Early Evidence for Zika Virus Circulation among Aedes aegypti Mosquitoes, Rio de Janeiro, Brazil.

During 2014-2016, we conducted mosquito-based Zika virus surveillance in Rio de Janeiro, Brazil. Results suggest that Zika virus was probably introduced into the area during May-November 2013 via multiple in-country sources. Furthermore, our results strengthen the hypothesis that Zika virus in the Americas originated in Brazil during October 2012-May 2013.

Contribution of fish farming ponds to the production of immature Anopheles spp. in a malaria-endemic Amazonian town.

BACKGROUND: In the past decade fish farming has become an important economic activity in the Occidental Brazilian Amazon, where the number of new fish farms is rapidly increasing. One of the primary concerns with this phenomenon is the contribution of fishponds to the maintenance and increase of the anopheline mosquito population, and the subsequent increase in human malaria burden. This study reports the results of a 2-year anopheline abundance survey in fishponds and natural water bodies in a malaria-endemic area in northwest Brazil. The objective of this study was to investigate the contribution of natural water bodies (rivers, streams, creeks, ponds, and puddles) and artificial fishponds as breeding sites for Anopheles spp. in Mâncio Lima, Acre and to investigate the effect of limnological and environmental variables on Anopheles spp. larval abundance. METHODS: Natural water bodies and fishponds were sampled at eight different times over 2 years (early, mid and late rainy season, dry season) in the Amazonian town of Mâncio Lima, Acre. Anopheline larvae were collected with an entomological dipper, and physical, chemical and ecological characteristics of each water body were measured. Management practices of fishpond owners were ascertained with a systematic questionnaire. RESULTS: Fishponds were four times more infested with anopheline larvae than natural water bodies. Electrical conductivity and the distance to the nearest house were both significant inverse predictors of larval abundance in natural water bodies. The density of larvae in fishponds raised with increasing border vegetation. Fishponds owned by different farmers varied in the extent of anopheline larval infestation but ponds owned by the same individual had similar infestation patterns over time. Commercial fishponds were 1.7-times more infested with anopheline larvae compared to fishponds for family use. CONCLUSIONS: These results suggest that fishponds are important breeding sites for anopheline larvae, and that adequate management activities, such as removal of border vegetation could reduce the abundance of mosquito larvae, most importantly Anopheles darlingi.

Association among house infestation index, dengue incidence, and sociodemographic indicators: surveillance using geographic information system.

BACKGROUND: We identified dengue transmission areas by using the Geographic Information Systems located at local surveillance units of the Itaboraí municipality in state of Rio de Janeiro. We considered the association among the house infestation index, the disease incidence, and sociodemographic indicators during a prominent dengue outbreak in 2007 and 2008. METHODS: In this ecological study, the Local Surveillance Units (UVLs) of the municipality were used as spatial pattern units. For the house analysis, we used the period of higher vector density that occurred previous to the larger magnitude epidemic range of dengue cases. The average dengue incidence rates calculated in this epidemic range were smoothed using the Bayesian method. The associations among the House Infestation Index (HI), the Bayesian rate of the average dengue incidence, and the sociodemographic indicators were evaluated using a Pearson's correlation coefficient. The areas that were at a higher risk of dengue occurrence were detected using a kernel density estimation with the kernel quartic function. RESULTS: The dengue transmission pattern in Itaboraí showed that the increase in the vector density preceded the increase in incidence. The HI was positively correlated to the Bayesian dengue incidence rate (r = 0.641; p = 0.01). The higher risk areas were those that were close to the main highways. In the Kernel density estimation analysis, we observed that the regions that were at a higher risk of dengue were those that were located in the UVLs and had the highest population densities; these locations were typically located along major highways. Four nuclei were identified as epicenters of high risk. CONCLUSIONS: The spatial analysis units used in this research, i.e., UVLs, served as a methodological resource for examining the compatibility of different information sources concerning the disease, the vector indices, and the municipal sociodemographic aspects and were arranged in distinct cartographic bases. Dengue is a multi-scale geographic phenomenon, and using the UVLs as analysis units made it possible to differentiate the dengue occurrence throughout the municipality. The methodological approach used in this research helped improve the Itaboraí municipality monitoring activities and the local territorial monitoring in other municipalities that are affected by this public health issue.

Discrepancies between Aedes aegypti identification in the field and in the laboratory after collection with a sticky trap.

Currently, sticky traps are regularly employed to assist in the surveillance of Aedes aegypti infestation. We tested two alternative procedures for specimen identification performed by local health agents: directly in the field, as recommended by certain manufacturers, or after transportation to the laboratory. A total of 384 sticky traps (MosquiTRAP) were monitored monthly during one year in four geographically representative Brazilian municipalities. When the same samples were inspected in the field and in the laboratory, large differences were noted in the total number of mosquitoes recorded and in the number of specimens identified as Ae. aegypti by both procedures. Although field identification has the potential to speed vector surveillance, these results point to uncertainties in the evaluated protocol.

Male accessory gland substances from Aedes albopictus affect the locomotor activity of Aedes aegypti females.

Dengue is one of the world's most important mosquito-borne diseases and is usually transmitted by one of two vector species: Aedes aegypti or Aedes albopictus . These two diurnal mosquitoes are frequently found coexisting in similar habitats, enabling interactions between adults, such as cross-mating. The objective of this study was to assess cross-mating between Ae. aegypti females and Ae. albopictus males under artificial conditions and evaluate the locomotor activity of Ae. aegypti virgin females injected with male accessory gland (MAG) homogenates to infer the physiological and behavioural responses to interspecific mating. After seven days of exposure, 3.3-16% of Ae. aegypti females mated with Ae. albopictus males. Virgin Ae. aegypti females injected with conspecific and heterospecific MAGs showed a general decrease in locomotor activity compared to controls and were refractory to mating with conspecific males. The reduction in diurnal locomotor activity induced by injections of conspecific or heterospecific MAGs is consistent with regulation of female reproductive activities by male substances, which are capable of sterilising female Ae. aegypti through satyrisation by Ae. albopictus.

Spatio-Temporal Cluster Detection of Dengue, Chikungunya, and Zika Viruses' Infection in Rio de Janeiro State from 2010 to 2019.

Dengue (DENV), chikungunya (CHIKV), and Zika (ZIKV) virus infections are widespread throughout the Rio de Janeiro state. The co-circulation of these emergent arboviruses constitutes a serious public health problem, resulting in outbreaks that can spatially and temporally overlap. Environmental conditions favor the presence, maintenance, and expansion of Aedes aegypti, the primary vector of these urban arboviruses. This study assessed the detection of clusters of urban arboviruses in the Rio de Janeiro state from 2010 to 2019. Notified cases of dengue, chikungunya, and Zika were grouped by year according to the onset of symptoms and their municipality of residence. The study period recorded the highest number of dengue epidemics in the state along with the simultaneous circulation of chikungunya and Zika viruses. The analyzes showed that the central municipalities of the metropolitan regions were associated with higher risk areas. Central municipalities in metropolitan regions were the first most likely clusters for dengue and Zika, and the second most likely cluster for chikungunya. Furthermore, the northwest and north regions were comprised clusters with the highest relative risk for the three arboviruses, underscoring the impact of these arboviruses in less densely populated regions of Brazil. The identification of high-risk areas over time highlights the need for effective control measures, targeted prevention and control interventions for these urban arboviral diseases.

Entomological Surveillance of Aedes Mosquitoes: Comparison of Different Collection Methods in an Endemic Area in RIO de Janeiro, Brazil.

Using collection methods for Aedes adults as surveillance tools provides reliable indices and arbovirus detection possibilities. This study compared the effectiveness of different methods for collecting Ae. aegypti and Ae. albopictus and detecting arboviruses circulating in field-caught female specimens. Collection sites were defined in urban, peri-urban, and rural landscapes in two Brazilian cities. Collections were performed using Adultraps (ADT), BG-Sentinel (BGS), CDC-like traps (CDC), and indoor (ASP-I) and outdoor (ASP-O) aspiration during the rainy and dry seasons of 2015 and 2016. Generalized linear mixed models were used to model the effectiveness of each collection method. A total of 434 Ae. aegypti and 393 Ae. albopictus were collected. In total, 64 Ae. aegypti and sixteen Ae. albopictus female pools were tested for DENV, CHIKV, ZIKV, or YFV; none were positive. Positivity and density were linear at low densities (<1 specimen); thereafter, the relationship became non-linear. For Ae. aegypti, ADT and CDC were less effective, and ASP-I and ASP-O were as effective as BGS. For Ae. albopictus, all collection methods were less effective than BGS. This study highlights the need for an integrated surveillance method as an effective tool for monitoring Aedes vectors.

Dengue, Chikungunya, and Zika: Spatial and Temporal Distribution in Rio de Janeiro State, 2015-2019.

Simultaneous spatial circulation of urban arboviral diseases, such as dengue, chikungunya, and Zika, is a major challenge. In this ecological study of urban arboviruses performed from 2015 to 2019, we analyzed the spatial and temporal dynamics of these arboviruses in all 92 municipalities and nine health regions of Rio de Janeiro state. Annual cumulative incidences are presented for all three arboviruses throughout the study period. Spatial analyses of the three studied arboviruses showed distinct behaviors among municipalities and health regions. Co-circulation of the three arboviruses in the state and a heterogeneous spatiotemporal pattern was observed for each disease and region, with dengue having a higher annual incidence during the five years of the study, as well as two consecutive epidemic years in the state. The increase in transmission in different regions of the state in one year culminated in an epidemic in the state in the following year. A high annual cumulative incidence of chikungunya occurred in municipalities from 2017 to 2019 and of Zika only in 2016. Some municipalities with higher population densities showed higher incidences for some arboviruses and appeared to contribute to the dissemination to cities of lower demographic density and maintenance of these urban arboviruses. Thus, regions recording increased incidences of the three diseases in their territories for long periods should be considered municipal poles, as they initiated and sustained high transmission within their region.

Spatial and Temporal Distribution of Aedes aegypti and Aedes albopictus Oviposition on the Coast of Paraná, Brazil, a Recent Area of Dengue Virus Transmission.

Aedes aegypti and Aedes albopictus are considered the most important vectors of arboviruses in the world. Aedes aegypti is the primary vector of dengue, urban yellow fever, chikungunya and zika in Brazil, and Ae. albopictus is considered a potential vector. Distribution patterns and the influence of climatic variables on the oviposition of Ae. aegypti and Ae. albopictus were evaluated in Morretes, a tourist city in the coastal area of Paraná State, Brazil, which has recently been experiencing cases of dengue fever. Eggs were collected using ovitraps over a period of one year (September 2017 to September 2018) and reared from hatching until the emergence of the adults. Both Aedes species were found in anthropized areas with a high human density index. Findings suggest that the monthly average temperature (LRT = 16.65, p = 0.001) had significant positive influences on the oviposition of the Aedes species. Considering the wide distribution of DENV around the Paraná coast and the presence of Ae. albopictus alongside Ae. aegypti, studies on natural arbovirus infection patterns and seasonality are recommended in the region.

[ARBOALVO: territorial stratification for definition of areas for prompt response by surveillance and timely control of urban arbovirus infections]. / ARBOALVO: estratificação territorial para definição de áreas de pronta resposta para vigilância e controle de arboviroses urbanas em tempo oportuno.

The study aimed to present the methodological proposal entitled "Prompt Response", modelled in the cities of Belo Horizonte (Minas Gerais State) and Natal (Rio Grande do Norte State), Brazil. The proposal aims to identify and demarcate priority areas for timely targeting of surveillance activities, aiming to reduce the intensity and velocity in the spread of epidemics in endemic urban areas. The methodology uses three variables that represent the necessary causes for the production and reproduction of dengue: notified cases (virus), Aedes eggs (vector), and population (host). This was an ecological study that used data from three information planes aggregated in finer temporal and spatial scales of 3 to 4 weeks and 400 to 600-meter grids, respectively. The prompt response areas were defined by Scan statistical analysis with definition of simultaneous spatial clusters for the three planes via the SaTScan program. In Natal, the areas defined as prompt response occupied, on average, 15.2% of the city's territory and concentrated 67.77% of the dengue cases in the period following demarcation of the prompt response areas. In Belo Horizonte, the observed proportions were 64.16% of cases in 23.23% of the territory. These results were obtained in two cities with different socioenvironmental and geographic realities and distinct epidemiological profiles, indicating that the methodology can be applied to different urban realities, allowing control programs to concentrate on reduced portions of the territory and impacting a high percentage of cases in timely fashion.

O objetivo deste trabalho foi apresentar a proposta metodológica denominada de "Pronta Resposta" modelada nas cidades de Belo Horizonte (Minas Gerais) e Natal (Rio Grande do Norte), Brasil. A metodologia visa identificar e delimitar áreas prioritárias para o direcionamento das ações de vigilância em tempo oportuno, buscando a redução da intensidade e velocidade da dispersão de epidemias em áreas urbanas endêmicas. Para tanto, a metodologia utiliza três variáveis, que representam as causas necessárias para a produção e reprodução da dengue: casos notificados (vírus), ovos de Aedes (vetor) e população (hospedeiro). Trata-se de um estudo ecológico que utilizou os dados dos três planos de informações agregados em escalas temporais e espaciais mais finas, de três a quatro semanas e grades de 400 a 600 metros respectivamente. As áreas de pronta resposta foram definidas por meio de análise estatística de varredura Scan, com definição de clusters espaciais simultâneos para os três planos por meio do programa SaTScan. Os resultados observados foram: na cidade de Natal, as áreas definidas como pronta resposta ocuparam em média 15,2% do território do município e concentraram 67,77% dos casos de dengue do período posterior ao utilizado na delimitação das áreas de pronta resposta, e em Belo Horizonte, os números observados foram de 64,16% dos casos em 23,23% do território. Esses resultados foram obtidos em duas cidades com realidades socioambientais e geográficas diferentes e com perfis epidemiológicos também distintos, apontando que a metodologia pode ser aplicada em diferentes realidades urbanas, criando a possibilidade de os programas de controle atuarem em porções reduzidas do território e impactar num alto percentual de casos em tempo oportuno.

El objetivo del trabajo fue presentar la propuesta metodológica, denominada de "Resposta Rápida", modelada en las ciudades de Belo Horizonte (Minas Gerais) y Natal (Rio Grande do Norte), Brasil. Esta última tiene como meta identificar y delimitar áreas prioritarias para la ejecución de acciones de vigilancia en el momento oportuno, buscando la reducción de la intensidad y velocidad de la dispersión de epidemias en áreas urbanas endémicas. Para tal fin, la metodología utiliza tres variables, que representan las causas necesarias para la producción y reproducción del dengue: casos notificados (virus), huevos de Aedes (vector) y población (huésped). Se trata de un estudio ecológico que utilizó los datos de los tres planos de información agregados en escalas temporales y espaciales más finas, de 3 a 4 semanas y tablas de 400 a 600 metros respectivamente. Las áreas de respuesta rápida se definieron a través del análisis estadístico de exploración Scan, con definición de clústeres espaciales simultáneos para los tres planos mediante el programa SaTScan. Los resultados observados fueron: en la ciudad de Natal, las áreas definidas como de respuesta rápida ocuparon de media un 15,2% del territorio del municipio y concentraron un 67,77% de los casos de dengue del período posterior al utilizado en la delimitación de las áreas de respuesta rápida y, en Belo Horizonte, los números observados fueron un 64,16% de los casos en un 23,23% del territorio. Estos resultados se obtuvieron en dos ciudades con realidades socioambientales y geográficas diferentes y con perfiles epidemiológicos también distintos, apuntando que la metodología se puede aplicar en diferentes realidades urbanas. Dando la posibilidad de que los programas de control actúen en secciones reducidas del territorio e impactar en un alto porcentaje de casos en el momento oportuno.

ArboAlvo: stratification method for territorial receptivity to urban arboviruses.

OBJECTIVE: To present the urban arboviruses (dengue, zika and chikungunya) stratification methodology by the territorial receptivity Index, an instrument for the surveillance and control of these diseases, which considers the heterogeneity of an intra-municipal territory. METHODS: Ecological study that uses as unit of analysis the areas covered by health centers in Belo Horizonte. For the development of a territorial receptivity index, indicators of socio-environmental determination of urban arboviruses were selected in order to integrate the analysis of main components. The resulting components were weighted by the analytic hierarchy process and combined via map algebra. RESULTS: The territorial receptivity index showed great heterogeneity of urban infrastructure conditions. The areas classified with high and very high receptivity correspond to approximately 33% of the occupied area and are mainly concentrated in the administrative planning regions of East, Northeast, North, West, and Barreiro, especially in areas surrounding the municipality. When the density of dengue cases and Aedes eggs, from 2016, were superimposed with the stratification by the index of territorial receptivity to urban arboviruses, areas of very high receptivity had a high density of cases and Aedes eggs - higher than that observed in other areas of the city, which corresponds to a very small percentage of the municipal territory (13.5%). CONCLUSION: The analyses indicate the need for the development of adequate surveillance and control actions for each context, overcoming the logic of homogeneous allocation throughout the territory.

Expression of trypsin-like serine peptidases in pre-imaginal stages of Aedes aegypti (Diptera: Culicidae).

This study reports the biochemical characterization and comparative analyses of highly active serine proteases in the larval and pupal developmental stages of Aedes aegypti (Linnaeus) using substrate-SDS-PAGE. Zymographic analysis of larval stadia detected proteolytic activity in 6-8 bands with apparent molecular masses ranging from 20 to 250 kDa, with activity observed from pH 5.5 to 10.0. The pupal stage showed a complex proteolytic activity in at least 11 bands with apparent Mr ranging from 25 to 250 kDa, and pH optimum at 10.0. The proteolytic activities of both larval and pupal stages were strongly inhibited by phenyl-methyl sulfonyl-fluoride and N-α-Tosyl-L-lysine chloromethyl ketone hydrochloride, indicating that the main proteases expressed by these developmental stages are trypsin-like serine proteases. The enzymes were active at temperatures ranging from 4 to 85°C, with optimal activity between 37 and 60°C, and low activity at 85°C. Comparative analysis between the proteolytic enzymes expressed by larvae and pupae showed that substantial changes in the expression of active trypsin-like serine proteases occur during the developmental cycle of A. aegypti.

Analysis of climate factors and dengue incidence in the metropolitan region of Rio de Janeiro, Brazil.

Dengue is a re-emerging disease, currently considered the most important mosquito-borne arbovirus infection affecting humankind, taking into account both its morbidity and mortality. Brazil is considered an endemic country for dengue, such that more than 1,544,987 confirmed cases were notified in 2019, which means an incidence rate of 735 for every 100 thousand inhabitants. Climate is an important factor in the temporal and spatial distribution of vector-borne diseases, such as dengue. Thus, rainfall and temperature are considered macro-factors determinants for dengue, since they directly influence the population density of Aedes aegypti, which is subject to seasonal fluctuations, mainly due to these variables. This study examined the incidence of dengue fever related to the climate influence by using temperature and rainfall variables data obtained from remote sensing via artificial satellites in the metropolitan region of Rio de Janeiro, Brazil. The mathematical model that best fits the data is based on an auto-regressive moving average with exogenous inputs (ARMAX). It reproduced the values of incidence rates in the study period and managed to predict with good precision in a one-year horizon. The approach described in present work may be replicated in cities around the world by the public health managers, to build auxiliary operational tools for control and prevention tasks of dengue, as well of other arbovirus diseases.

A Perspective on Inhabited Urban Space: Land Use and Occupation, Heat Islands, and Precarious Urbanization as Determinants of Territorial Receptivity to Dengue in the City of Rio De Janeiro.

INTRODUCTION: Rio de Janeiro is the second-largest city in Brazil, with strong socio-spatial segregation, and diverse and heterogeneous land use, occupation, and landscapes. The complexity of dengue requires the construction of surveillance and control tools that take into account the historical, social, economic, and environmental processes mediated in the territory as a central axis of public policy. In this context, this study aimed to stratify the city into areas of receptivity to dengue, using innovative "territorial indicators" because they are built based on the actual occupation of the territory. METHODS: We designed and constructed 17 indicators that sought to characterize the transformed and inhabited space according to receptivity to dengue. We used data on land use and occupation, connectivity, climate, and landscape. We developed the dengue receptivity through principal component analysis (PCA), using multiple criteria analysis and map algebra integrated in a GIS platform. RESULTS: The most receptive areas were concentrated in the transition between the north and west zones of the city, a region of unconsolidated urban sprawl. The areas of greatest receptivity had the highest incidence and density of Aedes eggs during the study period. The correlation between receptivity index and incidence rate was positive in the epidemic years. CONCLUSION: The proposed set of indicators was able to identify areas of greater receptivity, such as regions of disorderly urban sprawl, with a concentration of social and environmental processes that are related to the occurrence of dengue outbreaks and high vector density. On the other hand, population immunity plays an important role in the spatial distribution of dengue during non-epidemic years.

High-Throughput Method for Detection of Arbovirus Infection of Saliva in Mosquitoes Aedes aegypti and Ae. albopictus.

Vector competence refers to the ability of a vector to acquire, maintain, and transmit a pathogen. Collecting mosquito saliva in medium-filled capillary tubes has become the standard for approximating arbovirus transmission. However, this method is time-consuming and labor-intensive. Here we compare the capillary tube method to an alternative high-throughput detection method the collection of saliva on paper cards saturated with honey, with (FTA card) and without (filter paper) reagents for the preservation of nucleic acid for Aedes aegypti and Aedes albopictus mosquitoes infected with two emerging genotypes of the chikungunya virus (CHIKV). Model results showed that the Asian genotype CHIKV dissemination in the harvested legs of both Ae. aegypti and Ae. albopictus increased the odds of females having a positive salivary infection and higher salivary viral titers, while for the IOL genotype the same effect was observed only for Ae. aegypti. Of the three tested detection methods, the FTA card was significantly more effective at detecting infected saliva of Ae. aegypti and Ae. albopictus females than the capillary tube and filter paper was as effective as the capillary tube for the Asian genotype. We did not find significant effects of the detection method in detecting higher viral titer for both Asian and IOL genotypes. Our results are discussed in light of the limitations of the different tested detection methods.

Diversity of mosquito (Diptera: Culicidae) vectors in a heterogeneous landscape endemic for arboviruses.

BACKGROUND: In Brazil and several countries in the Americas, where dengue, chikungunya and Zika are cocirculating, there is a need to understand how different mosquito species relate to landscape and humans. Mosquito ecology and distribution, especially at finer spatial scales, are key factors to study since the relationship of mosquito communities to their habitats might have important consequences in the risk of disease transmission to humans. The aim of this study was to evaluate the diversity of resident culicids along heterogeneous landscapes in different endemic cities for dengue, chikungunya and Zika. METHODS: Fourteen collection sites were randomly selected in six landscapes characterized as urban, periurban and rural along two endemic metropolitan cities in Rio de Janeiro, Brazil: Itaboraí and Cachoeiras de Macacu, Rio de Janeiro. In each site, adult mosquito collections were performed using different traps and backpack aspiration. Collections took place during the rainy and dry seasons of 2015 and 2016. To measure diversity in each landscape, we generated species accumulation curves and used different indexes: rarefied species richness, Chao1-bc and ACE-1. Mosquito habitat segregation along different land use types was measured with a partial canonical correspondence analysis (pCCA). Generalized linear mixed models (GLMM) were used to model the probability of occurrence of the most abundant species along an Urban-Forest gradient. RESULTS: A total of 13,462 adult mosquitoes from 10 genera and 41 species were collected. The most abundant species were Culex quinquefasciatus Say, 1823, Aedes aegypti (Linnaeus, 1762) and Aedes albopictus (Skuse, 1895). There was a significant association between rarefied species richness and landscape, with higher richness in the Rural landscape. The number of observed species was matched only in the Urban landscape. Most species showed segregation along an Urban-Forest gradient, and the great majority were associated with forested habitats. We were able to fit prediction models for six mosquito species. DISCUSSION: The paper discusses the impact of human activities on landscape and its effects on mosquito populations, focusing on the segregation of different known vector species and their proximity to human altered environments. Most of these species are known arbovirus vectors and knowledge of their distribution are key elements that health authorities should take into account when planning arbovirus surveillance and vector control activities.

The Asian tiger mosquito in Brazil: Observations on biology and ecological interactions since its first detection in 1986.

Aedes (Stegomyia) albopictus is a mosquito originating from the Asian continent, which was detected in the Americas in 1985 and Brazil in 1986. Due to its rapid expansion throughout Brazil, this species has already been reported in 26 of the 27 federative units of Brazil. In this review, we evaluate some of the biological, epidemiological and ecological characteristics of Ae. albopictus through critical analysis of their importance in the pathogen transmission dynamics, since its first record in the country. We show that immature forms of this species are frequently found in artificial breeding sites whereas females exhibit anthropophilic behavior despite its eclecticism on blood feeding. In addition, Ae. albopictus shows advantages in interspecific competition with Ae. aegypti for both immature and adult stages. Taking together, these aspects as well as its vector competence indicate that Ae. albopictus could act as a bridge vector between sylvatic and urban pathogen transmission cycles. We conclude by pointing to the need of continuous surveillance of Ae. albopictus in Brazil and raise several questions that still need to be answered.

Interspecific Mating Effects on Locomotor Activity Rhythms and Refractoriness of Aedes albopictus (Diptera: Culicidae) Females.

This study tests the hypotheses that the locomotor activity of Ae. albopictus females is not significantly altered by the presence of accessory gland (AG) extracts from conspecific and heterospecific males, and that Ae. albopictus females remain receptive to mating with conspecific males even after receiving AG of Ae. aegypti males. Virgin Ae. albopictus females were injected with saline (control group), AG extracts of Ae. aegypti males (aegMAG) or AG extracts of Ae. albopictus males (albMAG). Locomotor activity was evaluated under 12 h of light and 12 h of darkness at 25 °C. All live Ae. albopictus females were subsequently exposed to conspecific males for 48 h, and their spermathecae were dissected for the presence of sperm. Females injected with aegMAG and albMAG showed significant decreases in total, diurnal and diurnal without lights-on Period activities. Females injected with aegMAG showed significant decreases in nocturnal and nocturnal without lights-off period activities. Females injected with albMAG showed significant decreases in lights-off activity. A total of 83% of Ae. albopictus females injected with aegMAG and 10% of females injected with albMAG were inseminated by conspecific males. These results, coupled with our previous paper on MAG and interspecific mating effects on female Ae. aegypti, demonstrate contrasting outcomes on locomotor activities and loss of sexual receptivity, both conspecific and heterospecific MAGs capable of sterilizing virgin Ae. aegypti, but only conspecific MAGs sterilizing Ae. albopictus, whereas locomotor activities were depressed in females of both species after heterospecific and conspecific injections or treatments.

Seasonal dynamics of Aedes aegypti (Diptera: Culicidae) in the northernmost state of Brazil: a likely port-of-entry for dengue virus 4.

Roraima is the northernmost state of Brazil, bordering both Venezuela and Guyana. Appropriate climate and vector conditions for dengue transmission together with its proximity to countries where all four dengue serotypes circulate make this state, particularly the capital Boa Vista, strategically important for dengue surveillance in Brazil. Nonetheless, few studies have addressed the population dynamics of Aedes aegypti in Boa Vista. In this study, we report temporal and spatial variations in Ae. aegypti population density using ovitraps in two highly populated neighbourhoods; Centro and Tancredo Neves. In three out of six surveys, Ae. aegypti was present in more than 80% of the sites visited. High presence levels of this mosquito suggest ubiquitous human exposure to the vector, at least during part of the year. The highest infestation rates occurred during the peak of the rainy seasons, but a large presence was also observed during the early dry season (although with more variation among years). Spatial distribution of positive houses changed from a sparse and local pattern to a very dense pattern during the dry-wet season transition. These results suggest that the risk of dengue transmission and the potential for the new serotype invasions are high for most of the year.

Experimental Vertical Transmission of Chikungunya Virus by Brazilian and Florida Aedes Albopictus Populations.

Chikungunya virus (CHIKV) is a vector-borne alphavirus transmitted by the bites of mosquitoes, specifically infected, female mosquitoes of the invasive Aedes species. In nature, CHIKV can be maintained by vertical transmission, a phenomenon that relates to the transfer of CHIKV from the infected parent to their offspring within the ovary or during oviposition. In the present study, we conducted laboratory experiments to determine vertical transmission with Ae. albopictus populations from Brazil and Florida. Parental Ae. albopictus females were orally infected with the emergent Asian genotype of CHIKV in the first gonotrophic cycle (infectious blood meal) and tested for vertical transmission following the second (non-infectious blood meal) gonotrophic cycle. CHIKV infection and CHIKV viral titer in parental females were significantly related to population origin, with Brazilian Ae. albopictus showing higher viral dissemination and viral titer than the Florida population. Experimental vertical transmission of CHIKV was documented in one pool of female and four pools of male Ae. albopictus from Brazil (minimum infection rate, MIR, of 0.76% and 2.86%, respectively, for females and males). For the Florida population of Ae. albopictus, only one pool of males was positive for CHIKV infection, with an MIR of 1.06%. Our results demonstrate that Ae. albopictus populations from Brazil and Florida show heterogeneous CHIKV dissemination and vertical transmission, which may contribute to the epidemiology of CHIKV and may be particularly relevant to virus survival during inter-epidemic periods.