Phytochemical and antibacterial screening of mistletoe (Agelanthus dodoniesfolius (DC)) collected from shea butter tree (Vitelleria paradoxa)

The increase in the multi-drugs resistant strains of bacteria is a great concern to public health. For long, various plant-derived compounds have been used as drugs. Agelanthus dodoneifolius (DC) refers to ‘Kauchi’ in Hausa has been used ethno-botanically by the Hausa and Fulani ethnic group of Northern Nigeria for the treatment of many human and animal diseases. Such diseases include diarrhea, dysentery, and stomach ache. In this study, the phytochemical screening and antibacterial activity of the stem bark and leaves extracts of mistletoe plant (A. dodoneifolius) was evaluated. The plant sample was qualitatively screened for phytochemicals using a standard procedure. The antibacterial activity was examined using the standardized suspension method. The phytochemical screening revealed the presence of tannins, steroid, alkaloid, anthraquinones and glycosides. The results of antibacterial activity of the A. dodoneifolius showed that S. aureus was more susceptible to methanolic extract of stem bark and leaves extracts producing the largest diameter of inhibition zone of (17 mm) and (15 mm) at the concentration of 10 mg/ml respectively. These results validated the traditional use of A. dodoneisfolius and more phytochemical screenings are necessary to fully explore this species which may lead to development of a novel antibacterial agent.Keywords: Agelanthus Dodoneisfolius, Antibacterial Activity, Synergetic Effec

Controlling Schistosomiasis: Significant Decrease of Anaemia Prevalence One Year after a Single Dose of Praziquantel in Nigerien Schoolchildren

The World Health Organization's recommendation for the control of urinary schistosomiasis is to reduce morbidity by reducing the prevalence of heavy infections. In Niger, where urinary schistosomiasis is endemic along the Niger River valley and in proximity to ponds, a national control programme for schistosomiasis and soil-transmitted helminth was launched in 2004 with the financial support of the Gates Foundation through the Schistosomiasis Control Initiative. In the framework of the monitoring and evaluation of the control programme, a follow-up of school children took place in eight sentinel sites. The aim of this study was to assess the evolution of Schistosoma haematobium infection and associated morbidity after a single-dose administration of praziquantel and albendazole. Before treatment, the overall prevalence of S. heamatobium infection was 75.4% and anaemia (haemoglobin <11.5 g/dl) was present in 61.6% of the study sample. One year after a single-dose praziquantel treatment (administered by dose-pole) co-administered with albendazole (400 mg single dose) for de-worming, all morbidity markers of the infection decreased significantly. This study shows how a schistosomiasis control programme can benefit populations by improving their health status

La petite irrigation par les eaux souterraines, une solution durable contre la pauvreté et les crises alimentaires au Niger ?

In Sahelian countries, the development of irrigated agriculture is one of the solutions to avoid repetitive food crises. Considering south-western Niger as a regional case study, this paper demonstrates that increasing low-cost groundwater irrigation represents a long-term solution, using shallow, unconfined perennial groundwater, widely distributed in this region. Groundwater resources and soil characteristics were described and localized in space, quantified in volume and/or surface area, and their long-term potential estimated as a function of updated datasets. Data analysis demonstrates that similar to 50,000 to 160,000 ha (3 to 9% of present-day cultivated areas) could be turned into small irrigated fields using accessible shallow groundwater (water table depth <= 20 m). This would double the regional capacity for irrigation

Modélisation éco-hydrologique en zone agropastorale endoréique au Sahel : impact des pratiques agricoles et apport de la télédétection

International audienceLe Sahel est une région soumise à des aléas climatiques de plus en plus extrêmes. Sa forte croissance démographique le rend également particulièrement vulnérable concernant la gestion de l'eau, la sécurité alimentaire ou les risques hydro-climatiques. Dans ce contexte, la communauté scientifique s'attache à proposer des méthodologies facilitant le suivi des ressources en eau et végétales. Ces méthodologies reposent sur la compréhension et la modélisation du fonctionnement thermo-hydrique des grands types d'écosystèmes. Notre étude se focalise ainsi sur l'analyse de l'impact des pratiques agricoles dans les modèles de transfert Sol-Végétation-Atmosphère (SVA), outils dédiés à la quantification des bilans d'eau et d'énergie à la surface. Elle a comme objectif : i) d'identifier les processus clés régissant la répartition des flux permettant d'évaluer la pérennité des systèmes agricoles actuels face aux changements socio-climatiques, et ii) d'identifier les leviers d'action pour une adaptation durable de ces systèmes. Plus particulièrement, cette étude vise à mieux comprendre les impacts de la pratique de mise en jachère qui est traditionnellement conduite au Sahel agropastoral. Dans ce but, le modèle SiSPAT a été étalonné sur le site de mesure de Wankama, dans le Sud-Ouest du Niger, sur une parcelle agricole avec une mise en jachère suivie d'une culture de mil. L'étalonnage du modèle, mené année par année après la rotation, a permis de mettre en évidence les effets du labour effectué au moment de cette dernière sur les propriétés hydrodynamiques des premières couches du sol : hausse de 10 % de la porosité, conductivité hydraulique multipliée par 3.5, atténuation au fil des ans. Ceci impacte la capacité d'infiltration du sol, avec une infiltration plus importante et perdurant plusieurs années. La répartition entre évaporation et transpiration s'en trouve elle aussi impactée, au profit de la transpiration du fait du stockage de l'eau en profondeur. L'étude de la phase de rotation inverse (mil vers jachère) est également en cours d'analyse à l'aide des données disponibles et du modèle SiSPAT, afin de comprendre l'impact à plus long terme du cycle de rotation complet, tant sur les propriétés du sol que les processus d'infiltration et de recharge diffuse en milieu agricole

A remote sensing data fusion method for continuous daily evapotranspiration mapping at kilometric scale in Sahelian areas

International audienceThermal infrared (TIR) remote sensing-based ET estimates are very appealing for a wide range of scientific applications in hydrology. However, they are prone to infrequency due to satellite revisit interval and cloud cover. Temporal interpolation techniques or multi-resolution and multi-frequency data fusion approach have thus recently been studied to provide continuous ET estimates. It has been already shown that the interest of temporal interpolation techniques is limited to short return interval that is troublesome in Sahelian regions where mesoscale convective systems linked to the West African Monsoon (WAM) renders unusable most of TIR images during the rainy season. Here we developed a data fusion approach to provide remote sensing-based continuous daily ET estimates at kilometric resolution in Sahelian areas. The proposed algorithm fill gaps in MODIS-based ET estimates from EVASPA S-SEBI Sahel (E3S) using the Global Land Evaporation: the Amsterdam Methodology (GLEAM) product and/or ET estimates from a simple parametric model for typical Sahelian ecosystems as a normalized basis. The fusion algorithm is evaluated at the pixel scale against eddy-covariance measurements and simulations of a locally calibrated and validated land surface model (LSM) on a millet crop and a fallow of shrubby savannah in the southwest of the Republic of Niger. Consistency of the fusion approach is also evaluated at mesoscale by comparing it with a set of 20 regional LSMs. Globally both level of comparison highlight the very good agreement of ET estimates based on the fusion approach with both in situ measurements and LSMs simulations. We also show the benefit of such a fusion approach compared to linear temporal interpolation techniques of the ratio between ET and either incoming solar radiation or reference evapotranspiration. The main benefits are observed during the first months of the rainy season in the depiction of the surface response to rainfall events and consecutive drying up of the surface soil layer. We suggest that such a fusion approach could be later used in disaggregation chain to enhance field scaled ET estimates by the combination of coarse, moderate and high resolution remote sensing-based ET estimates

Review and evaluation of global evapotranspiration products in Sahelian region

International audienceEvapotranspiration (ET) is a key variable in the understanding of the hydrological cycle. However, in many regions, like the Sahelian Regions, there is a spatial scarcity of in-situ ET measurements, in spite of its vulnerability to water availability and food security problems. However, in the past decade, many spatialized ET products have been released. They use various calculation methods like physical or empirical modelling, upscaling of in-situ measurements or data fusion approaches. The aim of this study is to propose a quite exhaustive review and evaluation of global or continental ET products available over typical Sahelian ecosystems in both Senegal and Niger, in the frame of the EVAP’EAU project (ICIREWARD Unesco Center). 20 ET products have thus been evaluated at local scale, using flux tower measurements over a typical agropastoral ecosystems. A meso-scale (~150km) evaluation has also been performed, by doing a cross comparison of the products at different spatial aggregation levels. Results show that the products with the best temporal representation of ET have the lowest spatial resolution (>10km), and thus lack of spatial representativeness. On the other hand, higher resolution products (<1km) show a realistic spatial distribution but several issues on the representation of the ET cycle seasonality. Therefore, in order to tackle water and agricultural management issues, there is need for better spatialized ET estimates at both high spatial and temporal resolution in Sahelian region. This could be achieved by proposing new data fusion methods, dedicated to these issues. However, the upcoming TRISHNA (CNES-ISRO), LSTM (ESA) and SBG (NASA) satellite missions will help to fill this gap by providing TIR data and products with high spatial (~50m) and temporal (~2 days) resolution

Review and evaluation of global evapotranspiration products in Sahelian region

International audienceEvapotranspiration (ET) is a key variable in the understanding of the hydrological cycle. However, in many regions, like the Sahelian Regions, there is a spatial scarcity of in-situ ET measurements, in spite of its vulnerability to water availability and food security problems. However, in the past decade, many spatialized ET products have been released. They use various calculation methods like physical or empirical modelling, upscaling of in-situ measurements or data fusion approaches. The aim of this study is to propose a quite exhaustive review and evaluation of global or continental ET products available over typical Sahelian ecosystems in both Senegal and Niger, in the frame of the EVAP’EAU project (ICIREWARD Unesco Center). 20 ET products have thus been evaluated at local scale, using flux tower measurements over a typical agropastoral ecosystems. A meso-scale (~150km) evaluation has also been performed, by doing a cross comparison of the products at different spatial aggregation levels. Results show that the products with the best temporal representation of ET have the lowest spatial resolution (>10km), and thus lack of spatial representativeness. On the other hand, higher resolution products (<1km) show a realistic spatial distribution but several issues on the representation of the ET cycle seasonality. Therefore, in order to tackle water and agricultural management issues, there is need for better spatialized ET estimates at both high spatial and temporal resolution in Sahelian region. This could be achieved by proposing new data fusion methods, dedicated to these issues. However, the upcoming TRISHNA (CNES-ISRO), LSTM (ESA) and SBG (NASA) satellite missions will help to fill this gap by providing TIR data and products with high spatial (~50m) and temporal (~2 days) resolution

Modélisation physique du cycle couplé de l'eau et de l'énergie en conditions tropicales sèches : une expérimentation à l'échelle locale dans le Sahel cultivé (Sud ouest du Niger)

International audienceIn the dry tropics in general and, particularly in the African Sahel, agro-ecosystems and hydrosystems are very sensitive to climate variability and land management. In turn, it has been shown that soil moisture, vegetation and surface fluxes produce substantial feedback effects on rainfall-producing atmospheric convection. Therefore, it is of prime importance to understand and to model the dynamics of the soil-plant-atmosphere continuum in response to contrasted meteorological and terrestrial conditions for this area. The objective of this study is to produce a process-based model of water and energy transfers in the soil and land-atmosphere interface over an entire 5-year period, at local scale, for the two main land cover types of South-West Niger: millet-crop and fallow savannah. A comprehensive dataset is available over that whole period in two such fields of the Wankama catchment, making it a rather unique asset for West Africa. This area is typical of the central Sahel conditions, with 400-600 mm annual rainfall concentrated in the 4-5 months wet season, followed by the 7-8 months dry season. Soils are essentially sandy and prone to surface crusting, which induces a strong vertical contrast in hydrodynamic properties. The dataset used here includes 5 years of atmospheric forcing (rainfall, wind speed, sun and atmosphere radiation, air temperature and moisture) and validation variables (net radiation, turbulent fluxes and soil temperature and moisture profiles), recorded every 30 min. The seasonal course of vegetation phenology (LAI, height, biomass) and soil characteristics (particle size and density profiles) are also available. The SiSPAT (Simple Soil-Plant-Atmosphere Transfer, Braud et al., 1995) physically-based model is used for this study. It solves the mass and heat transfer system of equations in the soil, with vapour phase, coupled with a two-component (bare soil and one vegetation layer) water and energy budget at the surface-atmosphere interface. Main questions raised in this modeling exercise were, whether such a model could be adequately calibrated and validated for the two studied sites, using realistic parameter values and, what uncertainty would result for model outputs (surface fluxes and soil heat/water profiles). The model was calibrated over a 2-year period and then validated over the other three years, for both sites. In both cases, observations are reproduced about as well for the two periods. The variations in water and energy variables, over the five contrasting years and between land covers, are highlighted. Multi-year, field-based estimations of land surface water and energy budgets are hence produced, for the first time in this area to our knowledge. Given model performances, it is felt that it can be applied with reasonable confidence to much longer periods, reflecting the strong variability that characterizes the Sahel climate. This modeling experiment takes part in the ALMIP (AMMA Land Model Intercomparison) project, which aims at comparing land surface models at local and meso scales over a north-south eco-climate gradient represented by three West-African sites of the AMMA-CATCH observatory (RBV network)