Social and environmental determinants of Aedes aegypti infestation in Central Havana: results of a case-control study nested in an integrated dengue surveillance programme in Cuba

Automatic mapping of high-risk urban areas for Aedes aegypti infestation based on building facade image analysis

BACKGROUND

Dengue, Zika, and chikungunya, whose viruses are transmitted mainly by Aedes aegypti, significantly impact human health worldwide. Despite the recent development of promising vaccines against the dengue virus, controlling these arbovirus diseases still depends on mosquito surveillance and control. Nonetheless, several studies have shown that these measures are not sufficiently effective or ineffective. Identifying higher-risk areas in a municipality and directing control efforts towards them could improve it. One tool for this is the premise condition index (PCI); however, its measure requires visiting all buildings. We propose a novel approach capable of predicting the PCI based on facade street-level images, which we call PCINet.

METHODOLOGY

Our study was conducted in Campinas, a one million-inhabitant city in São Paulo, Brazil. We surveyed 200 blocks, visited their buildings, and measured the three traditional PCI components (building and backyard conditions and shading), the facade conditions (taking pictures of them), and other characteristics. We trained a deep neural network with the pictures taken, creating a computational model that can predict buildings' conditions based on the view of their facades. We evaluated PCINet in a scenario emulating a real large-scale situation, where the model could be deployed to automatically monitor four regions of Campinas to identify risk areas.

PRINCIPAL FINDINGS

PCINet produced reasonable results in differentiating the facade condition into three levels, and it is a scalable strategy to triage large areas. The entire process can be automated through data collection from facade data sources and inferences through PCINet. The facade conditions correlated highly with the building and backyard conditions and reasonably well with shading and backyard conditions. The use of street-level images and PCINet could help to optimize Ae. aegypti surveillance and control, reducing the number of in-person visits necessary to identify buildings, blocks, and neighborhoods at higher risk from mosquito and arbovirus diseases.

Local Economic Conditions Affect Aedes albopictus Management

Invasive mosquitoes are an emerging public health issue, as many species are competent vectors for pathogens. We assessed how multiple environmental and socio-economic factors affected the engagement of municipalities in Italy (n = 7679) in actions against Aedes albopictus, an invasive mosquito affecting human health and well-being, between 2000 and 2020. We collected information about mosquito control from official documents and municipal websites and modeled the role played by multiple environmental and socioeconomic factors characterizing each municipality through the random forest algorithm. Municipalities are more prone to manage A. albopictus if more urbanized, in lowlands and with long infestation periods. Moreover, these variables are more predictive of management in municipalities with a high median income and thus more economic resources. Only 25.5% of Italian municipalities approved regulations for managing A. albopictus, and very few of them were in Southern Italy, the most deprived area of the country. Our findings indicate that local economic conditions moderate the effect of other drivers of mosquito control and ultimately can lead to better management of A. albopictus. If the management of invasive mosquitoes, or other forms of global change, is subjected to local economic conditions, economic inequalities will jeopardize the success of large-scale policies, also raising issues of environmental and climate justice.

Density of Aedes aegypti (Diptera: Culicidae) in a low-income Brazilian urban community where dengue, Zika, and chikungunya viruses co-circulate

BACKGROUND

Low-income urban communities in the tropics often lack sanitary infrastructure and are overcrowded, favoring Aedes aegypti proliferation and arboviral transmission. However, as Ae. aegypti density is not spatially homogeneous, understanding the role of specific environmental characteristics in determining vector distribution is critical for planning control interventions. The objectives of this study were to identify the main habitat types for Ae. Aegypti, assess their spatial densities to identify major hotspots of arbovirus transmission over time and investigate underlying factors in a low-income urban community in Salvador, Brazil. We also tested the field-collected mosquitoes for arboviruses.

METHODS

A series of four entomological and socio-environmental surveys was conducted in a random sample of 149 households and their surroundings between September 2019 and April 2021. The surveys included searching for potential breeding sites (water-containing habitats) and for Ae. aegypti immatures in them, capturing adult mosquitoes and installing ovitraps. The spatial distribution of Ae. aegypti density indices were plotted using kernel density-ratio maps, and the spatial autocorrelation was assessed for each index. Visual differences on the spatial distribution of the Ae. aegypti hotspots were compared over time. The association of entomological findings with socio-ecological characteristics was examined. Pools of female Ae. aegypti were tested for dengue, Zika and chikungunya virus infection.

RESULTS

Overall, 316 potential breeding sites were found within the study households and 186 in the surrounding public spaces. Of these, 18 (5.7%) and 7 (3.7%) harbored a total of 595 and 283 Ae. aegypti immatures, respectively. The most productive breeding sites were water storage containers within the households and puddles and waste materials in public areas. Potential breeding sites without cover, surrounded by vegetation and containing organic matter were significantly associated with the presence of immatures, as were households that had water storage containers. None of the entomological indices, whether based on immatures, eggs or adults, detected a consistent pattern of vector clustering in the same areas over time. All the mosquito pools were negative for the tested arboviruses.

CONCLUSIONS

This low-income community displayed high diversity of Ae. aegypti habitats and a high degree of heterogeneity of vector abundance in both space and time, a scenario that likely reflects other low-income communities. Improving basic sanitation in low-income urban communities through the regular water supply, proper management of solid wastes and drainage may reduce water storage and the formation of puddles, minimizing opportunities for Ae. aegypti proliferation in such settings.

Features of the urban environment associated with Aedes aegypti abundance in high-rise public apartments in Singapore: An environmental case-control study

Aedes aegypti abundance in residential estates is hypothesized to contribute to localised outbreaks of dengue in Singapore. Knowing the factors in the urban environment underlying high Ae. aegypti abundance could guide intervention efforts to reduce Ae. aegypti breeding and the incidence of dengue. In this study, objective data on Ae. aegypti abundance in public apartment blocks estimated by Singapore's nationally representative Gravitrap surveillance system was obtained from the National Environmental Agency. Low and high abundance status public apartment blocks were classified based on the Gravitrap Aegypti Index, corresponding to the lowest and highest quartiles respectively. An environmental case-control study was conducted, wherein a blinded assessment of urban features hypothesised to form breeding habitats was conducted in 50 randomly sampled public apartment blocks with low and high abundance statuses each. Logistic regression was performed to identify features that correlated with abundance status. A multivariable logistic model was created to determine key urban features found in corridors and void decks which were predictive of the Ae. aegypti abundance status of the public apartment block. At a statistical level of significance of 0.20, the presence of gully traps [Odds Ratio (OR): 1.34, 95% Confidence Interval (CI): 1.10, 1.66], age of the public apartment block [OR: 2.23, 95% CI: 1.48, 3.60], housing price [OR: 0.33, 95% CI: 0.16, 0.61] and corridor cleanliness [OR: 0.67, 95% CI: 0.40, 1.07] were identified as important predictors of abundance status. To reduce Ae. aegypti abundance around public apartment blocks and potential onward dengue transmission, gully traps could be remodelled or replaced by other drainage types. Routine inspections of Ae. aegypti breeding should be targeted at older and low-income neighbourhoods. Campaigns for cleaner corridors should be promoted.

Spatio-temporal dynamics of three diseases caused by Aedes-borne arboviruses in Mexico

Background

The intensity of transmission of Aedes-borne viruses is heterogeneous, and multiple factors can contribute to variation at small spatial scales. Illuminating drivers of heterogeneity in prevalence over time and space would provide information for public health authorities. The objective of this study is to detect the spatiotemporal clusters and determine the risk factors of three major Aedes-borne diseases, Chikungunya virus (CHIKV), Dengue virus (DENV), and Zika virus (ZIKV) clusters in Mexico.

Methods

We present an integrated analysis of Aedes-borne diseases (ABDs), the local climate, and the socio-demographic profiles of 2469 municipalities in Mexico. We used SaTScan to detect spatial clusters and utilize the Pearson correlation coefficient, Randomized Dependence Coefficient, and SHapley Additive exPlanations to analyze the influence of socio-demographic and climatic factors on the prevalence of ABDs. We also compare six machine learning techniques, including XGBoost, decision tree, Support Vector Machine with Radial Basis Function kernel, K nearest neighbors, random forest, and neural network to predict risk factors of ABDs clusters.

Results

DENV is the most prevalent of the three diseases throughout Mexico, with nearly 60.6% of the municipalities reported having DENV cases. For some spatiotemporal clusters, the influence of socio-economic attributes is larger than the influence of climate attributes for predicting the prevalence of ABDs. XGBoost performs the best in terms of precision-measure for ABDs prevalence.

Conclusions

Both socio-demographic and climatic factors influence ABDs transmission in different regions of Mexico. Future studies should build predictive models supporting early warning systems to anticipate the time and location of ABDs outbreaks and determine the stand-alone influence of individual risk factors and establish causal mechanisms.

Social and housing indicators of dengue and chikungunya in Indian adults aged 45 and above: Analysis of a nationally representative survey (2017-18)

Background

Dengue and chikungunya (CHIKV) are the two major vector-borne diseases of serious public health concern in India. Studies on socioeconomic and housing determinants of dengue and CHIKV at a pan-India level are lacking. Here, we took advantage of the recently carried out Longitudinal Ageing Study in India (LASI) carried out across all the states and Union Territories of India to study the social indicators of dengue and CHIKV in India.

Methods

LASI-1 (2017-2018) data on the self-reported period prevalence of dengue and CHIKV from 70,932 respondents aged ≥45 years were used for this analysis. The state-wise distribution of dengue and CHIKV was mapped. Prevalence was estimated for each study variable, and the difference was compared using the χ2 test. The adjusted odds ratios (AOR) of the socioeconomic and housing variables for dengue and CHIKV were estimated using the multiple logistic regression model.

Results

Urban residence is the major socio-economic indicator of dengue and CHIKV (dengue AOR: 1.57, 95% CI: 1.18-2.11; CHIKV AOR: 1.84, 95% CI: 1.36-2.49). The other notable indicator is wealth; rich respondents have higher odds of dengue and CHIKV. Adults older than 54 years and those with high school education and above are associated with a lower likelihood of dengue and CHIKV. In addition, CHIKV is associated with scheduled and forward castes, households with improper toilet facilities, open defecation, and kutcha house type.

Conclusions

Despite the limitation that the data is only from adults ≥ 45, this analysis provides important insights into the socioeconomic and housing variables associated with higher odds of dengue and CHIKV in India. Understanding these determinants may assist in the national planning of prevention and control strategies for dengue and CHIKV.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13690-022-00868-5.

Knowledge, Attitudes, Beliefs, and Practices Regarding Dengue in La Réunion Island, France

Since 2017, La Réunion island has been facing a major epidemic of dengue. Despite actions carried out by the anti-vector control department, public authorities have failed to contain this epidemic. As individual involvement is key to success in vector control, we carried out a mixed-methods study on population knowledge, attitudes, beliefs, and practices (KABP) regarding dengue infection risk in La Réunion. The study combined quantitative data collected through a questionnaire administered to a representative sample of 622 people to assess the use of protective measures and the perception of severity and risk of dengue, and a sample of 336 people to assess the level of knowledge and concern about dengue, as well as qualitative data collected through semi-structured interviews among 11 individuals who had previously completed the questionnaire. The study results show that 63% of the surveyed population had a good level of knowledge associated with age, education, and socio-professional category variables—78% considered dengue to be a serious threat, and concern was estimated at 6/10, while 71% were likely to use protective measures. The interviews revealed contradictory behaviors in the implementation of recommended actions, in conflict with personal beliefs regarding respect of human body and nature. The study also revealed a loss of confidence in public authorities.

Forest Coverage and Socioeconomic Factors Associated with Dengue in El Salvador, 2011-2013

Dengue virus serotypes 1, 2, 3, and 4 are transmitted by Aedes aegypti and Aedes albopictus mosquitoes, which cause illness in an estimated 100 million annually. Although dengue viruses are endemic throughout El Salvador, very little is known about their ecology and epidemiology. The principal methods to prevent and reduce dengue cases are through vector control and by adoption of a vaccine. In addition, understanding the environmental and socioeconomic factors associated with dengue could contribute to case reduction by targeting prevention efforts in dengue hotspots. This study investigated environmental and socioeconomic factors associated with dengue cases in El Salvador. Dengue cases were obtained from 2011 to 2013 for 262 municipalities. The mean incidence was determined for each municipality for the 3 year period. Negative binomial regression models evaluated the relationship between dengue cases and the environmental factors elevation, forest coverage, mean annual temperature, and cumulative precipitation. Twelve socioeconomic and infrastructure variables and their relationship with dengue were also investigated by using negative binomial regression. A total of 29,764 confirmed dengue cases were reported. The mean dengue incidence for 2011-2013 was 135/100,000. The highest number of dengue cases occurred in San Salvador and surrounding municipalities, as well as in two additional cities, Santa Ana and San Miguel; the highest incidence of dengue cases (per 100,000) occurred in cities in the west and at the center of the country. Significant environmental variables associated with dengue included temperature, precipitation, and non-forested area. The socioeconomic variables poverty rate, illiteracy rate, and school attendance, and the infrastructure variables percent of homes with sanitary service, municipal trash service, electricity, and cement brick flooring, as well as population density, were also significant predictors of dengue. Understanding these environmental and socioeconomic factors and their relationship with dengue will help design and implement timely prevention strategies and vector control to reduce dengue in El Salvador.

The Impact of Sociological and Environmental Factors for Dengue Infection in Kuala Lumpur, Malaysia

BACKGROUND

Dengue incidence has grown dramatically around the world in recent years. Vector control is the only method to reduce dengue incidence due to the lack of a vaccine available. By understanding the factors contributed to the vector densities such as environmental and sociological factors, dengue prevention and control may succeed.

OBJECTIVE

This study is aimed at determining the impact of sociological and environmental factors contributing to dengue cases.

METHODS

The study surveyed 379 respondents with dengue history. The socio-environmental factors were evaluated by chi-square and binary regression.

RESULT

The chi-square results revealed sociological factors associated between family with dengue experience such as older age (p =0.012), fewer than four people in the household (p= 0.008), working people (p= 0.004) and apartment/terrace houses (p=0.023). Similarly, there is a significant association between respondent's dengue history and houses that are shaded with vegetation (p= 0.012) and the present of public playground areas near the residential (p = 0.011).

CONCLUSION

The study identified socio-environmental factors that play an important role in the abundance of Aedes mosquitoes and also for the local dengue control measures.

Climatic and socio-economic factors supporting the co-circulation of dengue, Zika and chikungunya in three different ecosystems in Colombia

Dengue, Zika and chikungunya are diseases of global health significance caused by arboviruses and transmitted by the mosquito Aedes aegypti, which is of worldwide circulation. The arrival of the Zika and chikungunya viruses to South America increased the complexity of transmission and morbidity caused by these viruses co-circulating in the same vector mosquito species. Here we present an integrated analysis of the reported arbovirus cases between 2007 and 2017 and local climate and socio-economic profiles of three distinct Colombian municipalities (Bello, Cúcuta and Moniquirá). These locations were confirmed as three different ecosystems given their contrasted geographic, climatic and socio-economic profiles. Correlational analyses were conducted with both generalised linear models and generalised additive models for the geographical data. Average temperature, minimum temperature and wind speed were strongly correlated with disease incidence. The transmission of Zika during the 2016 epidemic appeared to decrease circulation of dengue in Cúcuta, an area of sustained high incidence of dengue. Socio-economic factors such as barriers to health and childhood services, inadequate sanitation and poor water supply suggested an unfavourable impact on the transmission of dengue, Zika and chikungunya in all three ecosystems. Socio-demographic influencers were also discussed including the influx of people to Cúcuta, fleeing political and economic instability from neighbouring Venezuela. Aedes aegypti is expanding its range and increasing the global threat of these diseases. It is therefore vital that we learn from the epidemiology of these arboviruses and translate it into an actionable local knowledge base. This is even more acute given the recent historical high of dengue cases in the Americas in 2019, preceding the COVID-19 pandemic, which is itself hampering mosquito control efforts.

Climate change could shift disease burden from malaria to arboviruses in Africa

Malaria is a long-standing public health problem in sub-Saharan Africa, whereas arthropod-borne viruses (arboviruses) such as dengue and chikungunya cause an under-recognised burden of disease. Many human and environmental drivers affect the dynamics of vector-borne diseases. In this Personal View, we argue that the direct effects of warming temperatures are likely to promote greater environmental suitability for dengue and other arbovirus transmission by Aedes aegypti and reduce suitability for malaria transmission by Anopheles gambiae. Environmentally driven changes in disease dynamics will be complex and multifaceted, but given that current public efforts are targeted to malaria control, we highlight Ae aegypti and dengue, chikungunya, and other arboviruses as potential emerging public health threats in sub-Saharan Africa.

Quantifying sociodemographic heterogeneities in the distribution of Aedes aegypti among California households

The spread of Aedes aegypti in California and other regions of the U.S. has increased the need to understand the potential for local chains of Ae. aegypti-borne virus transmission, particularly in arid regions where the ecology of these mosquitoes is less understood. For public health and vector control programs, it is helpful to know whether variation in risk of local transmission can be attributed to socio-demographic factors that could help to target surveillance and control programs. Socio-demographic factors have been shown to influence transmission risk of dengue virus outside the U.S. by modifying biting rates and vector abundance. In regions of the U.S. where Ae. aegypti have recently invaded and where residential areas are structured differently than those in the tropics where Ae. aegypti are endemic, it is unclear how socio-demographic factors modify the abundance of Ae. aegypti populations. Understanding heterogeneities among households in Ae. aegypti abundance will provide a better understanding of local vectorial capacity and is an important component of understanding risk of local Ae. aegypti-borne virus transmission. We conducted a cross-sectional study in Los Angeles County, California during summer 2017 to understand the causes of variation in relative abundance of Ae. aegypti among households. We surveyed 161 houses, representing a wide range of incomes. Surveys consisted of systematic adult mosquito collections, inspections of households and properties, and administration of a questionnaire in English or Spanish. Adult Ae. aegypti were detected at 72% of households overall and were found indoors at 12% of households. An average of 3.1 Ae. aegypti were collected per household. Ae. aegypti abundance outdoors was higher in lower-income neighborhoods and around older households with larger outdoor areas, greater densities of containers with standing water, less frequent yard maintenance, and greater air-conditioner use. We also found that Ae. aegypti abundance indoors was higher in households that had less window and door screening, less air-conditioner usage, more potted plants indoors, more rain-exposed containers around the home, and lower neighborhood human population densities. Our results indicate that, in the areas of southern California studied, there are behavioral and socio-demographic determinants of Ae. aegypti abundance, and that low-income households could be at higher risk for exposure to Ae. aegypti biting and potentially greater risk for Zika, dengue, and chikungunya virus transmission if a local outbreak were to occur.

Associations between household environmental factors and immature mosquito abundance in Quetzaltenango, Guatemala

BACKGROUND

Aedes aegypti-borne diseases are becoming major public health problems in tropical and sub-tropical regions. While socioeconomic status has been associated with larval mosquito abundance, the drivers or possible factors mediating this association, such as environmental factors, are yet to be identified. We examined possible associations between proximity to houses and roads and immature mosquito abundance, and assessed whether these factors and mosquito prevention measures mediated any association between household environmental factors and immature mosquito abundance.

METHODS

We conducted two cross-sectional household container surveys in February-March and November-December, 2017, in urban and rural areas of Quetzaltenango, Guatemala. We used principal components analysis to identify factors from 12 variables to represent the household environment. One factor which included number of rooms in house, electricity, running water, garbage service, cable, television, telephone, latrine, well, and sewer system, was termed "environmental capital." Environmental capital scores ranged from 0 to 5.5. Risk factors analyzed included environmental capital, and distance from nearest house/structure, paved road, and highway. We used Poisson regression to determine associations between distance to nearest house/structure, roads, and highways, and measures of immature mosquito abundance (total larvae, total pupae, and positive containers). Using cubic spline generalized additive models, we assessed non-linear associations between environmental capital and immature mosquito abundance. We then examined whether fumigation, cleaning containers, and distance from the nearest house, road, and highway mediated the relationship between environmental capital and larvae and pupae abundance.

RESULTS

We completed 508 household surveys in February-March, and we revisited 469 households in November-December. Proximity to paved roads and other houses/structures was positively associated with larvae and pupae abundance and mediated the associations between environmental capital and total numbers of larvae/pupae (p ≤ 0.01). Distance to highways was not associated with larval/pupal abundance (p ≥ 0.48). Households with the lowest and highest environmental capital had fewer larvae/pupae than households in the middle range (p < 0.01).

CONCLUSIONS

We found evidence that proximity to other houses and paved roads was associated with greater abundance of larvae and pupae. Understanding risk factors such as these can allow for improved targeting of surveillance and vector control measures in areas considered at higher risk for arbovirus transmission.

20 Years Spatial-Temporal Analysis of Dengue Fever and Hemorrhagic Fever in Mexico

BACKGROUND AND AIM

Dengue Fever (DF) is a human vector-borne disease and a major public health problem worldwide. In Mexico, DF and Dengue Hemorrhagic Fever (DHF) cases have increased in recent years. The aim of this study was to identify variations in the spatial distribution of DF and DHF cases over time using space-time statistical analysis and geographic information systems.

METHODS

Official data of DF and DHF cases were obtained in 32 states from 1995-2015. Space-time scan statistics were used to determine the space-time clusters of DF and DHF cases nationwide, and a geographic information system was used to display the location of clusters.

RESULTS

A total of 885,748 DF cases was registered of which 13.4% (n = 119,174) correspond to DHF in the 32 states from 1995-2015. The most likely cluster of DF (relative risk = 25.5) contained the states of Jalisco, Colima, and Nayarit, on the Pacific coast in 2009, and the most likely cluster of DHF (relative risk = 8.5) was in the states of Chiapas, Tabasco, Campeche, Oaxaca, Veracruz, Quintana Roo, Yucatán, Puebla, Morelos, and Guerrero principally on the Gulf coast over 2006-2015.

CONCLUSION

The geographic distribution of DF and DHF cases has increased in recent years and cases are significantly clustered in two coastal areas (Pacific and Gulf of Mexico). This provides the basis for further investigation of risk factors as well as interventions in specific areas.

Aedes Mosquito Infestation in Socioeconomically Contrasting Neighborhoods of Panama City

The global expansion and proliferation of Aedes aegypti and Aedes albopictus represents a growing public health threat due to their capacity to transmit a variety of arboviruses to humans, including dengue, chikungunya, and Zika. Particularly important in urban regions, where these species have evolved to breed in man-made containers and feed nearly exclusively on human hosts, the threat of vector-borne disease has risen in recent decades due to the growth of cities, progression of climate change, and increase in globalization. While the dynamics of Aedes populations in urban settings have been well studied in relation to ecological features of the landscape, relatively less is known about the relationship between neighborhood socioeconomic status and Aedes infestation. Here, we compare infestation levels of both A. aegypti and A. albopictus in four socioeconomically contrasting neighborhoods of urban Panama City, Panama. Our results indicate that infestation levels for both Aedes species vary between neighborhoods of contrasting socioeconomic status, being higher in neighborhoods having lower percentage of residents with bachelor degrees and lower monthly household income. Additionally, we find that proximity between socioeconomically contrasting neighborhoods can predict infestation levels by species, with A. aegypti increasing and A. albopictus decreasing with proximity between neighborhoods. These findings hold key implications for the control and prevention of dengue, chikungunya, and Zika in Panama, a region with ongoing arbovirus outbreaks and high economic inequity.

Surveillance of Aedes aegypti indoors and outdoors using Autocidal Gravid Ovitraps in South Texas during local transmission of Zika virus, 2016 to 2018

The yellow fever mosquito, Aedes aegypti, has facilitated the re-emergence of dengue virus (DENV) and emergence of chikungunya virus (CHIKV) and Zika virus (ZIKV) in the Americas and the Caribbean. The recent transmission of these arboviruses in the continental United States has been limited, to date, to South Florida and South Texas despite Ae. aegypti occurring over a much larger geographical region within the country. The main goal of our study was to provide the first long term longitudinal study of Ae. aegypti and enhance the knowledge about the indoor and outdoor relative abundance of Ae. aegypti as a proxy for mosquito-human contact in South Texas, a region of the United States that is at high risk for mosquito-borne virus transmission. Here, the relative abundance of indoors and outdoors mosquitoes of households in eight different communities was described. Surveillance was done weekly from September 2016 to April 2018 using the CDC Autocidal Gravid Ovitraps in low- and middle-income communities. A total of 69 houses were included in this survey among which 36 were in the low-income communities (n = 11 for Donna, n = 15 for Progresso, n = 5 for Mesquite, n = 5 for Chapa) and 33 in middle-income communities (n = 9 for La Feria, n = 8 for Weslaco, n = 11 for McAllen, and n = 5 for Rio Rico). Overall, Ae. aegypti was the dominant species (59.2% of collections, n = 7255) followed by Culex spp. mosquitoes (27.3% of collections, n = 3350). Furthermore, we demonstrated for Ae. aegypti that 1) outdoor relative abundance was higher compared to indoor relative abundance, 2) low-income communities were associated with an increase in mosquito relative abundance indoors when compared to middle-income communities, 3) no difference was observed in the number of mosquitoes collected outdoors between low-income and middle-income communities, and 4) warmer months were positively correlated with outdoor relative abundance whereas no seasonality was observed in the relative abundance of mosquitoes indoors. Additionally, Ae. aegypti mosquitoes collected in South Texas were tested using a specific ZIKV/CHIKV multiplex real-time PCR assay, however, none of the mosquitoes tested positive. Our data highlights the occurrence of mosquitoes indoors in the continental United States and that adults are collected nearly every week of the calendar year. These mosquito data, obtained concurrently with local ZIKV transmission of 10 locally acquired cases in nearby communities, represent a baseline for future studies in the Lower Rio Grande Valley (LRGV) including vector control interventions relying on the oviposition behavior to reduce mosquito populations and pathogen transmission.

Estimation of DENV-2 Transmission as a Function of Site-Specific Entomological Parameters from Three Cities in Colombia

Background:

Measuring dengue virus transmission in endemic areas is a difficult task as many variables drive transmission, and often are not independent of one another.

Objectives:

We aimed to determine the utility of vectorial capacity to explain the observed dengue infection rates in three hyperendemic cities in Colombia, and tested hypotheses related to three variables: mosquito density, effective vector competence, and biting rate.

Methods:

We estimated two of the most influential entomological variables related to cumulative vectorial capacity, which is a modification of the traditional vectorial capacity equation, of three Colombian mosquito populations. Laboratory studies were undertaken to measure vector competence and man biting rate of local mosquito populations. In addition, the assessment of cumulative vectorial capacity also incorporated site-specific estimations of mosquito density and the probability of daily survival from previous studies conducted in those cities.

Findings:

We found that the biting rates and mosquito infection rates differed among populations of mosquitoes from these three cities, resulting in differences in the site-specific measures of transmission potential. Specifically, we found that using site-specific entomological measures to populate the cumulative vectorial capacity equation was best at recapitulating observed mosquito infection rates when mosquito density was discounted compared to when we incorporated site-specific density measures.

Conclusions:

Specific mosquito-biting rate is likely sufficient to explain transmission differences in these three cities, confirming that this parameter is a critical parameter when predicting and assessing dengue transmission in three Colombian cities with different field observed transmission patterns.

The use of the "Lansaka Model" as the larval indices surveillance system for a sustainable solution to the dengue problem in southern Thailand

Background: Dengue has been spreading in Thailand for more than 50 years, and the community prevention of dengue transmission is an important strategy to help reduce outbreaks. The larval indices surveillance system is one of the most significant prevention methods at the household and district levels. Objective: This study sought to develop a larval indices surveillance system based on a specific community context. Method: Community participation action research (CPAR) studies represent a new approach to studying the high-risk dengue area of Lansaka district, Nakhon Si Thammarat province, Thailand. This study was conducted for 2 years (from 2013 to 2015) and applied the integrated concepts of 1) community capacity building, 2) epidemiology, 3) research design for health development, and 4) an online computer program. The method included five phases: 1) community preparation, 2) situation assessment, 3) the development of the surveillance system, 4) implementation, and 5) evaluation. Results: The model was designed in partnership with all the stakeholders from 44 villages across 5 sub-districts. The surveillance system consisted of seven steps at the household level based on primary care surveillance centers (PCSCs), as well as four components at the district level based on district surveillance centers (DSCs). The dengue morbidity rate decreased from 164, 151, and 135 cases/100,000 people in 2014, 2015, and 2016, respectively. Moreover, knowledge of both dengue and larval indices among village health volunteers (VHVs) increased significantly (p < .01). Conclusions: The results from the new system showed a decrease in both the larval indices level and morbidity rate; however, the levels remained higher than the standard. The active surveillance system requires continuous monitoring at both the household and district levels.

Saberes e práticas sobre controle do Aedes aegypti por diferentes sujeitos sociais na cidade de Salvador, Bahia, Brasil

Resumo: Devido à persistência da dengue e de outras arboviroses no Brasil, o poder público tem intensificado as ações de combate ao mosquito vetor Aedes aegypti. Os agentes de combate às endemias (ACE) e agentes comunitários de saúde (ACS), dentre outras atribuições, tornaram-se interlocutores e disseminadores de conhecimento na comunidade. O objetivo deste trabalho foi analisar os saberes e práticas sobre controle da dengue por diferentes sujeitos sociais: moradores e agentes. Foram realizadas entrevistas com moradores, ACE de campo e de mobilização e ACS em dois bairros de Salvador, Bahia, por meio da metodologia de grupo focal. Os moradores demonstraram incerteza sobre a forma de contágio e o perigo da dengue. Os ACE de campo apresentam-se em conflito, pela necessidade de informar à comunidade sobre aspectos que não dominam e demonstram um descontentamento pessoal no trabalho com um sentimento de desvalorização pela falta de qualificação. Os ACE de mobilização culpam a população e enfatizam a importância de si próprios como solução para o controle da dengue. Os ACS não apropriaram sua experiência de campo em seu discurso e se sentem desobrigados com respeito ao controle vetorial. Todos os grupos entrevistados concordam que a culpa da dengue recai sobre o poder público, e a solução para o problema está na educação. Percebe-se uma grande necessidade de intervenções educativas regulares, pautadas no diálogo e na sensibilização para lidar com a realidade cotidiana dos moradores, trazendo os indivíduos (moradores e agentes) como sujeitos do processo de construção de conhecimento. Pois, na metodologia atual, a disseminação de informação e conhecimento não é suficiente para promover melhorias na comunidade para o controle da dengue.

Use of Bacillus thuringiensis israelensis in integrated vector control of Aedes sp. in Sri Lanka: a prospective controlled effectiveness study

OBJECTIVES

The annual incidence of dengue has been increasing over the last few years in Sri Lanka with seasonal epidemics. Biological control of the vector has not been part of the integrated vector control implemented by the public health authorities of Sri Lanka so far. This pilot study assessed the effectiveness of using Bacillus thuringiensis israelensis (Bti) spray to control the Aedes mosquito vector population density.

METHODS

Prospective controlled effectiveness study in three administrative divisions of Colombo. Study areas were selected from urban, semiurban and rural administrative divisions within the district, and they were compared with two matching controls from the same division. Test areas received three cycles of Bti spraying 1 month apart. Control areas were not sprayed with Bti. Ovitrap and larval indices were calculated at baseline and 2 weeks after each spray cycle.

RESULTS

There was a significant improvement in the adult vector population (ovitrap index) in the test areas after three spray cycles, but this effect had disappeared after 8 weeks (no residual effect). There was no consistent positive impact on larval indices (premise, container and Breteau indices) after each spray cycle.

CONCLUSION

Bti might have a moderate impact on adult vector populations mediated via transient reductions in larval populations. However, this effect is not sustained probably due to rapid re-infestation. Bti spray, if implemented, can only play a supplementary role to other vector control methods.

Poverty and Arbovirus Outbreaks: When Chikungunya Virus Hits More Precarious Populations Than Dengue Virus in French Guiana

BACKGROUND

Since 2013, 3 successive arbovirus outbreaks, dengue (DENV), chikungunya (CHIKV), and Zika virus, have occurred in French Guiana (FG). The primary objective of this study was to describe the socioeconomic indicators of the first patients infected with CHIKV during the outbreak of 2014. The secondary objective was to compare those patients with patient infected by DENV and with the local population.

METHODS

A monocentric, retrospective, case-control study was conducted in Cayenne hospital in FG comparing a group of patients infected with CHIKV in 2014 with a group infected with DENV in 2013. Children aged less than 15 years and pregnant women were excluded.

RESULTS

A total of 168 CHIKV patients were compared with 168 DENV patients. Factors associated with CHIKV were living in poor neighborhoods (82% vs 44%; odds ratio [OR], 5.81; 95% confidence interval [CI], 3.35-10.2), having a precarious status (54% vs 33%; OR, 2.37; 95% CI, 1.49-3.78), and being born abroad (70% vs 35%; OR, 4.35; 95% CI, 2.69-7.06).

CONCLUSIONS

The present results suggest that early in the epidemic, the populations most at risk for CHIKV infection were the most socially vulnerable populations in the poorest neighborhoods, whereas DENV appeared to have affected a richer population and richer areas.

Aedes aegypti breeding ecology in Guerrero: cross-sectional study of mosquito breeding sites from the baseline for the Camino Verde trial in Mexico

Background

Understanding the breeding patterns of Aedes aegypti in households and the factors associated with infestation are important for implementing vector control. The baseline survey of a cluster randomised controlled trial of community mobilisation for dengue prevention in Mexico and Nicaragua collected information about the containers that are the main breeding sites, identified possible actions to reduce breeding, and examined factors associated with household infestation. This paper describes findings from the Mexican arm of the baseline survey.

Methods

In 2010 field teams conducted household surveys and entomological inspections in 11,995 households from 90 representative communities in the three coastal regions of Guerrero State, Mexico. We characterized Ae. aegypti breeding sites and examined the effect of two preventive measures: temephos application in water containers, and keeping the containers covered. We examined associations with household infestation, using bivariate and multivariate analysis adjusted for clustering effects.

Results

We conducted entomological inspections in 11,995 households. Among 45,353 water containers examined, 6.5% (2958/45,353) were positive for larvae and/or pupae. Concrete tanks (pilas) and barrels (tambos) together accounted for 74% of pupal productivity. Both covering water containers and inserting temephos were independently associated with a lower risk of presence of larvae or pupae, with the effect of covering (OR 0.22; 95% CIca 0.15–0.27) stronger than that of temephos (OR 0.66; 95% CIca 0.53–0.84). Having more than four water containers was associated with household infestation in both rural areas (OR 1.42; 95% CIca 1.17–1.72) and urban areas (1.81; 1.47–2.25), as was low education of the household head (rural: 1.27; 1.11–1.46, and urban: 1.39; 1.17–1.66). Additional factors in rural areas were: household head without paid work (1.31; 1.08–1.59); being in the Acapulco region (1.91; 1.06–3.44); and using anti-mosquito products (1.27; 1.09–1.47). In urban areas only, presence of temephos was associated with a lower risk of household infestation (0.44; 0.32–0.60).

Conclusion

Concrete tanks and barrels accounted for the majority of pupal productivity. Covering water containers could be an effective means of Ae. aegypti vector control, with a bigger effect than using temephos. These findings were useful in planning and implementing the Camino Verde trial intervention in Mexico.

Effects of socio-demographic characteristics and household water management on Aedes aegypti production in suburban and rural villages in Laos and Thailand

BACKGROUND

Dengue fever is a mosquito-borne disease accounting for 50-100 million annual cases globally. Laos and Thailand are countries in south-east Asia where the disease is endemic in both urban and rural areas. Household water storage containers, which are favourable breeding sites for dengue mosquitoes, are common in these areas, due to intermittent or limited access to water supply. This study assessed the effect of household water management and socio-demographic risk factors on Aedes aegypti infestation of water storage containers.

METHODS

A cross-sectional survey of 239 households in Laos (124 suburban and 115 rural), and 248 households in Thailand (127 suburban and 121 rural) was conducted. Entomological surveys alongside semi-structured interviews and observations were conducted to obtain information on Ae. aegypti infestation, socio-demographic factors and water management. Zero-inflated negative binomial regression models were used to assess risk factors associated with Ae. aegypti pupal infestation.

RESULTS

Household water management rather than socio-demographic factors were more likely to be associated with the infestation of water containers with Ae. aegypti pupae. Factors that was significantly associated with Ae. aegypti infestation were tanks, less frequent cleaning of containers, containers without lids, and containers located outdoors or in toilets/bathrooms.

CONCLUSIONS

Associations between Ae. aegypti pupae infestation, household water management, and socio-demographic factors were found, with risk factors for Ae. aegypti infestation being specific to each study setting. Most of the containers did not have lids, larvicides, such as temephos was seldom used, and containers were not cleaned regularly; factors are facilitating dengue vector proliferation. It is recommended that, in Lao villages, health messages should promote proper use and maintenance of tightly fitted lids, and temephos in tanks, which were the most infested containers. Recommendations for Thailand are that small water containers should be cleaned weekly. Furthermore, in addition to health messages on dengue control provided to communities, attention should be paid to larval control for indoor containers in rural villages. Temephos or other immature control measures such as the use of pyriproxyfen, antilarval bacteria, or larvivorous fish should be used where temephos resistance is prevalent. Dengue control is not possible without additional adult mosquito control and community participation.

Socioeconomic and environmental determinants of dengue transmission in an urban setting: An ecological study in Nouméa, New Caledonia

Background

Dengue is a mosquito-borne virus that causes extensive morbidity and economic loss in many tropical and subtropical regions of the world. Often present in cities, dengue virus is rapidly spreading due to urbanization, climate change and increased human movements. Dengue cases are often heterogeneously distributed throughout cities, suggesting that small-scale determinants influence dengue urban transmission. A better understanding of these determinants is crucial to efficiently target prevention measures such as vector control and education. The aim of this study was to determine which socioeconomic and environmental determinants were associated with dengue incidence in an urban setting in the Pacific.

Methodology

An ecological study was performed using data summarized by neighborhood (i.e. the neighborhood is the unit of analysis) from two dengue epidemics (2008–2009 and 2012–2013) in the city of Nouméa, the capital of New Caledonia. Spatial patterns and hotspots of dengue transmission were assessed using global and local Moran’s I statistics. Multivariable negative binomial regression models were used to investigate the association between dengue incidence and various socioeconomic and environmental factors throughout the city.

Principal findings

The 2008–2009 epidemic was spatially structured, with clusters of high and low incidence neighborhoods. In 2012–2013, dengue incidence rates were more homogeneous throughout the city. In all models tested, higher dengue incidence rates were consistently associated with lower socioeconomic status (higher unemployment, lower revenue or higher percentage of population born in the Pacific, which are interrelated). A higher percentage of apartments was associated with lower dengue incidence rates during both epidemics in all models but one. A link between vegetation coverage and dengue incidence rates was also detected, but the link varied depending on the model used.

Conclusions

This study demonstrates a robust spatial association between dengue incidence rates and socioeconomic status across the different neighborhoods of the city of Nouméa. Our findings provide useful information to guide policy and help target dengue prevention efforts where they are needed most.

Dengue virus is rapidly spreading throughout tropical and subtropical regions worldwide, possibly aided by environmental change, urbanization and/or increase in human mobility. Already present in 120 countries, dengue virus causes extensive disease burden and generates large economic costs. As dengue is mosquito-borne, its transmission pattern is strongly influenced by climate. However, dengue cases are not always distributed evenly throughout cities, where climate can be assumed to be homogenous. This suggests that other factors which are heterogeneously distributed in cities could play a role in dengue transmission, such as socioeconomic status and environmental factors (both natural and built). Identifying those factors is crucial to develop and target dengue prevention interventions, such as mosquito control and education. Our study uses dengue incidence statistics from two large epidemics in Nouméa, the capital of New Caledonia, to investigate which socioeconomic or environmental factors correlate with dengue incidence in an urban setting. Dengue incidence was consistently higher in neighborhoods where socioeconomic status was lower (i.e. lower revenue or higher unemployment) and often higher where the proportion of single-family houses in all buildings was higher. Our data suggest that, if resources are limited, prevention measures should be targeted in priority towards neighborhoods of lower socioeconomic status.

Dengue seroprevalence, seroconversion and risk factors in Dhaka, Bangladesh

BACKGROUND

Dengue virus (DENV) activity has been reported in Dhaka, Bangladesh since the early 1960s with the greatest burden of dengue fever and dengue hemorrhagic fever cases observed in 2000. Since this time, the intensity of dengue activity has varied from year to year, and its determining factors remained relatively unknown. In light of such gaps in knowledge, the main objectives of this study were to determine the magnitude of seroprevalence and seroconversion among the surveyed population, and establish the individual/household level risk factors for the presence of DENV antibodies among all age groups of target populations in the city of Dhaka.

METHODOLOGY/PRINCIPAL FINDINGS

Considering the lack of fine scale investigations on the factors driving dengue activity in Bangladesh, a prospective cohort study involving serological surveys was undertaken with participant interviews and blood donation across the city of Dhaka in 2012. Study participants were recruited from 12 of 90 wards and blood samples were collected during both the pre-monsoon (n = 1125) and post-monsoon (n = 600) seasons of 2012. The findings revealed that the seroprevalence in all pre-monsoon samples was 80.0% (900/1125) while the seropositivity in the pre-monsoon samples that had paired post-monsoon samples was 83.3% (503/600). Of the 97 paired samples that were negative at the pre-monsoon time point, 56 were positive at the post-monsoon time point. This resulted in a seroprevalence of 93.2% (559/600) among individuals tested during the post-monsoon period. Seroprevalence trended higher with age with children exhibiting a lower seropositivity as compared to adults. Results from this study also indicated that DENV strains were the only flaviviruses circulating in Dhaka in 2012. A multivariate analysis revealed that age, possession of indoor potted plants, and types of mosquito control measures were significant factors associated with DENV seroprevalence; while attendance in public/mass gatherings, and use of mosquito control measures were significantly associated with DENV seroconversion after adjusting for all other variables.

CONCLUSIONS/SIGNIFICANCE

Our study suggests that there is a high level of endemic dengue virus circulation in the city of Dhaka which has resulted in significant DENV seroprevalence among its residents. Seropositivity increased with age, however, a substantial proportion of children are at risk for DENV infections. Our serological analysis also documents considerable DENV seroconversion among study participants which indicates that a large proportion of the population in the city of Dhaka were newly exposed to DENV during the study period (pre-and post-monsoon 2012). High levels of seroconversion suggest that there was an intense circulation of DENV in 2012 and this may have resulted in a significant risk for viral associated illness. Findings of our study further indicated that home-based interventions, such as removing indoor potted plants and increased bed net use, in addition to vector control measures in public parks, would reduce exposure to DENV and further decrease risk of viral associated disease.

Socioeconomic and Ecological Factors Influencing Aedes aegypti Prevalence, Abundance, and Distribution in Dhaka, Bangladesh

This study examined household risk factors and prevalence, abundance, and distribution of immature Aedes aegypti and Aedes albopictus, and their association with socioeconomic and ecological factors at urban zonal and household levels in the city of Dhaka, Bangladesh. During the 2011 monsoon, 826 households in 12 randomly selected administrative wards were surveyed for vector mosquitoes. Results revealed that the abundance and distribution of immature Ae. aegypti and Ae. albopictus, and pupae-per-person indices did not vary significantly among the zones with varied socioeconomic status. Of 35 different types of identified wet containers, 30 were infested, and among the 23 pupae-positive container types, nine were defined as the "most productive" for pupae including: disposable plastic containers (12.2% of 550), sealable plastic barrels (12.0%), tires (10.4%), abandoned plastic buckets (9.6%), flower tub and trays (8.5%), refrigerator trays (6.5%), plastic bottles (6.4%), clay pots (4.9%), and water tanks (1.6%). When the function of the containers was assessed, ornamental, discarded, and household repairing and reconstruction-related container categories were found significantly associated with the number of pupae in the households. The purpose of storing water and income variables were significant predictors of possession of containers that were infested by vector mosquitoes.

Socio-economic and Climate Factors Associated with Dengue Fever Spatial Heterogeneity: A Worked Example in New Caledonia

BACKGROUND/OBJECTIVES

Understanding the factors underlying the spatio-temporal distribution of infectious diseases provides useful information regarding their prevention and control. Dengue fever spatio-temporal patterns result from complex interactions between the virus, the host, and the vector. These interactions can be influenced by environmental conditions. Our objectives were to analyse dengue fever spatial distribution over New Caledonia during epidemic years, to identify some of the main underlying factors, and to predict the spatial evolution of dengue fever under changing climatic conditions, at the 2100 horizon.

METHODS

We used principal component analysis and support vector machines to analyse and model the influence of climate and socio-economic variables on the mean spatial distribution of 24,272 dengue cases reported from 1995 to 2012 in thirty-three communes of New Caledonia. We then modelled and estimated the future evolution of dengue incidence rates using a regional downscaling of future climate projections.

RESULTS

The spatial distribution of dengue fever cases is highly heterogeneous. The variables most associated with this observed heterogeneity are the mean temperature, the mean number of people per premise, and the mean percentage of unemployed people, a variable highly correlated with people's way of life. Rainfall does not seem to play an important role in the spatial distribution of dengue cases during epidemics. By the end of the 21st century, if temperature increases by approximately 3 °C, mean incidence rates during epidemics could double.

CONCLUSION

In New Caledonia, a subtropical insular environment, both temperature and socio-economic conditions are influencing the spatial spread of dengue fever. Extension of this study to other countries worldwide should improve the knowledge about climate influence on dengue burden and about the complex interplay between different factors. This study presents a methodology that can be used as a step by step guide to model dengue spatial heterogeneity in other countries.

Developing a social autopsy tool for dengue mortality: a pilot study

BACKGROUND

Dengue fever is a public health problem in the tropical and sub-tropical world. Dengue cases have grown dramatically in recent years as well as dengue mortality. Colombia has experienced periodic dengue outbreaks with numerous dengue related-deaths, where the Santander department has been particularly affected. Although social determinants of health (SDH) shape health outcomes, including mortality, it is not yet understood how these affect dengue mortality. The aim of this pilot study was to develop and pre-test a social autopsy (SA) tool for dengue mortality.

METHODS AND FINDINGS

The tool was developed and pre-tested in three steps. First, dengue fatal cases and 'near misses' (those who recovered from dengue complications) definitions were elaborated. Second, a conceptual framework on determinants of dengue mortality was developed to guide the construction of the tool. Lastly, the tool was designed and pre-tested among three relatives of fatal cases and six near misses in 2013 in the metropolitan zone of Bucaramanga. The tool turned out to be practical in the context of dengue mortality in Colombia after some modifications. The tool aims to study the social, individual, and health systems determinants of dengue mortality. The tool is focused on studying the socioeconomic position and the intermediary SDH rather than the socioeconomic and political context.

CONCLUSIONS

The SA tool is based on the scientific literature, a validated conceptual framework, researchers' and health professionals' expertise, and a pilot study. It is the first time that a SA tool has been created for the dengue mortality context. Our work furthers the study on SDH and how these are applied to neglected tropical diseases, like dengue. This tool could be integrated in surveillance systems to provide complementary information on the modifiable and avoidable death-related factors and therefore, be able to formulate interventions for dengue mortality reduction.

Integrating participatory community mobilization processes to improve dengue prevention: an eco-bio-social scaling up of local success in Machala, Ecuador

BACKGROUND

This project investigates the effectiveness and feasibility of scaling-up an eco-bio-social approach for implementing an integrated community-based approach for dengue prevention in comparison with existing insecticide-based and emerging biolarvicide-based programs in an endemic setting in Machala, Ecuador.

METHODS

An integrated intervention strategy (IIS) for dengue prevention (an elementary school-based dengue education program, and clean patio and safe container program) was implemented in 10 intervention clusters from November 2012 to November 2013 using a randomized controlled cluster trial design (20 clusters: 10 intervention, 10 control; 100 households per cluster with 1986 total households). Current existing dengue prevention programs served as the control treatment in comparison clusters. Pupa per person index (PPI) is used as the main outcome measure. Particular attention was paid to social mobilization and empowerment with IIS.

RESULTS

Overall, IIS was successful in reducing PPI levels in intervention communities versus control clusters, with intervention clusters in the six paired clusters that followed the study design experiencing a greater reduction of PPI compared to controls (2.2 OR, 95% CI: 1.2 to 4.7). Analysis of individual cases demonstrates that consideration for contexualizing programs and strategies to local neighborhoods can be very effective in reducing PPI for dengue transmission risk reduction.

CONCLUSIONS

In the rapidly evolving political climate for dengue control in Ecuador, integration of successful social mobilization and empowerment strategies with existing and emerging biolarvicide-based government dengue prevention and control programs is promising in reducing PPI and dengue transmission risk in southern coastal communities like Machala. However, more profound analysis of social determination of health is called for to assess sustainability prospects.

Is dengue a disease of poverty? A systematic review

Policy prescriptions for combating dengue fever tend to focus on addressing environmental and social conditions of poverty. However, while poverty has long been considered a determinant of dengue, the research evidence for such a relationship is not well established. Results of a systematic review of the research literature designed to identify and assess the current state of the empirical evidence for the dengue-poverty link reveal a mixed story. Of 260 peer-reviewed articles referencing dengue-poverty relationships, only 12 English-language studies empirically assessed these relationships. Our analysis covering various social and economic conditions of poverty showed no clear associations with dengue rates. While nine of the 12 studies demonstrated some positive associations between measures of dengue and poverty (measured inconsistently through income, education, structural housing condition, overcrowding, and socioeconomic status), nine also presented null results and five with negative results. Of the five studies relating to access to water and sanitation, four reported null associations. Income and physical housing conditions were more consistently correlated with dengue outcomes than other poverty indicators. The small size of this sample, and the heterogeneity of measures and scales used to capture conditions of poverty, make it difficult to assess the strength and consistency of associations between various poverty indicators and dengue outcomes. At present, the global body of eligible English-language peer-reviewed literature investigating dengue-poverty relationships is too small to support a definitive relationship. We conclude that more research, particularly using standardized measures of both outcomes and indicators, is needed to support evidence-informed policies and approaches.

A social-ecological analysis of community perceptions of dengue fever and Aedes aegypti in Machala, Ecuador

Background

The growing burden of dengue fever and the lack of a vaccine or specific medical treatment have increased the urgency of the public health sector to identify alternative management strategies. A prevailing trend in Latin America has been a shift towards decentralized vector control programs with integrated management strategies, requiring significant intersectoral coordination, community engagement, and knowledge of the local social-ecological system (SES). Community perceptions and responses are a critical component of this system, since perceptions shape actions, and thus govern behavioral responses and acceptance of shifts in policy and management.

Methods

We investigated perceptions, misconceptions, and local SES risk factors for dengue in high risk communities located at the urban periphery and center in Machala, Ecuador. We facilitated twelve focus group discussions with community members using semi-structured question guides and causal diagrams. Focus groups were recorded, transcribed, and coded to identify emergent themes using qualitative methods for theme analysis. To estimate the relative importance of the themes in each study area, we tabulated the number of focus groups in which each theme was present. Household surveys (n = 79) were conducted to further explore these themes, and we compared survey responses from the two areas using descriptive statistics.

Results

We identified thirty biophysical, political-institutional, and community-household risk factors for dengue. People at the periphery identified a greater number of risk factors. Dengue control required considerable investment of time and resources, which presented a greater challenge for women and people at the periphery. Common misperceptions included confusion with other febrile diseases, lack of knowledge of transmission mechanisms, and misconceptions about mosquito behavior. People perceived that dengue control programs had been limited by the lack of inter-institutional coordination and lack of social cohesion.

Conclusions

There is a need for local, policy-relevant research that can be translated to strengthen the design, implementation, and evaluation of new dengue management strategies. This study contributes to a growing body of research in this area. Based on these findings, we identify key policy and management recommendations that will inform the ongoing transition to a decentralized dengue control program in Ecuador and other dengue endemic countries.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2458-14-1135) contains supplementary material, which is available to authorized users.

Integrating the public in mosquito management: active education by community peers can lead to significant reduction in peridomestic container mosquito habitats

Mosquito species that utilize peridomestic containers for immature development are commonly aggressive human biters, and because they often reach high abundance, create significant nuisance. One of these species, the Asian tiger mosquito Aedes albopictus, is an important vector of emerging infectious diseases, such as dengue, chikungunya, and Zika fevers. Integrated mosquito management (IMM) of Ae. albopictus is particularly difficult because it requires access to private yards in urban and suburban residences. It has become apparent that in the event of a public health concern due to this species, homeowners will have to be active participants in the control process by reducing mosquito habitats in their properties, an activity known as source reduction. However, limited attempts at quantifying the effect of source reduction by homeowners have had mixed results. Of note, many mosquito control programs in the US have some form of education outreach, however the primary approach is often passive focusing on the distribution of education materials as flyers. In 2010, we evaluated the use of active community peer education in a source reduction program, using AmeriCorps volunteers. The volunteers were mobilized over a 4-week period, in two areas with approximately 1,000 residences each in urban Mercer and suburban Monmouth counties in New Jersey, USA. The volunteers were first provided training on peridomestic mosquitoes and on basic approaches to reducing the number of container habitats for mosquito larvae in backyards. Within the two treatment areas the volunteers successfully engaged 758 separate homes. Repeated measures analysis of variance showed a significant reduction in container habitats in the sites where the volunteers actively engaged the community compared to untreated control areas in both counties. Our results suggest that active education using community peer educators can be an effective means of source reduction, and a critical tool in the arsenal against peridomestic mosquitoes.

Dengue vector dynamics (Aedes aegypti) influenced by climate and social factors in Ecuador: implications for targeted control

Background

Dengue fever, a mosquito-borne viral disease, is now the fastest spreading tropical disease globally. Previous studies indicate that climate and human behavior interact to influence dengue virus and vector (Aedes aegypti) population dynamics; however, the relative effects of these variables depends on local ecology and social context. We investigated the roles of climate and socio-ecological factors on Ae. aegypti population dynamics in Machala, a city in southern coastal Ecuador where dengue is hyper-endemic.

Methods/Principal findings

We studied two proximate urban localities where we monitored weekly Ae. aegypti oviposition activity (Nov. 2010-June 2011), conducted seasonal pupal surveys, and surveyed household to identify dengue risk factors. The results of this study provide evidence that Ae. aegypti population dynamics are influenced by social risk factors that vary by season and lagged climate variables that vary by locality. Best-fit models to predict the presence of Ae. aegypti pupae included parameters for household water storage practices, access to piped water, the number of households per property, condition of the house and patio, and knowledge and perceptions of dengue. Rainfall and minimum temperature were significant predictors of oviposition activity, although the effect of rainfall varied by locality due to differences in types of water storage containers.

Conclusions

These results indicate the potential to reduce the burden of dengue in this region by conducting focused vector control interventions that target high-risk households and containers in each season and by developing predictive models using climate and non-climate information. These findings provide the region's public health sector with key information for conducting time and location-specific vector control campaigns, and highlight the importance of local socio-ecological studies to understand dengue dynamics. See Text S1 for an executive summary in Spanish.

Risk factors related to dengue infections in primary school students: exploring students' basic knowledge of dengue and examining the larval indices in southern Thailand

Dengue is a major problem in southern Thailand.

OBJECTIVES

(1) To determine students' basic knowledge of dengue and (2) to examine the larval indices in primary schools and in the students' households.

METHODS

This study employed a cross-sectional quantitative and qualitative approach involving meetings with students, discussions with groups of teachers, a questionnaire investigating students' basic knowledge of dengue, and a survey of the larval indices in primary schools and in the students' households. The study consisted of three stages: (1) community preparation, (2) data collection and analysis, and (3) feedback.

RESULTS

A total of 306 students (from primary education levels 4-6) from five primary schools in the community were included in the study. Of a total of 15 items on the basic dengue questionnaire, only five were answered correctly by more than 80% of the students. Most of the knowledge items showed statistically significantly different distributions of correct, incorrect, and unknown answers (P ≤ 0.05, P ≤ 0.01, and P ≤ 0.001). The larval indices surveyed in the five schools and in 302 student households showed a high risk of dengue, with high indices in the five schools (Breteau Index: BI=200; House Index: HI=60; and Container Index: CI=7.94) and in the students' households (BI=754; HI=77; and CI=35).

CONCLUSION

Risk factors for dengue were related to the students' basic knowledge of dengue and to the larval indices in both the schools and the students' households. Additionally, a coordinated effort will be required to eliminate Aedes aegypti mosquito breeding sites in the community.

Relationship between Aedes aegypti production and occurrence of Escherichia coli in domestic water storage containers in rural and sub-urban villages in Thailand and Laos

In a cross-sectional survey in one rural and one suburban village each in Thailand and Laos the relationship between Aedes aegypti production and Escherichia coli contamination in household water storage containers was investigated. Entomological and microbiological surveys were conducted in 250 and 239 houses in Thailand and Laos, respectively. Entomological indices across all four villages were high, indicating a high risk for dengue transmission. Significantly more Ae. aegypti pupae were produced in containers contaminated with E. coli as compared to those that were not, with the odds of Ae. aegypti infested containers being contaminated with E. coli ranging from two to five. The level of E. coli contamination varied across container classes but contamination levels were not significantly associated with the number of pupae produced. We conclude that the observed relationship between Ae. aegypti production and presence of E. coli in household water storage containers suggests a causal relationship between dengue and diarrheal disease at these sites. How this relationship can be exploited for the combined and cost-effective control of dengue and diarrheal diseases requires further research.

Factors associated with dengue mortality in Latin America and the Caribbean, 1995-2009: an ecological study

In this study, we aimed to estimate the effect that environmental, demographic, and socioeconomic factors have on dengue mortality in Latin America and the Caribbean. To that end, we conducted an observational ecological study, analyzing data collected between 1995 and 2009. Dengue mortality rates were highest in the Caribbean (Spanish-speaking and non-Spanish-speaking). Multivariate analysis through Poisson regression revealed that the following factors were independently associated with dengue mortality: time since identification of endemicity (adjusted rate ratio [aRR] = 3.2 [for each 10 years]); annual rainfall (aRR = 1.5 [for each 10(3) L/m(2)]); population density (aRR = 2.1 and 3.2 for 20-120 inhabitants/km(2) and > 120 inhabitants/km(2), respectively); Human Development Index > 0.83 (aRR = 0.4); and circulation of the dengue 2 serotype (aRR = 1.7). These results highlight the important role that environmental, demographic, socioeconomic, and biological factors have played in increasing the severity of dengue in recent decades.

Human and environmental factors affecting Aedes aegypti distribution in an arid urban environment

Aedes aegypti has reappeared in urban communities in the southwestern U.S.A. in the 1990s after a 40-year absence. In 2003 and 2004, a systematic survey was conducted throughout metropolitan Tucson, AZ, to identify human and environmental factors associated with Ae. aegypti distribution within an arid urban area. Aedes aegypti presence and abundance were measured monthly using the Centers for Disease Control and Prevention enhanced oviposition traps at sampling sites established in a grid at 3- to 4-km intervals across the city. Sampling occurred in the summer rainy season (July through September), the peak of mosquito activity in the region. Multiple regression analyses were conducted to determine relationships between mosquito density and factors that could influence mosquito distribution. House age was the only factor that showed a consistent significant association with Ae. aegypti abundance in both years: older houses had more mosquito eggs. This is the 1st study of Ae. aegypti distribution at a local level to identify house age as an explanatory factor independent of other human demographic factors. Further research into the reasons why mosquitoes were more abundant around older homes may help inform and refine future vector surveillance and control efforts in the event of a dengue outbreak in the region.

Geographical gradient of mean age of dengue haemorrhagic fever patients in northern Thailand

Dengue haemorrhagic fever (DHF) is caused by dengue virus transmitted by Aedes mosquitoes; mean age of patients varies temporally and geographically. Variability in age of patients may be due to differences in transmission intensity or demographic structure. To compare these two hypotheses, the mean age of DHF patients from 90 districts in northern Thailand (1994-1996, 2002-2004) was regressed against (i) Aedes abundance or (ii) demographic variables (birthrate, average age) of the district. We also developed software to quantify direction and strength of geographical gradients of these variables. We found that, after adjusting for socioeconomics, climate, spatial autocorrelation, the mean age of patients was correlated only with Aedes abundance. The geographical gradient of mean age of patients originated from entomological, climate, and socioeconomic gradients. Vector abundance was a stronger determinant of mean age of patients than demographic variables, in northern Thailand.

Tools for thoughtful action: the role of ecosystem approaches to health in enhancing public health

The intimate interdependence of human health and the ecosystems in which we are embedded is now a commonplace observation. For much of the history of public health, this was not so obvious. After over a century of focus on diseases, their biologic causes and the correction of exposures (clean water and air) and facilitation of responses (immunizations and nutrition), public health discourse shifted to embrace the concept of determinants of health as extending to social, economic and environmental realms. This moved the discourse and science of public health into an unprecedented level of complexity just as public concern about the environment heightened. To address multifactorial, dynamic impacts on health, a new paradigm was needed which would overcome the separation of humans and ecosystems. Ecosystem approaches to health arose in the 1990s from a rich background of intellectual ferment as Canada wrestled with diverse problems ranging from Great Lakes contamination to zoonotic diseases. Canada's International Development Research Centre (IDRC) played a lead role in supporting an international community of scientists and scholars who advanced ecosystem approaches to health. These collective efforts have enabled a shift to a research paradigm that embraces transdisciplinarity, social justice, gender equity, multi-stakeholder participation and sustainability.

Spatial analysis of dengue and the socioeconomic context of the city of Rio de Janeiro (Southeastern Brazil)

OBJECTIVE

To analyze the dengue epidemic in relation to the socioeconomic context according to geographical areas.

METHODS

An ecological study was conducted in the municipality of Rio de Janeiro (Southeastern Brazil), in areas delimited as neighborhoods, based on information about notified dengue cases concerning residents in the municipality. The average incidence rate of dengue was calculated between the epidemiological weeks: 48th of 2001 and 20th of 2002. The occurrence of dengue was correlated with socioeconomic variables through Pearsons' correlation coefficient. Moran's global and local indexes were used to assess the spatial auto-correlation between dengue and the variables that significantly correlated with the disease. The multiple linear regression model and the conditional auto-regression spatial model were used to analyze the relationship between dengue and socioeconomic context.

RESULTS

The neighborhoods located in the west zone of the municipality presented high rates of average dengue incidence. The variables presenting significant correlation were: percentage of households connected with the general sanitary network, households with washing machines, and population density per urban area. Moran's spatial auto-correlation index revealed spatial dependence between dengue and the selected variables. The utilized models indicated percentage of households connected with the general sanitary network as the sole variable significantly associated with the disease. The residual figures in both models revealed significant spatial auto-correlation, with a positive Moran Index (p<0.001) for linear regression model, and a negative one (p=0.005) for the conditional auto-regression one.

CONCLUSIONS

Problems related to basic sanitation contribute decisively to increase the risk of the disease.

Revisão sistemática sobre estudos de espacialização da dengue no Brasil

O presente estudo objetivou realizar uma revisão sistemática sobre estudos de geoprocessamento do vetor da dengue e da doença no Brasil. A busca dos trabalhos foi realizada nas bases de dados Pubmed, Bireme e Scielo. A seleção foi realizada por critérios de inclusão, sendo estes: artigos originais sobre dengue e emprego de técnicas de geoprocessamento, publicados em inglês ou português de 1998 a 2007; trabalhos de finalização de curso; e trabalhos apresentados em congresso. Trabalhos que avaliaram essa doença em outros países foram excluídos. As palavras-chaves utilizadas na identificação dos artigos foram: "distribuição espacial e dengue", "dengue e geoprocessamento", "análise espacial e dengue", "Sistema de Informações Geográficas e dengue" e suas traduções para língua inglesa. Na base de busca do Scielo foram encontrados 15 artigos, dos quais selecionou-se 8; na Pubmed 11 trabalhos foram identificados, dos quais utilizou-se 3; e na Bireme, 20 trabalhos, dos quais selecionou-se 2. A revisão realizada permitiu analisar 7 estudos de espacialização dos casos de dengue, 5 trabalhos com vetores da dengue e um estudo que avaliou os casos e os vetores, simultaneamente. Foi freqüente a não-utilização de técnicas de geoprocessamento. Aspectos sociais foram freqüentemente associados à distribuição espacial da dengue. Desta forma, concluiu-se que os estudos de espacialização da dengue no Brasil, especialmente aqueles que avaliam os seus vetores, subutilizam as ferramentas do geoprocessamento. Os aspectos socioeconômicos são importantes para o entendimento da distribuição espacial da dengue.

Effect of dengue vector control interventions on entomological parameters in developing countries: a systematic review and meta-analysis

The aim of this review was to compare the effects of different dengue vector control interventions (i.e. biological control, chemical control, environmental management and integrated vector management) with respect to the following entomological parameters: Breteau index (BI), container index (CI), and house index (HI). We systematically searched PubMed, ISI Web of Science, Science Direct, the Dengue Bulletin of the World Health Organization and reference lists of retrieved articles on dengue vector control interventions in developing countries. We extracted data on the effectiveness of different dengue vector control interventions (defined as the relative reduction of an entomological measure caused by the intervention compared with the control or pre-intervention phase) and calculated a measure of combined relative effectiveness, with 95% confidence intervals (95% c.i.). We identified 56 publications covering 61 dengue vector control interventions. Integrated vector management was found to be the most effective method to reduce the CI, HI and BI, resulting in random combined relative effectiveness values of 0.12 (95% c.i. 0.02-0.62), 0.17 (95% c.i. 0.02-1.28) and 0.33 (95% c.i. 0.22-0.48), respectively. Environmental management showed a relatively low effectiveness of 0.71 (95% c.i. 0.55-0.90) for the BI, 0.49 (95% c.i. 0.30-0.79) for the CI and 0.43 (95% c.i. 0.31-0.59) for the HI. Biological control (relative effectiveness for the CI: 0.18) usually targeted a small number of people (median population size: 200; range 20-2500), whereas integrated vector management focused on larger populations (median: 12 450; range: 210-9 600 000). In conclusion, dengue vector control is effective in reducing vector populations, particularly when interventions use a community-based, integrated approach, which is tailored to local eco-epidemiological and sociocultural settings and combined with educational programmes to increase knowledge and understanding of best practice. New research should assess the density-dependent effectiveness of each control measure in order to estimate whether reducing vector numbers has an impact on dengue transmission when populations are at a critical threshold.

The unbearable lightness of technocratic efforts at dengue control

OBJECTIVE

To identify key elements that should provide an added value and assure sustainable effects of the deployment of technical tools for Aedes aegypti control.

METHODS

An observational study was conducted between April 2001 and March 2002 in 30 blocks (1574 houses) in the central zone of Guantanamo city. A trial that combined two complementary technical interventions, the distribution of new ground level water tanks and the intensive use of insecticide, was nested in May 2001. Another 30 blocks (1535 houses) were selected as control area. We assessed community perceptions and household risk behaviour at baseline and after 9 months, and measured the trial's impact through entomological indices.

RESULTS

Perceived self efficacy to solve A. aegypti infestation and prevent dengue was not modified. We found no changes in behaviour. In the study area the container indices decreased significantly from 0.7% before to 0.1% 1 month after the intervention. Six months later, they had increased to 2.7% and uncovered new water tanks constituted 75.9% of all breeding sites. Over the 9 months after the trial the average monthly house indices were similar in the study and control areas. A technical approach and lack of community involvement in the trial's implementation were the main causes of these short-lived results.

CONCLUSIONS

Top-down deployment of technical tools without active involvement of the community has a temporary effect and does not lead to the behavioural changes necessary for sustainable A. aegypti control.

An integrated ecosystem approach for sustainable prevention and control of dengue in Central Havana

The authors developed and evaluated a comprehensive participatory ecosystem health approach for preventing the transmission of dengue, the most prevalent vector-borne disease in Cuba and the Latin America-Caribbean region. The integrated surveillance system central to this initiative encompassed three main subsystems (environmental; entomological; clinical-epidemiologic), relying on extensive community involvement. The study was conducted in Central Havana, Cuba. Indicators from each subsystem were selected and mapped using a GIS procedure providing instant visualization by city block in the municipality. To elucidate the factors affecting control and prevention efforts, perceived needs and risks, as well as knowledge, attitudes, and behaviors related to dengue, were assessed. Specific factors associated with the presence of mosquito breeding sites and risks of dengue were examined in a case-control study.