1,171 research outputs found
Origin and fate of nitrogen pollution in groundwater traced by δ15N-NO3 and δ18O-NO3: the case of the suburban area of Dakar (Senegal).
No full textIn recent years, the rapid increase of the population in the region of Dakar, especially in suburban settlements, together with the lack of policies for urban waste management, has become a source of concern for water supply, needs, and quality
control. Approximately 80% of water resources in the region come from groundwater reservoirs. In order to identify the origin of groundwater pollution a survey of 26 piezometers and wells was conducted in march 2006. In this study, both major and trace
elements were measured as well as the stable isotopic signature of water molecules and dissolved compounds. Nitrates often exceed drinking water limits and are associated with microbiological pollutants, while sea water intrusion represents the major threat to rapidly declining groundwater quality. Stable isotopes of dissolved nitrates allow for the identification of urban sewage and fertilizers as a major source of contamination, and
the ability to define the distribution of their impacts. The occurrence of denitrification processes, although limited, suggest the potential for auto-purifi cation of the contaminated water, if the source of the pollution were to cease
Mobile laboratory reveals the circulation of Dengue virus serotype I of Asian origin in Medina Gounass (Guediawaye), Senegal
No full textWith the growing success of controlling malaria in Sub-Saharan Africa, the incidence of fever due to malaria is in decline, whereas the proportion of patients with non-malaria febrile illness (NMFI) is increasing. Clinical diagnosis of NMFI is hampered by unspecific symptoms but early diagnosis is a key factor for better patient care and for disease control. The aim of this study was to determine the arboviral aetiologies of NMFI in a low resources settings using a mobile laboratory based on Recombinase Polymerase Amplification (RPA) assays. The panel of tests for this study was expanded to five arboviruses including (Dengue virus (DENV), Zika virus (ZIKV), Yellow fever virus (YFV), Chikungunya virus (CHIKV), and Rift valley fever virus (RVFV). One hundred and four children aged between one month and 115 months were enrolled and screened. Three of 104 blood samples of children < 10 years presenting at an outpatient clinic tested positive for DENV. The results were confirmed by real-time RT-PCR, partial sequencing, and non structural protein 1 (NS1) antigen capture ELISA (Biorad, France). Phylogenetic analysis of the derived DENV-1 sequences clustered them with sequences of DENV-1 isolates from Guangzhou in China in 2014. In conclusion, this mobile setup proved reliable for the rapid identification of the causative agent of NMFI, with results consistent with those obtained in the reference laboratory`s settings
One-step RT-PCR for detection of Zika virus
No full textBackground: Zika virus (ZIKV) is an emerging mosquito-borne flavivirus circulating in Asia and Africa. Human infection induces an influenza-like syndrome that is associated with retro-orbital pain, oedema, lymphadenopathy, or diarrhea. Diagnosis of Zika fever requires virus isolation and serology, which are time consuming or cross-reactive. Objective: To develop a one-step RT-PCR assay to detect ZIKV in human serum. Study design: An assay targeting the envelope protein coding region was designed and evaluated for its specificity, detection limit, repeatability, and capacity to detect ZIKV isolates collected over a 40-year period from various African countries and hosts. Results: The assay's detection limit and repeatability were respectively 7.7 pfu/reaction and 100% in serum and L-15 medium; none of 19 other flaviviruses tested were detected. Conclusions: The assay is rapid, sensitive, and specific to detect ZIKV in cell culture or serum, but needs to be validated for diagnosis using clinical samples
Chikungunya Outbreak in Kedougou, Southeastern Senegal in 2009–2010
No full textBackground In Senegal, Chikungunya virus (CHIKV), which is an emerging mosquito-borne alphavirus, circulates in a sylvatic and urban/domestic cycle and has caused sporadic human cases and epidemics since 1960s. However, the real impact of the CHIKV sylvatic cycle in humans and mechanisms underlying its emergence still remains unknown. Methodology One thousand four hundred nine suspect cases of CHIKV infection, recruited from 5 health facilities located in Kedougou region, south-eastern Senegal, between May 2009 to March 2010, together with 866 serum samples collected from schoolchildren from 4 elementary schools in May and November 2009 from Kedougou were screened for anti-CHIKV immunoglobulin (Ig)M antibodies and, when appropriate, for viral nucleic acid by real-time polymerase chain reaction (rPCR) and virus isolation. In addition, mosquitoes collected in the same area from May 2009 to January 2010 were tested for CHIKV by rPCR and by virus isolation, and 116 monkeys sera collected from March 2010 to May 2010 were tested for anti-CHIKV IgM and neutralizing antibodies. Results The main clinical manifestations of the CHIKV suspect cases were headache, myalgia, and arthralgia. Evidence for CHIKV infection was observed in 1.4% (20 of 1409) of patients among suspect cases. No significant difference was observed among age or sex groups. In addition, 25 (2.9%) students had evidence of CHIKV infection in November 2009. Chikungunya virus was detected in 42 pools of mosquitoes, mainly from Aedes furcifer, and 83% of monkeys sampled were seropositive. Conclusions Our findings further documented that CHIKV is maintained in a sylvatic transmission cycle among monkeys and Aedes mosquitoes in Kedougou, and humans become infected by exposure to the virus in the forest.Additional co-authors: Kathryn A. Hanley, Anta T Dia, Denis Malvy, Scott C. Weaver, Amadou Alpha Sal
Water quality decline in coastal aquifers under anthropic pressure: the case of a suburban area of Dakar (Senegal).
No full textIn recent years, the unregulated increase of the population in coastal areas of developing countries has become source of concern for both water supply and quality control. In the region of Dakar (Senegal), approximately 80% of water resources come from groundwater reservoirs, which are increasingly affected by anthropogenic pressures. The identification of the main sources of pollution, and thus the aquifer vulnerability, is essential to provide a sound basis for the implementation of long-term geochemically based water management plans in this sub-Saharan area. With this aim, a hydrochemical and isotopic survey on 26 wells was performed in the so-called Peninsula of Cap-Vert. Results show that seawater intrusion represents the main process affecting groundwater chemical characteristics. Nitrates often exceed the World Health Organization drinking water limits: stable isotopes of dissolved nitrate ( δ15 N and δ18 O) indicate urban sewage and fertilizers as a major source of contamination. Results depict a complex situation in which groundwater is affected by direct and indirect infiltration of effluents, mixing with seawater and freshening processes from below. Besides the relevance of the investigation at a regional level, it represents a basis for decision-making processes in an integrated water resources management and in the planning of similar monitoring strategies for other urban coastal regions
Adolescent sexual and reproductive health in sub-Saharan Africa: who is left behind?
No full textAdolescent sexual and reproductive health (ASRH) continues to be a major public health challenge in sub-Saharan Africa where child marriage, adolescent childbearing, HIV transmission and low coverage of modern contraceptives are common in many countries. The evidence is still limited on inequalities in ASRH by gender, education, urban–rural residence and household wealth for many critical areas of sexual initiation, fertility, marriage, HIV, condom use and use of modern contraceptives for family planning. We conducted a review of published literature, a synthesis of national representative Demographic and Health Surveys data for 33 countries in sub-Saharan Africa, and analyses of recent trends of 10 countries with surveys in around 2004, 2010 and 2015. Our analysis demonstrates major inequalities and uneven progress in many key ASRH indicators within sub-Saharan Africa. Gender gaps are large with little evidence of change in gaps in age at sexual debut and first marriage, resulting in adolescent girls remaining particularly vulnerable to poor sexual health outcomes. There are also major and persistent inequalities in ASRH indicators by education, urban–rural residence and economic status of the household which need to be addressed to make progress towards the goal of equity as part of the sustainable development goals and universal health coverage. These persistent inequalities suggest the need for multisectoral approaches, which address the structural issues underlying poor ASRH, such as education, poverty, gender-based violence and lack of economic opportunity
Repertory of bacteria identified in West Africa by Maldi-Tof
No full textLe répertoire des bactéries est mal connu en Afrique du fait des méthodes d’étude essentiellement basées sur des techniques de culture sur milieux simples associées à des tests biochimiques, ce qui ne permet pas son exploration. Il a néanmoins été récemment bouleversé par l’usage systématique de la spectrométrie de masse de type MALDI-TOF MS.Au cours de nos travaux de thèse de doctorat, nous avons utilisé deux types de spectromètres de masse: le MALDI-TOF Vitek MS, nouvellement installé à Dakar; le MALDI-TOF Microflex LT, installé à Marseille. Les résultats que nous avons obtenus ont montré, pour la première fois, que la technique du MALDI-TOF est efficace et tout à fait adaptée en Afrique pour le diagnostic spécifique de routine. Cette performance a conduit le laboratoire clinique de l’HPD à opter pour son utilisation à la place des traditionnelles techniques d’identification phénotypique telles que les galeries API. Nous avons également confirmé que le MALDI-TOF est un puissant outil d’identification des espèces bactériennes rarement impliquées dans les maladies infectieuses humaines. De plus, cet outil nous a permis de détecter sept nouvelles espèces de bactéries isolées pour la première fois chez l’homme. En Afrique, il faudrait donc multiplier l’installation de spectromètre de masse MALDI-TOF, ou mettre en place des réseaux autour de plateformes MALDI-TOF sous-régionales partagées entre plusieurs structures sanitaires et/ou de recherche.The Africa bacteria repertory is unfamiliar because the available tools in this region are not allowed its best knowledge. In fact, bacteria are most often identified using culture techniques on simple media and biochemical tests which enable the identification of some common characters. These methods do not facilitate an exhaustive knowledge of the bacterial repertory; consequently they have recently been revolutionized by the systematic use of MALDI-TOF mass spectrometry (MS).In our thesis we used two mass spectrometers, respectively, MALDI-TOF Vitek MS currently installed at Dakar (Senegal) and MALDI-TOF Microflex LT installed in Marseille (France). In addition we have also confirmed that MALDI-TOF is a powerful tool for identifying bacterial species rarely involved in human infectious diseases. Thus in adopting the MALDI-TOF as a first-line tool in bacterial identification before Gram staining or other techniques of phenotypic identifications based on chemical characteristics, we discovered seven new species of bacteria isolated for first time in humans. Microbial identification using MALDI-TOF MS is currently feasible in Africa. Its performance and effectiveness in routine diagnosis of clinical microbiology laboratories have been proven. It is necessary either to increase the installation of MALDI-TOF, or establishing a network around a shared MALDI-TOF platform between several structures located in the same area, especially in the underdeveloped countries of Africa amortization of investment costs of the device, because it allowed reducing the time of reporting results and indirectly facilitating better care for patients
Mobile deployment of recombinase polymerase amplification based rapid diagnostics for Ebola virus disease in Guinea in 2015
No full textDevelopment and deployment of a rapid recombinase polymerase amplification Ebola virus detection assay in Guinea in 2015
No full textIn the absence of a vaccine or specific treatments for Ebola virus disease (EVD), early identification of cases is crucial for the control of EVD epidemics. We evaluated a new extraction kit (SpeedXtract (SE), Qiagen) on sera and swabs in combination with an improved diagnostic reverse transcription recombinase polymerase amplification assay for the detection of Ebola virus (EBOV-RT-RPA). The performance of combined extraction and detection was best for swabs. Sensitivity and specificity of the combined SE and EBOV-RT-RPA were tested in a mobile laboratory consisting of a mobile glovebox and a Diagnostics-in-a-Suitcase powered by a battery and solar panel, deployed to Matoto Conakry, Guinea as part of the reinforced surveillance strategy in April 2015 to reach the goal of zero cases. The EBOV-RT-RPA was evaluated in comparison to two real-time PCR assays. Of 928 post-mortem swabs, 120 tested positive, and the combined SE and EBOV-RT-RPA yielded a sensitivity and specificity of 100% in reference to one real-time RT-PCR assay. Another widely used real-time RT-PCR was much less sensitive than expected. Results were provided very fast within 30 to 60 min, and the field deployment of the mobile laboratory helped improve burial management and community engagement
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