges (71.9% infested) and medium barges (39.4% infested) accounted for most of the infestations. Notably, buses had an overall infestation rate of 12.5%. On large barges, the greatest number of Ae. aegypti adults were found in October, whereas most immatures were found in February followed by October. The vast majority of larvae (85.9%) and pupae (76.7%) collected in large barges were produced in puddles formed in cargo holds. CONCLUSIONS: Because larges barges provide suitable mosquito habitats (due to dark, damp cargo storage spaces and ample oviposition sites), we conclude that they likely serve as significant contributors to mosquitoes' propagule pressure across long distances throughout the Peruvian Amazon. This information can help anticipate vector population mixing and future range expansions of dengue and other viruses transmitted by Ae. aegypti.

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BACKGROUND AND OBJECTIVES: In the Peruvian Amazon, the dengue vector Aedes aegypti is abundant in large urban centers such as Iquitos. In recent years, it has also been found in a number of neighboring rural communities with similar climatic and socioeconomic conditions. To better understand Ae. aegypti spread, we compared characteristics of communities, houses, and containers in infested and uninfested communities. METHODS: We conducted pupal-demographic surveys and deployed ovitraps in 34 communities surrounding the city of Iquitos. Communities surveyed were located along two transects: the Amazon River and a 95 km highway. We calculated entomological indices, mapped Ae. aegypti presence, and developed univariable and multivariable logistic regression models to predict Ae. aegypti presence at the community, household, or container level. RESULTS: Large communities closer to Iquitos were more likely to be infested with Ae. aegypti. Within infested communities, houses with Ae. aegypti had more passively-filled containers and were more often infested with other mosquito genera than houses without Ae. aegypti. For containers, large water tanks/drums and containers with solar exposure were more likely to be infested with Ae. aegypti. Maps of Ae. aegypti presence revealed a linear pattern of infestation along the highway, and a scattered pattern along the Amazon River. We also identified the geographical limit of Ae. aegypti expansion along the highway at 19.3 km south of Iquitos. CONCLUSION: In the Peruvian Amazon, Ae. aegypti geographic spread is driven by human transportation networks along rivers and highways. Our results suggest that urban development and oviposition site availability drive Ae. aegypti colonization along roads. Along rivers, boat traffic is likely to drive long-distance dispersal via unintentional transport of mosquitoes on boats.

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