L'origine des mégalithes du Fond de Quarreux (Ardenne, Belgique)

Une étude de la répartition de mégalithes dans la vallée de l’Amblève à sa traversée des quartzites d’âge Cambrien de la Formation de La Venne à l’extrémité occidentale de la crête de la Vecquée a été réalisée. Elle a permis de montrer que les fortes concentrations présentes au Fond de Quarreux s’expliquent essentiellement par des apports des versants adjacents en environnement périglaciaire. L’étude sédimentologique de dépôts des vallées de la Chefna, du Ninglinspo et de l’Amblève elle-même permet de situer dans le Dryas récent des dépôts périglaciaires de couverture. Les mécanismes qui ont conduit à la situation actuelle ont agi de la même façon pendant tous les stades isotopiques marins (S.IM.) les plus froids du Quaternaire, c’est-à-dire les stades pairs #22 à #2. L’application de la force tractrice critique et de la puissance spécifique critique au calcul de la compétence de l’Amblève montre que le cours d’eau ne peut déplacer des blocs de plus 50 cm de diamètre dans les conditions climatiques actuelles. Il en résulte que les radeaux de glace ont dû assurer en climat périglaciaire l’essentiel de l’évacuation des mégalithes qui se sont trouvés dans le lit du cours d’eau depuis qu’il est incisé dans les quartzites cambriens de la Formation de La Venne.Origin of megaliths of the Fond de Quarreux (Ardenne, Belgium). Distribution of megaliths was studied in the Ambleve valley throughout its gorge developed within the quartzites of the Cambrian-aged La Venne Formation (Fond de Quarreux) in the south-eastern part of high Belgium. The high concentration of megaliths at this place can be essentially explained by mass movements which have occurred on the adjacent slopes in periglacial periods of cold Ocean Isotopic Stages in Quaternary times, and especially the coldest ones i.e. even O.I.S.#22 through #2. Stratigraphical studies of deposits in the Chefna and Ambleve valleys allowed us to place final periglacial deposits during the Younger Dryas. The critical shear stress and the critical unit stream power are used in order to evaluate the Ambleve River competence. It results that, under the present climatic conditions, this river cannot move boulders of more than 50 cm in diameter. Hence, it is concluded that ice rafting has been the main process responsible for carrying away the megaliths which have got the Ambleve river bed throughout the Quaternary Period.Peer reviewe

Epidemiological changes in meningococcal meningitis in Niger from 2008 to 2011 and the impact of vaccination.

BACKGROUND: The epidemiology of bacterial meningitis in the African 'meningitis belt' changes periodically. In order to design an effective vaccination strategy, we have examined the epidemiological and microbiological patterns of bacterial meningitis, and especially that of meningococcal meningitis, in Niger during the period 2008-2011. During this period a mass vaccination campaign with the newly developed meningococcal A conjugate vaccine (MenAfriVac®) was undertaken. METHOD: Cerebrospinal fluid samples were collected from health facilities throughout Niger and analysed by culture, seroagglutination and/or speciation polymerase chain reaction, followed by genogrouping PCR for Neisseria meningitidis infections. A sample of strains were analysed by multi-locus sequence typing. RESULTS: N. meningitidis serogroup A cases were prevalent in 2008 and 2009 [98.6% and 97.5% of all N. meningitidis cases respectively]. The prevalence of serogroup A declined in 2010 [26.4%], with the emergence of serogroup W Sequence Type (ST) 11 [72.2% of cases], and the serogroup A meningococcus finally disappeared in 2011. The geographical distribution of cases N. meningitidis serogroups A and W within Niger is described. CONCLUSION: The substantial decline of serogroup A cases that has been observed from 2010 onwards in Niger seems to be due to several factors including a major polysaccharide A/C vaccination campaign in 2009, the introduction of MenAfriVac® in 10 districts at risk in December 2010, the natural dynamics of meningococcal infection and the persistence of serogroup A sequence-type 7 for about 10 years. The emergence of serogroup W strains suggests that there may be a need for serogroup W containing vaccines in Niger in the coming years

Semi-empirical dissipation source functions for ocean waves: Part I, definition, calibration and validation

New parameterizations for the spectra dissipation of wind-generated waves are proposed. The rates of dissipation have no predetermined spectral shapes and are functions of the wave spectrum and wind speed and direction, in a way consistent with observation of wave breaking and swell dissipation properties. Namely, the swell dissipation is nonlinear and proportional to the swell steepness, and dissipation due to wave breaking is non-zero only when a non-dimensional spectrum exceeds the threshold at which waves are observed to start breaking. An additional source of short wave dissipation due to long wave breaking is introduced to represent the dissipation of short waves due to longer breaking waves. Several degrees of freedom are introduced in the wave breaking and the wind-wave generation term of Janssen (J. Phys. Oceanogr. 1991). These parameterizations are combined and calibrated with the Discrete Interaction Approximation of Hasselmann et al. (J. Phys. Oceangr. 1985) for the nonlinear interactions. Parameters are adjusted to reproduce observed shapes of directional wave spectra, and the variability of spectral moments with wind speed and wave height. The wave energy balance is verified in a wide range of conditions and scales, from gentle swells to major hurricanes, from the global ocean to coastal settings. Wave height, peak and mean periods, and spectral data are validated using in situ and remote sensing data. Some systematic defects are still present, but the parameterizations yield the best overall results to date. Perspectives for further improvement are also given.Comment: revised version for Journal of Physical Oceanograph

Airborne dust and high temperatures are risk factors for invasive bacterial disease

Background The Sahel region of West Africa has the highest bacterial meningitis attack and case fatality rate in the world. The effect of climatic factors on patterns of invasive respiratory bacterial disease is not well documented. Objective We aimed to assess the link between climatic factors and occurrence of invasive respiratory bacterial disease in a Sahel region of Niger. Methods We conducted daily disease surveillance and climatic monitoring over an 8-year period between January 1, 2003, and December 31, 2010, in Niamey, Niger, to determine risk factors for bacterial meningitis and invasive bacterial disease. We investigated the mechanistic effects of these factors on Streptococcus pneumoniae infection in mice. Results High temperatures and low visibility (resulting from high concentrations of airborne dust) were identified as significant risk factors for bacterial meningitis. Dust inhalation or exposure to high temperatures promoted progression of stable asymptomatic pneumococcal nasopharyngeal carriage to pneumonia and invasive disease. Dust exposure significantly reduced phagocyte-mediated bacterial killing, and exposure to high temperatures increased release of the key pneumococcal toxin pneumolysin through increased bacterial autolysis. Conclusion Our findings show that climatic factors can have a substantial influence on infectious disease patterns, altering density of pneumococcal nasopharyngeal carriage, reducing phagocytic killing, and resulting in increased inflammation and tissue damage and consequent invasiveness. Climatic surveillance should be used to forecast invasive bacterial disease epidemics, and simple control measures to reduce particulate inhalation might reduce the incidence of invasive bacterial disease in regions of the world exposed to high temperatures and increased airborne dust

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea

Neustonic microplastic and zooplankton abundance was determined in the North Western Mediterranean Sea during a summer cruise between July 9th and August 6th 2010, with a break between July 22th and 25th due to a strong wind event. Ninety percent of the 40 stations contained microplastic particles (size 0.3-5 mm) of various compositions: e.g., filaments, polystyrene, thin plastic films. An average concentration of 0.116 particles/m² was observed. The highest abundances (> 0.36 particles/m²) were observed in the shelf stations. The neustonic plastic particles concentrations were 5 times higher before than after the strong wind event which increased the mixing and the vertical repartition of plastic particles in the upper layers of the water column. The values rise in the same order of magnitude than in the North Pacific Gyre. The average ratio between microplastics and mesozooplankton weights was 0.5 for the whole survey and might induce a potential confusion for zooplankton feeders.Peer reviewe

Significant sequelae after bacterial meningitis in Niger: a cohort study

Beside high mortality, acute bacterial meningitis may lead to a high frequency of neuropsychological sequelae. The Sahelian countries belonging to the meningitis belt experience approximately 50% of the meningitis cases occurring in the world. Studies in Africa have shown that N. meningitidis could cause hearing loss in up to 30% of the cases, exceeding sometimes measles. The situation is similar in Niger which experiences yearly meningitis epidemics and where rehabilitation wards are rare and hearing aids remain unaffordable. The aim of this study was to estimate the frequency of neuropsychological sequelae after acute bacterial meningitis in four of the eight regions of Niger

The F4/AS01B HIV-1 Vaccine Candidate Is Safe and Immunogenic, But Does Not Show Viral Efficacy in Antiretroviral Therapy-Naive, HIV-1-Infected Adults: A Randomized Controlled Trial

The impact of the investigational human immunodeficiency virus type 1 (HIV-1) F4/AS01(B) vaccine on HIV-1 viral load (VL) was evaluated in antiretroviral therapy (ART)-naive HIV-1 infected adults.This phase IIb, observer-blind study (NCT01218113), included ART-naive HIV-1 infected adults aged 18 to 55 years. Participants were randomized to receive 2 (F4/AS01(B)_2 group, N=64) or 3 (F4/AS01(B)_3 group, N=62) doses of F4/AS01(B) or placebo (control group, N=64) at weeks 0, 4, and 28. Efficacy (HIV-1 VL, CD4(+) T-cell count, ART initiation, and HIV-related clinical events), safety, and immunogenicity (antibody and T-cell responses) were evaluated during 48 weeks.At week 48, based on a mixed model, no statistically significant difference in HIV-1 VL change from baseline was demonstrated between F4/AS01(B)_2 and control group (0.073 log(10)copies/mL [97.5% confidence interval (CI): -0.088; 0.235]), or F4/AS01(B)_3 and control group (-0.096 log(10)copies/mL [97.5% CI: -0.257; 0.065]). No differences between groups were observed in HIV-1 VL change, CD4(+) T-cell count, ART initiation, or HIV-related clinical events at intermediate timepoints. Among F4/AS01(B) recipients, the most frequent solicited symptoms were pain at injection site (252/300 doses), fatigue (137/300 doses), myalgia (105/300 doses), and headache (90/300 doses). Twelve serious adverse events were reported in 6 participants; 1 was considered vaccine-related (F4/AS01(B)_2 group: angioedema). F4/AS01(B) induced polyfunctional F4-specific CD4(+) T-cells, but had no significant impact on F4-specific CD8(+) T-cell and anti-F4 antibody levels.F4/AS01(B) had a clinically acceptable safety profile, induced F4-specific CD4(+) T-cell responses, but did not reduce HIV-1 VL, impact CD4(+) T-cells count, delay ART initiation, or prevent HIV-1 related clinical events

Analysing Spatio-Temporal Clustering of Meningococcal Meningitis Outbreaks in Niger Reveals Opportunities for Improved Disease Control

Meningococcal meningitis (MM) is an infection of the meninges caused by a bacterium, Neisseria meningitidis, transmitted through respiratory and throat secretions. It can cause brain damage and results in death in 5–15% of cases. Large epidemics of MM occur almost every year in sub-Saharan Africa during the hot, dry season. Understanding how epidemics emerge and spread in time and space would help public health authorities to develop more efficient strategies for the prevention and the control of meningitis. We studied the spatio-temporal distribution of MM cases in Niger from 2002 to 2009 at the scale of the health centre catchment areas (HCCAs). We found that spatial clusters of cases most frequently occurred within nine districts out of 42, which can assist public health authorities to better adjust allocation of resources such as antibiotics or rapid diagnostic tests. We also showed that the epidemics break out in different HCCAs from year to year and did not follow a systematic geographical direction. Finally, this analysis showed that surveillance at a finer spatial scale (health centre catchment area rather than district) would be more efficient for public health response: outbreaks would be detected earlier and reactive vaccination would be better targeted

Correction: A Seroepidemiological Study of Serogroup A Meningococcal Infection in the African Meningitis Belt.

[This corrects the article DOI: 10.1371/journal.pone.0147928.]

Risk factors for acquisition of meningococcal carriage in the African meningitis belt.

OBJECTIVE: To investigate potential risk factors for acquisition in seven countries of the meningitis belt. METHODS: Households were followed up every 2 weeks for 2 months, then monthly for a further 4 months. Pharyngeal swabs were collected from all available household members at each visit and questionnaires completed. Risks of acquisition over the whole study period and for each visit were analysed by a series of logistic regressions. RESULTS: Over the course of the study, acquisition was higher in: (i) 5-to 14-year olds, as compared with those 30 years or older (OR 3.6, 95% CI 1.4-9.9); (ii) smokers (OR 3.6, 95% CI 0.98-13); and (iii) those exposed to wood smoke at home (OR 2.6 95% CI 1.3-5.6). The risk of acquisition from one visit to the next was higher in those reporting a sore throat during the dry season (OR 3.7, 95% CI 2.0-6.7) and lower in those reporting antibiotic use (OR 0.17, 95% CI 0.03-0.56). CONCLUSIONS: Acquisition of meningococcal carriage peaked in school age children. Recent symptoms of sore throat during the dry season, but not during the rainy season, were associated with a higher risk of acquisition. Upper respiratory tract infections may be an important driver of epidemics in the meningitis belt