Richard Lalou

Antimalarial drug use in general populations of tropical Africa.

BackgroundThe burden of Plasmodium falciparum 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.MethodsThe 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.ResultsAccording 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).ConclusionAntimalarial 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, P. falciparum 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.

Evaluation of the effectiveness of malaria vector control measures in urban settings of Dakar by a specific anopheles salivary biomarker.

Standard entomological methods for evaluating the impact of vector control lack sensitivity in low-malaria-risk areas. The detection of human IgG specific to Anopheles gSG6-P1 salivary antigen reflects a direct measure of human–vector contact. This study aimed to assess the effectiveness of a range of vector control measures (VCMs) in urban settings by using this biomarker approach. The study was conducted from October to December 2008 on 2,774 residents of 45 districts of urban Dakar. IgG responses to gSG6-P1 and the use of malaria VCMs highly varied between districts. At the district level, specific IgG levels significantly increased with age and decreased with season and with VCM use. The use of insecticide-treated nets, by drastically reducing specific IgG levels, was by far the most efficient VCM regardless of age, season or exposure level to mosquito bites. The use of spray bombs was also associated with a significant reduction of specific IgG levels, whereas the use of mosquito coils or electric fans/air conditioning did not show a significant effect. Human IgG response to gSG6-P1 as biomarker of vector exposure represents a reliable alternative for accurately assessing the effectiveness of malaria VCM in low-malaria-risk areas. This biomarker tool could be especially relevant for malaria control monitoring and surveillance programmes in low-exposure/low-transmission settings.

Les migrants face au sida: entre gestion des risques et contrôle social. L'exemple de la vallée du fleuve Sénégal

Meme si de nombreux travaux ont deja mis en evidence l’existence d’une relation entre mobilite et sida, les mecanismes complexes sous-jacents a cette relation demeurent aujourd’hui mal connus. L’etude presentee ici s’appuie sur une enquete realisee en 2000 dans la vallee du fleuve Senegal ; elle examine explicitement le lien entre migration et comportements sexuels a risque en milieu de retour (risque de diffusion) en utilisant un cadre conceptuel qui tient compte : 1) de divers types de mobilite, 2) de contextes sociaux differents et 3) des non-migrants. Le niveau macrosocial est ici represente par le choix de deux zones de la vallee du fleuve Senegal fortement contrastees sur les plans de la mobilite et des contextes socio-economiques. De facon globale, les analyses montrent que l’ effet net de l’ experience migratoire est significatif dans certains contextes sociaux et selon la position sociale des migrants dans le milieu de retour. Les migrants internationaux echappent au risque social de stigmatisation en optant pour la fidelite, tandis que les migrants internes reduisent les risques d’infection par un usage frequent du preservatif. L’influence plutot inhibitrice de la migration sur les pratiques sexuelles a risque en milieu de retour pourrait expliquer la situation favorable du Senegal ou l’ epidemie du sida est moderee et relativement stable, comparativement a la plupart des pays de la region. Les actions d’information et d’education doivent tenir compte du contexte social en favorisant a la fois des comportements responsables chez les individus et des reponses communautaires tournees vers une protection solidaire.