Migration et sida en Afrique de l'Ouest : un état des connaissances

Depuis la découverte du Sida, la diffusion géographique du virus est, comme par évidence, liée à la circulation des hommes. Cependant, ce constat classique dissimule une relation entre mobilité et sida à la fois complexe et méconnue. Considérant l'Afrique de l'Ouest, notre propos est de mettre en lumière la complexité de cette association, à partir d'une revue critique de la littérature, et d'en extraire les principales explications. Il ressort que la personne mobile est tour à tour un individu soumis au risque de contracter le VIH, et un porteur de la maladie susceptible de la diffuser dans les populations rencontrées. Au regard du risque de diffusion, la littérature donne crédit au sens commun. Les prostituées, souvent étrangères, les transporteurs routiers, les commerçants internationaux, les migrants de travail ou encore les étudiants sont autant de populations mobiles qui favorisent la diffusion du sida. Le risque majoré de contamination par le sida des personnes mobiles a été envisagé surtout de façon théorique et par rapport aux migrants de travail. Le jeune homme, non accompagné, qu'est souvent le migrant de travail, est triplement exposé au risque d'infection. D'abord, son isolement affectif et son faible niveau économique produisent une situation de stress qui favorise les comportements sexuels à risque. Son décalage culturel et son illétrisme le rendent aussi moins réceptif aux campagnes de sensibilisation. Enfin, le migrant, en raison d'une santé plus fragile, est plus exposé au risque transfusionnel et aux injections par des aiguilles souillées. En dépit de leur intérêt, toutes ces analyses restent encore largement théorique et les quelques études empiriques se révèlent très contradictoires. En somme, la relation entre migration et sida dépasse le simple truisme, mais les mécanismes complexes qui relient ces deux phénomènes sont encore à déterminer et à valider. (Résumé d'auteur

Questionner la transition de la fécondité en milieu rural africain : les apports d’une démarche longitudinale et institutionnelle

Située au coeur du bassin arachidier du Sénégal, la zone d’étude de Niakhar est tout à fait représentative des régions rurales sahéliennes caractérisées par le maintien de modèles de fécondité élevée. En effet, les grandes tendances de la fécondité observées grâce au Système de Suivi Démographique de l’IRD font état du maintien des descendances nombreuses (environ huit enfants par femme); elles révèlent par ailleurs une augmentation des naissances et des grossesses avant le premier mariage. Pour comprendre les mécanismes sur lesquels se fondent les comportements de fécondité dans cette région, nous proposons d’explorer la pertinence de l’approche institutionnelle, telle que décrite dans les travaux de Mc Nicoll (1982), Grégory et Piché (1985), Piché et Poirier (1995), ou encore Lesthaeghe (1989). Ainsi, la mise en perspective de l’évolution du système de production agricole, des conditions environnementales et du fonctionnement de l’organisation sociale permet de mettre en lumière le sens que les populations de cette région donnent aux comportements démographiques et, en particulier, aux pratiques relatives à la fécondité.Amid the peanut basin, the Niakhar study zone is representative of the high fertility level of Sahelian rural areas. Long-term trends of fertility levels measured by a demographic surveillance system from IRD show still high completed fertility levels (almost 8 children per women). Results reveal an increase in premarital pregnancies and births. In order to understand mechanisms of fertility patterns in this region, we propose to investigate the relevance of institutional approaches as described by Mc Nicoll (1982), Grégory et Piché (1985), Piché et Poirier (1995), or also Lesthaeghe (1989). Thus, the drawing of a parallel between changes in agricultural production system, and the environmental and social organization, enables us to highlight how these rural populations perceive demographic behaviors, and in particular reproductive behaviors

Контролюючий моніторинг на територіях із забрудненням легкими нафтопродуктами

International audienc

Use of health care among the urban poor in Africa: Does the neighbourhood have an impact?

The aim of this paper is to evaluate the relative influence of neighbourhood and individual practices of care utilization in Dakar (Senegal). The data from a research program on urban malaria, made in Dakar, Senegal between 2008 and 2009. The sample was based on a two-stage sampling. A questionnaire survey covered 2952 households, of which we have selected those that have at least one case of fever (n = 1272) with one of their children under ten years two weeks before the passage of investigators. The analytical model of the use of health services developed by R. Andersen has been adapted for our conceptual framework. Our results showed's like many West African cities, self-medication is a common practice among all households in Dakar, especially the poorest. The non-use of health services is positively associated with individual characteristics such as education level, the level of social network and the level of health literacy of the mother / guardian of the sick child (p <1 %). Some characteristics of the neighborhood of residence, however, increase the use of health services among the poor (health care provision is nearest larger and better quality). Similarly, the cost of use is no longer a major obstacle when people perceive a high environmental risk (presence of stagnant water and mosquito abundance). The district of residence may help remove the financial barrier, and reduce inequalities in access, when resource space

Antimalarial drug use in general populations of tropical Africa

<p>Abstract</p> <p>Background</p> <p>The burden of <it>Plasmodium falciparum </it>malaria has worsened because of the emergence of chloroquine resistance. Antimalarial drug use and drug pressure are critical factors contributing to the selection and spread of resistance. The present study explores the geographical, socio-economic and behavioural factors associated with the use of antimalarial drugs in Africa.</p> <p>Methods</p> <p>The presence of chloroquine (CQ), pyrimethamine (PYR) and other antimalarial drugs has been evaluated by immuno-capture and high-performance liquid chromatography in the urine samples of 3,052 children (2–9 y), randomly drawn in 2003 from the general populations at 30 sites in Senegal (10), Burkina-Faso (10) and Cameroon (10). Questionnaires have been administered to the parents of sampled children and to a random sample of households in each site. The presence of CQ in urine was analysed as dependent variable according to individual and site characteristics using a random – effect logistic regression model to take into account the interdependency of observations made within the same site.</p> <p>Results</p> <p>According to the sites, the prevalence rates of CQ and PYR ranged from 9% to 91% and from 0% to 21%, respectively. In multivariate analysis, the presence of CQ in urine was significantly associated with a history of fever during the three days preceding urine sampling (OR = 1.22, p = 0.043), socio-economic level of the population of the sites (OR = 2.74, p = 0.029), age (2–5 y = reference level; 6–9 y OR = 0.76, p = 0.002), prevalence of anti-circumsporozoite protein (CSP) antibodies (low prevalence: reference level; intermediate level OR = 2.47, p = 0.023), proportion of inhabitants who lived in another site one year before (OR = 2.53, p = 0.003), and duration to reach the nearest tarmacked road (duration less than one hour = reference level, duration equal to or more than one hour OR = 0.49, p = 0.019).</p> <p>Conclusion</p> <p>Antimalarial drug pressure varied considerably from one site to another. It was significantly higher in areas with intermediate malaria transmission level and in the most accessible sites. Thus, <it>P. falciparum </it>strains arriving in cross-road sites or in areas with intermediate malaria transmission are exposed to higher drug pressure, which could favour the selection and the spread of drug resistance.</p

Bottom pressure signals at the TAG deep-sea hydrothermal field : evidence for short-period, flow-induced ground deformation

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 36 (2009): L19301, doi:10.1029/2009GL040006.Bottom pressure measurements acquired from the TAG hydrothermal field on the Mid-Atlantic Ridge (26°N) contain clusters of narrowband spectral peaks centered at periods from 22 to 53.2 minutes. The strongest signal at 53.2 min corresponds to 13 mm of water depth variation. Smaller, but statistically significant, signals were also observed at periods of 22, 26.5, 33.4, and 37.7 min (1–4 mm amplitude). These kinds of signals have not previously been observed in the ocean, and they appear to represent vertical motion of the seafloor in response to hydrothermal flow - similar in many ways to periodic terrestrial geysers. We demonstrate that displacements of 13 mm can be produced by relatively small flow-induced pressures (several kPa) if the source region is less than ∼100 m below the seafloor. We suggest that the periodic nature of the signals results from a non-linear relationship between fluid pore pressure and crustal permeability

Self-reported data: a major tool to assess compliance with anti-malarial combination therapy among children in Senegal

Background: Although there are many methods available for measuring compliance, there is no formal gold standard. Different techniques used to measure compliance were compared among children treated by the anti-malarial amodiaquine/sulphadoxine-pyrimethamine (AQ/SP) combination therapy, in use in Senegal between 2004 and 2006. Methods: The study was carried out in 2004, in five health centres located in the Thies region (Senegal). Children who had AQ/SP prescribed for three and one day respectively at the health centre were recruited. The day following the theoretical last intake of AQ, venous blood, and urine samples were collected for anti-malarial drugs dosage. Caregivers and children above five years were interviewed concerning children's drug intake. Results: Among the children, 64.7% adhered to 80% of the prescribed dose and only 37.7% were strict full adherent to the prescription. There was 72.7% agreement between self-reported data and blood drug dosage for amodiaquine treatment. Concerning SP, results found that blood dosages were 91.4% concordant with urine tests and 90% with self-reported data based on questionnaires. Conclusion: Self-reported data could provide useful quantitative information on drug intake and administration. Under strict methodological conditions this method, easy to implement, can be used to describe patients' behaviors and their use of new anti-malarial treatment. Self-reported data is a major tool for assessing compliance in resource poor countries. Blood and urine drug dosages provide qualitative results that confirm any drug intake. Urine assays for SP could be useful to obtain public health data, for example on chemoprophylaxis among pregnant women

Asymptomatic Carriage of Plasmodium in Urban Dakar: The Risk of Malaria Should Not Be Underestimated

Introduction: The objective of this study was to measure the rate of asymptomatic carriage of plasmodium in the Dakar region two years after the implementation of new strategies in clinical malaria management. Methodology: Between October and December 2008, 2952 households selected in 50 sites of Dakar area, were visited for interviews and blood sampling. Giemsa-stained thick blood smears (TBS) were performed for microscopy in asymptomatic adult women and children aged 2 to 10 years. To ensure the quality of the microscopy, we performed a polymerase chai

IgG responses to the gSG6-P1 salivary peptide for evaluating human exposure to Anopheles bites in urban areas of Dakar region, Sénégal

<p>Abstract</p> <p>Background</p> <p>Urban malaria can be a serious public health problem in Africa. Human-landing catches of mosquitoes, a standard entomological method to assess human exposure to malaria vector bites, can lack sensitivity in areas where exposure is low. A simple and highly sensitive tool could be a complementary indicator for evaluating malaria exposure in such epidemiological contexts. The human antibody response to the specific <it>Anopheles </it>gSG6-P1 salivary peptide have been described as an adequate tool biomarker for a reliable assessment of human exposure level to <it>Anopheles </it>bites. The aim of this study was to use this biomarker to evaluate the human exposure to <it>Anopheles </it>mosquito bites in urban settings of Dakar (Senegal), one of the largest cities in West Africa, where <it>Anopheles </it>biting rates and malaria transmission are supposed to be low.</p> <p>Methods</p> <p>One cross-sectional study concerning 1,010 (505 households) children (n = 505) and adults (n = 505) living in 16 districts of downtown Dakar and its suburbs was performed from October to December 2008. The IgG responses to gSG6-P1 peptide have been assessed and compared to entomological data obtained in or near the same district.</p> <p>Results</p> <p>Considerable individual variations in anti-gSG6-P1 IgG levels were observed between and within districts. In spite of this individual heterogeneity, the median level of specific IgG and the percentage of immune responders differed significantly between districts. A positive and significant association was observed between the exposure levels to <it>Anopheles gambiae </it>bites, estimated by classical entomological methods, and the median IgG levels or the percentage of immune responders measuring the contact between human populations and <it>Anopheles </it>mosquitoes. Interestingly, immunological parameters seemed to better discriminate the exposure level to <it>Anopheles </it>bites between different exposure groups of districts.</p> <p>Conclusions</p> <p>Specific human IgG responses to gSG6-P1 peptide biomarker represent, at the population and individual levels, a credible new alternative tool to assess accurately the heterogeneity of exposure level to <it>Anopheles </it>bites and malaria risk in low urban transmission areas. The development of such biomarker tool would be particularly relevant for mapping and monitoring malaria risk and for measuring the efficiency of vector control strategies in these specific settings.</p