Analyse Par Approche Hydrogeochimique De La Distribution Spatiale De La Salinite Des Eaux De La Nappe Et Des Sables Quaternaires Du Secteur Des Niayes Du Gandiolais (Littoral Nord Senegalais)

Dans le Gandiolais, la nappe des sables quaternaires, fortement salée sur la majeure partie de la zone, est utilisée pour irriguer les cultures et pose de véritables difficultés pour la durabilité du système maraicher. La salinisation secondaire du sol irrigué et la réaction du complexe absorbant dépendent principalement des paramètres intrinsèques, particulièrement la texture du sol. L’objet de cet article est d’analyser la distribution spatiale de la salinité en tenant en compte les caractéristiques granulométriques du complexe absorbant. L'approche hydrogéochimique basée sur les relations de concentration permet d'apprécier les modalités de conservation in situ entre les eaux d'irrigation et le sol exploité. Les résultats obtenus ont confirmé que la texture grossière de type sables moyens à fins permet un lessivage rapide des sels solubles sur tout le profil. Les sols restent globalement calcimagnésiens même si les eaux d'irrigation sont globalement chlorurées sodiques et potassiques ou sulfatées sodiques. Cependant, cette forte perméabilité du complexe constitue un risque de surconcentration ionique dans la nappe. Les retours d'irrigation associés aux engrais accentuent la minéralisation de la nappe des sables quaternaires. In the Gandiolais, the groundwater of the quaternary sands, heavily salted over most of the area, is used to irrigate crops and poses real difficulties for the sustainability of the market gardening system. Secondary salinization of the irrigated soil and the reaction of the absorbing complex depend mainly on the intrinsic parameters, particularly the texture of the soil. The purpose of this article is to analyze the spatial distribution of salinity taking into account the particle size characteristics of the absorbent complex.The hydrogeochemical approach based on the relations of concentration makes it possible to appreciate the process of conservation in situ between the irrigation water and the exploited soil. The results obtained confirmed that the coarse texture of medium-to-fine sand type allows rapid leaching of soluble salts over the entire profile. Soils remain globally calcimagnesian although the irrigation water is globally sodium chloride and potassium or sodium sulphated. However, this high permeability of the complex constitutes a risk of ionic overconcentration in the aquifer. Irrigation returns associated with fertilizers accentuate the mineralization of the groundwater of the quaternary sands

The modified retrosigmoid approach: a how I do it

BACKGROUND: The traditional retrosigmoid (RS) approach provides limited exposure of the inferior compartment of the CPA, while radical skull base approaches are demanding and associated with significant morbidity. METHODS: This study outlines the relevant surgical anatomy and the different surgical steps of a modified retrosigmoid (MRS) approach. RESULTS: The MRS provides enhanced exposure of the CPA and deep vascular structures resulting from a modified RS craniotomy and limited exposure of the sigmoid sinus. CONCLUSION: In selected posterior fossa lesions, this cisternal approach is a straightforward corridor that can be routinely performed as a safe alternative to radical cranial base approaches

QUANTIFICATION DE LA SÉCHERESSE MÉTÉOROLOGIQUE PAR DES INDICES STANDARDISES DE PRÉCIPITATION DANS LA VALLÉE DU FLEUVE SÉNÉGAL DE 1980 À 2017

International audienceLes sécheresses qui ont des répercussions sur la disponibilité de l'eau, la production agricole et les exploitations d'élevage, sont généralement identifiées et caractérisées à l'aide d'indices de sécheresse. La présente étude porte sur le potentiel d'utilisation de l'indice standardisé de précipitation (SPI) et de l’indice standardisé de précipitations-évapotranspiration (SPEI) basé sur les précipitations pour reproduire les sécheresses météorologiques observées dans la vallée du fleuve Sénégal. Les sécheresses historiques survenues de 1980 à 2017 ont été examinées et l'analyse du SPI montre un bon accord avec les épisodes de sécheresse enregistrés. Le SPI a également été utilisé pour étudier l’évolution temporelle de la sécheresse et sa gravité. Les sécheresses les plus graves dans le bassin se sont produites au cours des années 1983, 1984, 1992, 2014. L’intensité des sécheresses s'est avérée légère à modérée, malgré la présence de cas de sécheresse sévère à extrême comme en 1984. Les sécheresses les plus longues dans le bassin ont eu lieu au cours de huit années consécutives, de 1980 à 1987. Les valeurs du SPI étaient parfois inférieures à -1 pour ces années sur des échelles de temps de 1, 3, 6 et 12 mois. Les valeurs du SPI sur 12 mois sur cette période sont de -2,25 pour le pas de 1 mois, -1,7 pour les 3 mois, -1,2 pour les 6 mois et -2,2 pour les 12 mois. Ces valeurs du SPI suggèrent une sécheresse modérée (SPI 6 mois) à extrême (SPI 1 mois et 12 mois)

Training on Climate Risk Management in Agricultural Advisory Services in Senegal

The phenomenon of climate change encompasses all sectors of life, and its impact on the agricultural sector (farming and livestock breeding) is well established. Faced with these challenges of adaptation and survival, it is important to raise awareness among all those involved (technicians and producers) of the basic concepts and decision-support tools needed to derive maximum benefit from agricultural activities. It was against this backdrop that AICCRA set up a train-the-trainer program with the support of universities, agricultural technicians, producers' organizations and agricultural technology extension services. A model curriculum was selected at an earlier event in Dakar from December 05 to 10, 2022 (Fleur de Lys Point E). A train-the-trainer workshop was organized in Saly from March 06 to 16, 2023 to validate and improve the training modules. The AICCRA project (Accelerating Impacts of CGIAR Climate Research in Africa), is a three (3) year project (2021-2023) funded by the World Bank (IDA) in six (6) African countries: Ethiopia, Kenya, Zambia, Ghana, Mali and Senegal. The main objective of AICCRA-Senegal is to strengthen the technical, institutional and human capacities needed to improve the transfer of climate-related information, decision-making tools. and technologies in support of scaling-up efforts to strengthen the resilience of agricultural and livestock value chains, particularly in arid zones. As part of this training program, AICCRA aims to improve and facilitate access to climate information services and climate-smart agricultural technologies for the project's target farmers, via extension agents. AICCRA therefore aims to help build producers' resilience and make it easier for them to understand weather and climate phenomena, so they can forecast and plan their farming activities effectively. Capacity building for intermediate users, in particular of agricultural extension and advisory services (EAS) in Senegal and five other target countries is a key element of AICCRA's strategy for achieving this objective

Effectiveness of Seasonal Malaria Chemoprevention in Children under Ten Years of Age in Senegal: A Stepped-Wedge Cluster-Randomised Trial.

BACKGROUND: Seasonal Malaria Chemoprevention (SMC) with sulfadoxine-pyrimethamine (SP) plus amodiaquine (AQ), given each month during the transmission season, is recommended for children living in areas of the Sahel where malaria transmission is highly seasonal. The recommendation for SMC is currently limited to children under five years of age, but, in many areas of seasonal transmission, the burden in older children may justify extending this age limit. This study was done to determine the effectiveness of SMC in Senegalese children up to ten years of age. METHODS AND FINDINGS: SMC was introduced into three districts over three years in central Senegal using a stepped-wedge cluster-randomised design. A census of the population was undertaken and a surveillance system was established to record all deaths and to record all cases of malaria seen at health facilities. A pharmacovigilance system was put in place to detect adverse drug reactions. Fifty-four health posts were randomised. Nine started implementation of SMC in 2008, 18 in 2009, and a further 18 in 2010, with 9 remaining as controls. In the first year of implementation, SMC was delivered to children aged 3-59 months; the age range was then extended for the latter two years of the study to include children up to 10 years of age. Cluster sample surveys at the end of each transmission season were done to measure coverage of SMC and the prevalence of parasitaemia and anaemia, to monitor molecular markers of drug resistance, and to measure insecticide-treated net (ITN) use. Entomological monitoring and assessment of costs of delivery in each health post and of community attitudes to SMC were also undertaken. About 780,000 treatments were administered over three years. Coverage exceeded 80% each month. Mortality, the primary endpoint, was similar in SMC and control areas (4.6 and 4.5 per 1000 respectively in children under 5 years and 1.3 and 1.2 per 1000 in children 5-9 years of age; the overall mortality rate ratio [SMC: no SMC] was 0.90, 95% CI 0.68-1.2, p = 0.496). A reduction of 60% (95% CI 54%-64%, p < 0.001) in the incidence of malaria cases confirmed by a rapid diagnostic test (RDT) and a reduction of 69% (95% CI 65%-72%, p < 0.001) in the number of treatments for malaria (confirmed and unconfirmed) was observed in children. In areas where SMC was implemented, incidence of confirmed malaria in adults and in children too old to receive SMC was reduced by 26% (95% CI 18%-33%, p < 0.001) and the total number of treatments for malaria (confirmed and unconfirmed) in these older age groups was reduced by 29% (95% CI 21%-35%, p < 0.001). One hundred and twenty-three children were admitted to hospital with a diagnosis of severe malaria, with 64 in control areas and 59 in SMC areas, showing a reduction in the incidence rate of severe disease of 45% (95% CI 5%-68%, p = 0.031). Estimates of the reduction in the prevalence of parasitaemia at the end of the transmission season in SMC areas were 68% (95% CI 35%-85%) p = 0.002 in 2008, 84% (95% CI 58%-94%, p < 0.001) in 2009, and 30% (95% CI -130%-79%, p = 0.56) in 2010. SMC was well tolerated with no serious adverse reactions attributable to SMC drugs. Vomiting was the most commonly reported mild adverse event but was reported in less than 1% of treatments. The average cost of delivery was US$0.50 per child per month, but varied widely depending on the size of the health post. Limitations included the low rate of mortality, which limited our ability to detect an effect on this endpoint. CONCLUSIONS: SMC substantially reduced the incidence of outpatient cases of malaria and of severe malaria in children, but no difference in all-cause mortality was observed. Introduction of SMC was associated with an overall reduction in malaria incidence in untreated age groups. In many areas of Africa with seasonal malaria, there is a substantial burden in older children that could be prevented by SMC. SMC in older children is well tolerated and effective and can contribute to reducing malaria transmission. TRIAL REGISTRATION: ClinicalTrials.gov NCT00712374

Evolution of the Pyrethroids Target-Site Resistance Mechanisms in Senegal: Early Stage of the Vgsc-1014F and Vgsc-1014S Allelic Frequencies Shift.

The evolution and spread of insecticide resistance mechanisms amongst malaria vectors across the sub-Saharan Africa threaten the effectiveness and sustainability of current insecticide-based vector control interventions. However, a successful insecticide resistance management plan relies strongly on evidence of historical and contemporary mechanisms circulating. This study aims to retrospectively determine the evolution and spread of pyrethroid resistance mechanisms among natural Anopheles gambiae s.l. populations in Senegal. Samples were randomly drawn from an existing mosquito sample, collected in 2013, 2017, and 2018 from 10 sentinel sites monitored by the Senegalese National Malaria Control Programme (NMCP). Molecular species of An. gambiae s.l. and the resistance mutations at the Voltage-gated Sodium Channel 1014 (Vgsc-1014) locus were characterised using PCR-based assays. The genetic diversity of the Vgsc gene was further analyzed by sequencing. The overall species composition revealed the predominance of Anopheles arabiensis (73.08%) followed by An. gambiae s.s. (14.48%), Anopheles coluzzii (10.94%) and Anopheles gambiae-coluzii hybrids (1.48%). Both Vgsc-1014F and Vgsc-1014S mutations were found in all studied populations with a spatial variation of allele frequencies from 3% to 90%; and 7% to 41%, respectively. The two mutations have been detected since 2013 across all the selected health districts, with Vgsc-L1014S frequency increasing over the years while Vgsc-1014F decreasing. At species level, the Vgsc-1014F and Vgsc-1014S alleles were more frequent amongst An. gambiae s.s. (70%) and An. arabiensis (20%). The Vgsc gene was found to be highly diversified with eight different haplotypes shared between Vgsc-1014F and Vgsc-1014S. The observed co-occurrence of Vgsc-1014F and Vgsc-1014S mutations suggest that pyrethroid resistance is becoming a widespread phenomenon amongst malaria vector populations, and the NMCP needs to address this issue to sustain the gain made in controlling malaria

Evolution of the Ace-1 and Gste2 Mutations and Their Potential Impact on the Use of Carbamate and Organophosphates in IRS for Controlling Anopheles gambiae s.l., the Major Malaria Mosquito in Senegal

Widespread of insecticide resistance amongst the species of the Anopheles gambiae complex continues to threaten vector control in Senegal. In this study, we investigated the presence and evolution of the Ace-1 and Gste2 resistance genes in natural populations of Anopheles gambiae s.l., the main malaria vector in Senegal. Using historical samples collected from ten sentinel health districts, this study focused on three different years (2013, 2017, and 2018) marking the periods of shift between the main public health insecticides families (pyrethroids, carbamates, organophosphates) used in IRS to track back the evolutionary history of the resistance mutations on the Ace-1 and Gste2 loci. The results revealed the presence of four members of the Anopheles gambiae complex, with the predominance of An. arabiensis followed by An. gambiae, An. coluzzii, and An. gambiae-coluzzii hybrids. The Ace-1 mutation was only detected in An. gambiae and An. gambiae-coluzzii hybrids at low frequencies varying between 0.006 and 0.02, while the Gste2 mutation was found in all the species with a frequency ranging between 0.02 and 0.25. The Ace-1 and Gste2 genes were highly diversified with twenty-two and thirty-one different haplotypes, respectively. The neutrality tests on each gene indicated a negative Tajima's D, suggesting the abundance of rare alleles. The presence and spread of the Ace-1 and Gste2 resistance mutations represent a serious threat to of the effectiveness and the sustainability of IRS-based interventions using carbamates or organophosphates to manage the widespread pyrethroids resistance in Senegal. These data are of the highest importance to support the NMCP for evidence-based vector control interventions selection and targeting