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Trend and Return Level Analysis of Extreme Rainfalls in Senegal

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Journal of Water Resource and Protection 2022年第3期14卷 221-237页

作者： Mamadou Sarr mahamat adoum moussa El Hadji Deme Bouya Diop Laboratoire des Sciences de l’Atmosphère et des Océans Matériaux-Energies-Dispositifs (LSAOMED) Université Gaston Berger Saint-Louis Sénégal Ecole Nationale Supérieur des TIC (ENASTIC) N’Djamena Tchad Laboratoire d’Etudes et de Recherches en Statistique et Développement (LERSTAD) Université Gaston Berger Saint-Louis Sénégal

In recent years, Senegal has been confronted with increasingly frequent and damaging extreme events. In the context of climate change, we conducted this study to characterize the trends of rainfall extremes in Senegal. In this work, we used daily rainfall data from 27 stations in Senegal from the period 1951 to 2005 (55 years). To study their linear trends, non-stationary extreme value models with time as a covariate are fitted to evaluate them. Our results indicate a decreasing trend of extreme rainfalls at most of the stations except for 5 stations. However, the decreasing trends are only significant for two stations (Thiès and Kidira), however, this can only be taken as information that climate change may have already impacted extreme rainfalls. For the 20-year and 30-year return periods, the results show that they have undergone changes, in fact for almost all stations, the trends in return periods are decreasing.

关键词： Climate Change Extreme Rainfall Rain Trend Return Level Senegal

Spatial and Temporal Distribution of Rainfall Breaks in Senegal

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American Journal of Climate Change 2021年第4期10卷 533-560页

作者： Bara Ndiaye mahamat adoum moussa Malick Wade Abdoulaye Sy Abdoulaye Bouya Diop Aichetou Dia Diop Bouya Diop Aboubakary Diakhaby Laboratoire des Sciences de l’Atmosphère et de Océans Matériaux énergie Dispositifs (LSAOMED) Saint-Louis Senegal

This study analyzes the spatio-temporal distribution of daily rainfall data from 13 stations in the country of Senegal located in the North-West of Africa. These data, covering the period 1950-2010, are extracted from the database of the Regional Study Center for the Improvement of Drought Adaptation (CERAAS). They allow to calculate, in each station, dry episodes and their sequences and the results reveal a latitudinal variability of class 1 breaks (1 - 3 days) with the highest values recorded in the south. Unlike the class 2 episodes (greater or equal than 15 days), the latitudinal gradient is less pronounced but they are more frequent in the north. For most of the regions studied, a break in the trend towards an increase in dry sequences can be noted, most often at the beginning of the 1970s, which coincides with the start of the great drought of the 1970s decade. For all sites, the frequency of dry episodes of class 1 (1 - 3 days) exceeds 70%. The frequency of class 2 of dry episodes (greater or equal than 15 days) decreased from 30% in 1951-1970 to 18% in 1991-2010 in the region of Thiès;from 25% in 1951-1970 to 20% in 1991-2010 in Louga;from 22% in 1951-1970 to 18% in 1991-2010 in Tamba;23% in 1951-1970 to 15% in 1991-2010 in Ziguinchor;25% in 1951-1970 to 16% in 1991-2010 in Kolda;22% in 1951-1970 to 18% in 1991-2010 in Diourbel and finally 20% in 1951-1970 to 17% in 1991-2010 in Fatick. Over the whole period of study, the spatial distribution of the number of dry periods in class 1 is higher in the South than in the Center and in the North of Senegal. For class 2 breaks, the latitudinal gradient is less pronounced and the minimum number of dry periods in this class is recorded in the south, especially in Ziguinchor. However, the maximum is observed in the Center. In the Northern region (Saint-Louis), classes 3 and 4 are much more frequent. This spatial variability of rainfall breaks is clearly associated with the rainfall gradient between the North and the S

关键词： Rainfall Rainfall Breaks Great Drought Senegal Consecutive Dry Days

Characterization of Spatio-Temporal Variability of Irradiation, Nebulosity and Aerosols Optical Depth in 10˚North-20˚North African Band

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American Journal of Climate Change 2022年第2期11卷 155-171页

作者： Abdoulaye Bouya Diop Abdoulaye Sy Malick Wade Abdoul Karim Mbodj Abdou Karim Farota adoum mahamat moussa Babacar Niang Aicha Dia Diop Bara Ndiaye Bouya Diop Amadou Thierno Gaye Aboubakary Diakhaby LSAO-MED Gaston Berger University Saint Louis Senegal CERDI Clermont Auvergne University Clermont Auvergne France University of Tchad Djamena Tchad LPAOSF ESP Cheikh Anta Diop Univesity Dakar Senegal

This work concerns the 10? North, 20? North African band. Area renowned for having some of the poorest countries in the world. It is also home to the Sahelian strip and part of the Sahara. The countries in this zone have a relatively low electrification rate compared to the enlightened country. To solve this problem, these countries want to turn to renewable energies such as photovoltaics (renewable energy obtained through solar radiation). Therefore, understanding the behavior of irradiation and cloudiness in the 10 - 20 band becomes necessary. The application of the empirical orthogonal functions to the different cloud layers and to the irradiation reveals a seasonality of the latter, in particular compared to the first modes of the empirical orthogonal functions (EOF1). Indeed, by filtering in time and space to isolate solar radiation and cloudiness, the EOF1 expresses respectively 94.3% of the variation of descending solar radiation in clear sky in the 10 - 20 band. Note 65.7% for global radiation, 54.4% for cloudiness at 450 hPa, 69.6% for cloudiness between 800 hPa and 450 hPa, 76.6% for low cloudiness, 61.4% for total cloudiness. These results allow us to say that we have generally good sunshine over several months, with little cloud cover in this band. However, since this zone is considered to be part of the main aerosol emission source zones, it is important in their temporal consideration of the optical depth. By doing the wavelet analysis on the optical depth data from Dakar and Banizoumbou, we note that the average dust presence spectrum over the entire period from 1997 to 2019 in the two stations with a slight shift compared to the peaks and the maximum observed value. A sign that there is a strong presence of dust in this area and that it should be taken into account for any photovoltaic installation in this area.

关键词： Sahel Irradiation Cloudiness Aerosol EOF Wavelet

Study of the Spatio-Temporal Variability of Rainfall in the Northern Region of Senegal

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Journal of Geoscience and Environment Protection 2023年第4期11卷 1-14页

作者： Aichétou Dia Diop Abdoul Karim Mbodji El Hadji Deme Malick Wade mahamat adoum moussa Abdoulaye Bouya Diop Younousse Biaye Djiby Sarr Abdou Karim Farota Aboubakary Diakhaby Bouya Diop Laboratoire des Sciences de l’Atmosphère et des Océans Matériaux Energies Dispositifs UGB Saint Louis Senegal Laboratoire D’études et de Recherches en Statistiques et Développement University Gaston Berger (UGB) Saint Louis Senegal Ecole Nationale Supérieure des TIC N’Djamena Tchad

Senegal is a country of the Sahel. In this region, most of the populations live from agro-pastoral activities. The northern zone of Senegal is strongly influenced by river cultures. And the dynamics of the Senegal River are dependent on rainfall. The rainfall in the area is very closely linked to the dynamics of the atmosphere. The study of the spatio-temporal variability of rainfall in the northern region of Senegal requires quality rainfall observation data. It includes the Ferlo and the Senegal River valley, in particular the regions of Louga (department of Linguère included), Saint-Louis (departments of Dagana and Podor included) and Matam. These stations have been defined since Le Borgne (1988). The difficulty of having quality rain observation data can be resolved by using more accessible and good quality satellite data. Using satellite data, namely MSWEP, CRU, TAMSAT, ARC and PERSIANN, we showed the return of precipitation that appeared in 2000 and the unimodal cycle of precipitation in our study area. These data were validated using the correlation coefficient, the bias, the RMSE and the Nash index with observation data from the Regional Study Center for the Improvement of Adaptation to Drought (CERASS). The CRU data is then retained. Thus, this study made it possible to show the zonal distribution of rainfall in the northern zone of Senegal.

关键词： Rainfall in the Northern Region of Senegal Variability of Rainfall Satellite Data The Zonal Distribution of Rainfall

The Dust Comportment in the Latitudinal Band 10°North - 20°North in Africa: Emission and Deposition

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Journal of Geoscience and Environment Protection 2022年第5期10卷 139-159页

作者： Abdoulaye Bouya Diop Abdoulaye Sy Abdoul Karim Mbodji Abdou Karim Farota Malick Wade adoum mahamat moussa Babacar Niang Aichetou Dia Diop Bara Ndiaye Bouya Diop Amadou Thierno Gaye Aboubakary Diakhaby Gaston Berger University of Saint Louis Saint Louis Senegal University of Clermont Auvergne Clermont-Ferrand France University of Chad Ndjamena Chad Cheikh Anta Diop University of Dakar Dakar Senegal

The three measurement periods: the TOMS Nimbus-7 TOMSN7L3 v008 from 1978 to 1993, the TOMS EP TOMSEPL3 v008 from 1996 to 2005 and the OMI OMTO3d v003 from 2004 to 2008 have allowed the presence of dust to be observed in the 10°North to 20°North latitudinal band (10 - 20 band) of Africa. The 10 - 20 band has a permanent dust presence. The AERONET data show AOD peaks exceeding 2 in Senegal and Niger (on an AOD scale). The statistical study reveals intra-annual relationships in deposition. In Senegal, a significant deposition is observed.

关键词： Dust Source Area AOD 10° North - 20° North African Band Deposition Sahel

Evaluation of the Strategy and Efficacy of Treatment of Chronic Viral Hepatitis C with the Sofosbuvir/Daclatasvir Combination in a Resource-Limited Country

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Open Journal of Gastroenterology 2024年第7期14卷 233-240页

作者： Mayanna Habkreo Ali mahamat moussa Adama Ahmed Ngare Abdraman Kossou Tahir mahamat Saleh Maire Dehainsala mahamat Ali Hachim mahamat Ali Bolti Oumaima Djarma Joseph Madtoingue Service de Gastroentrologie/Mdecine Interne du Centre Hospitalier Universitaire la Rfrence Nationale NDjamena Chad Service de Gastroentrologie du Centre Hospitalier Universitaire la Renaissance NDjamena Chad Service de Maladies Infectieuses du Centre Hospitalier Universitaire la Renaissance NDjamena Chad Service de Maladies Infectieuses du Centre Hospitalier Universitaire la Rfrence Nationale NDjamena Chad

Introduction: The treatment of viral hepatitis C (HCV), a major public health problem, has evolved considerably since the introduction of direct-acting anti-virals (DAAs). The aim of this study was to evaluate the strategy for initiating treatment with Sofosbuvir/Daclatasvir, and also to assess its efficacy. Patients and Methods: Included were patients aged at least 15 years, with detectable hepatitis C viremia and treated with a pan-genotypic Sofosbuvir/Daclatasvir regimen at the Centre “Hospitalier Universitaire la Référence Nationale de N’Djamena” between October 2019 and October 2023. The APRI score was used to assess fibrosis. Cure was defined by an undetectable viral load 12 weeks after the end of treatment. Results: A total of 835 patients were included (sex ratio 1.55, mean age 50.5 ± 13.73, extremes 20 and 84 years). The 60 - 69 age group was the most represented. The mean APRI score was 0.42 ± 0.29, with extremes of 0.019 and 1.84. The mean viral load was 2,316,193.086 IU/mL. All subjects had good renal function. Cytolysis was absent in 70% of cases. Without genotyping, a pan-genotypic regimen was used in all patients: Sofosbuvir (400 mg)/Daclatasvir (60 mg). The cure rate was 99.4%, with good tolerability. However, four cases of failure were recorded out of the 668 patients who underwent follow-up HCV-PCR testing after 12 weeks of treatment. Conclusion: The Sofosbuvir/Daclatasvir regimen is highly effective, with an excellent safety profile. However, the still high cost of these molecules limits their accessibility to a large proportion of patients.

关键词： Efficacy Tolerance Sofosbuvir/Daclatasvir HCV Chad

Eradication Treatment of Helicobacter pylori Infection: Evaluation of Therapeutic Strategies in N’Djamena

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Open Journal of Gastroenterology 2024年第2期14卷 59-67页

作者： Mayanna Habkréo Ali mahamat moussa Tahir mahamat Saleh Djerabet Franckly Fany Haby Mairé Dehainssala Adama Ngaré mahamat Ali Hachim Service de Medecine Interne et Gastroenterologie Centre Hospitalier Universitaire La Reference Nationale N’Djamena Tchad Service de Medecine Interne Centre Hospitalier Universitaire La Renaissance N’Djamena Tchad Service de Médecine Hopital de l’Amitié Tchad-Chine N’Djamena Tchad

Background: Helicobacter pylori (Hp) infection is the most widespread bacterial infection in the world. The infection is generally acquired in childhood, but can persist into adulthood. Eradication therapy has undergone several modifications. The aim of this study was to evaluate the different therapeutic strategies used in the eradication of Helicobacter pylori infection in the Centre Hospitalier Universitaire La Reference Nationale of N’Djaména. Patients and Methods: This was a prospective, descriptive analytical study spread over one year, from September 2021 to September 2022. Patients at least 15 years of age presenting with dyspeptic symptoms, seen consecutively in a hepato-gastroenterology consultation and with a positive stool test for H. pylori infection, were included in the study. Equally, 1/3 of patients were treated with dual or triple therapy. The remaining third received quadritherapy. Results: A total of 268 patients were included in the study (mean age 38.40 ± 14.66 with extremes of 16 and 80 years). Males predominated in 58% of cases. Overall therapeutic efficacy was 88.9%. According to different therapeutic strategies, efficacy was 90.75% for dual therapy with PPI (Rabeprazole) and Amoxicillin. On the other hand, efficacy was 87% and 88.88% for PPI-based triple therapy and dual antibiotic therapy, and for PPI-based quadruple therapy and triple antibiotic therapy. Conclusion: H. pylori infection is a common disease in Chad. Dual therapy with rabeprazole combined with a high dose of amoxicillin over a period of at least two weeks showed similar if not better efficacy than triple or quadruple therapy.

关键词： Helicobacter pylori Therapeutic Strategies Eradication Dyspepsia Chad

Visceral Leishmaniasis at the National Reference University Hospital Center of N’Djamena (Chad): Epidemiological, Clinical, Diagnostic, Therapeutic and Prognostic Aspects

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Advances in Infectious Diseases 2024年第2期14卷 478-486页

作者： Joseph Mad-Toïngué mahamat Ali Ahmat Oumaïma mahamat Djarma Alifa Adjibera Philippe Ali mahamat moussa Ngakoutou Rangar Choua Ouchemi mahamat Ali Bolti Djiddi Ali Sougoudi Mamissou Didi mahamat Doungous Atim Service des Maladies Infectieuses CHU de Référence Nationale N’Djamena Chad Service de Gastroentérologie et Médecine Interne CHU de Référence Nationale N’Djamena Chad Service de Pneumologie et Phtisiologie CHU de Référence Nationale N’Djamena Chad Service de Chirurgie viscérale CHU de Référence Nationale N’Djamena Chad Service de Médecine CHU de la Renaissance N’Djamena Chad

Introduction: leishmaniasis is a group of parasitic diseases caused by a parasite of the genus Leishmania transmitted by the bite of an infected vector called a sandfly. There are four forms. Visceral leishmaniasis is the most severe form. The aim of our work is to study the epidemiological, clinical, diagnostic, therapeutic and prognostic aspects of the disease in the Infectious Diseases Department of the Centre Hospitalier Universitaire de Référence Nationale in N'Djaména. Methodology: Patients were recruited on the basis of clinical signs suggestive of visceral leishmaniasis, i.e. prolonged fever, splenomegaly and altered general condition. Biological confirmation was performed with a rapid diagnostic test using recombinant K39 parasite antigen, which is known to have good specificity and sensitivity. Epidata version 3.1 software was used to process patient data. Results: From 05/04/21 to 15/12/23, 153 positive cases were managed. The mean age of patients was 18 years, with a sex ratio of 9.2. Of these patients, 103 (67.3%) had recently stayed at gold mining sites. Patients testing positive were treated with sodium stibogluconate combined with paromomycin for 17 days. The mortality rate was 13.2%. Conclusion: Leishmaniasis is a serious and little-known disease in Chad. In order to respond to the disease, it is necessary to reinforce the capacities of health structures and to carry out appropriate actions in the outbreaks.

关键词： Visceral Leishmaniasis Gold Mining Sites Chad

Genomic Profile of SARS-COV-2 Associated with COVID-19 Outbreaks in N’Djamena, Chad

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Advances in Bioscience and Biotechnology 2024年第7期15卷 432-442页

作者： Mathieu Hota Henry Yandai Fissou Dezoumbe Koutaya Djallaye Djimtoïbaye mahamat moussa Ali cole Doctorale Sciences Techniques et Environnement Universit de NDjamena NDjamena Tchad Institut de Recherche en Elevage pour le Dveloppement NDjamena Tchad Laboratoire des Grandes pidmies Tropicales du CHU le Bon Samaritain NDjamena Tchad Facult des Sciences de la Sant Humaine (FSSH) Universit de NDjamena NDjamena Tchad

Background: SARS-CoV-2 has circulated worldwide with dramatic consequences. In Chad, we have no data reported of variants. The aim of this study was to identify the SARS-CoV-2 variants that circulated during the epidemic from 2020 to 2021. Methods: This is a cross-sectional, descriptive study carried out between 2020 and 2021. Samples from patients with suspected COVID-19 were tested in five laboratories in N’Djamena. One hundred quality samples of the positives were sequenced in Kinshasa using Oxford nanopore technologies minion and the Protocol Midnight SARS-CoV2. Data were processed using Excel version 16 software. Results: Of the 100 samples sequenced, 77 (77%) produced sequences, 23 (23%) did not. The genomic profiles were wild-type Wuhan and minor mutations (19A, 19B (A), 20A (B.1, B.2), 20B (AV.1), 20D (B.1.1.1 /C.36), 20C), variant of concern Alpha (20I), variant of concern Delta (21A/J), variant of interest Eta (21D), variant of concern Omicron (21K) and unclassified variant under surveillance (B.1.640). Of these variants, the maximums were detected in patients aged 26 - 35 with 30.26% and 25.26% in 36 - 45. However, 24.67% were in travelers and 75.32% in residents, 35.06% in those vaccinated against COVID-19 and 62.33% in non-vaccinates. The estimated case-fatality rate was 2.44% (107/4374). Conclusion: This work has provided preliminary data on COVID-19 and SARS-CoV-2 variants circulating during the 2020-2021 epidemics in Chad.

关键词： COVID-19 SARS-CoV-2 Genomic Profile Variant Chad