RESUMEN
BACKGROUND: Urogenital schistosomiasis is a neglected tropical disease most prevalent in sub-Saharan Africa. In the Senegal river basin, the construction of the Diama dam led to an increase and endemicity of schistosomiasis. Since 2009, praziquantel has frequently been used as preventive chemotherapy in the form of mass administration to Senegalese school-aged children without monitoring of the treatment efficacy and the prevalence after re-infection. This study aims to determine the current prevalence of urogenital schistosomiasis (caused by Schistosoma haematobium), the efficacy of praziquantel, and the re-infection rates in children from five villages with different water access. METHODS: The baseline prevalence of S. haematobium was determined in August 2020 in 777 children between 5 and 11 years old and a single dose of praziquantel (40 mg/kg) was administered to those positive. The efficacy of praziquantel and the re-infection rates were monitored 4 weeks and 7 months after treatment, respectively, in 226 children with a high intensity of infection at baseline. RESULTS: At the baseline, prevalence was low among children from the village of Mbane who live close to the Lac de Guiers (38%), moderate among those from the villages of Dioundou and Khodit, which neighbor the Doue river (46%), and very high at Khodit (90.6%) and Guia (91.2%) which mainly use an irrigation canal. After treatment, the observed cure rates confirmed the efficacy of praziquantel. The lowest cure rate (88.5%) was obtained in the village using the irrigation canal, while high cure rates were obtained in those using the lake (96.5%) and the river (98%). However, high egg reduction rates (between 96.7 and 99.7%) were obtained in all the villages. The re-infection was significantly higher in the village using the canal (42.5%) than in the villages accessing the Lac de Guiers (18.3%) and the Doue river (14.8%). CONCLUSION: Praziquantel has an impact on reducing the prevalence and intensity of urogenital schistosomiasis. However, in the Senegal river basin, S. haematobium remains a real health problem for children living in the villages near the irrigation canals, despite regular treatment, while prevalence is declining from those frequenting the river and the Lac de Guiers. Trial registration ClinicalTrials.gov, NCT04635553. Registered 19 November 2020 retrospectively registered, https://www. CLINICALTRIALS: gov/ct2/show/NCT04635553?cntry=SN&draw=2&rank=4.
Asunto(s)
Antihelmínticos , Esquistosomiasis Urinaria , Niño , Animales , Humanos , Preescolar , Praziquantel/uso terapéutico , Esquistosomiasis Urinaria/tratamiento farmacológico , Esquistosomiasis Urinaria/epidemiología , Reinfección/tratamiento farmacológico , Senegal/epidemiología , Prevalencia , Ríos , Schistosoma haematobium , Abastecimiento de Agua , Antihelmínticos/uso terapéuticoRESUMEN
In West Africa, Schistosoma spp. are capable of infecting multiple definitive hosts, a lifecycle feature that may complicate schistosomiasis control. We characterized the evolutionary relationships among multiple Schistosoma mansoni isolates collected from snails (intermediate hosts), humans (definitive hosts), and rodents (definitive hosts) in Senegal. On a local scale, diagnosis of S. mansoni infection ranged 3.8%-44.8% in school-aged children, 1.7%-52.6% in Mastomys huberti mice, and 1.8%-7.1% in Biomphalaria pfeifferi snails. Our phylogenetic framework confirmed the presence of multiple S. mansoni lineages that could infect both humans and rodents; divergence times of these lineages varied (0.13-0.02 million years ago). We propose that extensive movement of persons across West Africa might have contributed to the establishment of these various multihost S. mansoni clades. High S. mansoni prevalence in rodents at transmission sites frequented by humans further highlights the implications that alternative hosts could have on future public health interventions.
Asunto(s)
Biomphalaria , Schistosoma mansoni , África Occidental , Animales , Ratones , Filogenia , Schistosoma mansoni/genética , Senegal/epidemiologíaRESUMEN
Clarias gariepinus (African catfish) and Oreochromis niloticus (Tilapia fish) from the right North bank of the Senegal River in Mauritania (Rosso, Boghé, and Kaédi) were sampled during 1-year monitoring and tested for lead (Pb), cadmium (Cd), and mercury (Hg) levels. Fishing from the Senegal River is an essential source of food for the local population and these two species are the most common. Muscle presents higher Hg concentrations than liver and gills for both species. Gill Hg concentrations from Kaédi are higher than Boghé and Rosso for both species. The Cd levels measured in gills were low in the different locations and revealed high variation throughout the 1-year study. No significant differences were observed between concentrations of Cd in Clarias gariepinus and Oreochromis niloticus parts. Statistical treatment did not show a considerable variation of Pb concentration between the different parts, revealing lower levels in gills from Boghé than the ones from Kaédi and Rosso. The associated human health risk was calculated from the concentration levels using the target hazard quotient (THQ) approach. Even though all the THQ values and the hazard index were lower than 1 for the determined trace metals when the exposure frequency was not greater than three times a week, eating frequency in the studied locations sometimes is greater than five, thus posing a health risk, especially at Kaédi and Boghé.
Asunto(s)
Bagres/metabolismo , Cíclidos/metabolismo , Monitoreo del Ambiente/métodos , Metales Pesados/análisis , Ríos/química , Contaminantes Químicos del Agua/análisis , Animales , Branquias/química , Humanos , Hígado/química , Mauritania , Músculos/química , Medición de Riesgo , Alimentos Marinos/análisisRESUMEN
The objective of this work was to identify possible correlations between physicochemical parameters (water temperature, water flow velocity, electrical conductivity, dissolved oxygen, salinity, pH, nitrates, and phosphates) and the spatial distribution in the Senegal River delta of snail species that are intermediate hosts of human schistosomes. Eight water points (ME1 to ME4, NE1 and NE2, TA1 and TA2) were selected in the villages of Menguègne Boye, Ndellé Boye, and Thilla for biweekly monitoring of these snails and the physicochemical parameters of the water. The results show that the spatial distribution of the snail populations is related to pH, dissolved oxygen (mg/l), conductivity, temperature (ÌC), and water flow velocity (m/s).
Asunto(s)
Vectores de Enfermedades , Ríos , Caracoles/fisiología , Caracoles/parasitología , Animales , Concentración de Iones de Hidrógeno , Oxígeno/análisis , Densidad de Población , Schistosoma/aislamiento & purificación , Schistosoma/fisiología , Senegal , Temperatura , Agua/químicaRESUMEN
Introduction: The advent of Diama and Manantali dams in the eighties has altered the schistosomiasis profile in the Senegal River Basin, with the appearance of an intestinal form in the Delta and a high prevalence of the urinary form in all ecological areas of the basin. Methods: The present study was mainly designed to re-evaluate the prevalence of schistosomiasis after many years of mass drug administration with praziquantel 600 mg allowing analysis of the pertinence of World Health Organisation guidelines in terms of dosing frequency, particularly in the Senegal River Basin. Stools and urine from 1,215 public school children from 24 villagesidentified in three ecological areas of the Senegal River Basin (Delta, valley, upper basin), were examined. Results: The results of thisstudy show the endemic prevalences of urinary schistosomiasisin all ecological areas ofthe Senegal River Basin: 57.4% in the Delta, 32.5% in the Valley and 25.1% in the upper basin. The prevalence of the intestinalschistosomiasisform was 21.8 % in the Delta, and this form has also entered the valley. Conclusion: The results ofthisstudy confirm that schistosomiasis is still a public health problem in the Senegal River Basin despite several series of mass praziquantel 600 mg administration. This situation requires detailed reflection concerning dosing frequencies of this drug in the Senegal River basin and the need to take social behaviours and sociological realities into account in order to eradicate schistosomiasis.
Asunto(s)
Praziquantel/uso terapéutico , Servicios Preventivos de Salud , Esquistosomiasis/epidemiología , Esquistosomiasis/prevención & control , Adolescente , Animales , Niño , Preescolar , Femenino , Humanos , Masculino , Mauritania/epidemiología , Prevalencia , Servicios Preventivos de Salud/organización & administración , Servicios Preventivos de Salud/normas , Evaluación de Programas y Proyectos de Salud , Ríos , Senegal/epidemiologíaRESUMEN
This study describes the changes in hydrology, zooplankton communities and abundance in the Senegal River Estuary (SRE) before and after the breaching of the sandbar in October 2003. Samples were taken in 2003 at 3 stations located upstream (DI), in mid estuary (HY) and downstream (RM), and in 2005 at the same stations (RM becoming Old River Mouth: ORM), plus the new river mouth (NRM) resulting from the morphological evolution of the SRE. The study showed marked seasonal variations that affected the structure and distribution of zooplankton as well as major changes caused by the sandbar opening: increased marine influence throughout the whole SRE, changes in the horizontal gradients, arrival of euryhaline species and increase in meroplankton, in particular decapod larvae, transformation of the ORM area into a slackwater area with limited exchanges and the highest zooplankton numbers during high waters.
Asunto(s)
Biodiversidad , Ecosistema , Estuarios , Zooplancton/fisiología , Animales , Hidrología , Densidad de Población , Estaciones del Año , SenegalRESUMEN
Following major water development schemes in the 1980s, schistosomiasis has become a serious parasitic disease of children living in the Senegal River Basin. Both urogenital (Schistosoma haematobium) and intestinal (Schistosoma mansoni) schistosomiasis can be highly prevalent in school-aged children, with many individuals infected with both parasites. In order to investigate the transmission and re-infection dynamics of both parasite species, single and mixed infection foci at three villages (Nder and Temeye; S. mansoni and S. haematobium foci and Guia; S. haematobium focus) were studied. In each focus infected children were identified and selected for a 12-month study involving two treatments with praziquantel (40mg/kg) three weeks apart at the beginning of the study and again 6 months into the study. Urine and stool samples were examined for schistosome eggs before and at 6 weeks and 6 months after chemotherapy. Prevalence and intensity of infection were recorded for each child at each time point. Before treatment, in all three villages, the prevalence and intensity of infection was extremely high for both S. mansoni (79-100%) and S. haematobium (81-97%). With the first round of chemotherapy sufficient cure rates (CRs) of both species were achieved in all villages (38-96%) with high egg reduction rates (ERRs) (97-99%). The data show that high and rapid re-infection rates occur, especially for S. mansoni, within a six-month period following treatment. Re-infection must be highly linked to ecological and seasonal factors. The persistence of S. mansoni in Nder could raise concern as levels of infection intensity remain high (geometric mean intensity at baseline 653epg changed to 705epg at 12 months) after four rounds of chemotherapy. This phenomenon could be explained by extremely rapid re-infection dynamics or a sub-optimal efficacy of praziquantel against S. mansoni in this village. High intensities in mixed infections may influence disease epidemiology and control warranting further studies. The disease situation in the SRB must be monitored closely and new treatment regimes should be designed and implemented to control schistosomiasis in the school-age population.