Prévalence de la brucellose, chlamydiose et toxoplasmose chez les petits ruminants au Mali : résultats d’une enquête séro-épidemiologique

Au Mali, l’élevage des espèces à cycle court en général et celui des petits ruminants en particulier constitue une source précieuse de revenus et de protéines pour les populations. Cependant, au nombre des contraintes à l’amélioration de la productivité de cet élevage, figurent les pertes en reproduction, dont les causes demeurent mal connues. Les données relatives au rôle de certaines infections microbiennes comme la brucellose à Brucella ovis, chlamydiose et la toxoplasmose sont quasi inexistantes. L’objet de la présente étude a été d’évaluer la prévalence sérologique de ces pathologies, susceptibles de causer des pertes en reproduction chez ces espèces animales. Elle a couvert quatre sites dont Kéniébougou (Cercle de Ségou), Nioro (Cercle de Nioro), Bougouni (Cercle de Bougouni) et Briga (Cercle de Koro), choisis en collaboration étroite avec les services techniques d’encadrement et éleveurs de petits ruminants desdites localités. Au total 872 sérums (368 ovins et 504 caprins) issus des sujets présentant des signes de perte en reproduction ont été testés par la méthode Elisa indirecte. Parmi ceux-ci, 81 (9,28 %) se sont révélés positifs (1,26 % en brucellose à Brucella ovis, 3,55 % en chlamydiose à Chlamydia abortus et 4,47 % en toxoplasmose à Toxoplasma gondii). Les anticorps mis en évidence sont considérés comme d’origine infectieuse, les animaux n’ayant jamais été vaccinés contre les maladies investiguées, ce qui confirme la circulation des agents étiologiques des trois infections abortives parmi les populations de petits ruminants au Mali

Sélection participative des variétés de sorgho à l’aide d’essais multilocaux dans deux zones cibles

Variety development for sorghum requires multi-location testing for yielding ability. In West-Africa, where adaptation to specific zones of rainfall distribution is crucial for the success of a variety, these multi-location trials need to be conducted within any specific zone of adaptation. As most West-African countries lack sufficient research station capacity for this type of yield testing, we have developed a trial design and experiments with a sharing of roles and responsibilities between farmers, NGO's and researchers that allow for effective varietal differentiation in the target environment across a wide range of production conditions within a zone. The added advantage of farmer participation in this early stage of variety evaluation is that farmers also evaluate a wide range of other traits that are essential for making a variety a success

Elastic-viscoplastic notch correction methods

International audienceNeuber's type methods are dedicated to obtain fast estimation of elastic-plastic state at stress concentrations from elastic results. To deal with complex loadings, empirical rules are necessary and do not always give satisfying results. In this context, we propose a new approach based on homogenization techniques. The plastic zone is viewed as an inclusion in an infinite elastic matrix which results in relationships between the elastic solution of the problem and estimated stress-strain state at the notch tip. Three versions of the notch correction method are successively introduced, a linear one which directly uses Eshelby's solution to compute stresses and strains at the notch, a non-linear method that takes into account plastic accommodation through a ββ-rule correction and, finally, the extended method that is based on the transformation field analysis methods. All the notch correction methods need calibration of localization tensors. The corresponding procedures are proposed and analyzed. The methods are compared on different simulation cases of notched specimens and the predictive capabilities of the extended method in situations where plasticity is not confined at the notch are demonstrated. Finally, the case of a complex multiperforated specimen is addressed

Clinical risk factors associated with multidrug-resistant tuberculosis (MDR-TB) in Mali

Background: MDR-TB is a major threat to global TB control. In 2015, 580,000 were treated for MDR-TB worldwide. The worldwide roll-out of GeneXpert MTB/RIF® has improved diagnosis of MDR-TB; however, in many countries laboratories are unable to assess drug resistance and clinical predictors of MDR-TB could help target suspected patients. In this study, we aimed to determine the clinical factors associated with MDR-TB in Bamako, Mali. Methods: We performed a cross-sectional study of 214 patients with presumed MDR-TB admitted to University of Bamako Teaching Hospital, Point-G between 2007 and 2016. We calculated crude and adjusted odds ratios for MDR-TB disease diagnosis using SPSS. Results: We found that age ≤40 years (OR = 2.56. 95% CI: 1.44–4.55), two courses of prior TB treatment (OR = 3.25, 95% CI: 1.44–7.30), TB treatment failure (OR = 3.82, 95% CI 1.82–7.79), sputum microscopy with 3+ bacilli load (OR = 1.98, 95% CI: 1.13–3.48) and a history of contact with a TB patient (OR = 2.48, 95% CI: 1.11–5.50) were significantly associated with confirmation of MDR-TB disease. HIV was not a risk factor for MDR-TB (aOR = 0.88, 95% CI: 0.34–1.94). Conclusion: We identified several risk factors that could be used to identify MDR-TB suspects and prioritize them for laboratory confirmation. Prospective studies are needed to understand factors associated with TB incidence and clinical outcomes of TB treatment and disease. Keywords: Multi-Drug Resistant Tuberculosis, Risk factors, Mal

Electromechanical models of ferroelectric materials

Models of the electromechanical behaviour of ferroelectric materials are reviewed. Starting from the constitutive relationships for piezoelectrics and estimates of the response of piezoelectric composites, the development of models is traced from the macro-scale through to the micro-scale. Derivations of models based on extensions of classical plasticity and crystal plasticity theory are given, following the literature, and example applications of these models are shown. The formation of domain patterns is discussed and minimum energy methods based on the concept of compatibility are used to derive typical domain patterns for tetragonal and rhombohedral ferroelectrics. Methods for modelling the evolution of domain patterns are described. Finally the outlook for future directions in modelling of ferroelectrics is discussed