Gérard Salem

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

BackgroundDespite 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.MethodsThe 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.ResultsOverall 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.ConclusionMalaria 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.

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

BackgroundIn 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.MethodsThe 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%.ResultsOverall, 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.ConclusionThe 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.

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.

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.

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

BackgroundGeographical objectives and probabilistic methods are difficult to reconcile in a unique health survey. Probabilistic methods focus on individuals to provide estimates of a variables 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.MethodsWe 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.ApplicationWe applied this strategy in a health survey carried out in Vientiane, Lao Peoples 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.ConclusionThis 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.

The Perceived Value of Passive Animal Health Surveillance: The Case of Highly Pathogenic Avian Influenza in Vietnam

Economic evaluations are critical for the assessment of the efficiency and sustainability of animal health surveillance systems and the improvement of their efficiency. Methods identifying and quantifying costs and benefits incurred by public and private actors of passive surveillance systems (i.e. actors of veterinary authorities and private actors who may report clinical signs) are needed. This study presents the evaluation of perceived costs and benefits of highly pathogenic avian influenza (HPAI) passive surveillance in Vietnam. Surveys based on participatory epidemiology methods were conducted in three provinces in Vietnam to collect data on costs and benefits resulting from the reporting of HPAI suspicions to veterinary authorities. A quantitative tool based on stated preference methods and participatory techniques was developed and applied to assess the non‐monetary costs and benefits. The study showed that poultry farmers are facing several options regarding the management of HPAI suspicions, besides reporting the following: treatment, sale or destruction of animals. The option of reporting was associated with uncertain outcome and transaction costs. Besides, actors anticipated the release of health information to cause a drop of markets prices. This cost was relevant at all levels, including farmers, veterinary authorities and private actors of the upstream sector (feed, chicks and medicine supply). One benefit associated with passive surveillance was the intervention of public services to clean farms and the environment to limit the disease spread. Private actors of the poultry sector valued information on HPAI suspicions (perceived as a non‐monetary benefit) which was mainly obtained from other private actors and media.

When private actors matter: Information-sharing network and surveillance of Highly Pathogenic Avian Influenza in Vietnam

The effectiveness of animal health surveillance systems depends on their capacity to gather sanitary information from the animal production sector. In order to assess this capacity we analyzed the flow of sanitary information regarding Highly Pathogenic Avian Influenza (HPAI) suspicions in poultry in Vietnam. Participatory methods were applied to assess the type of actors and likelihood of information sharing between actors in case of HPAI suspicion in poultry. While the reporting of HPAI suspicions is mandatory, private actors had more access to information than public actors. Actors of the upstream sector (medicine and feed sellers) played a key role in the diffusion of information. The central role of these actors and the influence of the information flow on the adoption by poultry production stakeholders of behaviors limiting (e.g. prevention measures) or promoting disease transmission (e.g. increased animal movements) should be accounted for in the design of surveillance and control programs.

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.

Perspectives on Applied Spatial Analysis to Animal Health A Case of Rodents in Thailand

Abstract:  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.

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

BackgroundMany 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.MethodsThis 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.ResultsFive 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.ConclusionThis 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.