ABSTRACT
Background and justification: The Republic of Djibouti is located in the Horn of Africa, on the Gulf of Aden and the Bab-el-Mandeb detroit, at the southern entrance to the Red Sea. Prior to its independence in 1977, the Republic of Djibouti was known by two names: "Côte française des Somalis" until 1967, then "Territoire Français de Afars et Issas". As part of our doctoral research on the ecology of mosquitoes in Djibouti, we noted a lack of information on the species encountered, and felt it essential to draw up a list of species before embarking on ecological monitoring. The aim of this work is to survey publications on mosquitoes in Djibouti and to synthesize data from this scientific literature in order to update the national inventory of Culicidae. Materials and methods: An exhaustive search of electronic bibliographic databases (PubMed, Scopus, HAL Open Archive, Science Direct and Google Scholar) was carried out. Reference lists were filtered to access additional articles in order to obtain more data. Two keywords were used: "Djibouti" and "French Territory of Afars and Issas". A selection of scientific publications on Djibouti mosquitoes and/or diseases transmitted by mosquito vectors was made. Researches were conducted in articles selected. The names of the species listed were checked and validated by referring to the site Mosquito Taxonomic Inventory. Results: A total of 13 studies, published between 1970 and 2023, were found. Over the years, the composition of the Culicidae fauna has become well known. In part, the movement of people traveling to and from neighboring countries has been linked to the detection of new species and the reappearance of mosquito species in Djibouti. Numerous studies have been carried out over the years, including purely taxonomic studies and others focusing on the incrimination of mosquito vectors and the characterization of the pathogens they transmit. A total of 37 species, belonging to two subfamilies (Anophelinae and Culicinae), of mosquitoes divided between 7 genera (Aedes, Anopheles, Culex, Culiseta, Lutzia, Mimomyia and Uranotaenia) have been mentioned across the country. The number of species per genus is distributed as follows: 5 species of Aedes including 1 subspecies, 14 species of Anopheles including two subspecies, 12 species of Culex including 1 subspecies, 1 species for each of the genera Culiseta and Lutzia and finally 2 species respectively for the genera Mimomiya and Uranotaenia. Five species have been incriminated as vectors of diseases such as malaria, dengue fever, yellow fever, West Nile virus and chikungunya. Others are known for their potential role in pathogen transmission, including Zika and Rift Valley virus. Discussion - Conclusion: The bibliographical research enabled us to summarize the research carried out over more than half a century in the history of Djibouti, and to update the inventory of the country's mosquitoes, which now includes 37 species. Species names were reviewed and updated, and the case of Anopheles gambiae was also addressed. Two species mentioned as part of the Culicidae fauna of Djibouti appeared to be doubtful and are up for discussion. These results provide a useful information base for defining vector control priorities in Djibouti. They will also inform, guide and facilitate future consultations of our database. In addition, this study will help to identify research ways on mosquitoes in Djibouti.
Subject(s)
Culicidae , Animals , Culicidae/classification , Culicidae/physiology , Djibouti , Mosquito Vectors/classificationSubject(s)
Anti-Bacterial Agents , Carbapenem-Resistant Enterobacteriaceae , Carbapenems , Klebsiella Infections , Klebsiella pneumoniae , Humans , Klebsiella pneumoniae/drug effects , Klebsiella pneumoniae/isolation & purification , Klebsiella pneumoniae/genetics , Klebsiella Infections/microbiology , Klebsiella Infections/drug therapy , Animals , Carbapenems/pharmacology , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/therapeutic use , Carbapenem-Resistant Enterobacteriaceae/drug effects , Carbapenem-Resistant Enterobacteriaceae/isolation & purification , Carbapenem-Resistant Enterobacteriaceae/genetics , Djibouti/epidemiology , Fishes/microbiology , Microbial Sensitivity Tests , Virulence , Fish Diseases/microbiologyABSTRACT
ETHNOPHARMACOLOGICAL RELEVANCE: Djibouti was a country where malaria has been endemic for centuries. The local population use the plants as repellents or first aid for uncomplicated malaria. AIM OF THE STUDY: The aim was, for the first time, to collect and identify plants used by the local population to treat malaria and select the most interesting plants (those that are more commontly used, more available, and have fewer studies). These plants were evaluated for their antiplasmodial activity as well as their cytotoxicity on human cell lines for the most active ones. MATERIALS AND METHODS: A semi-structured questionnaire was developed for this study to collect information about the use and identity of botanical drugs used to treat malaria. The use-reports (percentage) of each plant were recorded to determine their use importance. Also, the availability status of the plants was assessed; and those in critical condition were discarded excluded from further study. Fifteen plants, out of the 41 listed, were extracted with hydro alcohol, ethyl acetate, and dichloromethane for biological testing. Chloroquine-resistant strain FcB-1 of P. falciparum and a human diploid embryonic lung cell line were used for the antiplasmodial test, and to assess the cytotoxicity for human cells respectively. Preliminary analysis of extract constituents was carried out using thin layer chromatography (TLC). RESULTS: This study identifies 41 plant taxa belonging to 32 families and records their use against malaria. Balanites rodunfolia, belonging to the Zygophyllaceae family, was the most commonly used plant, representing 44 % of use-reports. It was followed by Cadaba rodunfolia (15 %) from the Capparaceae family, and then the three species of Aloe: Aloe djiboutiensis (8.2 %), Aloe ericahenriettae (3.4 %), and Aloe rigens (3.4 %) from the Asphodelaceae family. The leaves are the most commonly used part of the plants to treat malaria, accounting for 76 % of usage. The preparation methods were decoction (52 %), maceration (29 %), and boiling (19 %). The administration routes were by oral (80 %), inhalation 19 %), and bathing (1 %). The best antiplasmodial activities were observed in the dichloromethane extracts of Cymbopogon commutatus and the ethyl acetate extracts of Aloe rigens and Terminalia brownii, with IC50 values of 9.8, 5, and 7.5 µg/mL, respectively. Their toxicity/activity levels were very favorable with selectivity indices of 5.6, 8.1, and 11.8 for C. commutatus, A. rigens, and T. Brownii, respectively. CONCLUSION: Forty-one species of botanical drugs were listed as being used to treat malaria in Djibouti. All fifteen selected species showed antiplasmodial activity (IC50 < 50 µg/mL). This work will help guide the valorization of botanical drugs used to treat malaria in Djibouti.
Subject(s)
Aloe , Antimalarials , Malaria, Falciparum , Malaria , Plants, Medicinal , Humans , Antimalarials/pharmacology , Antimalarials/therapeutic use , Plants, Medicinal/chemistry , Pharmaceutical Preparations , Plant Extracts/pharmacology , Plant Extracts/therapeutic use , Plant Extracts/chemistry , Djibouti , Methylene Chloride/therapeutic use , Malaria/drug therapy , Malaria, Falciparum/drug therapy , Plasmodium falciparumABSTRACT
The emergence of carbapenem resistance is a major public health threat in sub-Saharan Africa but remains poorly understood, particularly at the human-animal-environment interface. This study provides the first One Health-based study on the epidemiology of Carbapenemase-Producing Gram-Negative Bacteria (CP-GNB) in Djibouti City, Djibouti, East Africa. In total, 800 community urine samples and 500 hospital specimens from humans, 270 livestock fecal samples, 60 fish samples, and 20 water samples were collected and tested for carbapenem resistance. The overall estimated CP-GNB prevalence was 1.9 % (32/1650 samples) and specifically concerned 0.3 % of community urine samples, 2.8 % of clinical specimens, 2.6 % of livestock fecal samples, 11.7 % of fish samples, and 10 % of water samples. The 32 CP-GNB included 19 Escherichia coli, seven Acinetobacter baumannii, five Klebsiella pneumoniae, and one Proteus mirabilis isolate. Short-read (Illumina) and long-read (Nanopore) genome sequencing revealed that carbapenem resistance was mainly associated with chromosomal carriage of blaNDM-1, blaOXA-23, blaOXA-48, blaOXA-66, and blaOXA-69 in A. baumannii, and with plasmid carriage in Enterobacterales (blaNDM-1 and blaOXA-181 in E. coli, blaNDM-1, blaNDM-5 and blaOXA-48 in K. pneumoniae, and blaNDM-1 in P. mirabilis). Moreover, 17/32 CP-GNB isolates belonged to three epidemic clones: (1) A. baumannii sequence type (ST) 1697,2535 that showed a distribution pattern consistent with intra- and inter-hospital dissemination; (2) E. coli ST10 that circulated at the human-animal-environment interface; and (3) K. pneumoniae ST147 that circulated at the human-environment interface. Horizontal exchanges probably contributed to carbapenem resistance dissemination in the city, especially the blaOXA-181-carrying ColKP3-IncX3 hybrid plasmid that was found in E. coli isolates belonging to different STs. Our study highlights that despite a relatively low CP-GNB prevalence in Djibouti City, plasmids harboring carbapenem resistance circulate in humans, animals and environment. Our findings stress the need to implement preventive and control measures for reducing the circulation of this potentially emerging public health threat.
Subject(s)
Bacterial Proteins , Escherichia coli , Humans , Animals , Escherichia coli/genetics , Djibouti/epidemiology , Bacterial Proteins/genetics , beta-Lactamases/genetics , Plasmids , Klebsiella pneumoniae , Carbapenems , Genomics , Water , Anti-Bacterial Agents/pharmacology , Microbial Sensitivity TestsABSTRACT
A 3-year-old male originating from Djibouti presented with a cervical mass evolving for 2 months. Tuberculous lymphadenopathy was suspected based on biopsy results, and he improved quickly on standard antituberculous quadritherapy. Subsequently some features of the mycobacterium that grew in culture were unusual. The isolate was eventually identified as Mycobacterium canettii , a peculiar species of the Mycobacterium tuberculosis complex.
Subject(s)
Lymphadenopathy , Mycobacterium tuberculosis , Mycobacterium , Tuberculosis, Lymph Node , Male , Humans , Child, Preschool , Tuberculosis, Lymph Node/diagnosis , Tuberculosis, Lymph Node/drug therapy , DjiboutiABSTRACT
BACKGROUND: The Republic of Djibouti is a malaria endemic country that was in pre-elimination phase in 2006-2012. From 2013, however, malaria has re-emerged in the country, and its prevalence has been increasing every year. Given the co-circulation of several infectious agents in the country, the assessment of malaria infection based on microscopy or histidine-rich protein 2 (HRP2)-based rapid diagnostic tests (RDT) has shown its limitations. This study, therefore, aimed to assess the prevalence of malaria among febrile patients in Djibouti city using more robust molecular tools. METHODS: All suspected malaria cases reported to be microscopy-positive were randomly sampled (n = 1113) and included in four health structures in Djibouti city over a 4-year period (2018-2021), mainly during the malaria transmission season (January-May). Socio-demographic information was collected, and RDT was performed in most of the included patients. The diagnosis was confirmed by species-specific nested polymerase chain reaction (PCR). Data were analysed using Fisher's exact test and kappa statistics. RESULTS: In total, 1113 patients with suspected malaria and available blood samples were included. PCR confirmed that 788/1113 (70.8%) were positive for malaria. Among PCR-positive samples, 656 (83.2%) were due to Plasmodium falciparum, 88 (11.2%) Plasmodium vivax, and 44 (5.6%) P. falciparum/P. vivax mixed infections. In 2020, P. falciparum infections were confirmed by PCR in 50% (144/288) of negative RDTs. After the change of RDT in 2021, this percentage decreased to 17%. False negative RDT results were found more frequently (P < 0.05) in four districts of Djibouti city (Balbala, Quartier 7, Quartier 6, and Arhiba). Malaria occurred less frequently in regular bed net users than in non-users (odds ratio [OR]: 0.62, 95% confidence interval [CI]: 0.42-0.92). CONCLUSIONS: The present study confirmed the high prevalence of falciparum malaria and, to a lesser extent, vivax malaria. Nevertheless, 29% of suspected malaria cases were misdiagnosed by microscopy and/or RDT. There is a need to strengthen the capacity for diagnosis by microscopy and to evaluate the possible role of P. falciparum hrp2 gene deletion, which leads to false negative cases of P. falciparum.
Subject(s)
Malaria, Falciparum , Malaria, Vivax , Malaria , Humans , Djibouti/epidemiology , Antigens, Protozoan/genetics , Malaria, Falciparum/diagnosis , Malaria, Falciparum/epidemiology , Malaria, Vivax/diagnosis , Malaria, Vivax/epidemiology , Plasmodium falciparum/genetics , Diagnostic Tests, Routine/methodsABSTRACT
We describe the influence of seasonal meteorologic variations and rainfall events on Anopheles stephensi mosquito populations during a 40-month surveillance study at a US military base in Djibouti. Focusing surveillance and risk mitigation for An. stephensi mosquitoes when climatic conditions are optimal presents an opportunity for malaria prevention and control in eastern Africa.
Subject(s)
Anopheles , Malaria , Animals , Humans , Malaria/epidemiology , Malaria/prevention & control , Djibouti , Seasons , Mosquito VectorsABSTRACT
During 2019-2020, a chikungunya outbreak occurred in Djibouti City, Djibouti, while dengue virus and malaria parasites were cocirculating. We used blotting paper to detect arbovirus emergence and confirm that it is a robust method for detecting and monitoring arbovirus outbreaks remotely.
Subject(s)
Arboviruses , Chikungunya Fever , Chikungunya virus , Dengue Virus , Dengue , Zika Virus Infection , Humans , Chikungunya Fever/epidemiology , Chikungunya virus/genetics , Djibouti/epidemiology , Disease Outbreaks , Dengue/epidemiology , Zika Virus Infection/epidemiologyABSTRACT
Anopheles stephensi, an invasive malaria vector native to South Asia and the Arabian Peninsula, was detected in Djibouti's seaport, followed by Ethiopia, Sudan, Somalia, and Nigeria. If An. stephensi introduction is facilitated through seatrade, similar to other invasive mosquitoes, the identification of at-risk countries are needed to increase surveillance and response efforts. Bilateral maritime trade data is used to (1) identify coastal African countries which were highly connected to select An. stephensi endemic countries, (2) develop a prioritization list of countries based on the likelihood of An. stephensi introduction through maritime trade index (LASIMTI), and (3) use network analysis of intracontinental maritime trade to determine likely introduction pathways. Sudan and Djibouti were ranked as the top two countries with LASIMTI in 2011, which were the first two coastal African countries where An. stephensi was detected. With Djibouti and Sudan included as source populations, 2020 data identify Egypt, Kenya, Mauritius, Tanzania, and Morocco as the top countries with LASIMTI. Network analysis highlight South Africa, Mauritius, Ghana, and Togo. These tools can prioritize efforts for An. stephensi surveillance and control in Africa. Surveillance in seaports of identified countries may limit further expansion of An. stephensi by serving as an early warning system.
Subject(s)
Anopheles , Malaria , Animals , Humans , Anopheles/physiology , Malaria/epidemiology , Mosquito Vectors/physiology , Ethiopia , DjiboutiABSTRACT
The global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has highlighted the disparity between developed and developing countries for infectious disease surveillance and the sequencing of pathogen genomes. The majority of SARS-CoV-2 sequences published are from Europe, North America, and Asia. Between April 2020 and January 2022, 795 SARS-CoV-2-positive nares swabs from individuals in the U.S. Navy installation Camp Lemonnier, Djibouti, were collected, sequenced, and analyzed. In this study, we described the results of genomic sequencing and analysis for 589 samples, the first published viral sequences for Djibouti, including 196 cases of vaccine breakthrough infections. This study contributes to the knowledge base of circulating SARS-CoV-2 lineages in the under-sampled country of Djibouti, where only 716 total genome sequences are available at time of publication. Our analysis resulted in the detection of circulating variants of concern, mutations of interest in lineages in which those mutations are not common, and emerging spike mutations.
Subject(s)
COVID-19 , Vaccines , COVID-19/epidemiology , COVID-19/prevention & control , Djibouti/epidemiology , Genome, Viral , Humans , Mutation , SARS-CoV-2/geneticsABSTRACT
Deletions of pfhrp2 and paralogue pfhrp3 (pfhrp2/3) genes threaten Plasmodium falciparum diagnosis by rapid diagnostic test. We examined 1,002 samples from suspected malaria patients in Djibouti City, Djibouti, to investigate pfhrp2/3 deletions. We performed assays for Plasmodium antigen carriage, pfhrp2/3 genotyping, and sequencing for 7 neutral microsatellites to assess relatedness. By PCR assay, 311 (31.0%) samples tested positive for P. falciparum infection, and 296 (95.2%) were successfully genotyped; 37 (12.5%) samples were pfhrp2+/pfhrp3+, 51 (17.2%) were pfhrp2+/pfhrp3-, 5 (1.7%) were pfhrp2-/pfhrp3+, and 203 (68.6%) were pfhrp2-/pfhrp3-. Histidine-rich protein 2/3 antigen concentrations were reduced with corresponding gene deletions. Djibouti P. falciparum is closely related to Ethiopia and Eritrea parasites (pairwise GST 0.68 [Ethiopia] and 0.77 [Eritrea]). P. falciparum with deletions in pfhrp2/3 genes were highly prevalent in Djibouti City in 2019-2020; they appear to have arisen de novo within the Horn of Africa and have not been imported.
Subject(s)
Malaria, Falciparum , Plasmodium falciparum , Antigens, Protozoan/genetics , Diagnostic Tests, Routine , Djibouti/epidemiology , Ethiopia , Gene Deletion , Histidine/genetics , Humans , Malaria, Falciparum/diagnosis , Malaria, Falciparum/epidemiology , Plasmodium falciparum/genetics , Protozoan Proteins/genetics , Protozoan Proteins/metabolismABSTRACT
Since the first case of COVID-19 in Djibouti in March 2020 up to the end of May 2021, the country experienced two major epidemic waves of confirmed cases and deaths. The first wave in 2020 progressed more slowly in Djibouti compared with other countries in the Eastern Mediterranean Region. The second wave in 2021 appeared to be more aggressive in terms of the number and severity of cases, as well as the overall fatality rate. This study describes and analyses the epidemiology of these two waves of the COVID-19 pandemic in Djibouti and highlights lessons learnt from the National Plan for Introduction and Deployment of COVID-19 vaccines developed and implemented by the Ministry of Health of Djibouti.From 17 March 2020 up to 31 May 2021, Djibouti officially reported 11 533 confirmed cases of COVID-19 with 154 related deaths (case fatality rate, CFR: 1.3%), with an attack rate of 1.2%. The first epidemic wave began in epidemiological week 16/2020 (12-18 April) and ended in epidemiological week 25/2020 (14-20 June) with 4274 reported cases and 46 deaths (CFR: 1.1%). The second wave began in epidemiological week 11/2021 (14-20 March) and ended in epidemiological week 18/2021 (2-8 May) with 5082 reported cases and 86 deaths (CFR: 1.7%).A vaccination campaign was launched by the President of the Republic in March 2021; approximately 1.6% of the population were vaccinated in only two months' time. Early Preparedness, multisectoral and multicoordinated response, and collaboration with WHO are among the major lessons learnt during the pandemic in Djibouti.
Subject(s)
COVID-19 , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19 Vaccines , Djibouti/epidemiology , Humans , Pandemics/prevention & control , VaccinationABSTRACT
INTRODUCTION: In this paper we report on our experience of diagnosis, treatment and follow up of cases of cancer of the oesophagus treated in Balbala Cheiko Hospital and in the Djibouty Military Hospital. Oesophageal cancer, mainly squamous cellular type, is the prevalent cancer of the gastrointestinal tract (GIT) observed in our two Hospitals. Djibouti is a small pacific country located in the Horn of Africa in the tropics, bordered by Somaliland in the south, Ethiopia in the southwest, Eritrea in the north and the Red Sea and the Gulf of Aden in the east. Yemen lies across the Gulf of Aden. Djibouti is the principal maritime port for Ethiopia. The country was formerly French Somaliland and it became independent from France in June 1977. It is a multi-ethnic nation with a population of just over 900,000. MATERIAL AND METHODS: From January 2011 to April 2021, we observed 159 patients diagnosed with cancer of the oesophagus: 89 females representing 56 % and 70 males representing 44 %. An Oesophageal Cancer Card (see Annex 1) was completed for each patient. 107 patients (67.30%) reported regularly (twice a week) chewing of khat (see Annex 2) and 68 patients (42,76%) regularly smoked more than 20 cigarettes and drank more than three very hot cups of coffee or tea per day. All patients underwent an oesophagoscopy with biopsy. Squamous Cell Carcinoma (OSCC) was confirmed by histology in all cases, 89 of them being females (64%) which is surprisingly different from data reported in the literature which reports a general prevalence of males. 60 patients (37.7 % of the total) underwent surgery. The Ivor-Lewis operation was the most frequent type of surgery and was done in 44 patients (66.6%). RESULTS: Our ten years experience involved two hospitals serving a large area. Cancer of the oesophagus (OC) was the prevalent gastrointestinal cancer we observed, second only to female breast cancer. There are no facilities in the country for radiotherapy. It is very difficult to report on long term survival because most of patients live in rural areas which are very difficult to reach and they rarely return for medical check-ups. The best survival recorded was a 48 year old Afar male who was still alive 6 years after an Ivor-Lewis operation was performed for squamous carcinoma on 3 April 2014 and checked on September 2020. A further 6 patients (2 males and 4 females, 3 with adenocarcinoma and 3 with squamous cell carcinoma) recently checked are still alive and come in regularly for check-up. CONCLUSIONS: Oesophageal cancer is one of the most frequent cancers found in the Horn of Africa and our experience in Djibouti confirms the data of the literature 16,28,29. A peculiarity in our study is the high prevalence in the female population. Our recommendation is to set-up an oesophageal cancer unit (OCU) with a team of specialists: gastroenterologist, surgical oncologist, anaesthesiologists, pathologists, nutritionalists and trained nurses who could ensure, not only hospital support, but also the active post operative follow up of patients. The implementation of a National Cancer Register would be mandatory. KEY WORDS: Oesophageal Cancer, Ivor Lewis Operation, Follow up, Djibouti.
Subject(s)
Esophageal Neoplasms , Esophagectomy , Africa , Djibouti/epidemiology , Esophageal Neoplasms/epidemiology , Esophageal Neoplasms/surgery , Female , Hospitals , Humans , Male , Middle AgedABSTRACT
The aim of this study was to determine the prevalence, antimicrobial susceptibility pattern and associated factors of urinary tract infection (UTI) among pregnant women attending Hargeisa Group Hospital (HGH), Hargeisa, Somaliland. A cross-sectional study was conducted at HGH, Hargeisa, Somaliland and participants were selected by systematic random sampling technique. Clean catch midstream urine samples were collected from 422 participants and cultured and antimicrobial susceptibility pattern was determined for the isolates. Univariable and multivariable logistic regression analyses were utilized to identify the independent risk factors for UTI. The prevalence of UTI was 16.4% (95% CI 13.3-19.9). The predominant bacteria isolate was E. coli (43.5%) followed by Coagulase negative staphylococcus (CoNS) 11(16%), S. aureus 9(13%), K. pneumonia 6(8.7%), Pseudomonas aeruginosa 5(7.2%), Proteus mirabilis 4(5.8%), Citrobacter spp 3(4.4%) and M. morganii 1(1.5%) Gram negative bacilli were resistant to ampicillin (96%) and tetracycline (71.4%) and Gram-positive cocci were also resistant to ampicillin (90%), tetracycline (55%). Multidrug resistance was observed in 85.5% of bacterial isolated. No formal education participants, previous history of catheterization and previous history of UTI had 3.18, 3.22 and 3.73 times respectively more likely to develop UTI than their counterparts. Culture and susceptibility test is vital for appropriate management of UTI in the study area.
Subject(s)
Anti-Bacterial Agents/therapeutic use , Drug Resistance, Multiple, Bacterial , Gram-Negative Bacteria/drug effects , Gram-Negative Bacterial Infections/epidemiology , Gram-Positive Bacteria/drug effects , Gram-Positive Bacterial Infections/epidemiology , Urinary Tract Infections/epidemiology , Adolescent , Adult , Ampicillin/therapeutic use , Cross-Sectional Studies , Djibouti/epidemiology , Female , Gram-Negative Bacteria/growth & development , Gram-Negative Bacteria/isolation & purification , Gram-Negative Bacterial Infections/drug therapy , Gram-Negative Bacterial Infections/microbiology , Gram-Positive Bacteria/growth & development , Gram-Positive Bacteria/isolation & purification , Gram-Positive Bacterial Infections/drug therapy , Gram-Positive Bacterial Infections/microbiology , Hospitals , Humans , Microbial Sensitivity Tests , Pregnancy , Prevalence , Tetracycline/therapeutic use , Urinary Tract Infections/drug therapy , Urinary Tract Infections/microbiologyABSTRACT
Within the East African Rift System (EARS), the complex Ali-Sabieh aquifers system, located in the south of the Republic of Djibouti, was overexploited and subjected to anthropogenic and/or geogenic pollution with high concentrations of dissolved nitrate (up to 181 mg/l) and sulfates (up to 1540 mg/l). This study is the first undertaken on the hydrochemistry of this aquifer system, combining geochemical tools and multi-isotope - δ2H(H2O), δ18O(H2O), δ18O(SO4), δ34S(SO4), δ15N(NO3), δ18O(NO3), δ13C(DIC), and 14C- was used to decipher the origin and fate of different nitrate and sulfate sources to groundwater. The groundwater samples of the region show a chemical evolution from fresh Ca(Na)-bicarbonate to brackish Na-Cl , mainly due to water-rock interaction. The combined chloride and water isotope data show that evaporation and transpiration are present, with the latter occurring primarily in the shallow alluvial aquifer waters. Inspection of δ15N(NO3) vs. δ18O(NO3) and NO3/Cl vs. Cl diagrams show that dissolved nitrates are primarily of anthropogenic origin. In particular, higher nitrate concentrations may be related to animal manure used as organic fertilizers during agricultural activities. Sulfates are from a natural origin related to the interaction of water with gypsum of hydrothermal or sedimentary origin. SO4/Cl ratio and isotopic composition show that dissolved sulfates in saline and ancient groundwater of the Cretaceous sandstone aquifer (between 7.4 ± 2.2 and 5.8 ± 1.4 k-years before the present) are generated by interaction with gypsum from oxidation of pre-existing (Jurassic?) sulfides. This work highlight that isotopic ratios of the two molecules -δ18O(SO4), δ34S(SO4), δ15N(NO3), δ18O(NO3)- are not sufficient for tracing the origin of nitrate and sulfates in groundwater, but that a complete hydrogeochemical study is needed. In the absence of this, the relatively high concentration of chloride and sulfates could be wrongly linked to the anthropogenic source of nitrate (manure or sewage).
Subject(s)
Groundwater , Water Pollutants, Chemical , Animals , Djibouti , Environmental Monitoring , Nitrates/analysis , Nitrogen Isotopes/analysis , Sulfates , Water Pollutants, Chemical/analysisABSTRACT
Hg and 210Po were measured in the muscle tissue of commercially important fish species collected in the main coastal cities of the Djiboutian coast (Tadjoura Gulf) to evaluate the potential risk associated with their consumption. The levels of Hg among the different species ranged from 0.02 to 1.69 mg/kg w.w and exceeded tolerable limits as reported by the national regulation (2000-0727/PR/MAEM) and the Codex Alimentarius. The probabilistic distributions of health hazard were evaluated through Monte-Carlo simulation, which confirmed the carcinogenic risk from Hg. The levels of 210Po ranged from 4.1 to 134.5 Bq/kg w.w among muscle tissues of the eight commercially important species. The carcinogenic risk was in an unacceptable range and simulation revealed that children were the most vulnerable population. The results obtained confirms that the health impact is reduced when consuming two servings per week.