Particularités et stratification du paludisme à Madagascar

Les facteurs de diversité du paludisme à Madagascar sont de trois ordres: les parasites ; en sus de #P. falciparum, #P. vivax est très important ; la transmission qui détermine la stabilité du paludisme et provoque le développement de défenses spécifiques ; l'homme : la présence d'éléments d'origine asiatique explique la présence de #P. vivax ; les activités humaines sont fortement responsables de la prolifération des vecteurs. Les vecteurs, #An. gambiae, #An. arabiensis, #An. funestus appartiennent à la faune de l'Afrique continentale et sont probablement d'introduction récente car ils n'ont pas subi de processus d'endémisation. Les gîtes créés par l'homme, en particulier les rizières, jouent un rôle prépondérant dans le développement d'#An. gambiae et d'#An. funestus sur les plateaux et dans le sud. On distingue cinq faciès épidémiologiques très voisins de leurs homologues du continent africain : faciès équatorial sur la côte orientale ; faciès tropical sur la côte occidentale au nord de Morondava ; faciès des plateaux analogue au faciès austral du sud du continent ; faciès du sud qui se rapproche du faciès sahélien ; enfin, les zones sans paludisme. Dans les deux premiers, le paludisme est stable, dans les deux suivants, il est instable et c'est sur les plateaux que se manifestent les grandes épidémies, en particulier celle de 1985-88. Cette variété des faciès épidémiologiques impose une diversification des méthodes de lutte prise en compte dans le plan d'opération actuel. Les pulvérisations intradomiciliaires limitées aux plateaux ont donné des résultats spectaculaires. (Résumé d'auteur

Thérapies traditionnelles aux Comores

Cet article présente un tableau général des divers moyens de protection des dangers et de guérison des maux, mis en oeuvre dans la société comorienne. Islamisée de façon continue depuis des siècles, cette société développe aussi une vision populaire du monde et des pratiques magico-religieuses plus ou moins tolérées par l'indulgence de l'islam local. Religion et pratiques populaires ont été elles-mêmes apportées par des groupes de population d'origine africaine, indonésienne, arabe ou malgache, qui ont juxtaposé ou mêlé divers systèmes de représentations. Leurs points communs sont : une vision déterminée d'un monde dominé par des déséquilibres et des concordances à respecter, justifiant l'observance de l'astrologie et le respect d'interdits; un relativisme social qui attribue à l'autre les intentions malveillantes qui ont provoqué le mal, les désordres et les problèmes qui affectent l'être humain, ou sa famille, dans sa vie quotidienne. (Résumé d'auteur

Impacts of soil management and climate on saturated and near-saturated hydraulic conductivity: analyses of the Open Tension-disk Infiltrometer Meta-database (OTIM)

Saturated and near-saturated soil hydraulic conductivities Kh (mm h−1) determine the partitioning of precipitation into surface runoff and infiltration and are fundamental to soils' susceptibility to preferential flow. Recent studies found indications that climate factors influence Kh, which is highly relevant in the face of climate change. In this study, we investigated relationships between pedoclimatic factors and Kh and also evaluated effects of land use and soil management. To this end, we collated the Open Tension-disk Infiltrometer Meta-database (OTIM), which contains 1297 individual data entries from 172 different publication sources. We analysed a spectrum of saturated and near-saturated hydraulic conductivities at matric potentials between 0 and 100 mm. We found that methodological details like the direction of the wetting sequence or the choice of method for calculating infiltration rates to hydraulic conductivities had a large impact on the results. We therefore restricted ourselves to a subset of 466 of the 1297 data entries with similar methodological approaches. Correlations between Ks and Kh at higher supply tensions decreased especially close to saturation, indicating a different flow mechanism at and very close to saturation than towards the dry end of the investigated tension range. Climate factors were better correlated with topsoil near-saturated hydraulic conductivities at supply tensions ≥ 30 mm than soil texture, bulk density and organic carbon content. We find it most likely that the climate variables are proxies for soil macropore networks created by the respective biological activity, pedogenesis and climate-specific land use and management choices. Due to incomplete documentation in the source publications of OTIM, we were able to investigate only a few land use types and agricultural management practices. Land use, tillage system and soil compaction significantly influenced Kh, with effect sizes appearing comparable to the ones of soil texture and soil organic carbon. The data in OTIM show that experimental bias is present, introduced by the choice of measurement time relative to soil tillage, experimental design or data evaluation procedures. The establishment of best-practice rules for tension-disk infiltrometer measurements would therefore be helpful. Future studies are needed to investigate how climate shapes soil macropore networks and how land use and management can be adapted to improve soil hydraulic properties. Both tasks require large numbers of new measurement data with improved documentation on soil biology and land use and management history.</p

Genes flow by the channels of culture: the genetic imprint of matrilocality in Ngazidja, Comoros Islands

International audienc

The epidemiological transition in Antananarivo, Madagascar: an assessment based on death registers (1900–2012)

Background: Madagascar today has one of the highest life expectancies in sub-Saharan Africa, despite being among the poorest countries in the continent. There are relatively few detailed accounts of the epidemiological transition in this country due to the lack of a comprehensive death registration system at the national level. However, in Madagascar's capital city, death registration was established around the start of the 20th century and is now considered virtually complete. Objective: We provide an overview of trends in all-cause and cause-specific mortality in Antananarivo to document the timing and pace of the mortality decline and the changes in the cause-of-death structure. Design: Death registers covering the period 1976–2012 were digitized and the population at risk of dying was estimated from available censuses and surveys. Trends for the period 1900–1976 were partly reconstructed from published sources. Results: The crude death rate stagnated around 30‰ until the 1940s in Antananarivo. Mortality declined rapidly after the World War II and then resurged again in the 1980s as a result of the re-emergence of malaria and the collapse of Madagascar's economy. Over the past 30 years, impressive gains in life expectancy have been registered thanks to the unabated decline in child mortality, despite political instability, a lasting economic crisis and the persistence of high rates of chronic malnutrition. Progress in adult survival has been more modest because reductions in infectious diseases and diseases of the respiratory system have been partly offset by increases in cardiovascular diseases, neoplasms, and other diseases, particularly at age 50 years and over. Conclusions: The transition in Antananarivo has been protracted and largely dependent on anti-microbial and anti-parasitic medicine. The capital city now faces a double burden of communicable and non-communicable diseases. The ongoing registration of deaths in the capital generates a unique database to evaluate the performance of the health system and measure intervention impacts

Geographical and environmental approaches to urban malaria in Antananarivo (Madagascar)

<p>Abstract</p> <p>Background</p> <p>Previous studies, conducted in the urban of Antananarivo, showed low rate of confirmed malaria cases. We used a geographical and environmental approach to investigate the contribution of environmental factors to urban malaria in Antananarivo.</p> <p>Methods</p> <p>Remote sensing data were used to locate rice fields, which were considered to be the principal mosquito breeding sites. We carried out supervised classification by the maximum likelihood method. Entomological study allowed vector species determination from collected larval and adult mosquitoes. Mosquito infectivity was studied, to assess the risk of transmission, and the type of mosquito breeding site was determined. Epidemiological data were collected from November 2006 to December 2007, from public health centres, to determine malaria incidence. Polymerase chain reaction was carried out on dried blood spots from patients, to detect cases of malaria. Rapid diagnostic tests were used to confirm malaria cases among febrile school children in a school survey.</p> <p>A geographical information system was constructed for data integration. Altitude, temperature, rainfall, population density and rice field surface area were analysed and the effects of these factors on the occurrence of confirmed malaria cases were studied.</p> <p>Results</p> <p>Polymerase chain reaction confirmed malaria in 5.1% of the presumed cases. Entomological studies showed <it>An. arabiensis </it>as potential vector. Rice fields remained to be the principal breeding sites. Travel report was considered as related to the occurrence of <it>P. falciparum </it>malaria cases.</p> <p>Conclusion</p> <p>Geographical and environmental factors did not show direct relationship with malaria incidence but they seem ensuring suitability of vector development. Absence of relationship may be due to a lack of statistical power. Despite the presence of <it>An. arabiensis</it>, scarce parasitic reservoir and rapid access to health care do not constitute optimal conditions to a threatening malaria transmission. However, imported malaria case is suggestive to sustain the pocket transmission in Antananarivo.</p