Prevalence of occult hepatitis B virus infection among blood donors in Ouagadougou, Burkina Faso

Background: In Burkina Faso, the polymerase chain reaction (PCR) assay is not routinely used in the biological qualification of blood donations and this constitutes a risk factor for the transmission of occult hepatitis B virus (HBV) infection during blood transfusion. The objective of this study is to determine the prevalence of occult B infection (OBI) among blood donors for the purposes of improved blood safety in Burkina Faso. Methodology: A descriptive cross-sectional study of 300 HBsAg negative blood donors was conducted in the city of Ouagadougou, Burkina Faso from April to October 2020. Anti-HBc antibody was determined using the BOSON® brand rapid tests. HBV DNA was detected in 75 selected donors by real-time PCR (rt PCR) using the 7500 Fast Real Time PCR assay technique. Results: Of the 300 HBsAg negative donors, 208 (69.3%) were males while 92 (30.7%) were females, with average age of 30.18 years. Anti-HBc antibody was detected in 39 cases (13%). Of the 75 donor samples tested by rt PCR, 3 (4%) were positive for HBV DNA (occult B infection); 2 of which were anti-HBc antibody positive (seropositive OBI) while 1 was anti-HBc antibody negative (seronegative OBI). Conclusion: Given the prevalence of OBI of 4% in this study and its consequences in blood recipients, it appears necessary that in addition to the classic serological markers of hepatitis B, to test for the presence of HBV DNA among blood donors in order to improve transfusion safety. Keywords: Prevalence, Occult B infection; Blood donors, Ouagadougou.   French title: Prévalence de l'infection occulte par le virus de l'hépatite B chez les donneurs de sang à Ouagadougou, Burkina Faso Contexte: Au Burkina Faso, la polymérase chain réaction (PCR) n’est pas utilisée lors de la qualification biologique des dons et cela constitue un facteur de risque de transmission de l’Infection Occulte du virus B (VHB) lors des transfusions sanguines. L’objectif de cette étude était de déterminer la prévalence de l’infection occulte B chez les donneurs de sang en vue d’une meilleure sécurité transfusionnelle. Méthodologie: Une étude transversale prospective, réalisée d’avril à octobre 2020 dans la ville de Ouagadougou incluant 300 donneurs de sang AgHBs négatif. L’anticorps anti HBc a été déterminé par les tests rapides de marque BOSON®. L’ADN du VHB a été recherché chez 75 donneurs par PCR en temps réel (rt PCR) avec le 7500 Fast Real Time PCR. Résultats: Parmi les 300 donneurs AgHBs négatifs, 208 (69,3%) étaient des hommes et 92 (30,7%) des femmes. L’âge moyen était de 30,18 ans. La recherche de l’Ac anti-HBc était positive dans 39 cas (13 %). Parmi les 75 échantillons passés à la rt PCR, 3 (4%) étaient positifs pour l’ADN du VHB. Sur les 3 cas d’ADN VHB positifs, 2 (66,67%) étaient positifs Ac anti HBc et 1 (33,33%) Ac anti HBc négatif. Conclusion: Compte tenu de la prévalence de l’infection occulte B et ses conséquences chez les donneurs de sang et chez les receveurs, il devient nécessaire de rechercher, en plus des marqueurs sérologiques classiques de l’hépatite B, l’ADN VHB pour une meilleure sécurité transfusionnelle. Mots clés: Prévalence, Infection occulte de l’HBV, Donneurs de sang, Ouagadougou &nbsp

Processing and Properties of Bar-Shaped Single-Seeded and Multi-Seeded YBCO Bulk Superconductors by a Top-Seeded Melt Growth Technique

© 2016 The Author(s)The fabrication of (RE)-Ba-Cu-O bulk superconductors, where RE is a rare-earth element such as Y, Gd and Sm, is both time consuming and expensive due to the complexity of the melt process and the slow growth rate of large, single grains. In this study, different approaches to the fabrication of bar-shaped, bulk YBCO superconductors are investigated and compared using single- and multiple-seeding techniques via top-seeded melt growth (TSMG). Both the microstructural and superconducting properties of the bulk samples are investigated, including trapped field, critical current density, critical temperature and levitation force. The results of this study indicate that, in general, the superconducting properties of YBCO fabricated by a single-seeded process are significantly better than those of samples fabricated by a four-seeded process for non-bridge seeds. The differences between the samples are less pronounced in the levitation force measurements, however. In this paper, we attempt to explain the reasons for the similarities and differences observed between bulk samples fabricated by the different single- and multi-seeded processes.This work was supported by the King Abdulaziz City for Science and Technology (KACST)

Residual mother-to-child transmission of HIV in Burkina Faso

Background: Burkina Faso is one of the countries in West Africa most affected by the HIV/AIDS pandemic, despite the implementation of a mother-to-child HIV transmission prevention program as a strategy to reduce the risk of vertical transmission of the disease.Objective: To assess the current risk of mother-to-child transmission of HIV in Burkina Faso.Materials and methods: A prospective study was conducted between December 2014 and July 2016, in the 13 health regions of Burkina Faso. Women who were screened HIV-positive during a prenatal consultation were followed until delivery. Their babies received dry blood spot (DBS) at birth, at week 6 and at 1year, to screen for HIV.Results: Overall, 186 pregnant women were included in the study, with a mean age of 29.17±6.13 years. Of their children, 430 DBS actually received a PCR test, giving a 91.1% PCR implementation rate. After analyses, 6 (1.3%) babies were identified as carriers of HIV1. The newborn’s serological status was associated with delivery pattern (p=0.000), the administration of antiretroviral drugs to the mother after delivery (p=0.0064), the administration of Nevirapine to the newborn at birth (p=0.022), the use of contraceptive methods after delivery (p=0.028) and the presence of breast affections/infections since delivery (p=0.013).Conclusion: The results of our study are encouraging and demonstrate the effectiveness of interventions in the mother-tochild prevention program (PMTCT) for HIV-positive pregnant women can be improved through early initiation of triple therapy in early pregnancy and improved adherence to antiretroviral (ARV) therapy.Keywords: Burkina Faso, HIV/AIDS, mother-to-child transmission, antiretroviral drugs, pregnant wome

Large microwave generation from d.c. driven magnetic vortex oscillators in magnetic tunnel junctions

Spin polarized current can excite the magnetization of a ferromagnet through the transfer of spin angular momentum to the local spin system. This pure spin-related transport phenomena leads to alluring possibilities for the achievement of a nanometer scale, CMOS compatible and tunable microwave generator operating at low bias for future wireless communications. Microwave emission generated by the persitent motion of magnetic vortices induced by spin transfer effect seems to be a unique manner to reach appropriate spectral linewidth. However, in metallic systems, where such vortex oscillations have been observed, the resulting microwave power is much too small. Here we present experimental evidences of spin-transfer induced core vortex precessions in MgO-based magnetic tunnel junctions with similar good spectral quality but an emitted power at least one order of magnitude stronger. More importantly, unlike to others spin transfer excitations, the thorough comparison between experimental results and models provide a clear textbook illustration of the mechanisms of vortex precessions induced by spin transfer

Meningococcal carriage and cerebrospinal meningitis after MenAfriVac mass immunization in Burkina Faso

The aims of this study were to evaluate the impact of conjugate vaccine A, MenAfriVac, on Neisseria meningitidis (Nm) asymptomatic carriage and cerebrospinal meningitis in three health districts (Bogodogo, Kaya, and Dandé) of Burkina Faso. Asymptomatic carriage of Nm was assessed by performing cross-sectional studyrepeated (rounds 1 to 10) before and after introduction of the conjugate vaccine against serogroup A of N. meningitidis (NmA), MenAfriVac. In each round at least 1,500 people were enrolled in each district for a month. Data oncases of meningococcal meningitis in the three studied health districts were collected through meningitides epidemiological surveillance of Burkina Faso.Nm was identified in680 of 23,885 throat swabs before vaccination (2. 84%)withNmYasthe dominant serogroup(1.87%). During the same period (2009 and 2010), 891 cases of suspected meningitis were reported in the three health districts among whom 42 were due toNm (4.71%) withNmX (3.70%) asthe most frequently identified serogroup. After vaccination, Nm was identified in 1117 of 27,245 pharyngeal samples (6.42%); NmX (4.42%) wasthe dominantserogroup. From 2011 to 2013, 965 cases of suspected meningitis were reported in all health facilities in the three studied health districts located in the geographical study area; 91 was due toNm (9.43%) andNmWasthe most commonserogroup(52 cases= 5.38%).After introduction of conjugate vaccine A (MenAfriVac), the NmAserogroup almost disappeared both in asymptomatic carriers and in patients with cerebrospinal meningitis. However the presence of the NmW and NmXserogroups, which appear to have replaced serogroup A, is very worrying with regard to meningitis prevention and control in Burkina Faso. It appears necessary to strengthen surveillance and laboratory diagnosis of the different meningococcal serogroups circulating in Africa.Keywords: meningococcal meningitis, serogroups W and X, meningococcal carriage, MenAfriVac

Phenotypic and genotypic characterization of meningococcal carriage and disease isolates in Burkina Faso after mass vaccination with a serogroup a conjugate vaccine

BACKGROUND: The conjugate vaccine against serogroup A Neisseria meningitidis (NmA), MenAfriVac, was first introduced in mass vaccination campaigns of the 1-29-year-olds in Burkina Faso in 2010. The aim of this study was to genetically characterize meningococcal isolates circulating in Burkina Faso before and up to 13 months after MenAfriVac mass vaccination. METHODS: A total of 1,659 meningococcal carriage isolates were collected in a repeated cross-sectional carriage study of the 1-29-year-olds in three districts of Burkina Faso in 2010 and 2011, before and up to 13 months after mass vaccination. Forty-two invasive isolates were collected through the national surveillance in Burkina Faso in the same period. All the invasive isolates and 817 carriage isolates were characterized by serogroup, multilocus sequence typing and porA-fetA sequencing. RESULTS: Seven serogroup A isolates were identified, six in 2010, before vaccination (4 from carriers and 2 from patients), and one in 2011 from an unvaccinated patient; all were assigned to sequence type (ST)-2859 of the ST-5 clonal complex. No NmA carriage isolate and no ST-2859 isolate with another capsule were identified after vaccination. Serogroup X carriage and disease prevalence increased before vaccine introduction, due to the expansion of ST-181, which comprised 48.5% of all the characterized carriage isolates. The hypervirulent serogroup W ST-11 clone that was responsible for most of meningococcal disease in 2011 and 2012 was not observed in 2010; it appeared during the epidemic season of 2011, when it represented 40.6% of the serogroup W carriage isolates. CONCLUSIONS: Successive clonal waves of ST-181 and ST-11 may explain the changing epidemiology in Burkina Faso after the virtual disappearance of NmA disease and carriage. No ST-2859 strain of any serogroup was found after vaccination, suggesting that capsule switching of ST-2859 did not occur, at least not during the first 13 months after vaccination

Dynamics of germs responsible for acute bacterial meningitis in Burkina Faso in the last ten years (2005-2014)

The aim of this study was to analyze ten (10) years of epidemiological surveillance data of meningitis in Burkina Faso for high risk germs patterns identification in order to contribute to the strengthening of prevention strategies.A retrospective study of the past decade (2005- 2014) of cases of acute bacterial meningitis occurred in the thirteen health regions, collected through epidemiological surveillance data meningitis in Burkina Faso. From a total of 88 057 suspected cases of acute bacterial meningitis, we recorded 9134 deaths. From the laboratory confirmed cases, the identified germs were as follows: 56.79% of Neisseria meningitidis, 41.09% of Streptococcus pneumoniae and 2.13% of Haemophilus influenzae. Among the meningococcus isolated, we observed the following distribution: 23.11% of NmA, 58.84% of NmW and 18% of NmX.Mortality associated with acute bacterial meningitis remains still high in Burkina Faso despite the complete disappearance of NmA since 2012, after the conjugate vaccine A (MenAfriVac) has been introduced in this country. However the emergence of NmX, the reemergence of NmW and the persistence of high prevalence of Streptococcus pneumoniae are a major concern in the fight against meningitis in Burkina Faso. So, it is necessary, in addition to the strengthening of surveillance, diagnosis and case management to develop and make available and accessible a conjugate trivalent vaccine against NmA the NmX and NmW serogroups.Keywords: meningococcal meningitis, W and X serogroups, Streptococcus pneumoniae, MenAfriVa

Optimal control of vortex core polarity by resonant microwave pulses

In a vortex-state magnetic nano-disk, the static magnetization is curling in the plane, except in the core region where it is pointing out-of-plane, either up or down leading to two possible stable states of opposite core polarity p. Dynamical reversal of p by large amplitude motion of the vortex core has recently been demonstrated experimentally,raising fundamental interest for potential application in magnetic storage devices. Here we demonstrate coherent control of p by single and double microwave pulse sequences, taking advantage of the resonant vortex dynamics in a perpendicular bias magnetic field. Optimization of the microwave pulse duration required to switch p allows to experimentally infer the characteristic decay time of the vortex core in the large oscillation regime. It is found to be more than twice shorter than in the small oscillation regime, raising the fundamental question of the non-linear behaviour of magnetic dissipation

Difference of clinical features in childhood Mycoplasma pneumoniae pneumonia

<p>Abstract</p> <p>Background</p> <p><it>M. pneumoniae </it>pneumonia (MP) has been reported in 10-40% of community-acquired pneumonia cases. We aimed to evaluate the difference of clinical features in children with MP, according to their age and chest radiographic patterns.</p> <p>Methods</p> <p>The diagnosis of MP was made by examinations at both admission and discharge and by two serologic tests: the indirect microparticle agglutinin assay (≥1:40) and the cold agglutinins titer (≥1:32). A total of 191 children with MP were grouped by age: ≤2 years of age (29 patients), 3-5 years of age (81 patients), and ≥6 years of age (81 patients). They were also grouped by pneumonia pattern: bronchopneumonia group (96 patients) and segmental/lobar pneumonia group (95 patients).</p> <p>Results</p> <p>Eighty-six patients (45%) were seroconverters, and the others showed increased antibody titers during hospitalization. Among the three age groups, the oldest children showed the longest duration of fever, highest C-reactive protein (CRP) values, and the most severe pneumonia pattern. The patients with segmental/lobar pneumonia were older and had longer fever duration and lower white blood cell (WBC) and lymphocyte counts, compared with those with bronchopneumonia. The patient group with the most severe pulmonary lesions had the most prolonged fever, highest CRP, highest rate of seroconverters, and lowest lymphocyte counts. Thrombocytosis was observed in 8% of patients at admission, but in 33% of patients at discharge.</p> <p>Conclusions</p> <p>In MP, older children had more prolonged fever and more severe pulmonary lesions. The severity of pulmonary lesions was associated with the absence of diagnostic IgM antibodies at presentation and lymphocyte count. Short-term paired IgM serologic test may be mandatory for early and definitive diagnosis of MP.</p

Disentangling astroglial physiology with a realistic cell model in silico

Electrically non-excitable astroglia take up neurotransmitters, buffer extracellular K+ and generate Ca2+ signals that release molecular regulators of neural circuitry. The underlying machinery remains enigmatic, mainly because the sponge-like astrocyte morphology has been difficult to access experimentally or explore theoretically. Here, we systematically incorporate multi-scale, tri-dimensional astroglial architecture into a realistic multi-compartmental cell model, which we constrain by empirical tests and integrate into the NEURON computational biophysical environment. This approach is implemented as a flexible astrocyte-model builder ASTRO. As a proof-of-concept, we explore an in silico astrocyte to evaluate basic cell physiology features inaccessible experimentally. Our simulations suggest that currents generated by glutamate transporters or K+ channels have negligible distant effects on membrane voltage and that individual astrocytes can successfully handle extracellular K+ hotspots. We show how intracellular Ca2+ buffers affect Ca2+ waves and why the classical Ca2+ sparks-and-puffs mechanism is theoretically compatible with common readouts of astroglial Ca2+ imaging