93484 research outputs found
Sort by
Application of the FTA elute card coupled with visual colorimetric loop-mediated isothermal amplification for the rapid diagnosis of Streptococcus agalactiae in farmed tilapia (Oreochromis niloticus)
No full textA method combining the FTA Elute card and visual colorimetric loop-mediated isothermal amplification (FTA-e/LAMP) was tested to diagnose Streptococcus agalactiae infections in vitro and in vivo. FTA-e/LAMP consists of two main steps: first, the FTA card is used to extract DNA and then a colorimetric loop-mediated isothermal amplification (LAMP) reaction is carried out on the extracted DNA. In vitro sensitivity was 1.9 x 10(2) CFU/mL, and regarding specificity, all nine S. agalactiae strains tested positive. All Streptococcus spp. tested negative, except for S. dysgalactiae, thereby indicating the need for another set of primers to distinguish this species from S. agalactiae. To diagnose S. agalactiae infections using FTA-e/LAMP in vivo, two experimental trials on juvenile Oreochromis niloticus infected with bovine or piscine strains were carried out. Sensitivity in symptomatic fish was 100%, and 50.7% of fish without signs were positive. All negative control fish tested negative (n = 28). No bacteria were detected after 16 days post-infection (dpi). Accuracy during the first week (1-7 dpi) was 89% and decreased to 44% thereafter (10-22 dpi). FTA-e/LAMP results suggest that this method is a promising tool for early and fast diagnosis of S. agalactiae on tilapia farms
Improved genetic map identified major QTLs for drought tolerance- and iron deficiency tolerance-related traits in groundnut
No full textA deep understanding of the genetic control of drought tolerance and iron deficiency tolerance is essential to hasten the process of developing improved varieties with higher tolerance through genomics-assisted breeding. In this context, an improved genetic map with 1205 loci was developed spanning 2598.3 cM with an average 2.2 cM distance between loci in the recombinant inbred line (TAG 24 x ICGV 86031) population using high-density 58K single nucleotide polymorphism (SNP) "Axiom_Arachis" array. Quantitative trait locus (QTL) analysis was performed using extensive phenotyping data generated for 20 drought tolerance- and two iron deficiency tolerance-related traits from eight seasons (2004-2015) at two locations in India, one in Niger, and one in Senegal. The genome-wide QTL discovery analysis identified 19 major main-effect QTLs with 10.0-33.9% phenotypic variation explained (PVE) for drought tolerance- and iron deficiency tolerance- related traits. Major main-effect QTLs were detected for haulm weight (20.1% PVE), SCMR (soil plant analytical development (SPAD) chlorophyll meter reading, 22.4% PVE), and visual chlorosis rate (33.9% PVE). Several important candidate genes encoding glycosyl hydrolases; malate dehydrogenases; microtubule-associated proteins; and transcription factors such as MADS-box, basic helix-loop-helix (bHLH), NAM, ATAF, and CUC (NAC), and myeloblastosis (MYB) were identified underlying these QTL regions. The putative function of these genes indicated their possible involvement in plant growth, development of seed and pod, and photosynthesis under drought or iron deficiency conditions in groundnut. These genomic regions and candidate genes, after validation, may be useful to develop molecular markers for deploying genomics-assisted breeding for enhancing groundnut yield under drought stress and iron-deficient soil conditions
Epidemiology and prevalence of extended-spectrum beta-lactamase- and carbapenemase-producing Enterobacteriaceae in humans, animals and the environment in West and Central Africa
No full textExtended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) and carbapenemase-producing Enterobacteriaceae (CPE) are widespread. Here we used the 'One Health' approach to determine knowledge gaps on ESBL-E and CPE in West and Central Africa. We searched all articles on ESBL-E and CPE in these African regions published in PubMed, African Journals Online and Google Scholar from 2000 onwards. Among the 1201 articles retrieved, we selected 165 studies (West Africa, 118; Central Africa, 47) with data from 22 of the 26 West and Central Africa countries. Regarding the settings, 136 articles focused only on humans (carriage and/or infection), 6 articles on humans and animals, 13 on animals, 1 on humans and the environment, 8 on the environment and 1 on humans, animals and environments. ESBL-E prevalence ranged from 11-72% in humans and 7-79% in aquatic environments (wastewater). In animals, ESBL-E prevalence hugely varied: 0% in cattle, 11-36% in chickens, 20% in rats, 21-71% in pigs and 32-75% in dogs. The blu(CTX-M-15) gene was the predominant ESBL-encoding gene and was associated with plasmids of incompatibility groups F, H, K, Y, N, II and R. CPE were studied only in humans. Class B metallo-beta-lactamases (NDM) and class D oxacillinases (OXA-48 and OXA-181) were the most common carbapenemases. Our results show major knowledge gaps, particularly on ESBL and CPE in animals and the environment, that might limit antimicrobial resistance management in these regions. The results also emphasise the urgent need to improve active surveillance programmes in each country and to support antimicrobial stewardship
Growth and collapse of the 2018-2019 lava dome of Merapi volcano
No full textLava dome collapses are a major threat to the population living near such volcanoes. However, it is not possible to forecast collapses reliably because the mechanisms are not clearly understood, due partly to the lack of continuous observations of such events. To address this need for field data, we have developed new monitoring stations, which are adapted to the volcanic environment. The stations tracked the complete evolution of the 2018-2019 lava dome of Merapi volcano (Indonesia) and the associated pyroclastic density currents. During the 14 months of activity, the stations acquired thermal, high-resolution visual images and movies in stereoscopic configurations. The dome developed on a plateau flanked by steep sides (similar to 40 degrees-50 degrees) inside the crater, which was open to the SE. We observed that the dome behaved in a viscous manner (with a viscosity of 10(9) Pa s for the interior to 10(13) Pa s for external parts of the dome) on gentle slopes, and in a brittle way (friction angle similar to 35 degrees, cohesion < 100 kPa) on slopes steeper than 35 degrees. Thus, the lava dome was unable to grow on the outer slopes of the plateau and a significant volume of lava (350-750 x 10(3) m(3)) accumulated and collapsed daily to the SE in relatively small volumes (< 10,000 m(3)), preventing the lava dome from reaching the critical volume necessary for pyroclastic density currents to form and threaten the surrounding population. The cause of the small and frequent collapses was purely gravitational during the dome activity. This suggests that relatively small differences in the summit morphology can control dome evolution, favouring either a lava dome restricted to a small volume and leading to only a minor crisis, or more voluminous dome growth and a catastrophic collapse
Une autre histoire du développement : l'échec perpétuel. Tome 1 : Le Grand développement 1
No full textDepuis les années 1960, l'aide aux pays du Sud (pays en développement) a connu des changements majeurs tant dans les institutions (passage au multilatéralisme p.ex.) que dans les modalités d'intervention (ultralibéralisme et participation sociale p.ex.). Malgré cette capacité d'adaptation, le constat est accablant : les pays du Sud les plus développés, tels les pays émergents, ne doivent rien aux programmes internationaux de développement et les pays les moins développés n'ont amorcé aucun démarrage. Du constat d'inefficacité chronique émergent trois questions. Les deux premières concernent la pérennité de l'inefficacité : d'un point de vue politique, comment un tel dispositif se maintient-il ? Du point de vue conceptuel, sur quel malentendu repose le développement ? L'inefficacité conduit à examiner depuis le niveau international jusqu'aux terrains les pratiques d'interventions et leurs résultats en même temps que les acteurs et leurs discours.L'aide inefficace tient largement à l'entente entre pays du Sud et pays du Nord, tous plus préoccupés par les moyens mis en oeuvre que par des résultats tangibles.La troisième interrogation concerne les récipiendaires qui, eux, souhaitent des résultats : comment refondre le dispositif de développement pour améliorer l'efficacité des programmes ? Si l'échec est la norme, les rares succès méritent l'attention.Or, des succès d'ampleur nationale ont existé avant la dérégulation mondiale des années 1990. C'est le cas des petits producteurs étroitement encadrés par l'Etat au Mexique et de ceux de Thaïlande en régime libéral avec le succès phénoménal du maraîchage d'exportation. Ces deux pays montrent la réactivité des paysanneries dès lors que les prix sont incitatifs et les crédits adaptés. Plus précisément, il s'agit moins d'économie que de politique quand les prix sont soutenus et que le crédit est adapté au risque inhérent aux petits producteurs : c'est ce que j'appelle le "Grand développement" (tomes 1 et 2). Le "Petit développement" est l'innombrable somme des projets locaux (participation sociale, vulgarisation, microcrédits, aides diverses, etc.). L'échec y est chronique par le malentendu paternaliste sur la nature des paysanneries et par l'absence d'intérêt envers le Grand développement. Le Système de développement est l'objet du tome
Assessment of groundwater quality in the Bokoya Massif (Central Rif, Northern Morocco) using several analytical techniques
No full textSince ancient times, groundwater exploitation has been the ideal and least expensive means of stabilizing populations and avoiding migratory flows, especially in rural and arid areas. However, the uncontrolled extraction and use of groundwater can lead to contamination by natural processes or human activities. In this work, we studied the quality of groundwater sources in the Bokoya Massif, Morocco. During April 2018, a total of 96 water samples were taken from 81 wells and 15 springs distributed across the entire massif. Various physicochemical analyses of the samples were performed, including analyses of EC, TDS, HCO3-, SO42-, Ca2+, Mg2+, Na+, K+, PO43-, NO3-, NO2-, NH4+, and Cl-. These analyses showed that the water samples were neutral to slightly basic and strongly mineralized. From a potability perspective, the main issues with the studied groundwater sources were their hardness (98% of the water samples were hard or very hard) and their high nitrate concentrations (36% of the samples exceeded the nitrate limit specified by the World Health Organization). The nitrate concentrations were higher in the samples taken in urbanized areas. In terms of their suitability for irrigation, only 41 of the samples (42.7%) presented water quality ranging from excellent to permissible according to the Wilcox classification. In addition to this quality problem, the flow from each source decreased by an average of of 73% during the dry period, with 24 of the water sources drying up completely
Triggered crustal earthquake swarm across subduction segment boundary after the 2016 Pedernales, Ecuador megathrust earthquake
No full textMegathrust ruptures and the ensuing postseismic deformation cause stress changes that may induce seismicity on upper plate crustal faults far from the coseismic rupture area. In this study, we analyze seismic swarms that occurred in the north Ecuador area of Esmeraldas, beginning two months after the 2016 M-w 7.8 Pedernales, Ecuador megathrust earthquake. The Esmeraldas region is 70 km from the Pedernales rupture area in a separate segment of the subduction zone. We characterize the Esmeraldas sequence, relocating the events using manual arrival time picks and a local a-priori 3D velocity model. The earthquake locations from the Esmeraldas sequence outline an upper plate fault or shear zone. The sequence contains one major swarm and several smaller swarms. Moment tensor solutions of several events include normal and strike-slip motion and non-double-couple components. During the main swarm, earthquake hypocenters increase in distance from the first event over time, at a rate of a few hundred meters per day, consistent with fluid diffusion. Events with similar waveforms occur within the sequence, and a transient is seen in time series of nearby GPS stations concurrent with the seismicity. The events with similar waveforms and the transient in GPS time series suggest that slow aseismic slip took place along a crustal normal fault during the sequence. Coulomb stress calculations show a positive Coulomb stress change in the Esmeraldas region, consistent with seismicity being triggered by the Pedernales mainshock and large aftershocks. The characteristics of the seismicity indicate that postseismic deformation involving fluid flow and slow slip activated upper plate faults in the Esmeraldas area. These findings suggest the need for further investigation into the seismic hazard potential of shallow upper plate faults and the potential for megathrust earthquakes to trigger slow-slip and shallow seismicity across separate segments of subduction zones
Stock enhancement of Culter mongolicus : assessment of growth, recapture and release size in the Yangtze lakes
No full textThe release of piscivorous fishes is considered crucial to alleviate eutrophication and fish miniaturization, as well as to develop sustainable fisheries management strategy for Yangtze lakes. In order to promote the stock enhancement programme of a new released piscivorous fish species Culter mongolicus, growth, recapture rates, reproduction and impact of size-at-release for hatchery-reared juveniles were evaluated in three Yangtze shallow lakes during a five-year period. C. mongolicus displayed important growth capability with a body weight reaching commercial size (> 500 g) during the second released year and about 1500 g in the third year. However, a sharp decline of growth appeared quickly after several years of releasing, indicating possible issue of density-dependent growth caused by over-stocking. The recapture rates for one-month-old juveniles were less than 5%, but increased to more than 20 % when one-year-old fingerlings were selected as release size. Gonad examination and catch analysis showed that released juveniles could not succeed in building the recruitment stock due to over fishing. Thus hatchery-reared juveniles should be released annually. Management actions that prioritize the release of fewer but larger fingerlings will improve the recapture rate and subsequent economic benefit. A new stock enhancement strategy that changes the present release-catch cycle from two years to one was proposed accordingly
