Biology subjects

Stewart-Ibarra, A. M.

Publications and source records attributed to Stewart-Ibarra, A. M..

16 recordsLinked to original sources

bioRxiv2023

Systematic literature review about educational interventions evaluated through entomological indices or practices to prevent the presence of or eliminate breeding sites of Aedes

BackgroundCommunity participation is a critical element in the management of Aedes breeding sites. Many educational interventions have been conducted to encourage prevention and elimination of breeding sites among different community actors, such as government-run programs for vector surveillance aimed at preventing and eliminating breeding sites at the household level within a community. Getting people involved in prevention and elimination of vector breeding sites in their communities requires communication and social mobilization strategies to promote and reinforce those prevention actions that, in turn, should be effective from the entomological standpoint. Methodology/Principal FindingsArticles published in English, Spanish, and Portuguese, were reviewed to assess whether educational interventions targeting Aedes were effective in reducing entomological indicators or in improving practices to prevent the presence of or eliminate breeding sites. The most widely used indicators were the larval indices, and the practices to reduce/eliminate breeding sites. We found that using a community-based approach adapted to the eco-epidemiological and sociocultural scenarios explain the reduction of entomological indicators by educational interventions. Conclusions/SignificanceThose who design or implement educational interventions should strengthen the evaluation of those interventions using qualitative approaches that provide a more complete picture of the social context and barriers/facilitators to implementing vector control. Engaging school children in cross-sectorial collaboration involving the health and education spheres promotes the participation of the community in vector surveillance and reduces the risk of arboviral disease transmission. Author summaryDengue, Zika, and chikungunya are mosquito-borne diseases that represent a major global public health problem. These diseases are transmitted mainly through the bite of the Aedes aegypti vector mosquito and, to a lesser extent, Ae. albopictus. Getting people involved in prevention and elimination of mosquitos in their communities requires communication and social mobilization strategies to promote and reinforce those prevention actions that, in turn, should be effective from the entomological standpoint. The success of vector control programs has been demonstrated to lie in a comprehensive effort involving key community participation and intersectoral alliances. In addition, the participation of schoolchildren to mobilize their families in the prevention of breeding sites and the management of mosquito populations is recommended. In this article, we proposed to conduct a systematic review of scientific publications that evaluate the effects of educational interventions on Aedes through entomological indicators. As a result, we obtained only 26 articles that evaluated the efficacy of educational interventions in reducing vector populations out of 732 articles reviewed. The selected articles were published in both English and Spanish, and to a lesser extent in Portuguese, which highlights the importance of avoiding language bias in systematic reviews. As a conclusion of our work, we can mention that the interventions that incorporated the social context and the barriers/facilitators for the implementation of vector control were the most successful. In addition, we emphasize the importance of involving schoolchildren to promote community participation in vector surveillance.

scientific communication and education↗

bioRxiv2022

Community engagement through student-led science for dengue prevention during the COVID-19 pandemic in Cordoba, Argentina.

BackgroundDuring 2019-2020 while COVID-19 pandemic, the Americas were facing the biggest dengue fever epidemic in recent history. Traditional vector control programs, based on insecticide application have been insufficient to control the spread of dengue fever. Several studies suggest refocusing on education with the aim of an integrated vector management strategy within the local ecological-community context. We aim to assess community perceptions, knowledge, attitude, preventive practice, and action through student-led science assignments regarding dengue fever, prevention, and socio-ecological factors in temperate Cordoba, Argentina. MethodsThe study was conducted during the COVID-19 quarantine when schools switched to online education for the first time. Several activities through Google Classroom platform included a survey to one students family member, and an outdoor activity to assess their attitudes and to clean the backyard and gardens. ResultsSignificant number of respondents developed good preventive practices and increased their knowledge about the vector and disease highlighting that 75% of responders knew that dengue fever was transmitted by a mosquito, 81.96% declared having obtained knowledge regarding dengue and vector through television, 56% affirm that dengue is a severe illness, 67% of respondents admitted that individuals play an important role in the prevention of dengue. Regarding mosquito control activities, 90% of respondents reported turning containers. ConclusionsThis highlights the need for school programs with curricula to address vector biology and the prevention of vector-borne diseases not only during activity periods when mosquitoes batter people but all year long to do real prevention.

scientific communication and education↗

bioRxiv2020

Household and climate factors influence Aedes aegypti risk in the arid city of Huaquillas, Ecuador

Arboviruses transmitted by Aedes aegypti (e.g., dengue, chikungunya, Zika) are of major public health concern on the arid coastal border of Ecuador and Peru. This high transit border is a critical disease surveillance site due to human movement-associated risk of transmission. Local level studies are thus integral to capturing the dynamics and distribution of vector populations and social-ecological drivers of risk, to inform targeted public health interventions. Our study examines factors associated with household-level Ae. aegypti presence in Huaquillas, Ecuador, while accounting for spatial and temporal effects. From January to May of 2017, adult mosquitoes were collected from a cohort of households (n = 63) in clusters (n = 10), across the city of Huaquillas, using aspirator backpacks. Household surveys describing housing conditions, demographics, economics, travel, disease prevention, and city services were conducted by local enumerators. This study was conducted during the normal arbovirus transmission season (January - May), but during an exceptionally dry year. Household level Ae. aegypti presence peaked in February, and counts were highest in weeks with high temperatures and a week after increased rainfall. Presence of Ae. aegypti was highly variable between clusters. Hierarchical generalized linear models were used to explore household social-ecological variables and female Ae. aegypti presence. Houses with Ae. aegypti used larvicide in water tanks and had high awareness of dengue transmission. We found that homes were more likely to have Ae. aegypti when heads of household had lived in the neighborhoods for longer than average (>22 years), when households had more occupants than average (>4.5), had a female head of household, and received more frequent garbage collection. Ae. aegypti presence was less likely in households with reliable water supply and septic systems. Based on our findings, infrastructure access, urban occupancy patterns, and seasonal climate are important considerations for vector control in this city, and even in dry years, this arid environment supports Ae. aegypti breeding habitat. Author summaryMosquito transmitted infectious diseases are a growing concern around the world. The yellow fever mosquito (Aedes aegypti) has been responsible for recent major outbreaks of disease, including dengue fever and Zika. This mosquito prefers to bite humans and lay its eggs in artificial containers such as water tanks and planters. This makes Ae. aegypti well suited to become established in growing urban areas. Controlling these mosquitoes has been an important way to reduce the risk of disease transmission. Studies that are undertaken to understand local factors that contribute to the continued survival of the mosquito can be used to inform control practices. We conducted a study in the largest city on the border of Ecuador and Peru where we collected adult mosquitoes from houses and surveyed household members about their behaviors, perceptions, and housing infrastructure associated with the mosquito vector. Mosquitoes were most numerous in weeks with high temperatures and a week after increased rainfall. Larvicide was a commonly used control strategy in homes where Ae. aegypti was present. We found that houses that had more people, female heads of household, heads of household that had lived in the neighborhood for a long time, and had unreliable water service, were more likely have mosquitoes present, while houses that used septic systems were less likely to have mosquitoes present.

ecology↗

bioRxiv2020

Climate explains geographic and temporal variation in mosquito-borne disease dynamics on two continents

Climate drives population dynamics through multiple mechanisms, which can lead to seemingly context-dependent effects of climate on natural populations. For climate-sensitive diseases such as dengue, chikungunya, and Zika, climate appears to have opposing effects in different contexts. Here we show that a model, parameterized with laboratory measured climate-driven mosquito physiology, captures three key epidemic characteristics across ecologically and culturally distinct settings in Ecuador and Kenya: the number, timing, and duration of outbreaks. The model generates a range of disease dynamics consistent with observed Aedes aegypti abundances and laboratory-confirmed arboviral incidence with variable accuracy (28 - 85% for vectors, 44 - 88% for incidence). The model predicted vector dynamics better in sites with a smaller proportion of young children in the population, lower mean temperature, and homes with piped water and made of cement. Models with limited calibration that robustly capture climate-virus relationships can help guide intervention efforts and climate change disease projections.

ecology↗

bioRxiv2020

A decade of arbovirus emergence in the temperate southern cone of South America: dengue, Aedes aegypti and climate dynamics in Cordoba, Argentina

BackgroundArgentina is located at the southern temperate range of arboviral transmission by the mosquito Aedes aegypti and has experienced a rapid increase in disease transmission in recent years. Here we present findings from an entomological surveillance study that began in Cordoba, Argentina, following the emergence of dengue in 2009. MethodsFrom 2009 to 2017, larval surveys were conducted monthly, from November to May, in 600 randomly selected households distributed across the city. From 2009 to 2013, ovitraps (n=177) were sampled weekly to monitor the oviposition activity of Ae. aegypti. We explored seasonal and interannual dynamics of entomological variables and dengue transmission. Cross correlation analysis was used to identify significant lag periods. ResultsAedes aegypti were detected over the entire study period, and abundance peaked during the summer months (January to March). We identified a considerable increase in the proportion of homes with juvenile Ae. aegypti over the study period (from 5.7% of homes in 2009-10 to 15.4% of homes in 2016-17). Aedes aegypti eggs per ovitrap and larval abundance were positively associated with temperature in the same month. Autochthonous dengue transmission peaked in April, following a peak in imported dengue cases in March; autochthonous dengue was not positively associated with vector or climate variables. ConclusionsThis longitudinal study provides insights into the complex dynamics of arbovirus transmission and vector populations in a temperate region of arbovirus emergence. Our findings suggest that Cordoba is well suited for arbovirus disease transmission, given the stable and abundant vector populations. Further studies are needed to better understand the role of regional human movement. Author summaryThere is an increasing risk of arbovirus transmission in temperate regions. Argentina is located at the southern range of dengue virus transmission by the Aedes aegypti mosquito. In the last decade, epidemics of dengue fever have emerged for the first time in the city of Cordoba, Argentina. We present the study design and findings from an entomological surveillance study in Cordoba, which began following the emergence of dengue in 2009. We found that Ae. aegypti were most abundant from January to March, followed by a peak in local dengue transmission in April. Over the study period, we noted a considerable increase in the proportion of homes with Ae. aegypti. Vector indices were positively associated with warmer temperatures, which have been increasing in this region. However, the timing of local dengue transmission appears to be driven by the appearance of imported dengue cases associated with human movement. These results highlight the important role of long term surveillance studies in areas of disease emergence.

ecology↗

bioRxiv2019

Ingested insecticide to control Aedes aegypti: Developing a novel dried attractive toxic sugar bait device for intra-domiciliary control

BackgroundIllnesses transmitted by Aedes aegypti (Linnaeus, 1762) such as dengue, chikungunya and Zika comprise a considerable global burden; mosquito control is the primary public health tool to reduce disease transmission. Current interventions are inadequate and insecticide resistance threatens the effectiveness of these options. Dried attractive bait stations (DABS) are a novel mechanism to deliver insecticide to Ae. aegypti. The DABS are a high-contrast 28 inch2 surface coated with dried sugar-boric acid solution. Ae. aegypti are attracted to DABS by visual cues only, and the dried sugar solution elicits an ingestion response from Ae. aegypti landing on the surface. The study presents the development of the DABS and tests of their impact on Ae. aegypti mortality in the laboratory and a series of semi-field trials. MethodsWe conducted multiple series of laboratory and semi-field trials to assess the survivability of Ae. aegypti mosquitoes exposed to the DABS. For laboratory experiments we assessed the lethality, the killing mechanism, and the shelf life of the device through controlled experiments. In the semi-field trials, we released laboratory-reared female Ae. aegypti into experimental houses typical of peri-urban tropical communities in South America in three trial series with six replicates each. Laboratory experiments were conducted in Quito, Ecuador, and semi-field experiments were conducted in Machala, Ecuador - an area with abundant wild populations of Ae. aegypti and endemic arboviral transmission. ResultsIn the laboratory, complete lethality was observed after 48 hours regardless of physiological status of the mosquito. The killing mechanism was determined to be through ingestion, as the boric acid disrupted the gut of the mosquito. In experimental houses, total mosquito mortality was greater in the treatment house for all series of experiments (p<0.0001). ConclusionsThe DABS devices were effective at killing female Ae. aegypti under a variety of laboratory and semi-field conditions. DABS are a promising intervention for interdomiciliary control of Ae. aegypti and arboviral disease prevention.

ecology↗

bioRxiv2019

Severity Index for Suspected Arbovirus (SISA): machine learning for accurate prediction of hospitalization in subjects suspected of arboviral infection

BackgroundDengue, chikungunya, and Zika are arboviruses of major global health concern. Decisions regarding the clinical management of suspected arboviral infection are challenging in resource-limited settings, particularly when deciding on patient hospitalization. The objective of this study was to determine if hospitalization of individuals with suspected arboviral infections could be predicted using subject intake data.\n\nMethodology/Principal FindingsTwo prediction models were developed using data from a surveillance study in Machala, a city in southern coastal Ecuador with a high burden of arboviral infections. Data was obtained from subjects who presented at sentinel medical centers with suspected arboviral infection (November 2013 to September 2017). The first prediction model--called the Severity Index for Suspected Arbovirus (SISA)-- used only demographic and symptom data. The second prediction model--called the Severity Index for Suspected Arbovirus with Laboratory (SISAL)--incorporated laboratory data. These models were selected by comparing the prediction ability of seven machine learning algorithms; the area under the receiver operating characteristic curve from the prediction of a test dataset was used to select the final algorithm for each model. After eliminating those with missing data, the SISA dataset had 534 subjects, and the SISAL dataset had 98 subjects. For SISA, the best prediction algorithm was the generalized boosting model, with an AUC of 0.91. For SISAL, the best prediction algorithm was the elastic net with an AUC of 0.94. A sensitivity analysis revealed that SISA and SISAL are not directly comparable to one another.\n\nConclusions/SignificanceBoth SISA and SISAL were able to predict arbovirus hospitalization with a high degree of accuracy in our dataset. These algorithms will need to be tested and validated on new data from future patients. Machine learning is a powerful prediction tool and provides an excellent option for new management tools and clinical assessment of arboviral infection.\n\nAuthor SummaryPatient triage is a critical decision for clinicians; patients with suspected arbovirus infection are difficult to diagnose as symptoms can be vague and molecular testing can be expensive or unavailable. Determining whether these patients should be hospitalized or not can be challenging, especially in resource-limited settings. Our study included data from 543 subjects with a diagnosis of suspected dengue, chikungunya, or Zika infection. Using a machine learning approach, we tested the ability of seven algorithms to predict hospitalization status based on the signs, symptoms, and laboratory data that would be available to a clinician at patient intake. Using only signs and symptoms, we were able to predict hospitalization with high accuracy (94%). Including laboratory data also resulted in highly accurate prediction of hospitalization (92%). This tool should be test in future studies with new subject data. Upon further development, we envision a simple mobile application to aid in the decision-making process for clinicians in areas with limited resources.

epidemiology↗

bioRxiv2019

Co-developing climate services for public health: stakeholder needs and perceptions for the prevention and control of Aedes-transmitted diseases in the Caribbean.

BackgroundSmall island developing states (SIDS) in the Caribbean region are challenged with managing the health outcomes of a changing climate. Health and climate sectors have partnered to co-develop climate services to improve the management of these diseases, for example, through the development of climate-driven early warning systems. The objective of this study was to identify health and climate stakeholder perceptions and needs in the Caribbean, with respect to the development of climate services for arboviruses (e.g. dengue, chikungunya, and Zika).\n\nMethodsStakeholders included public decision makers and practitioners from the climate and health sectors at the regional (Caribbean) level and from the countries of Dominica and Barbados. From April to June 2017, we conducted interviews (n=41), surveys (n=32), and national workshops with stakeholders. Survey responses were tabulated and audio recordings were transcribed and analyzed using qualitative coding to identify responses by research topic, country/region, and sector.\n\nResultsHealth practitioners indicated that their jurisdiction is currently experiencing an increased risk of diseases transmitted by Ae. aegypti due to climate variability, and most anticipated that this risk will increase in the future. National health sectors reported financial limitations and a lack of technical expertise in geographic information systems (GIS), statistics, and modeling, which constrained their ability to implement climate services for arboviruses. National climate sectors were constrained by a lack of personnel. Stakeholders highlighted the need to strengthen partnerships with the private sector, academia, and civil society. They identified a gap in local research on climate-arbovirus linkages, which constrained the ability of the health sector to make informed decisions. Strategies to strengthen the climate-health partnership included a top-down approach by engaging senior leadership, multi-lateral collaboration agreements, national committees on climate and health, and shared spaces of dialogue. Mechanisms for mainstreaming climate services for health operations to control arboviruses included climate-health bulletins and an online GIS platform that would allow for regional data sharing and the generation of spatiotemporal epidemic forecasts.\n\nConclusionsThese findings support the creation of interdisciplinary and intersectoral communities of practices and the co-design of climate services for the Caribbean public health sector. By fostering the effective use of climate information within health policy, research and practice, nations will have greater capacity to adapt to a changing climate.

scientific communication and education↗

bioRxiv2018

Phenotypic and genotypic resistance to commonly used insecticides in Aedes aegypti among four cities in southern Ecuador

Insecticide resistance (IR) can undermine efforts to control vector species of public health importance. Aedes aegypti is the main vector of resurging diseases in the Americas such as yellow fever and dengue, as well as recently emerging chikungunya and Zika viruses, which have caused unprecedented epidemics in the region. Vector control remains the primary public health intervention to prevent outbreaks of Aedes transmitted diseases. In many high-risk regions, like southern Ecuador, we have limited information on IR in Ae. aegypti. In this study, IR status in Ae. aegypti was measured across four cities in El Oro Province in Ecuador using phenotypic assays and genetic screening for alleles associated with resistance to pyrethroid insecticides. Bottle bioassays showed significant inter-seasonal variation in resistance to deltamethrin, a pyrethroid insecticide commonly used by the Ministry of Health, and alpha cypermethrin, as well as differences in deltamethrin resistance between cities. There was also a significant difference in phenotypic response to the organophosphate, Malathion, between two of the cities during the second sampling season. Genotyping showed moderate to high frequencies of the V1016I and F1534C resistance alleles in all four cites. Frequency of resistance genotypes varied significantly between cities in the first sampling season, and not in the later seasons, suggesting a possible selective response to vector control activity. Overall, resistance levels were highest in Machala, a city where dengue is hyperendemic and where insecticide use has historically been more intense than in the other cities included in the study. Despite statistically significant evidence that resistance alleles conferred phenotypic resistance, there was not precise correspondence between these indicators. We found that 17.6% of F1534C and 45.6% of V1016I mutant mosquitoes were susceptible in the bottle bioassays. This study shows there is spatiotemporal variability in IR in southern Ecuador, and serves as an initial examination of the genotypic and phenotypic indicators of IR in this region, providing important information to guide the vector control interventions by the public health sector.

epidemiology↗

bioRxiv2018

Geographic shifts in Aedes aegypti habitat suitability in Ecuador using larval surveillance data and ecological niche modeling: implications of climate change for public health vector control

Arboviral disease transmission by Aedes mosquitoes poses a major challenge to public health systems in Ecuador, where constraints on health services and resource allocation call for spatially informed management decisions. Employing a unique dataset of larval occurrence records provided by the Ecuadorian Ministry of Health, we used ecological niche models (ENMs) to estimate the current geographic distribution of Aedes aegypti in Ecuador, using mosquito presence as a proxy for risk of disease transmission. ENMs built with the Genetic Algorithm for Rule-Set Production (GARP) algorithm and a suite of environmental variables were assessed for agreement and accuracy. The top model of larval mosquito presence was projected to the year 2050 under various combinations of greenhouse gas emissions scenarios and models of climate change. Under current climatic conditions, larval mosquitoes were not predicted in areas of high elevation in Ecuador, such as the Andes mountain range, as well as the eastern portion of the Amazon basin. However, all models projected to scenarios of future climate change demonstrated potential shifts in mosquito distribution, wherein range contractions were seen throughout most of eastern Ecuador, and areas of transitional elevation became suitable for mosquito presence. Encroachment of Ae. aegypti into mountainous terrain was estimated to affect up to 4,215 km2 under the most extreme scenario of climate change, an area which would put over 12,000 people currently living in transitional areas at risk. This distributional shift into communities at higher elevations indicates an area of concern for public health agencies, as targeted interventions may be needed to protect vulnerable populations with limited prior exposure to mosquito-borne diseases. Ultimately, the results of this study serve as a tool for informing public health policy and mosquito abatement strategies in Ecuador.\n\nAuthor summaryThe yellow fever mosquito (Aedes aegypti) is a medically important vector of arboviral diseases in Ecuador, such as dengue fever and chikungunya. Managing Ae. aegypti is a challenge to public health agencies in Latin America, where the use of limited resources must be planned in an efficient, targeted manner. The spatial distribution of Ae. aegypti can be used as a proxy for risk of disease exposure, guiding policy formation and decision-making. We used ecological niche models in this study to predict the range of Ae. aegypti in Ecuador, based on agency larval mosquito surveillance records and layers of environmental predictors (e.g. climate, altitude, and human population). The best models of current range were then projected to the year 2050 under a variety of greenhouse gas emissions scenarios and models of climate change. All modeled future scenarios predicted shifts in the range of Ae. aegypti, allowing us to assess human populations that may be at risk of becoming exposed to Aedes vectored diseases. As climate changes, we predict that communities living in areas of transitional elevation along the Andes mountain range are vulnerable to the expansion of Aedes aegypti.

epidemiology↗

bioRxiv2018

Zika Virus Outbreak, Barbados, 2015 - 2016

Barbados is a Caribbean island country of approximately 285,000 people, with a thriving tourism industry. In 2015, Zika spread rapidly throughout the Americas, and its proliferation through the Caribbean islands followed suit. Barbados reported its first confirmed autochthonous Zika transmission to the Pan American Health Organization (PAHO) in January 2016, a month before the global public health emergency was declared. Following detection of suspected Zika cases on Barbados in 2015, 926 individuals were described as suspected cases, and 147 lab confirmed cases were reported through December 2016, the end of the most recent epidemiological year. In this short report, we describe the epidemiological characteristics of 926 clinical case records which were originally suspected as cases of Zika, and which were subsequently sent for testing and confirmation; 147 were found positive for Zika, using RT-PCR methods, another 276 tested negative, and the remaining 503 were either pending results or still in the suspected category. Women were represented at about twice the rate of men in case records where sex was reported (71.9%), and confirmed cases (78.2%), and 19 of the confirmed positive cases were children under the age of 10.

epidemiology↗

bioRxiv2017

Quantifying Seasonal and Diel Variation in Anopheline and Culex Human Biting Rates in Southern Ecuador

BackgroundQuantifying mosquito biting rates for specific locations enables estimation of mosquito-borne disease risk, and can inform intervention efforts. Measuring biting itself is fraught with ethical concerns, so the landing rate of mosquitoes on humans is often used as a proxy measure. Southern coastal Ecuador was historically endemic for malaria (P. falciparum and P. vivax), although successful control efforts in the 2000s eliminated autochthonous transmission (since 2011). This study presents an analysis of data collected during the elimination period.\n\nMethodsWe examined human landing catch (HLC) data for three mosquito taxa: 2 malaria vectors, Anopheles albimanus and Anopheles punctimacula, and grouped Culex spp. These data were collected by the National Vector Control Service of the Ministry of Health over a 5-year time span (2007 - 2012) in five cities in southern coastal Ecuador, at multiple households, in all months of the year, during dusk-dawn (18:00-6:00) hours, often at both indoor and outdoor locations. Hurdle models were used to determine if biting activity was fundamentally different for the three taxa, and to identify spatial and temporal factors influencing bite rate. Due to the many different approaches to studying and quantifying bite rates in the literature, we also created a glossary of terms, to facilitate comparative studies in the future.\n\nResultsBiting trends varied significantly with species and time. All taxa exhibited exophagic feeding behavior, and outdoor locations increased both the odds and incidence of bites across taxa. An. albimanus was most frequently observed biting, with an average of 4.7 bites per hour. The highest and lowest respective months for significant biting activity were March and July for An. albimanus, July and August for An. punctimacula, and February and July for Culex spp.\n\nConclusionsFine-scale spatial and temporal differences exist in biting patterns among mosquito taxa in southern coastal Ecuador. This analysis provides detailed information for targeting vector control and household level behavioral interventions. These data were collected as part of routine vector surveillance conducted by the Ministry of Health, but such data have not been collected since. Reinstating such surveillance measures would provide important information to aid in preventing malaria re-emergence.

epidemiology↗

bioRxiv2017

Could The Recent Zika Epidemic Have Been Predicted?

Given knowledge at the time, the recent 2015-2016 zika virus (ZIKV) epidemic probably could not have been predicted. Without the prior knowledge of ZIKV being already present in South America, and given the lack of understanding of key epidemiologic processes and long-term records of ZIKV cases in the continent, the best related prediction was for potential risk of an Aedes-borne disease epidemic. Here we use a recently published two-vector capacity model to assess the predictability of the conditions conducive to epidemics of diseases like zika, chikungunya or dengue, transmitted by the independent or concurrent presence of Aedes aegypti and Aedes albopictus. We compare the potential risk of transmission forcing the model with the observed climate and with state-of-the-art operational forecasts from the North American Multi Model Ensemble (NMME), finding that the predictive skill of this new seasonal forecast system is highest for multiple countries in Latin America and the Caribbean during the December-February and March-May seasons, and slightly lower -but still of potential use to decision-makers- for the rest of the year. In particular, we find that above-normal suitable conditions for the occurrence of the zika epidemic at the beginning of 2015 could have been successfully predicted for several zika hotspots, and in particular for Northeast Brazil: the heart of the epidemic. Nonetheless, the initiation and spread of an epidemic depends on the effect of multiple factors beyond climate conditions, and thus this type of approach must be considered as a guide and not as a formal predictive tool of vector-borne epidemics.

epidemiology↗

bioRxiv2017

The social and spatial ecology of dengue presence and burden during an outbreak in Guayaquil, Ecuador, 2012

Dengue fever, a mosquito-borne viral disease, is an ongoing public health problem in Ecuador and throughout the tropics, yet we have a limited understanding of the disease transmission dynamics in these regions. The objective of this study was to characterize the spatial dynamics and social-ecological risk factors associated with a recent dengue outbreak in Guayaquil, Ecuador. We examined georeferenced dengue cases (n = 4,248) and block-level census data variables to identify potential social-ecological variables associated with the presence and burden of dengue fever in Guayaquil in 2012. We applied LISA and Morans I tests to analyze hotspots of dengue cases and used multimodel selection in R computing language to identify covariates associated with dengue incidence at the census zone level. Significant hotspots of dengue transmission were found near the North Central and Southern portions of Guayaquil. Significant risk factors for presence of dengue included poor housing conditions (e.g., poor condition of ceiling, floors, and walls), access to paved roads, and receipt of remittances. Counterintuitive positive correlations with dengue presence were observed with several municipal services such as garbage collection and access to piped water. Risk factors for the increased burden of dengue included poor housing conditions, garbage collection, receipt of remittances, and sharing a property with more than one household. Social factors such as education and household demographics were negatively correlated with increased dengue burden. Our findings elucidate underlying differences with dengue presence and burden and indicate the potential to develop dengue vulnerability and risk maps to inform disease prevention and control - information that is also relevant for emerging epidemics of chikungunya and zika.\n\nHighlightsO_LIIn 2012, Guayaquil, Ecuador had a large outbreak of dengue cases\nC_LIO_LIDengue case presence and burden exhibited spatial heterogeneity at the census block level\nC_LIO_LISocial-ecological drivers of case presence and burden differed in this outbreak, highlighting the need to model both types of epidemiological data\nC_LIO_LIAccess to municipal resources such as garbage collection and piped water had counterintuitive relationships with dengue presence, but poor housing, garbage collection and remittances correlated to dengue burden.\nC_LIO_LIOur findings inform risk mapping and vector control and surveillance allocation, relevant to this and other concurrent emergent epidemics such as chikungunya and zika\nC_LI

epidemiology↗

bioRxiv2017

Environmental cholera (Vibrio cholerae) dynamics in an estuarine system in southern coastal Ecuador

Cholera emergence is strongly linked to local environmental and ecological context. The 1991-2004 pandemic emerged in Peru and spread north into Ecuadors El Oro province, making this a key site for potential re-emergence. Machala, El Oro, is a port city of 250,000, near the Peruvian border. Many livelihoods depend on the estuarine system, from fishing for subsistence and trade, to domestic water use. In 2014, we conducted biweekly sampling for 10 months in five estuarine locations, across a gradient of human use, and ranging from inland to ocean. We measured water characteristics implicated in V. cholerae growth and persistence: pH, temperature, salinity, and algal concentration, and evaluated samples in five months for pathogenic and non-pathogenic Vibrio cholerae, by polymerase chain reaction (PCR). We found environmental persistence of strains O1 and O139, but no evidence for toxigene presence. V. cholerae presence was coupled to algal and salinity concentration, and sites exhibited considerable seasonal and spatial heterogeneity. This study indicates that environmental conditions in Machala are optimal for human cholera re-emergence, with risk peaking during September, and higher risk near urban periphery low-income communities. This highlights a need for surveillance of this coupled cholera- estuarine system to anticipate potential future outbreaks.

epidemiology↗

bioRxiv2017

The high burden of dengue and chikungunya in southern coastal Ecuador: Epidemiology, clinical presentation, and phylogenetics from a prospective study in Machala in 2014 and 2015

Here we report the findings from the first two years of an arbovirus surveillance study conducted in Machala, Ecuador, a dengue endemic region (2014-2015). Patients with suspected dengue virus (DENV) infections (index cases, n=324) were referred from five Ministry of Health clinical sites. A subset of DENV positive index cases (n = 44) were selected, and individuals from the index household and four neighboring homes within 200-meters were recruited (n = 400). Individuals who entered the study, other than index cases, are referred to as associates. In 2014, 70.9% of index cases and 35.6% of associates had acute or recent DENV infections. In 2015, 28.3% of index cases and 12.8% of associates had acute or recent DENV infections. For every DENV infection captured by passive surveillance, we detected an additional three acute or recent DENV infections in associates. Of associates with acute DENV infections, 68% reported dengue-like symptoms, with the highest prevalence of symptomatic acute infections in children under 10 years of age. The first chikungunya virus (CHIKV) infections were detected on epidemiological week 12 in 2015. 43.1% of index cases and 3.5% of associates had acute CHIKV infections. No Zika virus infections were detected. Phylogenetic analyses of isolates of DENV from 2014 revealed genetic relatedness and shared ancestry of DENV1, DENV2 and DENV4 genomes from Ecuador with those from Venezuela and Colombia, indicating presence of viral flow between Ecuador and surrounding countries. Enhanced surveillance studies, such as this, provide high-resolution data on symptomatic and inapparent infections across the population.

epidemiology↗