53 research outputs found
La brucellose en Afrique occidentale et son incidence sur la santĂ© publique. RĂ©sultats de dix enquĂȘtes Ă©pidĂ©miologiques effectuĂ©es en CĂŽte-d'Ivoire, Haute-Volta et Niger de 1970 Ă 1973
Utilisant ring-tests, rĂ©actions allergologiques et sĂ©rologiques, les auteurs ont Ă©tudiĂ© l'Ă©pidĂ©miologie de la brucellose en Afrique de l'Ouest au cours de dix enquĂȘtes couplĂ©es, humaines et animales, oĂč plus de 120 villages ont Ă©tĂ© prospectĂ©s par sondage alĂ©atoire. Chez les animaux, 4 108 ring-tests et 1 225 sĂ©rologies et, chez l'homme, 12 739 intradermo-rĂ©actions et 11 990 sĂ©rologies ont Ă©tĂ© effectuĂ©es. La maladie animale existe partout et concerne les diffĂ©rentes espĂšces, en particulier les bovins, mais Ă des taux trĂšs variables selon les rĂ©gions, le Sud Ă©tant plus atteint que le Nord. Chez l'homme, la maladie intĂ©resse essentiellement les populations pastorales du sahel, tandis qu'ailleurs, elle affecte surtout les bergers et leurs familles, les rĂ©actions allergologiques positives Ă©tant plus frĂ©quentes chez l'homme que chez la femme et chez l'adulte que chez l'enfan
Epidemiology of Coxiella burnetii infection in Africa: a OneHealth systematic review
Background:
Q fever is a common cause of febrile illness and community-acquired pneumonia in resource-limited settings. Coxiella burnetii, the causative pathogen, is transmitted among varied host species, but the epidemiology of the organism in Africa is poorly understood. We conducted a systematic review of C. burnetii epidemiology in Africa from a âOne Healthâ perspective to synthesize the published data and identify knowledge gaps.<p></p>
Methods/Principal Findings:
We searched nine databases to identify articles relevant to four key aspects of C. burnetii epidemiology in human and animal populations in Africa: infection prevalence; disease incidence; transmission risk factors; and infection control efforts. We identified 929 unique articles, 100 of which remained after full-text review. Of these, 41 articles describing 51 studies qualified for data extraction. Animal seroprevalence studies revealed infection by C. burnetii (≤13%) among cattle except for studies in Western and Middle Africa (18â55%). Small ruminant seroprevalence ranged from 11â33%. Human seroprevalence was <8% with the exception of studies among children and in Egypt (10â32%). Close contact with camels and rural residence were associated with increased seropositivity among humans. C. burnetii infection has been associated with livestock abortion. In human cohort studies, Q fever accounted for 2â9% of febrile illness hospitalizations and 1â3% of infective endocarditis cases. We found no studies of disease incidence estimates or disease control efforts.<p></p>
Conclusions/Significance:
C. burnetii infection is detected in humans and in a wide range of animal species across Africa, but seroprevalence varies widely by species and location. Risk factors underlying this variability are poorly understood as is the role of C. burnetii in livestock abortion. Q fever consistently accounts for a notable proportion of undifferentiated human febrile illness and infective endocarditis in cohort studies, but incidence estimates are lacking. C. burnetii presents a real yet underappreciated threat to human and animal health throughout Africa.<p></p>
From bore-soliton-splash to a new wave-to-wire wave-energy model
We explore extreme nonlinear water-wave amplification in a contraction or, analogously, wave amplification in crossing seas. The latter case can lead to extreme or rogue-wave formation at sea. First, amplification of a solitary-water-wave compound running into a contraction is disseminated experimentally in a wave tank. Maximum amplification in our boreâsolitonâsplash observed is circa tenfold. Subsequently, we summarise some nonlinear and numerical modelling approaches, validated for amplifying, contracting waves. These amplification phenomena observed have led us to develop a novel wave-energy device with wave amplification in a contraction used to enhance wave-activated buoy motion and magnetically induced energy generation. An experimental proof-of-principle shows that our wave-energy device works. Most importantly, we develop a novel wave-to-wire mathematical model of the combined wave hydrodynamics, wave-activated buoy motion and electric power generation by magnetic induction, from first principles, satisfying one grand variational principle in its conservative limit. Wave and buoy dynamics are coupled via a Lagrange multiplier, which boundary value at the waterline is in a subtle way solved explicitly by imposing incompressibility in a weak sense. Dissipative features, such as electrical wire resistance and nonlinear LED loads, are added a posteriori. New is also the intricate and compatible finite-element spaceâtime discretisation of the linearised dynamics, guaranteeing numerical stability and the correct energy transfer between the three subsystems. Preliminary simulations of our simplified and linearised wave-energy model are encouraging and involve a first study of the resonant behaviour and parameter dependence of the device
Origin of Ozone NO(x) in the Tropical Troposphere: A Photochemical Analysis of Aircraft Observations Over the South Atlantic Basin
The photochemistry of the troposphere over the South Atlantic basin is examined by modeling of aircraft observations up to 12-km altitude taken during the TRACE A expedition in September-October 1992. A close balance is found in the 0 to 12-km column between photochemical production and loss Of O3, with net production at high altitudes compensating for weak net loss at low altitudes. This balance implies that O3 concentrations in the 0-12 km column can be explained solely by in situ photochemistry; influx from the stratosphere is negligible. Simulation of H2O2, CH3OOH, and CH2O concentrations measured aboard the aircraft lends confidence in the computations of O3 production and loss rates, although there appears to be a major gap in current understanding of CH2O chemistry in the marine boundary layer. The primary sources of NO(x) over the South Atlantic Basin appear to be continental (biomass burning, lightning, soils). There is evidence that NO(x) throughout the 0 to 12-km column is recycled from its oxidation products rather than directly transported from its primary sources. There is also evidence for rapid conversion of HNO3 to NO(x) in the upper troposphere by a mechanism not included in current models. A general representation of the O3 budget in the tropical troposphere is proposed that couples the large scale Walker circulation and in situ photochemistry. Deep convection in the rising branches of the Walker circulation injects NO(x) from combustion, soils, and lightning to the upper troposphere, leading to O3 production; eventually, the air subsides and net O3 loss takes place in the lower troposphere, closing the O3 cycle. This scheme implies a great sensitivity of the oxidizing power of the atmosphere to NO(x) emissions in the tropics
Brucellosis in Sub-Saharan Africa:Current challenges for management, diagnosis and control
Brucellosis is a highly contagious zoonosis caused by bacteria of the genus Brucella and affecting domestic and wild mammals. In this paper, the bacteriological and serological evidence of brucellosis in Sub-Saharan Africa (SSA) and its epidemiological characteristics are discussed. The tools available for the diagnosis and treatment of human brucellosis and for the diagnosis and control of animal brucellosis and their applicability in the context of SSA are presented and gaps identified. These gaps concern mostly the need for simpler and more affordable antimicrobial treatments against human brucellosis, the development of a B. melitensis vaccine that could circumvent the drawbacks of the currently available Rev 1 vaccine, and the investigation of serological diagnostic tests for camel brucellosis and wildlife. Strategies for the implementation of animal vaccination are also discussed.Publishe
Towards silicon-photonics based THz links?
International audienceWith the surge in mega-data communications, wireless networks are entering a revolution which has now taken off with 5G. From a user perspective, the main challenge is providing fast and agile connections in all usage scenarios. Considering the data-rates expected to be delivered to users (some urban areas with 1000 users per cell) the overall data collected by future base-stations will rapidly reach the Terabit/s range, translating to peak data-rates per user of around 1 Gbit/s. In this context point-to-point ultra-fast links with ultra-low latency must be enabled
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