Diagnostic des Contraintes de Mise en Valeur Rizicole des Sols Fluvio-Marins du Marigot de Bignona, Basse Casamance, Sénégal

Situé en Basse Casamance, sud-ouest du Sénégal, le marigot de Bignona, a été durement éprouvé par la sécheresse des années 1970. La baisse pluviométrique et de l’écoulement fluvial y ont entraîné la salinisation et l’acidification des rizières. L’objectif de l’étude est d’analyser les contraintes de mise en valeur rizicole des sols fluvio-marins du marigot de Bignona pour la proposition de stratégies d’aménagement durables. Sept localités (Tenghory Transgambienne, Tenghory, Boutolate, Bindago, Piran, Koutenghor et Diourou) ont été choisies. Ce choix est motivé par l’ampleur de la dégradation des rizières par salinisation et acidification. La méthodologie comprend des enquêtes de terrain, l’analyse d’échantillons de sol et une cartographie de l’occupation du sol. Les résultats montrent une salinisation et une acidification généralisées des rizières dans le marigot de Bignona, avec une conductivité électrique comprise entre 0,01 et 9,77 mS/cm et un pH entre 4,7 à 7,8. L’intrusion marine et l’oxydation de la pyrite sont, respectivement, les principaux facteurs responsables de la salinisation et l’acidification de ces sols. L’accumulation du fer en conditions anaérobies induit une autre contrainte, en l’occurrence la toxicité ferreuse. La combinaison de stratégies apparaît comme la meilleure méthode pour développer la riziculture dans le marigot de Bignona. vvvvLocated in Lower Casamance, southwestern Senegal, the Bignona valley was severely affected by the drought of the 1970s. The drop in rainfall and river flow brought about salinization and acidification of rice fields. The objective of this study is to analyze the constraints of rice growing in fluviomarine soils of the Bignona valley, in order to propose sustainable management strategies. Seven localities (Tenghory Transgambienne, Tenghory, Boutolate, Bindago, Piran, Koutenghor and Diourou) were selected. This choice is motivated by the important degradation of rice fields by salinization and acidification. The methodology includes field surveys, soil sample analysis and land cover mapping. The results show widespread salinization and acidification of rice-field soils, with soil electrical conductivity between 0.01 and 9.77 mS/cm and pH values between 4,7 to 7,8. Marine intrusion and pyrite oxidation are, respectively, the main factors responsible for the salinization and acidification of these soils. The iron accumulation under anaerobic conditions induces another soil management constraint, namely the iron toxicity, which greatly affects the performance of rice growing. The combination of strategies appears as the most appropriate method to promote rice growing in the Bignona valley

Origin of trunk damage in West African savanna trees: the interaction of fire and termites

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Caractérisation de souches de Bacillus entomopathogènes isolées au Sénégal et étude de leur toxicité pour les vecteurs du paludisme

Notre étude porte sur la recherche des nouvelles souches de #Bacillus entomopathogènes susceptibles d'être utilisées dans la lutte contre les insectes vecteurs du paludisme au Sénégal. 194 souches de #Bacillus thuringiensis et 9 souches de #Bacillus sphaericus ont été isolées de l'environnement ou d'insectes. Le typage flagellaire, l'analyse du profil électrophorétique des protéines cristallines et les bioessais sur insectes ont permis d'isoler 27 souches actives sur moustiques (#Culex pipiens, #Aedes aegypti et #Anopheles stephensi). Le paludisme étant un problème majeur de santé publique au Sénégal, la toxicité de ces souches a été recherchée vis à vis des 2 principaux vecteurs du paludisme au Sénégal, #Anopheles gambiae et #Anopheles arabiensis. Ceci nous a permis de mettre en évidence parmi ces 27 souches, 20 souches ayant un niveau d'activité comparable à celui de #Bacillus thuringiensis israelenis qui est actuellement la souche la plus active sur moustiques. Ces souches ont des DL50 autour de 10(exp -5) pour #Anopheles gambiae et #Anopheles arabiensis$ et 70% d'entre elles sont du sérotype H14. Elles peuvent être retenues comme candidates à la lutte biologique contre les vecteurs du paludisme au Sénégal. (Résumé d'auteur

Caractérisation de souches de Bacillus entomopathogènes isolées au Sénégal et étude de leur toxicité pour les vecteurs du paludisme

Notre étude porte sur la recherche des nouvelles souches de #Bacillus entomopathogènes susceptibles d'être utilisées dans la lutte contre les insectes vecteurs du paludisme au Sénégal. 194 souches de #Bacillus thuringiensis et 9 souches de #Bacillus sphaericus ont été isolées de l'environnement ou d'insectes. Le typage flagellaire, l'analyse du profil électrophorétique des protéines cristallines et les bioessais sur insectes ont permis d'isoler 27 souches actives sur moustiques (#Culex pipiens, #Aedes aegypti et #Anopheles stephensi). Le paludisme étant un problème majeur de santé publique au Sénégal, la toxicité de ces souches a été recherchée vis à vis des 2 principaux vecteurs du paludisme au Sénégal, #Anopheles gambiae et #Anopheles arabiensis. Ceci nous a permis de mettre en évidence parmi ces 27 souches, 20 souches ayant un niveau d'activité comparable à celui de #Bacillus thuringiensis israelenis qui est actuellement la souche la plus active sur moustiques. Ces souches ont des DL50 autour de 10(exp -5) pour #Anopheles gambiae et #Anopheles arabiensis$ et 70% d'entre elles sont du sérotype H14. Elles peuvent être retenues comme candidates à la lutte biologique contre les vecteurs du paludisme au Sénégal. (Résumé d'auteur

Effects of shade tree legumes on cacao biomass and bean yields after 20 years of intercropping in Ivory Coast

International audienceThe choice of tree species planted with cacao trees is essential for ensuring the efficiency and sustainability of cacao farming systems. This raises the question of the long-term impact of associated tree legumes (ATLs) on cacao bean yields and biomass accumulation. This study was carried out in accordance with four-block randomised experimental design in Divo (Ivory Coast, West Africa). The study involved cacao-Albizia lebbeck (Cacao-Alb) and cacao-Acacia mangium (Cacao-Aca) intercrops and unshaded cacao plots (Control). After 20 years of intercropping, we assessed cacao dendrometry (height, circumference, biomass, and biomass C-stock) and production (number of pods per tree and bean yield at the plot level) as well as soil fertility (soil organic matter (SOM) concentration) at various distances from ATLs (D1:0–1.75 m; D2:3.25–5 m; D3:7–9 m). The distance from the ATLs had no significant effect on the measured cacao dendrometric parameters, except for cacao height. In contrast, the Cacao-Aca association had a negative impact on the SOM concentration (−22%), cacao tree height (−6.15%), and productivity parameters (biomass: −12.4%; bean yield: −43%). However, Cacao-Alb and the Control had no significant differences in terms of SOM, tree biomass, or bean production. Intercropping cacao with the tested tree legumes did not enhance cacao productivity and, in some cases, hindered it, depending on the ATL species. This study highlighted the importance of identifying appropriate shade tree legume species that could be promoted in cacao-based agroforestry systems

Role of deoxyribose catabolism in colonization of the murine intestine by pathogenic escherichia coli strains

International audienceWe previously suggested that the ability to metabolize deoxyribose, a phenotype encoded by the deoK operon, is associated with the pathogenic potential of Escherichia coli strains. Carbohydrate metabolism is thought to provide the nutritional support required for E. coli to colonize the intestine. We therefore investigated the role of deoxyribose catabolism in the colonization of the gut, which acts as a reservoir, by pathogenic E. coli strains. Molecular and biochemical characterization of 1,221 E. coli clones from various collections showed this biochemical trait to be common in the E. coli species (33.6%). However, multivariate analysis evidenced a higher prevalence of sugar-metabolizing E. coli clones in the stools of patients from countries in which intestinal diseases are endemic. Diarrhea processes frequently involve the destruction of intestinal epithelia, so it is plausible that such clones may be positively selected for in intestines containing abundant DNA, and consequently deoxyribose. Statistical analysis also indicated that symptomatic clinical disorders and the presence of virulence factors specific to extraintestinal pathogenic E. coli were significantly associated with an increased risk of biological samples and clones testing positive for deoxyribose. Using the streptomycin- treated-mouse model of intestinal colonization, we demonstrated the involvement of the deoK operon in gut colonization by two pathogenic isolates (one enteroaggregative and one uropathogenic strain). These results, indicating that deoxyribose availability promotes pathogenic E. coli growth during host colonization, suggest that the acquisition of this trait may be an evolutionary step enabling these pathogens to colonize and persist in the mammalian intestine

Describing, analysing and understanding the effects of the introduction of HIV self-testing in West Africa through the ATLAS programme in Côte d'Ivoire, Mali and Senegal.

BACKGROUND: The ATLAS programme aims to promote and implement HIV self-testing (HIVST) in three West African countries: Côte d'Ivoire, Mali, and Senegal. During 2019-2021, in close collaboration with the national AIDS implementing partners and communities, ATLAS plans to distribute 500,000 HIVST kits through eight delivery channels, combining facility-based, community-based strategies, primary and secondary distribution of HIVST. Considering the characteristics of West African HIV epidemics, the targets of the ATLAS programme are hard-to-reach populations: key populations (female sex workers, men who have sex with men, and drug users), their clients or sexual partners, partners of people living with HIV and patients diagnosed with sexually transmitted infections and their partners. The ATLAS programme includes research support implementation to generate evidence for HIVST scale-up in West Africa. The main objective is to describe, analyse and understand the social, health, epidemiological effects and cost-effectiveness of HIVST introduction in Côte d'Ivoire, Mali and Senegal to improve the overall HIV testing strategy (accessibility, efficacy, ethics). METHODS: ATLAS research is organised into five multidisciplinary workpackages (WPs): Key Populations WP: qualitative surveys (individual in-depth interviews, focus group discussions) conducted with key actors, key populations, and HIVST users. Index testing WP: ethnographic observation of three HIV care services introducing HIVST for partner testing. Coupons survey WP: an anonymous telephone survey of HIVST users. Cost study WP: incremental economic cost analysis of each delivery model using a top-down costing with programmatic data, complemented by a bottom-up costing of a representative sample of HIVST distribution sites, and a time-motion study for health professionals providing HIVST. Modelling WP: Adaptation, parameterisation and calibration of a dynamic compartmental model that considers the varied populations targeted by the ATLAS programme and the different testing modalities and strategies. DISCUSSION: ATLAS is the first comprehensive study on HIV self-testing in West Africa. The ATLAS programme focuses particularly on the secondary distribution of HIVST. This protocol was approved by three national ethic committees and the WHO's Ethical Research Committee

Multicenter Study of Street Foods in 13 Towns on Four Continents by the Food and Environmental Hygiene Study Group of the International Network of Pasteur and Associated Institutes

Archives de Journal of Food Protection (https://jfoodprotection.org/toc/food/65/1)International audienceAn international multicenter study of ready-to-eat foods, sandwiches, and ice creams or sorbets sold in the streets and their vendors was carried out to assess the microbiological quality of these foods and to identify characteristics of the vendors possibly associated with pathogens. Thirteen towns in Africa, America, Asia, and Oceania were involved in the study. A single protocol was used in all 13 centers: representative sampling was by random selection of vendors and a sample of foods bought from each of these vendors at a time and date selected at random. Microbiological analyses were carried out using standardized Association Française de Normalisation methods, and the use of a standardized questionnaire to collect data concerning the characteristics of the vendors. Fifteen surveys were carried out, with 3,003 food samples from 1,268 vendors. The proportion of unsatisfactory food samples was between 12.7 and 82.9% for ice creams and sorbets and between 11.3 and 92% for sandwiches. For ice creams and sorbets, the sale of a large number of units (>80 per day) increased the risk of unsatisfactory food by a factor of 2.8 (95% confidence interval [CI]: 1.5 to 5.1), lack of training in food hygiene by 6.6 (95% CI: 1.1 to 50). and by a factor of 2.8 (95% CI: 1.4 to 5.4) for mobile vendors. These risk factors were not identified for sandwiches, this difference may be due to the presence of a cooking step in their preparation. These results show that the poor microbiological quality of these street foods constitutes a potential hazard to public health, that the extent of this hazard varies between the cities studied, and that vendors' health education in food safety is a crucial factor in the prevention of foodborne infections