Spatial Assessment of Contact Between Humans and Anopheles and Aedes Mosquitoes in a Medium-Sized African Urban Setting, Using Salivary Antibody-Based Biomarkers.

BACKGROUND: Anarchic and poorly controlled urbanization led to an increased risk of mosquito-borne diseases (MBD) in many African cities. Here, we evaluate the spatial heterogeneity of human exposure to malaria and arboviral disease vectors in an urban area of northern Senegal, using antibody-based biomarkers of exposure to Anopheles and Aedes mosquito bites. METHODS: A cross-sectional study was undertaken during the rainy season of 2014 in 4 neighborhoods of Saint-Louis, a city in northern Senegal. Among children aged 6-59 months in each neighborhood, the dried blood spot technique was used to evaluate immunoglobulin G (IgG) responses to both gSG6-P1 (Anopheles) and Nterm-34-kDa (Aedes) salivary peptides as validated biomarkers of respective mosquito bite exposure. RESULTS: IgG response levels to gSG6-P1 and Nterm-34-kDa salivary peptides varied significantly between the 4 neighborhoods (P < .0001). The level of exposure to Aedes bites also varied according to household access to sanitation services (P = .027), whereas that of exposure to Anopheles bites varied according to insecticide-treated bed net use (P = .006). In addition, spatial clusters of high contact between humans and mosquitoes were identified inside 3 neighborhoods. CONCLUSIONS: Antibody-based biomarkers of exposure to Anopheles and Aedes mosquito bites could be helpful tools for evaluating the heterogeneity of exposure to malaria and arboviral disease vectors by national control programs.

The score of integrated disease surveillance and response adequacy (SIA): a pragmatic score for comparing weekly reported diseases based on a systematic review.

BACKGROUND: The Integrated Disease Surveillance and Response (IDSR) strategy implemented by the World Health Organization (WHO) in Africa has produced a large amount of data on participating countries, and in particular on the Democratic Republic of Congo (DRC). These data are increasingly considered as unevaluable and, therefore, as requiring a rigorous process of validation before they can be used for research or public health purposes. The aim of this study was to propose a method to assess the level of adequacy of IDSR morbidity data in reflecting actual morbidity. METHODS: A systematic search of English- and French-language articles was performed in Scopus, Medline, Science Direct, Springer Link, Cochrane, Cairn, Persée, and Erudit databases. Other types of documents were identified through manual searches. Selected articles focused on the determinants of the discrepancies (differences) between reported morbidity and actual morbidity. An adequacy score was constructed using some of the identified determinants. This score was applied to the 15 weekly reported diseases monitored by IDSR surveillance in the DRC. A classification was established using the Jenks method and a sensitivity analysis was performed. Twenty-three classes of determinants were identified in 35 IDSR technical guides and reports of outbreak investigations and in 71 out of 2254 researched articles. For each of the 15 weekly reported diseases, the SIA was composed of 12 items grouped in 6 dimensions. RESULTS: The SIA classified the 15 weekly reported diseases into 3 categories or types: high score or good adequacy (value > = 14), moderate score or fair adequacy (value > = 8 and < 14), and low score or low or non-adequacy (value < 8). Regardless of the criteria used in the sensitivity analysis, there was no notable variation in SIA values or categories for any of the 15 weekly reported diseases. CONCLUSION: In a context of sparse health information in low- and middle-income countries, this study developed a score to help classify IDSR morbidity data as usable, usable after adjustment, or unusable. This score can serve to prioritize, optimize, and interpret data analyses for epidemiological research or public health purposes.

Uneven malaria transmission in geographically distinct districts of Bobo-Dioulasso, Burkina Faso.

BACKGROUND: Urbanization is a main trend in developing countries and leads to health transition. Although non-communicable diseases are increasing in cities of low-income countries, vector-borne diseases such as malaria, are still present. In the case of malaria, transmission is lower than in rural areas, but is uneven and not well documented. In this study, we wanted to evaluate intra-urban malaria transmission in a West African country (Burkina Faso). METHODS: A cross-sectional study on 847 adults (35 to 59 year-old) and 881 children (6 months to 5 year-old) living in 1045 households of four districts (Dogona, Yeguere, Tounouma and Secteur 25) of Bobo-Dioulasso was performed between October and November 2013. The districts were selected according to a geographical approach that took into account the city heterogeneity. Malaria prevalence was evaluated using thick and thin blood smears. Human exposure to Anopheles bites was measured by assessing the level of IgG against the Anopheles gSG6-P1 salivary peptide. Adult mosquitoes were collected using CDC traps and indoor insecticide spraying in some houses of the four neighbourhoods. The Anopheles species and Plasmodium falciparum infection rate were determined using PCR assays. RESULTS: In this study, 98.5% of the malaria infections were due to Plasmodium falciparum. Malaria transmission occurred in the four districts. Malaria prevalence was higher in children than in adults (19.2 vs 4.4%), and higher in the central districts than in the peripheral ones (P = 0.001). The median IgG level was more elevated in P. falciparum-infected than in non-infected individuals (P < 0.001). Anopheles arabiensis was the main vector identified (83.2%; 227 of the 273 tested mosquito specimens). Five P. falciparum-infected mosquitoes were caught, and they were all caught in the central district of Tounouma where 28.6% (14/49) of the tested blood-fed mosquito specimens had a human blood meal. CONCLUSIONS: This study showed that urban malaria transmission occurred in Bobo-Dioulasso, in all the four studied areas, but mainly in central districts. Environmental determinants primarily explain this situation, which calls for better urban management.

Correction: Vialard, L., et al. Toward a Socio-Territorial Approach to Health: Health Equity in West Africa. Int. J. Environ. Res. Public Health 2017, 14, 106.

n/a.

Development of a spatial sampling protocol using GIS to measure health disparities in Bobo-Dioulasso, Burkina Faso, a medium-sized African city.

BACKGROUND: Many cities in developing countries experience an unplanned and rapid growth. Several studies have shown that the irregular urbanization and equipment of cities produce different health risks and uneven exposure to specific diseases. Consequently, health surveys within cities should be carried out at the micro-local scale and sampling methods should try to capture this urban diversity. METHODS: This article describes the methodology used to develop a multi-stage sampling protocol to select a population for a demographic survey that investigates health disparities in the medium-sized city of Bobo-Dioulasso, Burkina Faso. It is based on the characterization of Bobo-Dioulasso city typology by taking into account the city heterogeneity, as determined by analysis of the built environment and of the distribution of urban infrastructures, such as healthcare structures or even water fountains, by photo-interpretation of aerial photographs and satellite images. Principal component analysis and hierarchical ascendant classification were then used to generate the city typology. RESULTS: Five groups of spaces with specific profiles were identified according to a set of variables which could be considered as proxy indicators of health status. Within these five groups, four sub-spaces were randomly selected for the study. We were then able to survey 1045 households in all the selected sub-spaces. The pertinence of this approach is discussed regarding to classical sampling as random walk method for example. CONCLUSION: This urban space typology allowed to select a population living in areas representative of the uneven urbanization process, and to characterize its health status in regards to several indicators (nutritional status, communicable and non-communicable diseases, and anaemia). Although this method should be validated and compared with more established methods, it appears as an alternative in developing countries where geographic and population data are scarce.

Toward a Socio-Territorial Approach to Health: Health Equity in West Africa.

This study contributes to the literature about the effects of space and place on health by introducing a socio-territorial approach to urban health disparities in West Africa. It explores how urban spaces, specifically neighbourhoods, are shaped by social and economic relations and strategies of territorial control. We examine the potential influence of socio-territorial processes on vulnerability to disease, access to medical care, healthscapes, and illness experiences. Our research was conducted in Senegal and relied on a mixed methods design. We identified four neighbourhoods that represent the socio-spatial heterogeneity of the city of Saint-Louis and utilized the following methods: geographic and anthropological field research, household surveys, health knowledge and behaviour surveys, clinical exams, and illness interviews. Our results highlight the socio-territorial processes at work in each neighbourhood, clinical findings on three health measures (overweight, high blood pressure, and hyperglycaemia) and health experiences of individuals with hypertension or type II diabetes. We found significant differences in the prevalence of the three health measures in the study sites, while experiences managing hypertension and diabetes were similar. We conclude that a socio-territorial approach offers insight into the complex constellation of forces that produce health disparities in urban settings.

The Influence of Urbanization Modes on the Spatial Circulation of Flaviviruses within Ouagadougou (Burkina Faso).

Dengue is an emerging infectious disease of global significance. Although this virus has been reported for a long time, its significance within the burden of diseases in West Africa is not obvious, especially in Burkina Faso. Our objective was to evaluate flavivirus presence in Ouagadougou (Burkina Faso) and the link between anti-flavivirus antibody seroprevalence and urbanization modes. A population-based cross-sectional survey was conducted and 3015 children were enrolled from Ouagadougou districts with different types and degrees of urbanization (with/without equipment and high/low building density). Flavivirus (FLAV) IgM MAC-ELISA and FLAV indirect IgG ELISA were performed. Associations between FLAV IgG presence (sign of past infection) and various independent variables were assessed using the chi-square test and a multivariate logistic regression analysis. The apparent prevalence of past flavivirus infections among the enrolled children was 22.7% (95% CI: 22.4-26.7) (n = 685). Eleven children (0.4%; 95% CI: 0.61-2.14) were positive for FLAV IgM, indicating active transmission. Factors associated with flavivirus infection were identified among the enrolled children (age, sex), householders (educational level, asset index) and in the environment (building density, water access, waste management and house appearance); however, they showed great variability according to the city districts. The water access modality did not significantly influence FLAV IgG positivity. Conversely, apparently good practices of waste management had unexpected consequences (increased risk related to municipal dumpsters). Given the scale of ongoing urbanization and the spread of arboviral diseases, close collaboration between health and city stakeholders is needed.

[Knowledge co-production and local transfer to reduce inequalities of access to breast cancer screening]. / Transfert de connaissances pour réduire les inégalités infra-communales d’accès au dépistage du cancer du sein.

This paper describes a knowledge transfer experiment that has been conducted since September 2012 in Argenteuil (Val d'Oise, France). This experiment is part of an interventional research project called DeCL/C: "Knowledge translation on social and spatial inequalities: a tool to raise local awareness and mobilization to lessen cancer screening participation rate disparities': The project is carried out by health geographers from Paris Ouest University (UPO) and the National Association of Cities for Public Health (Elus, Sante Publique et Territoires, ESPT). It encompasses two main components: intervention designed to implement a knowledge co-production and transfer process among researchers, stakeholders and decision makers at various levels. This knowledge concerns social and spatial determinants of inequalities of access to breast cancer screening programmes in cities. The research is multidisciplinary (geography, sociology, political science, epistemology) and is designed to measure the impact of this knowledge co-production and transfer in terms of actions in the targeted cities (six cities in the Paris region) as well as the reduction of inequalities of access to breast cancer screening programmes. This article, based on knowledge transfer literature and an empirical experiment in Argenteuil, describes the ongoing knowledge transfer process. It also highlights Argenteuil stakeholders' and decision makers' interest in action and research. The analysis of the knowledge co-production, sharing and ownership process by local actors a e both "strategic" and "profound':

Trends in geographic mortality inequalities and their association with population changes in France, 1975-2006.

BACKGROUND: Although some studies have reported that population change is associated with spatial mortality inequalities, few of them have tried to take a dynamic approach to the association. The aim of this study was to explore and interpret the ecological association between the change in cause-specific mortality inequalities and population change over a 30-year period in areas exhibiting different deprivation and urbanization levels in France. METHODS: The French communes were classified by category of demographic change during the period 1962-2006. The changes in standardized mortality ratios were analysed by category over 5 inter-censal periods, taking into account degree of urbanization and deprivation quintile. The magnitude and significance of the associations for various causes of death were estimated using a Generalised Estimating Equation Poisson model. RESULTS: Overall, the change in relative mortality was negatively associated with population growth. For a compound annual population growth rate of 1% in 1990-99, the standardized mortality ratios decreased, on average, by 2.1% (95% confidence interval: -1.45 to -2.72). The association was stronger in urban areas, and reversed in the least deprived areas. The association was stronger and more significant for men, subjects aged less than 65 years and alcohol-related and violent deaths. CONCLUSION: This study highlights the significance of dynamic approaches. Population growth was associated with a decrease in relative mortality level; the direction and strength of the association varied depending on the socio-territorial characteristics. As is the case for English-speaking countries, in France, population growth may be considered a component of current social dynamics that are not measured by usual indicators.

Contrasting spatial distribution and risk factors for past infection with scrub typhus and murine typhus in Vientiane City, Lao PDR.

BACKGROUND: The aetiological diagnostic of fevers in Laos remains difficult due to limited laboratory diagnostic facilities. However, it has recently become apparent that both scrub and murine typhus are common causes of previous undiagnosed fever. Epidemiological data suggests that scrub typhus would be more common in rural areas and murine typhus in urban areas, but there is very little recent information on factors involved in scrub and murine typhus transmission, especially where they are sympatric - as is the case in Vientiane, the capital of the Lao PDR. METHODOLOGY AND PRINCIPAL FINDINGS: We therefore determined the frequency of IgG seropositivity against scrub typhus (Orientia tsutsugamushi) and murine typhus (Rickettsia typhi), as indices of prior exposure to these pathogens, in randomly selected adults in urban and peri-urban Vientiane City (n = 2,002, ≥35 years). Anti-scrub and murine typhus IgG were detected by ELISA assays using filter paper elutes. We validated the accuracy of ELISA of these elutes against ELISA using serum samples. The overall prevalence of scrub and murine typhus IgG antibodies was 20.3% and 20.6%, respectively. Scrub typhus seropositivity was significantly higher among adults living in the periphery (28.4%) than in the central zone (13.1%) of Vientiane. In contrast, seroprevalence of murine typhus IgG antibodies was significantly higher in the central zone (30.8%) as compared to the periphery (14.4%). In multivariate analysis, adults with a longer residence in Vientiane were at significant greater risk of past infection with murine typhus and at lower risk for scrub typhus. Those with no education, living on low incomes, living on plots of land with poor sanitary conditions, living in large households, and farmers were at higher risk of scrub typhus and those living in neighborhoods with high building density and close to markets were at greater risk for murine typhus and at lower risk of scrub typhus past infection. CONCLUSIONS: This study underscores the intense circulation of both scrub and murine typhus in Vientiane city and underlines difference in spatial distribution and risk factors involved in the transmission of these diseases.

Social and environmental malaria risk factors in urban areas of Ouagadougou, Burkina Faso.

BACKGROUND: Despite low endemicity, malaria remains a major health problem in urban areas where a high proportion of fevers are presumptively treated using anti-malarial drugs. Low acquired malaria immunity, behaviour of city-dwellers, access to health care and preventive interventions, and heterogenic suitability of urban ecosystems for malaria transmission contribute to the complexity of the malaria epidemiology in urban areas. METHODS: The study was designed to identify the determinants of malaria transmission estimated by the prevalence of anti-circumsporozoite (CSP) antibodies, the prevalence and density of Plasmodium falciparum infection, and the prevalence of malarial disease in areas of Ouagadougou, Burkina-Faso. Thick blood smears, dried blood spots and clinical status have been collected from 3,354 randomly chosen children aged 6 months to 12 years using two cross-sectional surveys (during the dry and rainy seasons) in eight areas from four ecological strata defined according to building density and land tenure (regular versus irregular). Demographic characteristics, socio-economic information, and sanitary and environmental data concerning the children or their households were simultaneously collected. Dependent variables were analysed using mixed multivariable models with random effects, taking into account the clustering of participants within compounds and areas. RESULTS: Overall prevalences of CSP-antibodies and P. falciparum infections were 7.7% and 16.6% during the dry season, and 12.4% and 26.1% during the rainy season, respectively, with significant differences according to ecological strata. Malaria risk was significantly higher among children who i) lived in households with lower economic or education levels, iii) near the hydrographic network, iv) in sparsely built-up areas, v) in irregularly built areas, vi) who did not use a bed net, vii) were sampled during the rainy season or ii) had traveled outside of Ouagadougou. CONCLUSION: Malaria control should be focused in areas which are irregularly or sparsely built-up or near the hydrographic network. Furthermore, urban children would benefit from preventive interventions (e.g. anti-vectorial devices or chemoprophylaxis) aimed at reducing malaria risk during and after travel in rural areas.

Socio-spatial disparities of obesity among adults in the urban setting of Ouagadougou, Burkina Faso.

OBJECTIVES: To document the prevalence and the socio-spatial variations of obesity and to identify individual and household characteristics, lifestyles and dietary practices contributing to obesity and its socio-spatial distribution. DESIGN: Population-based cross-sectional survey. We selected 1,570 households from four strata characterised as unstructured and low building-density (ULBD), unstructured and high building-density (UHBD), structured and low building-density (SLBD) and structured and high building-density (SHBD) areas. Structured areas are those that were allotted by the township authority (cadastral services), with public services; unstructured areas refer to those developed with no cadastral organisation. SETTING: Ouagadougou, the capital city of Burkina Faso. SUBJECTS: BMI was calculated in 2022 adults aged 35 years and above who were classified as obese when their BMI was >or=30 kg/m2. Obesity was investigated in relation to household and individual characteristics, lifestyles and dietary practices; adjusted odds ratios with 95 % confidence intervals were derived from a logistic regression model. RESULTS: The overall prevalence of obesity was 14.7 % (males 5.5 % and females 21.9 %). Age, gender, household equipment index, usual transport with motor vehicles and micronutrient-rich food consumption were associated with obesity. After adjustment for these factors, obesity remained associated with the area of residence: residents from SHBD areas were more likely to be obese than those from ULBD areas (OR = 1.41; 95 % CI 2.59,4.76). CONCLUSIONS: Obesity in Ouagadougou is a preoccupant problem that calls for more consideration. Thorough investigation is needed to assess the environmental factors that contribute to the socio-spatial disparity of obesity.

Hypertension, urbanization, social and spatial disparities: a cross-sectional population-based survey in a West African urban environment (Ouagadougou, Burkina Faso).

Data show that hypertension has become a public health problem in developing countries. Many studies have reported social disparities among the affected populations, but few of them pointed out spatial disparities within towns. We aimed to show that hypertension could be a good indicator of the medical change that occurs unequally in towns. A cross-sectional survey was done in April and October 2004 in Ouagadougou, Burkina Faso, among 2087 adults over 35 years old in different kinds of urban areas. Social and demographic data were collected and blood pressure was measured. Prevalence of hypertension was 40.2%. Age, body mass index, level of equipment, absence of community integration, absence of occupation, duration of residence over 20 years, protein-rich diet and absence of physical activity were identified as risk factors, but there were social and spatial disparities according to location of housing (parcelled-out or non-parcelled-out areas) and to integration within the town. The high rate of hypertension found in Ouagadougou and the heterogeneity of the risk within the population highlights that social and spatial risk factors have to be taken into account for the prevention of the non-transmissible diseases in countries in full process of urbanization and medical change.

Sampling in health geography: reconciling geographical objectives and probabilistic methods. An example of a health survey in Vientiane (Lao PDR).

BACKGROUND: Geographical objectives and probabilistic methods are difficult to reconcile in a unique health survey. Probabilistic methods focus on individuals to provide estimates of a variable's prevalence with a certain precision, while geographical approaches emphasise the selection of specific areas to study interactions between spatial characteristics and health outcomes. A sample selected from a small number of specific areas creates statistical challenges: the observations are not independent at the local level, and this results in poor statistical validity at the global level. Therefore, it is difficult to construct a sample that is appropriate for both geographical and probability methods. METHODS: We used a two-stage selection procedure with a first non-random stage of selection of clusters. Instead of randomly selecting clusters, we deliberately chose a group of clusters, which as a whole would contain all the variation in health measures in the population. As there was no health information available before the survey, we selected a priori determinants that can influence the spatial homogeneity of the health characteristics. This method yields a distribution of variables in the sample that closely resembles that in the overall population, something that cannot be guaranteed with randomly-selected clusters, especially if the number of selected clusters is small. In this way, we were able to survey specific areas while minimising design effects and maximising statistical precision. APPLICATION: We applied this strategy in a health survey carried out in Vientiane, Lao People's Democratic Republic. We selected well-known health determinants with unequal spatial distribution within the city: nationality and literacy. We deliberately selected a combination of clusters whose distribution of nationality and literacy is similar to the distribution in the general population. CONCLUSION: This paper describes the conceptual reasoning behind the construction of the survey sample and shows that it can be advantageous to choose clusters using reasoned hypotheses, based on both probability and geographical approaches, in contrast to a conventional, random cluster selection strategy.

Thirty years of use and improvement of remote sensing, applied to epidemiology: from early promises to lasting frustration.

Remote sensing, referring to the remote study of objects, was originally developed for Earth observation, through the use of sensors on board planes or satellites. Improvements in the use and accessibility of multi-temporal satellite-derived environmental data have, for 30 years, contributed to a growing use in epidemiology. Despite the potential of remote-sensed images and processing techniques for a better knowledge of disease dynamics, an exhaustive analysis of the bibliography shows a generalized use of pre-processed spatial data and low-cost images, resulting in a limited adaptability when addressing biological questions.

Perspectives on applied spatial analysis to animal health: a case of rodents in Thailand.

Geographic information systems (GIS) and remote sensing have been increasingly used in ecology and epidemiology, providing a spatial approach for animal health issues. Recent development of earth environmental satellites--i.e., their growing number, improving sensor resolutions and capabilities--has offered new opportunities to delineate possible habitats and understand animals and associated parasites in their environment, by identifying the nature and structure of land use, hydrological network, soil hydromorphy, and human settlements. Integrated into GIS, remotely sensed and other geo-referenced data allow both spatial and temporal analyses of animal ecology and health. However, a review of their applications has showed the poor quality of data sources and processing used, revealing limitations between theory and practical implementations. As an example, the assessment of the expected distribution of Bandicoot rats, main agricultural pest and vector of zoonoses in Phrae province (North Thailand), illustrates a rational use of spatial analysis, with the choice of relevant data, scales, and processing. Vegetation indices are computed on a TERRA ASTER image and further classified using elevation data. The biotopes of Bandicota indica and Bandicota savilei are delimited, providing a major source of knowledge for rodent and human health analyses.

Illness-related behaviour and utilization of oral health services among adult city-dwellers in Burkina Faso: evidence from a household survey.

BACKGROUND: In sub-Saharan Africa, the availability and accessibility of oral health services are seriously constrained and the provision of essential oral care is limited. Reports from the region show a very low utilization of oral health care services, and visits to dental-care facilities are mostly undertaken for symptomatic reasons. The objectives of the present study were to describe the prevalence of oral symptoms among adults in Ouagadougou, capital city of Burkina Faso and the use of oral health services and self-medication in response to these symptoms and to measure the associations between predisposing, enabling and needs factors and decisions to seek oral health care. METHODS: The conceptual design of the study was derived from both the Andersen-Newman model of health care utilization and the conceptual framework of the WHO International Collaborative Study of Oral Health Outcomes. Data were obtained by two-stage stratified sampling through four areas representative of different stages of urbanization of Ouagadougou. The final study population comprised 3030 adults aged 15 years or over and the response rate was 65%. RESULTS: Overall, 28% of the respondents had experienced an oral health problem during the past 12 months; a high proportion (62%) reported pain or acute discomfort affecting daily life. In response to symptoms, only 28% used oral health facilities, 48% used self-medication and 24% sought no treatment at all. Multivariate analyses revealed that several socio-economic and socio-cultural factors such as religious affiliation, material living conditions and participation in a social network were significantly associated with the use of oral health care services by adults who had experienced oral health problems during the previous year. CONCLUSION: The proportion of people who have obtained oral health care is alarmingly low in Ouagadougou and self-medication appears to be an important alternative source of care for adult city-dwellers. Decision-makers in sub-Saharan countries must seek to ensure that access to essential oral health care is improved.