Spatial expressions of sleeping sickness in Ivory Coast and Guinea Conakry remote sensing and spatial analysis contributions to map human African trypanosomiasis risk area

Las políticas coloniales de fin de siglo XIX son responsables de graves epidemias de la enfermedad del sueño en África Occidental. Poblaciones enteras fueron puestas en contacto con la mosca Tse-Tse acabando así con un equilibrio "natural" histórico-. Tras la independencia, y tras décadas de lucha eficaz contra la enfermedad, la Tripanosomiasis Humana Africana (THA) desaparece. Según la OMS (1996), hoy nos encontramos ante un nuevo contexto en el que se encuentran al menos 300.000 nuevos casos de los que sólo son reportados 25.000. Ante la ausencia de infraestructuras sanitarias y la situación de inestabilidad política de Guinea Conakry y en Costa de Marfil, es imposible disponer de datos fiables. Más que nunca es necesario advertir sobre la diferencia existente entre ausencia de datos y ausencia de enfermedad. Resulta urgente la promoción de métodos de cartografía de riesgos a pequeña escala geográfica como herramientas para el apoyo a la toma de decisiones en materia de atención sanitaria. Tras varias décadas, los satélites civiles de observación terrestre proporcionan imágenes cuya cobertura geográfica y resolución se adaptan bien a esta problemática. A modo de ejemplo, presentamos un método basado en teledetección y análisis espacial para la cartografía de zonas de riesgo de la enfermedad del sueño. El principio adoptado consiste en la conversión de las expresiones espaciales de la enfermedad, identificadas sobre el terreno, en indicadores de paisaje obtenibles de las imágenes.At the end of 19th century in western Africa sleeping sickness - Human African Trypanosomiasis - was responsible for a lot of death in an entire state of complete Disorganisation caused by foreign political intervention. A very large movement of important population modified historical natural equilibrium and humans were in active contact with the disease's vector, the Tse- Tse fly. After independence, in relation with few decades of systematic and efficient sanitary struggle sleeping sickness disappeared. Currently we are in a new context; the disease is reviviscente. In 1996 a WHO report signalled that more than 25,000 new cases in inter-tropical Western Africa were reported. In reality it is believed that probably 300,000 new persons were affected. However, without efficient sanitary structure it is impossible to dispose of true data and to treat population most of which is ineluctably condemned. In that context - aggravated by the political instability - it is an emergency to promote new methods for large scale diagnoses to help sanitary decision rules. From few years ago, spatial resolution and geographical coverage of remote sensing give images of hearth adapted to a smoothness description of landscape on large surface. The method we propose, founded on image analysis and geostatiscal analyses, consists on translating spatial expression of disease identified from field study on environmental risk factors deductible from space imagery. Results consist on probability risk map on large coverage. We hope it will help struggling against disease. Our approach was situated at the level of elementary digit of sickness and their interconnection. Two examples of sickness spatial expression are presented: one in Guinea Conakry and the other in Ivory Coast

Spatial expressions of sleeping sickness in Ivory Coast and Guinea Conakry remote sensing and spatial analysis contributions to map human African trypanosomiasis risk area

Las políticas coloniales de fin de siglo XIX son responsables de graves epidemias de la enfermedad del sueño en África Occidental. Poblaciones enteras fueron puestas en contacto con la mosca Tse-Tse acabando así con un equilibrio "natural" histórico-. Tras la independencia, y tras décadas de lucha eficaz contra la enfermedad, la Tripanosomiasis Humana Africana (THA) desaparece. Según la OMS (1996), hoy nos encontramos ante un nuevo contexto en el que se encuentran al menos 300.000 nuevos casos de los que sólo son reportados 25.000. Ante la ausencia de infraestructuras sanitarias y la situación de inestabilidad política de Guinea Conakry y en Costa de Marfil, es imposible disponer de datos fiables. Más que nunca es necesario advertir sobre la diferencia existente entre ausencia de datos y ausencia de enfermedad. Resulta urgente la promoción de métodos de cartografía de riesgos a pequeña escala geográfica como herramientas para el apoyo a la toma de decisiones en materia de atención sanitaria. Tras varias décadas, los satélites civiles de observación terrestre proporcionan imágenes cuya cobertura geográfica y resolución se adaptan bien a esta problemática. A modo de ejemplo, presentamos un método basado en teledetección y análisis espacial para la cartografía de zonas de riesgo de la enfermedad del sueño. El principio adoptado consiste en la conversión de las expresiones espaciales de la enfermedad, identificadas sobre el terreno, en indicadores de paisaje obtenibles de las imágenes.At the end of 19th century in western Africa sleeping sickness - Human African Trypanosomiasis - was responsible for a lot of death in an entire state of complete Disorganisation caused by foreign political intervention. A very large movement of important population modified historical natural equilibrium and humans were in active contact with the disease's vector, the Tse- Tse fly. After independence, in relation with few decades of systematic and efficient sanitary struggle sleeping sickness disappeared. Currently we are in a new context; the disease is reviviscente. In 1996 a WHO report signalled that more than 25,000 new cases in inter-tropical Western Africa were reported. In reality it is believed that probably 300,000 new persons were affected. However, without efficient sanitary structure it is impossible to dispose of true data and to treat population most of which is ineluctably condemned. In that context - aggravated by the political instability - it is an emergency to promote new methods for large scale diagnoses to help sanitary decision rules. From few years ago, spatial resolution and geographical coverage of remote sensing give images of hearth adapted to a smoothness description of landscape on large surface. The method we propose, founded on image analysis and geostatiscal analyses, consists on translating spatial expression of disease identified from field study on environmental risk factors deductible from space imagery. Results consist on probability risk map on large coverage. We hope it will help struggling against disease. Our approach was situated at the level of elementary digit of sickness and their interconnection. Two examples of sickness spatial expression are presented: one in Guinea Conakry and the other in Ivory Coast

Écologie, télédétection et SIG: les écotopes du grand tétras dans le Haut-Jura

Utilisés conjointement, les données de satellites à haute résolution spatiale et les systèmes d'informations géographiques fournissent des résultats intéressants pour l'écologie. À titre d'exemple, nous présentons une étude des écotopes du grand tétras dans le massif du Jura, réalisée en deux temps : une analyse de texture d'image (Spot panchromatique), son intégration à des données topographiques et thématiques par l'intermédiaire d'un SIG. Les résultats obtenus se présentent sous la forme de cartes de potentiels des milieux à accueillir le grand tétras

The Impacts of Urban Morphology on Housing Indoor Thermal Condition in Hoi An City, Vietnam

Assessing the impact of urban morphology on the indoor thermal condition of housing in a tourism city in central Vietnam — Hoi An City is the main objective of this study. The research process is carried out by a variety of methods including in situ surveys, measuring with temperature sensors, data analysis and map analysis. Four houses, located in two areas with different urban forms, were selected for measurement within one month to investigate the differences in housing indoor temperature. The impact of urban morphology on housing was thereafter determined. Temperature sensors were permanently installed in 4 houses; based on these empirical measurements and data collected, the paper addresses solutions to improve urban morphology and indoor thermal condition

Assessing the relevance of digital elevation models to evaluate glacier mass balance : application to Austre Lovénbreen (Spitsbergen, 79 ° N)

International audienceThe volume variation of a glacier is the actual indicator of long term and short term evolution of the glacier behaviour. In order to assess the volume evolution of the Austre Lovénbreen (79 • N) over the last 47 years, we used multiple historical datasets, complemented with our high density GPS tracks acquired in 2007 and 2010. The improved altitude resolution of recent measurement techniques, including phase corrected GPS and LiDAR, reduces the time interval between datasets used for volume subtraction in order to compute the mass balance. We estimate the sub-metre elevation accuracy of most recent measurement techniques to be sufficient to record ice thickness evolutions occurring over a 3 year duration at polar latitudes. The systematic discrepancy between ablation stake measurements and DEM analysis, widely reported in the literature as well as in the current study, yields new questions concerning the similarity and relationship between these two measurement methods. The use of Digital Elevation Model (DEM) has been an attractive alternative measurement technique to estimate glacier area and volume evolution over time with respect to the classical in situ measurement techniques based on ablation stakes. With the availability of historical datasets, whether from ground based maps, aerial photography or satellite data acquisition, such a glacier volume estimate strategy allows for the extension of the analysis duration beyond the current research programmes. Furthermore, these methods do provide a continuous spatial coverage defined by its cell size whereas interpolations based on a limited number of stakes display large spatial uncertainties. In this document, we focus on estimating the altitude accuracy of various datasets acquired between 1962 and 2010, using various techniques ranging from topographic maps to dual frequency skidoo-tracked GPS receivers and the classical aerial and satellite photogrammetric techniques

Monitoring seasonal snow dynamics using ground based high resolution photography (Austre Lovenbreen, Svalbard, 79°N)

International audienceArctic glaciers are reliable indicators of global climate changes. However, monitoring snow and ice dynamics in Arctic regions is challenging: some fast but key events can be missed since they are short in time but significant in the hydrological budget. In the context of long term monitoring with high temporal and spatial resolutions of the snow cover dynamics, automated digital cameras were installed around the Austre Lovénbreen glacier basin (Spitsbergen, Norway, 79 N). Despite data losses due to rough weather conditions and control electronics failure, a dataset of 2411 pictures (out of an expected 3294) was gathered over a 1 year hydrological period to assess the snow coverage of the glacier as a function of time with daily resolution. 73% of the total number of expected images was thus recorded, with gaps associated with temporary electronics or data storage failure. The six camera stations oriented so as to observe the glacier itself provide a surface coverage of 96%. Furthermore, geometric corrections of the pictures, using reference ground control points located on the glacier through GPS receivers, yield a quantitative information from initially qualitative images. Projecting the resulting mosaic of the images gathered from six cameras on a GIS allows for the precise monitoring of ice-related processes, and especially the snow coverage evolution over time. This paper summarizes our current understanding of such dynamics, based on the analysis of daily mosaics of images allowing for the observation of both long term evolution on the seasonal scale and the short term events on a weekly scale. Such results demonstrated over one typical full hydrological season (April-October 2009) that snow coverage evolves following discrete steps, either due to water precipitation or warm events, with a snow coverage ranging from 100% (april) to 37% (September

High density coverage investigation of The Austre LovénBreen (Svalbard) using Ground Penetrating Radar

COMInternational audienceA three week field survey over April 2010 allowed for the acquisition of 120 Ground Penetrating Radar (GPR) profiles, adding to a 40 km long walk across an Arctic glacier. The profiles were acquired using a Mal°a equipment with 100 MHz antennas, walking slowly enough to record a 2.224 s trace every 30 cm on the average. Some acquisitions were repeated with 50 MHz or 200 MHz antenna to improve data quality. The GPR was coupled to a GPS system to position traces. Each profile has been manually edited using standard GPR data processing, to pick the reflection arrival time from the ice-bedrock interface. Traveltimes were converted to ice thickness using a velocity of 0.17 m/ns. Dual-frequency GPS mapping and snow coverage thickness were acquired during the same survey. Using interpolation methods, we derived the underlying bedrock topography and evaluated the ice volume

Deriving ice thickness, glacier volume and bedrock morphology of the Austre Lovénbreen (Svalbard) using Ground-penetrating Radar

International audienceThe Austre Lovénbreen is a 4.6 km2 glacier on the Archipelago of Svalbard (79°N) that has been surveyed over the last 47 years in order of monitoring in particular the glacier evolution and associated hydrological phenomena in the context of nowadays global warming. A three-week field survey over April 2010 allowed for the acquisition of a dense mesh of Ground-penetrating Radar (GPR) data with an average of 14683 points per km2 (67542 points total) on the glacier surface. The profiles were acquired using a Mala equipment with 100 MHz antennas, towed slowly enough to record on average every 0.3 m, a trace long enough to sound down to 189 m of ice. One profile was repeated with 50 MHz antenna to improve electromagnetic wave propagation depth in scattering media observed in the cirques closest to the slopes. The GPR was coupled to a GPS system to position traces. Each profile has been manually edited using standard GPR data processing including migration, to pick the reflection arrival time from the ice-bedrock interface. Snow cover was evaluated through 42 snow drilling measurements regularly spaced to cover all the glacier. These data were acquired at the time of the GPR survey and subsequently spatially interpolated using ordinary kriging. Using a snow velocity of 0.22 m/ns, the snow thickness was converted to electromagnetic wave travel-times and subtracted from the picked travel-times to the ice-bedrock interface. The resulting travel-times were converted to ice thickness using a velocity of 0.17 m/ns. The velocity uncertainty is discussed from a common mid-point profile analysis. A total of 67542 georeferenced data points with GPR-derived ice thicknesses, in addition to a glacier boundary line derived from satellite images taken during summer, were interpolated over the entire glacier surface using kriging with a 10 m grid size. Some uncertainty analysis were carried on and we calculated an averaged ice thickness of 76 m and a maximum depth of 164 m with a relative error of 11.9%. The volume of the glacier is derived as 0.3487±0.041 km3. Finally a 10-m grid map of the bedrock topography was derived by subtracting the ice thicknesses from a dual-frequency GPS-derived digital elevation model of the surface. These two datasets are the first step for modelling thermal evolution of the glacier and its bedrock, as well as the main hydrological network

Plague Circulation and Population Genetics of the Reservoir Rattus rattus: The Influence of Topographic Relief on the Distribution of the Disease within the Madagascan Focus.

International audienceBACKGROUND: Landscape may affect the distribution of infectious diseases by influencing the population density and dispersal of hosts and vectors. Plague (Yersinia pestis infection) is a highly virulent, re-emerging disease, the ecology of which has been scarcely studied in Africa. Human seroprevalence data for the major plague focus of Madagascar suggest that plague spreads heterogeneously across the landscape as a function of the relief. Plague is primarily a disease of rodents. We therefore investigated the relationship between disease distribution and the population genetic structure of the black rat, Rattus rattus, the main reservoir of plague in Madagascar. METHODOLOGYPRINCIPAL FINDINGS: We conducted a comparative study of plague seroprevalence and genetic structure (15 microsatellite markers) in rat populations from four geographic areas differing in topology, each covering about 150-200 km(2) within the Madagascan plague focus. The seroprevalence levels in the rat populations mimicked those previously reported for humans. As expected, rat populations clearly displayed a more marked genetic structure with increasing relief. However, the relationship between seroprevalence data and genetic structure differs between areas, suggesting that plague distribution is not related everywhere to the effective dispersal of rats. CONCLUSIONSSIGNIFICANCE: Genetic diversity estimates suggested that plague epizootics had only a weak impact on rat population sizes. In the highlands of Madagascar, plague dissemination cannot be accounted for solely by the effective dispersal of the reservoir. Human social activities may also be involved in spreading the disease in rat and human populations