Effet de l'intensification de l'élevage et d'une gestion améliorée de la fumure animale sur l'efficience d'utilisation de l'azote en systèmes mixtes agriculture-élevage au centre du Sénégal

L'efficience d'utilisation des nutriments est l'un des défis majeurs d'une production agricole durable. Les systèmes polyculture-élevage dominent en Afrique subsaharienne ; ils sont essentiellement à bas niveau d'intrants. L'azote dans ces systèmes est recyclé en plusieurs étapes pouvant occasionner des pertes importantes. Cette étude analyse les flux d'azote dans trois systèmes mixtes " ruminants-céréales sèches " du bassin arachidier du Sénégal. Les flux apparents d'azote ont été quantifiés dans 5 fermes pour une année complète en vue de comparer i) un système extensif basé sur l'élevage mobile de zébus et le pâturage des résidus de culture et de la végétation spontanée (système 1), ii) à un système intensif basé sur l'embouche traditionnelle de zébus à l'étable (système 2) et iii) à un système intensif amélioré, proche du système 2, incluant des pratiques améliorées de gestion du fumier telles que la couverture du tas de fumier et son enfouissement à l'épandage (système 3). Trois types d'efficience ont été calculés : l'efficience alimentaire (NPE), l'efficience de recyclage (NRE), et l'efficience globale (NFE). A l'échelle de l'exploitation, la NFE augmente du système 1 au système 3 (de 38% à 89%, respectivement). La NPE est plus élevée que la NRE en système 1 (26% contre 12%) et en système 2 (40% contre 18%). Pour le système 3, la NRE est augmentée de façon importante grâce aux pratiques améliorées de gestion du fumier. Par conséquent, la transition d'un système d'élevage extensif vers un système d'élevage plus intensif a un impact positif sur la productivité des ruminants et des cultures, surtout si cette intensification est associée à des pratiques améliorées de gestion du fumier. La distinction de trois types d'efficience met en question la vision classique de la faible efficience des systèmes agricoles tropicaux car elle souligne leur capacité élevée à recycler les éléments nutritifs

Acute febrile illness and influenza disease burden in a rural cohort dedicated to malaria in Senegal, 2012-2013

Background African populations are considered to be particularly vulnerable to fever illnesses, including malaria, and acute respiratory disease, owing to limited resources and overcrowding. However, the overall burden of influenza in this context is poorly defined and incidence data for African countries are scarce. We therefore studied the fever syndrome incidence and more specifically influenza incidence in a cohort of inhabitants of Dielmo and Ndiop in Sokone district, Senegal. Methods Daily febrile-illness data were prospectively obtained from January 2012 to December 2013 from the cohort of the villages of Dielmo and Ndiop, initially dedicated to the study of malaria. Nasopharyngeal swabs were collected from, and malaria diagnosis tests (thick blood smears) carried out on, every febrile individual during clinical visits; reverse transcriptase- polymerase chain reaction was used to identify influenza viruses in the samples. Binomial negative regression analysis was used to study the relationship between the monthly incidence rate and various covariates. Results In Dielmo and Ndiop, the incidence ofmalaria has decreased, but fever syndromes remain frequent. Among the 1036 inhabitants included in the cohort, a total of 1,129 episodes of fever were reported. Influenza was present all year round with peaks in October-December 2012 and August 2013. The fever, ILI and influenza incidence density rates differed significantly between age groups. At both sites, the adjusted incidence relative risks for fever syndromes and ILI were significantly higher in the [6-24 months) than other age groups: 7.3 (95% CI: [5.7-9.3]) and 16.1 (95% CI: [11.1-23.3]) respectively. The adjusted incidence relative risk for influenza was significantly higher for the [0-6 months) than other age groups: 9.9 (95% CI: [2.9-33.6]). At both sites, incidence density rates were lowest among adults > = 50 years. Conclusions In this rural setting in Senegal, influenza was most frequent among the youngest children. Preventive strategies targeting this population should be implemented

Abundances and search for vertical stratification in the atmospheres of four HgMn stars

Using high resolution, high-S/N archival UVES spectra, we have performed a detailed spectroscopic analysis of 4 chemically peculiar HgMn stars (HD 71066, HD 175640, HD 178065 and HD 221507). Using spectrum synthesis, mean photospheric chemical abundances are derived for 22 ions of 16 elements. We find good agreement between our derived abundances and those published previously by other authors. For the 5 elements that present a sufficient number of suitable lines, we have attempted to detect vertical chemical stratification by analyzing the dependence of derived abundance as a function of optical depth. For most elements and most stars we find no evidence of chemical stratification with typical 3\sigma upper limits of \Delta\log N_elem/N_tot~0.1-0.2 dex per unit optical depth. However, for Mn in the atmosphere of HD 178065 we find convincing evidence of stratification. Modeling of the line profiles using a two-step model for the abundance of Mn yields a local abundance varying approximately linearly by ~0.7 dex through the optical depth range log \tau_5000=-3.6 to -2.8.Comment: 11 figures, 9 tables, table 6-9 (online material), accepted by MNRA

Cost-effectiveness analysis of introducing RDTs for malaria diagnosis as compared to microscopy and presumptive diagnosis in central and peripheral public health facilities in Ghana.

Cost-effectiveness information on where malaria rapid diagnostic tests (RDTs) should be introduced is limited. We developed incremental cost-effectiveness analyses with data from rural health facilities in Ghana with and without microscopy. In the latter, where diagnosis had been presumptive, the introduction of RDTs increased the proportion of patients who were correctly treated in relation to treatment with antimalarials, from 42% to 65% at an incremental societal cost of Ghana cedis (GHS)12.2 (US$8.3) per additional correctly treated patients. In the "microscopy setting" there was no advantage to replacing microscopy by RDT as the cost and proportion of correctly treated patients were similar. Results were sensitive to a decrease in the cost of RDTs, which cost GHS1.72 (US$1.17) per test at the time of the study and to improvements in adherence to negative tests that was just above 50% for both RDTs and microscopy

A GIS for the management of fisheries in West Africa: Preliminary application to the octopus stock in Senegal

A preliminary application of a Geographical Information System (GIS), based on a georeferenced database including data from commercial fishing and oceanographic surveys, and on geographical objects describingthe physical and juridical environment, trawl operations and artisanal fishing sites, is presented. An ArcView environment is used to show spatial and temporal phenomena. Seasonal distribution charts for Octopusvulgaris and for the main associated finfish species on the Senegalese continental shelf reveal that octopuses are particularly abundant on the deep part of the continental shelf off Casamance and the Grande Côteduring the cool season. Warm-season distribution seems to be more coastal. The results allow the interactions between artisanal and industrial fisheries and areas of potential conflicts to be identified. The intensity of these interactions for resource access and space allocation is highly correlated to season. The results also provide alternative explanations for fisheries management, e.g. on the degree of respect for or the relevance of the limitsof regulated fishing areas and spatial fishing unit strategies according to the main seasons