On-site sanitation density and groundwater quality: Evidence from remote sensing and in situ observations in the thiaroye aquifer, Senegal

© 2020 The Authors. In rapidly urbanising low-income towns and cities, there remains an absence of scientific evidence and regulatory structures to sustain the quality and quantity of groundwater used for low-cost water supplies and to reconcile this with continued use of the subsurface for low-cost sanitation. Here, we analyse the relationship between the density of on-site sanitation and shallow groundwater quality in the Thiaroye aquifer of Quaternary sands in Dakar, Senegal. On-site sanitation was mapped using object-oriented classification and visual interpretation of high-resolution, optical satellite images and ground-truthing surveys. Groundwater quality was assessed over a three-year period (2017–2019) from a network of 61 sources comprising boreholes, dug-wells, hand tubewells and piezometers. More than 253,000 on-site sanitation facilities are identified over an area of 520 km2 with densities ranging from 1 to 70 per hectare. A moderate, statistically significant linear relationship (r2 = 0.55, p « 0.01) is found between the density of on-site sanitation facilities and nitrate concentrations in sampled groundwater sources. Groundwater contamination beyond the WHO drinking-water guideline value (50 mg/L) occurs where densities of on-site sanitation facilities exceed 4 (±4) per hectare, a threshold commonly surpassed in peri-urban areas underlain by the Thiaroye aquifer of Dakar

Association between childhood diarrhoeal incidence and climatic factors in urban and rural settings in the health district of Mbour, Senegal

We assessed the association between childhood diarrhoeal incidence and climatic factors in rural and urban settings in the health district of Mbour in western Senegal. We used monthly diarrhoeal case records among children under five years registered in 24 health facilities over a four-year period (2011-2014). Climatic data (i.e., daily temperature, night temperature and rainfall) for the same four-year period were obtained. We performed a negative binomial regression model to establish the relationship between monthly diarrhoeal incidence and climatic factors of the same and the previous month. There were two annual peaks in diarrhoeal incidence: one during the cold dry season and one during the rainy season. We observed a positive association between diarrhoeal incidence and high average temperature of 36 °C and above and high cumulative monthly rainfall at 57 mm and above. The association between diarrhoeal incidence and temperature was stronger in rural compared to urban settings, while higher rainfall was associated with higher diarrhoeal incidence in the urban settings. Concluding, this study identified significant health-climate interactions and calls for effective preventive measures in the health district of Mbour. Particular attention should be paid to urban settings where diarrhoea was most common in order to reduce the high incidence in the context of climatic variability, which is expected to increase in urban areas in the face of global warming

Prevalence of diarrhoea and risk factors among children under five years old in Mbour, Senegal: a cross-sectional study

Diarrhoeal diseases remain an important cause of mortality and morbidity among children, particularly in low- and middle-income countries. In Senegal, diarrhoea is responsible for 15% of all deaths in children under the age of five and is the third leading cause of childhood deaths. For targeted planning and implementation of prevention strategies, a context-specific understanding of the determinants of diarrhoeal diseases is needed. The aim of this study was to identify risk factors of diarrhoeal diseases in children under the age of five in Mbour, Senegal.; Between February and March 2014, a cross-sectional survey was conducted in four zones of Mbour to estimate the burden of diarrhoeal diseases (i.e. diarrhoea episodes in the 2 weeks preceding the survey) and associated risk factors. The zones covered urban central, peri-central, north peripheral and south peripheral areas. Overall, 596 households were surveyed by a questionnaire, yielding information on sociodemographic, environmental and hygiene behavioural factors. Univariable and multivariable logistic regression analyses were used to identify risk factors associated with the occurrence of diarrhoea.; The reported prevalence of diarrhoea among children under the age of five during the 2 weeks preceding the survey was 26%. Without adjustment, the highest diarrhoea prevalence rates were observed in the peri-central (44.8%) and urban central zones (36.3%). Multivariable regression revealed significant associations between diarrhoeal diseases and unemployment of mothers (adjusted odds ratio [aOR] = 1.62, 95% confidence interval [CI]: 1.18-2.23), use of open bags for storing household waste (aOR = 1.75, 95% CI: 1.00-3.02), evacuation of household waste in public streets (aOR = 2.07, 95% CI: 1.20-3.55), no treatment of stored drinking water (aOR = 1.69, 95% CI: 1.11-2.56) and use of shared toilets (aOR = 1.69, 95% CI: 1.11-2.56).; We found a high prevalence of diarrhoea in children under the age of five in Mbour, with the highest prevalence occurring in the central and peri-central areas. These findings underscore the need for public health interventions to alleviate the burden of diarrhoea among vulnerable groups. Promotion of solid waste disposal and reduction of wastewater exposure should be implemented without delay

Molecular diagnostics by PCR of poxviruses (Orthopoxvirus (OPV) and Molluscum contagiosum virus (MCV)) in Cote d'Ivoire West Africa

The Orthopoxvirus (OPV) and the Molluscum contagiosum virus (MCV) are Poxviruses involved in viruses skin lesions in humans. OPV infects many vertebrates and MCV mainly infects humans. A diagnostic confusion is often observed between the clinical lesions due to the different Poxviruses firstly and secondly with other viruses like the virus of the chickenpox. In Côte d'Ivoire, the diagnosis of MCV remains essentially clinical and that of OPV is non-existent despite the risk of circulation of the virus. This study aims to implementthe molecular detection of the OPV and the MVC in Côte d'Ivoire. Material and method: Cowpoxvirus DNA and 21 DNA extracts from suspicious cutaneous lesions of the MCV were analyzed by conventional PCR. The consensus primers (EACP1, EACP2) designed from the surface hemagglutin gene were used for the detection of the OPVs and the primers (MCV1, MCV2) targeting the K fragment of the MCV were used for the MCV’s detection . A growing dilution series of the Cowpoxvirus DNA and the MCV allowed the study of the method’s sensitivity used. The DNAs of S.aureus, M. ulcerans, VZV, HSV, the Measles virus and Varicella virus were used for the specificity tests. Results: The detection of the OPV from the Cowpoxvirus viral strain was positive with a positivity threshold at 10-1 dilution. That of the MCV DNA from the suspected MCV's lesion was positive with a positivity threshold of up to 10 -6 dilution. No non-specific amplification was observed with the DNAs of the other pathogens responsible for lesions Cutaneous. The clinical diagnosis of the MCV was confirmed by PCR in 18 out of the 21 patients, ie 85.71%. On the 3 patients with a negative MCV PCR, 2 were positive for the OPV PCR , reflecting the risk of confusion between clinical lesions due to Poxviruses.Keyvords: Molecular diagnostic, Poxviruses, West Afric

Changes in the Molecular Epidemiology of Pediatric Bacterial Meningitis in Senegal After Pneumococcal Conjugate Vaccine Introduction.

BACKGROUND: Bacterial meningitis is a major cause of mortality among children under 5 years of age. Senegal is part of World Health Organization-coordinated sentinel site surveillance for pediatric bacterial meningitis surveillance. We conducted this analysis to describe the epidemiology and etiology of bacterial meningitis among children less than 5 years in Senegal from 2010 and to 2016. METHODS: Children who met the inclusion criteria for suspected meningitis at the Centre Hospitalier National d'Enfants Albert Royer, Senegal, from 2010 to 2016 were included. Cerebrospinal fluid specimens were collected from suspected cases examined by routine bacteriology and molecular assays. Serotyping, antimicrobial susceptibility testing, and whole-genome sequencing were performed. RESULTS: A total of 1013 children were admitted with suspected meningitis during the surveillance period. Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus accounted for 66% (76/115), 25% (29/115), and 9% (10/115) of all confirmed cases, respectively. Most of the suspected cases (63%; 639/1013) and laboratory-confirmed (57%; 66/115) cases occurred during the first year of life. Pneumococcal meningitis case fatality rate was 6-fold higher than that of meningococcal meningitis (28% vs 5%). The predominant pneumococcal lineage causing meningitis was sequence type 618 (n = 7), commonly found among serotype 1 isolates. An ST 2174 lineage that included serotypes 19A and 23F was resistant to trimethoprim-sulfamethoxazole. CONCLUSIONS: There has been a decline in pneumococcal meningitis post-pneumococcal conjugate vaccine introduction in Senegal. However, disease caused by pathogens covered by vaccines in widespread use still persists. There is need for continued effective monitoring of vaccine-preventable meningitis

Impact of combining intermittent preventive treatment with home management of malaria in children less than 10 years in a rural area of Senegal: a cluster randomized trial

<p>Abstract</p> <p>Background</p> <p>Current malaria control strategies recommend (i) early case detection using rapid diagnostic tests (RDT) and treatment with artemisinin combination therapy (ACT), (ii) pre-referral rectal artesunate, (iii) intermittent preventive treatment and (iv) impregnated bed nets. However, these individual malaria control interventions provide only partial protection in most epidemiological situations. Therefore, there is a need to investigate the potential benefits of integrating several malaria interventions to reduce malaria prevalence and morbidity.</p> <p>Methods</p> <p>A randomized controlled trial was carried out to assess the impact of combining seasonal intermittent preventive treatment in children (IPTc) with home-based management of malaria (HMM) by community health workers (CHWs) in Senegal. Eight CHWs in eight villages covered by the Bonconto health post, (South Eastern part of Senegal) were trained to diagnose malaria using RDT, provide prompt treatment with artemether-lumefantrine for uncomplicated malaria cases and pre-referral rectal artesunate for complicated malaria occurring in children under 10 years. Four CHWs were randomized to also administer monthly IPTc as single dose of sulphadoxine-pyrimethamine (SP) plus three doses of amodiaquine (AQ) in the malaria transmission season, October and November 2010. Primary end point was incidence of single episode of malaria attacks over 8 weeks of follow up. Secondary end points included prevalence of malaria parasitaemia, and prevalence of anaemia at the end of the transmission season. Primary analysis was by intention to treat. The study protocol was approved by the Senegalese National Ethical Committee (approval 0027/MSP/DS/CNRS, 18/03/2010).</p> <p>Results</p> <p>A total of 1,000 children were enrolled. The incidence of malaria episodes was 7.1/100 child months at risk [95% CI (3.7-13.7)] in communities with IPTc + HMM compared to 35.6/100 child months at risk [95% CI (26.7-47.4)] in communities with only HMM (aOR = 0.20; 95% CI 0.09-0.41; <it>p </it>= 0.04). At the end of the transmission season, malaria parasitaemia prevalence was lower in communities with IPTc + HMM (2.05% versus 4.6% <it>p </it>= 0.03). Adjusted for age groups, sex, <it>Plasmodium falciparum </it>carriage and prevalence of malnutrition, IPTc + HMM showed a significant protective effect against anaemia (aOR = 0.59; 95% CI 0.42-0.82; <it>p </it>= 0.02).</p> <p>Conclusion</p> <p>Combining IPTc and HMM can provide significant additional benefit in preventing clinical episodes of malaria as well as anaemia among children in Senegal.</p

Evidence of improper sanitation on groundwater quality in Thiaroye aquifer, Dakar, Senegal : an isotopic approach

Contents: abstract and annexes II to XIIISome text in FrenchThe unconfined sand aquifer lying below the Thiaroye suburban areas bears a considerable groundwater resource which contributes up to 12,000 m3/d to the Dakar city water supply. Groundwater investigation in the Thiaroye quaternary sandy aquifer was carried out in order to evaluate variation and the anthropogenic influence on water quality. In this respect, long term quality monitoring as well as sources of pollution was investigated using chemical and isotopic data obtained from samples collected from hand dug wells, boreholes and piezometers. Stable isotopes analysis results of the dissolved nitrates were used to identify urban sewage and septic tanks as major source of contamination

Use of δ15N and δ18O-NO3 isotopes as indicators of nitrate sources in the quaternary sand aquifer of Thiaroye (Dakar, Senegal)

This one-page poster provides the breakdown of scientific results of nitrogen distribution in the Thiaroye aquifer reservoir. The study also measures the effectiveness and applicability of nitrogen and oxygen isotopes content in dissolved nitrates. The method assists in identifying nitrate sources and their resulting distribution in groundwater. The Thiaroye reservoir is a shallow aquifer composed of unconsolidated Quaternary Sand; the geology of the area is registered in the general context of the senegalo-mauritanian basin

Water quality decline in coastal aquifers under anthropic pressure: the case of a suburban area of Dakar (Senegal).

In 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

Impact of land use on groundwater quality in the Thiaroye unsewered suburb (Dakar Senegal) : Remote Sensing and GIS approach

Meeting: International Symposium "Coupling Sustainable and Groundwater Protection", 14 - 17 October 2008, Hannove