Monitoring forest cover change within different reserve types in southern Ghana.

Rapid population and economic growth quickly degrade and deplete forest resources in many developing countries, even within protected areas. Monitoring forest cover change is critical for assessing ecosystem changes and targeting conservation efforts. Yet the most biodiverse forests on the planet are also the most difficult to monitor remotely due to their frequent cloud cover. To begin to reconcile this problem, we develop and implement an effective and efficient approach to mapping forest loss in the extremely cloud-prevalent southern Ghana region using dense time series Landsat 7 and 8 images from 1999 to 2018, based on median value temporal compositing of a novel vegetation index called the spectral variability vegetation index (SVVI). Resultant land-cover and land-use maps yielded 90 to 94% mapping accuracies. Our results indicate 625 km2 of forest loss within the 9800-km2 total mapping area, including within forest reserves and their environs between circa 2003 and 2018. Within the reserves, reduced forest cover is found near the reserve boundaries compared with their interiors, suggesting a more degraded environment near the edge of the protected areas. A fully protected reserve, Kakum National Park, showed little forest cover change compared with many other less protected reserves (such as a production reserve-Subri River). Anthropogenic activities, such as mining, agriculture, and built area expansion, were the main land-use transitions from forest. The reserves and census districts that are located near large-scale open pit mining indicated the most drastic forest loss. No significant correlation was found between the magnitudes of forest cover change and population density change for reserves and within a 1.5-km buffer surrounding the reserves. While other anthropogenic factors should be explored in relation to deforestation, our qualitative analysis revealed that reserve protection status (management policies) appears to be an important factor. The mapping approach described in this study provided a highly accurate and effective means to monitor land-use changes in forested and cloud-prone regions with great promise for application to improved monitoring of moist tropical and other forests characterized by high cloud cover.

Do village-level normative and network factors help explain spatial variability in adolescent childbearing in rural Honduras?

Adolescent childbearing rates are higher in Central America than almost anywhere else. However, in this research we discovered that adolescent childbearing exhibits variability from one village to another, and we might discover factors associated with this spatial variability that can help us understand key characteristics underlying the pattern of early childbearing. To do this, we assessed the village-level normative and network factors associated with adolescent birth (birth taking place before age 20 years) in rural Honduras and evaluated the geographic dispersion of these patterns. We used full population data from 24,937 people in 176 villages (81% of the eligible population) to assess prevalence and patterns of adolescent childbearing among women. We modeled the predictors of adolescent births among women younger than 21 years. After accounting for individual demographic characteristics, one of the strongest predictors of adolescent birth within the population was village-level collective norms about the acceptability of adolescent childbearing, based on aggregating normative measures from the entire population. The proportion of women in the village who had given birth as an adolescent was also strongly associated with an individual girl's likelihood of having given birth as an adolescent. We used full village-level network analyses to calculate social cohesion within the village. Normative pressure was strongly associated with the likelihood of an adolescent birth in villages with high cohesion (high network density) and was not associated or had a weak association in villages with low cohesion. On the other hand, the longer a girl had lived in the village, the stronger the association between the overall proportion of women in that village who gave birth as adolescents and the girl's own likelihood of having done so. Spatial analyses suggest that levels of adolescent births vary spatially across villages, as do the village-level normative factors associated with them.

A Pattern-Based Definition of Urban Context Using Remote Sensing and GIS.

In Sub-Saharan Africa rapid urban growth combined with rising poverty is creating diverse urban environments, the nature of which are not adequately captured by a simple urban-rural dichotomy. This paper proposes an alternative classification scheme for urban mapping based on a gradient approach for the southern portion of the West African country of Ghana. Landsat Enhanced Thematic Mapper Plus (ETM+) and European Remote Sensing Satellite-2 (ERS-2) synthetic aperture radar (SAR) imagery are used to generate a pattern based definition of the urban context. Spectral mixture analysis (SMA) is used to classify a Landsat scene into Built, Vegetation and Other land covers. Landscape metrics are estimated for Built and Vegetation land covers for a 450 meter uniform grid covering the study area. A measure of texture is extracted from the SAR imagery and classified as Built/Non-built. SMA based measures of Built and Vegetation fragmentation are combined with SAR texture based Built/Non-built maps through a decision tree classifier to generate a nine class urban context map capturing the transition from unsettled land at one end of the gradient to the compact urban core at the other end. Training and testing of the decision tree classifier was done using very high spatial resolution reference imagery from Google Earth. An overall classification agreement of 77% was determined for the nine-class urban context map, with user's accuracy (commission errors) being lower than producer's accuracy (omission errors). Nine urban contexts were classified and then compared with data from the 2000 Census of Ghana. Results suggest that the urban classes appropriately differentiate areas along the urban gradient.

A global systematic review of Chagas disease prevalence among migrants.

Human migration has been identified as a potential factor for increased Chagas disease risk and has transformed the disease from a Latin American problem to a global one. We conducted a systematic review of the scientific literature between 2004-2014 in order to: summarize recent seroprevalence estimates of Chagas disease among Latin American migrants, in both endemic and non-endemic settings; compare seroprevalence estimates in migrants to countrywide prevalence estimates; and identify risk factors for Chagas disease among migrants. A total of 320 studies were screened and 23 studies were included. We found evidence that the prevalence of Chagas disease is higher than expected in some migrant groups and that reliance on blood donor screening prevalence estimates underestimates the burden of disease. Overall there is a dearth of high quality epidemiologic studies on the prevalence of Chagas disease in migrants, especially among intra-regional migrants within Latin America. Given that this zoonotic disease cannot likely be eradicated, improved surveillance and reporting is vital to continuing control efforts. More accurate health surveillance of both Latin American migrants and the Chagas disease burden will help countries appropriately scale up their response to this chronic disease. Overall, improved estimates of Chagas disease among migrants would likely serve to highlight the real need for better screening, diagnostics, and treatment of individuals living with the disease.

Agency, access, and Anopheles: neighborhood health perceptions and the implications for community health interventions in Accra, Ghana.

BACKGROUND: Social and environmental factors are increasingly recognized for their ability to influence health outcomes at both individual and neighborhood scales in the developing urban world. Yet issues of spatial heterogeneity in these complex environments may obscure unique elements of neighborhood life that may be protective or harmful to human health. Resident perceptions of neighborhood effects on health may help to fill gaps in our interpretation of household survey results and better inform how to plan and execute neighborhood-level health interventions. OBJECTIVE: We evaluate differences in housing and socioeconomic indicators and health, environment, and neighborhood perceptions derived from the analysis of a household survey and a series of focus groups in Accra, Ghana. We then explore how neighborhood perceptions can inform survey results and ultimately neighborhood-level health interventions. DESIGN: Eleven focus groups were conducted across a socioeconomically stratified sample of neighborhoods in Accra, Ghana. General inductive themes from the focus groups were analyzed in tandem with data collected in a 2009 household survey of 2,814 women. In-depth vignettes expand upon the three most salient emergent themes. RESULTS: Household and socioeconomic characteristics derived from the focus groups corroborated findings from the survey data. Focus group and survey results diverged for three complex health issues: malaria, health-care access, and sense of personal agency in promoting good health. CONCLUSION: Three vignettes reflecting community views about malaria, health-care access, and sense of personal agency in promoting good health highlight the challenges facing community health interventions in Accra and exemplify how qualitatively derived neighborhood-level health effects can help shape health interventions.

Urban Vegetation Cover and Vegetation Change in Accra, Ghana: Connection to Housing Quality.

The objectives are to (1) quantify, map, and analyze vegetation cover distributions and changes across Accra, Ghana, for 2002 and 2010; and (2) examine the statistical relationship between vegetation cover and a housing quality index (HQI) for 2000 at the neighborhood level. Pixel-level vegetation cover maps derived using threshold classification of 2002 and 2010 QuickBird normalized difference vegetation index images have very high overall accuracies and yield an estimate of 5.9 percent vegetation cover reduction over the study area between 2002 and 2010. A high degree of variance in vegetation cover for individual dates is explained by HQI at the neighborhood level, although minimal covariability between absolute or relative vegetation cover change and HQI for 2000 was observed.

Drinking Water in Transition: A Multilevel Cross-sectional Analysis of Sachet Water Consumption in Accra.

Rapid population growth in developing cities often outpaces improvements to drinking water supplies, and sub-Saharan Africa as a region has the highest percentage of urban population without piped water access, a figure that continues to grow. Accra, Ghana, implements a rationing system to distribute limited piped water resources within the city, and privately-vended sachet water-sealed single-use plastic sleeves-has filled an important gap in urban drinking water security. This study utilizes household survey data from 2,814 Ghanaian women to analyze the sociodemographic characteristics of those who resort to sachet water as their primary drinking water source. In multilevel analysis, sachet use is statistically significantly associated with lower overall self-reported health, younger age, and living in a lower-class enumeration area. Sachet use is marginally associated with more days of neighborhood water rationing, and significantly associated with the proportion of vegetated land cover. Cross-level interactions between rationing and proxies for poverty are not associated with sachet consumption after adjusting for individual-level sociodemographic, socioeconomic, health, and environmental factors. These findings are generally consistent with two other recent analyses of sachet water in Accra and may indicate a recent transition of sachet consumption from higher to lower socioeconomic classes. Overall, the allure of sachet water displays substantial heterogeneity in Accra and will be an important consideration in planning for future drinking water demand throughout West Africa.

Histogram Curve Matching Approaches for Object-based Image Classification of Land Cover and Land Use.

The classification of image-objects is usually done using parametric statistical measures of central tendency and/or dispersion (e.g., mean or standard deviation). The objectives of this study were to analyze digital number histograms of image objects and evaluate classifications measures exploiting characteristic signatures of such histograms. Two histograms matching classifiers were evaluated and compared to the standard nearest neighbor to mean classifier. An ADS40 airborne multispectral image of San Diego, California was used for assessing the utility of curve matching classifiers in a geographic object-based image analysis (GEOBIA) approach. The classifications were performed with data sets having 0.5 m, 2.5 m, and 5 m spatial resolutions. Results show that histograms are reliable features for characterizing classes. Also, both histogram matching classifiers consistently performed better than the one based on the standard nearest neighbor to mean rule. The highest classification accuracies were produced with images having 2.5 m spatial resolution.

Estimating spatial inequalities of urban child mortality.

BACKGROUND: Recent studies indicate that the traditional rural-urban dichotomy pointing to cities as places of better health in the developing world can be complicated by poverty differentials. Knowledge of spatial patterns is essential to understanding the processes that link individual demographic outcomes to characteristics of a place. A significant limitation, however, is the lack of spatial data and methods that offer flexibility in data inputs. OBJECTIVE: This paper tackles some of the issues in calculating intra-urban child mortality by combining multiple data sets in Accra, Ghana and applying a new method developed by Rajaratnam et al. (2010) that efficiently uses summary birth histories for creating local-level measures of under-five child mortality (5q0). Intra-urban 5q0 rates are then compared with characteristics of the environment that may be linked to child mortality. METHODS: Rates of child mortality are calculated for 16 urban zones within Accra for birth cohorts from 1987 to 2006. Estimates are compared to calculated 5q0 rates from full birth histories. 5q0 estimates are then related to zone measures of slum characteristics, housing quality, health facilities, and vegetation using a simple trendline R2 analysis. RESULTS: Results suggest the potential value of the Rajaratnam et al. method at the micro-spatial scale. Estimated rates indicate that there is variability in child mortality between zones, with a spread of up to 50 deaths per 1,000 births. Furthermore, there is evidence that child mortality is connected to environmental factors such as housing quality, slum-like conditions, and neighborhood levels of vegetation.

Income and health in Accra, Ghana: results from a time use and health study.

This paper uses newly collected household survey data from Accra, Ghana, to investigate whether incomes affect acute and chronic health outcomes in settings that can be considered representative for the large and rapidly growing urban centers of sub-Saharan Africa. The Time Use and Health Study in Accra collected information on incomes, current health status, and health care use from 5,484 persons in 1,250 households, each repeatedly sampled on a rolling basis for a period of 13 weeks. Data collection took place during September 2008-March 2010 to capture seasonal variations. The study found that incomes varied widely between households, and that a high fraction of persons lived below the poverty line. Despite this level of income poverty and an overall remarkably high burden of treatable disease, no systematic differences in self-reported and objectively measured health conditions were detected across socioeconomic groups.

Do the Most Vulnerable People Live in the Worst Slums? A Spatial Analysis of Accra, Ghana.

Slums are examples of localized communities within third world urban systems representing a range of vulnerabilities and adaptive capacities. This study examines vulnerability in relation to flooding, environmental degradation, social-status, demographics, and health in the slums of Accra, Ghana by utilizing a place-based approach informed by fieldwork, remote sensing, census data, and geographically weighted regression. The study objectives are threefold: (1) to move slums from a dichotomous into a continuous classification and examine the spatial patterns of the gradient, (2) develop measures of vulnerability for a developing world city and model the relationship between slums and vulnerability, and (3) to assess if the most vulnerable individuals live in the worst slums. A previously developed slum index is utilized, and four new measures of vulnerability are developed through principle components analysis, including a novel component of health vulnerability based on child mortality. Visualizations of the vulnerability measures assess spatial patterns of vulnerability in Accra. Ordinary least squares, spatial, and geographically weighted regression model the ability of the slum index to predict the four vulnerability measures. The slum index performs well for three of the four vulnerability measures, but is least able to predict health vulnerability underscoring the complex relationship between slums and child mortality in Accra. Finally, quintile analysis demonstrates the elevated prevalence of high vulnerability in places with high slum index scores.

When urban taps run dry: sachet water consumption and health effects in low income neighborhoods of Accra, Ghana.

Intraurban differentials in safe drinking water in developing cities have been exacerbated by rapid population growth that exceeds expansion of local water infrastructure. In Accra, Ghana, municipal water is rationed to meet demand, and the gap in water services is increasingly being filled by private water vendors selling packaged "sachet" water. Sachets extend drinking water coverage deeper into low-income areas and alleviate the need for safe water storage, potentially introducing a health benefit over stored tap water. We explore correlates of using sachets as the primary drinking water source for 2093 women in 37 census areas classified as slums by UN-Habitat, and links between sachet water and reported diarrhea episodes in a subset of 810 children under five. We find that neighborhood rationing exerts a strong effect on a household's likelihood of buying sachet water, and that sachet customers tend to be the poorest of the poor. Sachet use is also associated with higher levels of self-reported overall health in women, and lower likelihood of diarrhea in children. We conclude with implications for sachet regulation in Accra and other sub-Saharan cities facing drinking water shortages.

Intraurban mobility and its potential impact on the spread of blood-borne infections among drug injectors in Tijuana, Mexico.

We explored intraurban mobility of Tijuana, Mexico, injection drug users (IDUs). In 2005, 222 IDUs underwent behavioral surveys and infectious disease testing. Participants resided in 58 neighborhoods, but regularly injected in 30. From logistic regression, "mobile" IDUs (injecting ≥3 km from their residence) were more likely to cross the Mexico/U.S. border, share needles, and get arrested for carrying syringes-but less likely to identify hepatitis as an injection risk. Mobile participants lived in neighborhoods with less drug activity, treatment centers, or migrants, but higher marriage and home ownership rates. Mobile IDUs should be targeted for outreach and further investigation. The study's limitations are noted.

Sachet drinking water in Ghana's Accra-Tema metropolitan area: past, present, and future.

Population growth in West Africa has outpaced local efforts to expand potable water services, and private sector sale of packaged drinking water has filled an important gap in household water security. Consumption of drinking water packaged in plastic sachets has soared in West Africa over the last decade, but the long-term implications of these changing consumption patterns remain unclear and unstudied. This paper reviews recent shifts in drinking water, drawing upon data from the 2003 and 2008 Demographic and Health Surveys, and provides an overview of the history, economics, quality, and regulation of sachet water in Ghana's Accra-Tema Metropolitan Area. Given the pros and cons of sachet water, we suggest that a more holistic understanding of the drinking water landscape is necessary for municipal planning and sustainable drinking water provision.

Connecting the Dots Between Health, Poverty and Place in Accra, Ghana.

West Africa has a rapidly growing population, an increasing fraction of which lives in urban informal settlements characterized by inadequate infrastructure and relatively high health risks. Little is known, however, about the spatial or health characteristics of cities in this region or about the spatial inequalities in health within them. In this article we show how we have been creating a data-rich field laboratory in Accra, Ghana, to connect the dots between health, poverty, and place in a large city in West Africa. Our overarching goal is to test the hypothesis that satellite imagery, in combination with census and limited survey data, such as that found in demographic and health surveys (DHSs), can provide clues to the spatial distribution of health inequalities in cities where fewer data exist than those we have collected for Accra. To this end, we have created the first digital boundary file of the city, obtained high spatial resolution satellite imagery for two dates, collected data from a longitudinal panel of 3,200 women spatially distributed throughout Accra, and obtained microlevel data from the census. We have also acquired water, sewerage, and elevation layers and then coupled all of these data with extensive field research on the neighborhood structure of Accra. We show that the proportional abundance of vegetation in a neighborhood serves as a key indicator of local levels of health and well-being and that local perceptions of health risk are not always consistent with objective measures.

Health, Poverty, and Place in Accra, Ghana: Mapping Neighborhoods.

The overall objective of our research project is to understand the spatial inequality in health in Accra, the capital city of Ghana. We also utilize GIS technology to measure the association of adverse health and mortality outcomes with neighborhood ecology. We approached this in variety of ways, including multivariate analysis of imagery classification and census data. A key element in the research has been to obtain in-person interviews from 3,200 female respondents in the city, and then relate health data obtained from the women to the ecology of the neighborhoods in which they live. Detailed maps are a requirement for these field-based activities. However, commercially available street maps of Accra tend to be highly generalized and not very useful for the kind of health and social science research being undertaken by this project, The purpose of this paper is to describe street maps that were created for the project's office in downtown Accra and used to locate households of respondents. They incorporate satellite imagery with other geographic layers to provide the most important visual interpretation of the linkage between imagery and neighborhoods. Ultimately, through a detailed analysis of spatial disparities in health in Accra, Ghana, we aim to provide a model for the interpretation of urban health inequalities in cities of urbanizing and often poor countries.

Spatial Epidemiology of HIV among Injection Drug Users in Tijuana, Mexico.

The northwest border city of Tijuana is Mexico's fifth largest and is experiencing burgeoning drug use and human immunodeficiency virus (HIV) epidemics. Since local geography influences disease risk, we explored the spatial distribution of HIV among injection drug users (IDUs). From 2006-2007, 1056 IDUs were recruited using respondent-driven sampling, and then followed for eighteen months. Participants underwent semi-annual surveys, mapping, and testing for HIV, tuberculosis, and syphilis. Using Average Nearest Neighbor and Getis-Ord Gi* statistics, locations where participants lived, worked, bought and injected drugs were compared with HIV status and environmental and behavioral factors. Median age was thirty-seven years; 85 percent were male. Females had higher HIV prevalence than males (10.2 percent vs. 3.4 percent; p=0.001). HIV cases at baseline (n=47) most strongly clustered by drug injection sites (Z-Score -6.173; p < 0.001), with a 16 km2 hotspot near the Mexico/U.S. border, encompassing the red-light district. Spatial correlates of HIV included syphilis infection, female gender, younger age, increased hours on the street per day, and higher number of injection partners. Almost all HIV seroconverters injected within a 2.5 block radius of each other immediately prior to seroconversion. Only history of syphilis infection and female gender were strongly associated with HIV in the area where incident cases injected. Directional trends suggested a largely static epidemic until July-December 2008, when HIV spread to the southeast, possibly related to intensified violence and policing that spiked in the latter half of 2008. While clustering allows for targeting interventions, the dynamic nature of epidemics suggests the importance of mobile treatment and harm reduction programs.

Assessing the Utility of Satellite Imagery with Differing Spatial Resolutions for Deriving Proxy Measures of Slum Presence in Accra, Ghana.

Little research has been conducted on how differing spatial resolutions or classification techniques affect image-driven identification and categorization of slum neighborhoods in developing nations. This study assesses the correlation between satellite-derived land cover and census-derived socioeconomic variables in Accra, Ghana to determine whether the relationship between these variables is altered with a change in spatial resolution or scale. ASTER and Landsat TM satellite images are each used to classify land cover using spectral mixture analysis (SMA), and land cover proportions are summarized across Enumeration Areas in Accra and compared to socioeconomic data for the same areas. Correlation and regression analyses compare the SMA results with a Slum Index created from various socio-economic data taken from the Census of Ghana, as well as to data derived from a "hard" per-pixel classification of a 2.4 m Quickbird image. Results show that the vegetation fraction is significantly correlated with the Slum Index (Pearson's r ranges from -0.33 to -0.51 depending on which image-derived product is compared), and the use of a spatial error model improves results (multivariate model pseudo-R2 ranges from 0.37 to 0.40 by image product). We also find that SMA products derived from ASTER are a sufficient substitute for classification products derived from higher spatial resolution QB data when using land cover fractions as a proxy for slum presence, suggesting that SMA might be more cost-effective for deriving land cover fractions than the use of high-resolution imagery for this type of demographic analysis.

Adolescents' use of indoor tanning: a large-scale evaluation of psychosocial, environmental, and policy-level correlates.

OBJECTIVES: We evaluated psychosocial, built-environmental, and policy-related correlates of adolescents' indoor tanning use. METHODS: We developed 5 discrete data sets in the 100 most populous US cities, based on interviews of 6125 adolescents (aged 14-17 years) and their parents, analysis of state indoor tanning laws, interviews with enforcement experts, computed density of tanning facilities, and evaluations of these 3399 facilities' practices regarding access by youths. After univariate analyses, we constructed multilevel models with generalized linear mixed models (GLMMs). RESULTS: In the past year, 17.1% of girls and 3.2% of boys had used indoor tanning. The GLMMs indicated that several psychosocial or demographic variables significantly predicted use, including being female, older, and White; having a larger allowance and a parent who used indoor tanning and allowed their adolescent to use it; and holding certain beliefs about indoor tanning's consequences. Living within 2 miles of a tanning facility also was a significant predictor. Residing in a state with youth-access legislation was not significantly associated with use. CONCLUSIONS: Current laws appear ineffective in reducing indoor tanning; bans likely are needed. Parents have an important role in prevention efforts.

Exploring the relationships between dengue fever knowledge and Aedes aegypti breeding in St Catherine Parish, Jamaica: a pilot of enhanced low-cost surveillance.

PURPOSE: Dengue fever has re-emerged as an increasingly significant global health threat amid diminishing resources pledged for its control in developing nations. Efforts to limit breeding of the dengue vector Aedes aegypti are often hampered by lack of community awareness of the disease. METHODS: Sixty-eight households in St Catherine Parish, Jamaica completed a pilot knowledge, attitude, and practice questionnaire as part of a routine container survey for presence of A. aegypti larvae. RESULTS: Infestation levels were high according to traditional Stegomyia indices (Breteau index = 325); however, general knowledge of dengue symptoms, A. aegypti breeding sites, and preventive practices was low. After examining the links between demographic characteristics, dengue knowledge, and the number of breeding sites per house, higher educational achievement was associated with higher dengue knowledge, but also with more unprotected containers. Overall dengue knowledge was not associated with household container counts. Spatial statistics identified weak clustering of larvae-positive containers, and larvae were concentrated in three key container types. CONCLUSION: Residents may only understand the role of certain container types, and significant gaps in general knowledge of the disease may inhibit vector control. This pilot demonstrates the feasibility of conducting inexpensive, rapid assessment of community knowledge and breeding levels for local governments lacking the resources for a more methodologically robust vector assessment strategy.