Mycobacterium ulcerans is the causative agent of Buruli ulcer, a neglected tropical disease found in rural areas of West and Central Africa. Despite the ongoing efforts to tackle Buruli ulcer ...epidemics, the environmental reservoir of its pathogen remains elusive, underscoring the need for new approaches to improving disease prevention and management. In our study, we implemented a local-scale spatial clustering model and deciphered the genetic diversity of the bacteria in a small area of Benin where Buruli ulcer is endemic. Using 179 strain samples from West Africa, we conducted a phylogeographic analysis combining whole-genome sequencing with spatial scan statistics. The 8 distinct genotypes we identified were by no means randomly spread over the studied area. Instead, they were divided into 3 different geographic clusters, associated with landscape characteristics. Our results highlight the ability of M. ulcerans to evolve independently and differentially depending on location in a specific ecologic reservoir.
The use of a malaria early warning system (MEWS) to trigger prompt public health interventions is a key step in adding value to the epidemiological data routinely collected by sentinel surveillance ...systems.
This study describes a system using various epidemic thresholds and a forecasting component with the support of new technologies to improve the performance of a sentinel MEWS. Malaria-related data from 21 sentinel sites collected by Short Message Service are automatically analysed to detect malaria trends and malaria outbreak alerts with automated feedback reports.
Roll Back Malaria partners can, through a user-friendly web-based tool, visualize potential outbreaks and generate a forecasting model. The system already demonstrated its ability to detect malaria outbreaks in Madagascar in 2014.
This approach aims to maximize the usefulness of a sentinel surveillance system to predict and detect epidemics in limited-resource environments.
Buruli ulcer is a neglected tropical disease caused by Mycobacterium ulcerans, an environmental mycobacterium. Although transmission of M. ulcerans remains poorly understood, the main identified risk ...factor for acquiring Buruli ulcer is living in proximity of potentially contaminated water sources. Knowledge about the clinical features of Buruli ulcer and its physiopathology is increasing, but little is known about recurrence due to reinfection.
We describe two patients with Buruli ulcer recurrence due to reinfection with M. ulcerans, as demonstrated by comparisons of DNA from the strains isolated at the time of the first diagnosis and at recurrence. Based on the spatial distribution of M. ulcerans genotypes in this region and a detailed study of the behavior of these two patients with respect to sources of water as well as water bodies and streams, we formulated hypotheses concerning the sites at which they may have been contaminated.
Second episodes of Buruli ulcer may occur through reinfection, relapse or a paradoxical reaction. We formally demonstrated that the recurrence in these two patients was due to reinfection. Based on the sites at which the patients reported engaging in activities relating to water, we were able to identify possible sites of contamination. Our findings indicate that the non-random distribution of M. ulcerans genotypes in this region may provide useful information about activities at risk.
Buruli ulcer is a neglected tropical disease caused by M. ulcerans, an environmental mycobacterium. This cutaneous infectious disease affects populations with poor access to sanitation, safe water ...and healthcare living in rural areas of West and Central Africa. Stagnant open bodies of surface water and slow-running streams are the only risk factor identified in Africa, and there is no human-to-human transmission. Appropriate and effective prevention strategies are required for populations living in endemic areas. Based on a multidisciplinary approach in an area in which Buruli ulcer is endemic in South Benin, we investigated the link between all human-environment interactions relating to unprotected water and behaviors associated with Buruli ulcer risk likely to affect incidence rates. We characterised the sources of water as well as water bodies and streams used by communities, by conducting a prospective case-control study directly coupled with geographic field observations, spatial analysis, and the detection of M. ulcerans in the environment. A full list of the free surface waters used for domestic activities was generated for a set of 34 villages, and several types of human behaviour associated with a higher risk of transmission were identified: (i) prolonged walking in water to reach cultivated fields, (ii) collecting water, (iii) and swimming. Combining the results of the different analyses identified the risk factor most strongly associated with Buruli ulcer was the frequency of contact with unprotected and natural water, particularly in regularly flooded or irrigated lowlands. We confirm that the use of clean water from drilled wells confers protection against Buruli ulcer. These specific and refined results provide a broader scope for the design of an appropriate preventive strategy including certain practices or infrastructures observed during our field investigations. This strategy could be improved by the addition of knowledge about irrigation practices and agricultural work in low-lying areas.
The southern coastal belt of West Africa (SCWA) with its high population density and many major cities, combined to the low elevation and poor urban planning, is very vulnerable to floods resulting ...from extreme rainfall events. The aim of this paper is to analyze the characteristics of extreme rainfall in the SCWA during the 1981–2015 period, in terms of frequency, intensity, seasonality, and trends. Therefore, daily rainfall of 31 stations located in the southern part of Côte d’Ivoire, Ghana, Togo, and Benin and rainfall estimation products combining in situ observations and satellites rainfall estimation data have been used. For each station and pixel, the local 95th percentile (P95) computed on all rain days of at least 1 mm was used to define extreme rainfall events. Rainfall on the coastal belt is heavier than further inland, with P95 values reaching 82 and 52 mm/day for coastal and continental stations, respectively. Extreme rainfall along the coast occurs predominantly between May and July. Interannual variations of different indicators of extreme rainfall show a broad agreement between rain gauge data and rainfall estimates from CHIRPS (Climate Hazards Group InfraRed Precipitation with Station) data. In the southern part of Côte d’Ivoire and Togo/Benin, increase of number of extreme rainfall event (NP95) and stability number of days with rainfall less than P95 (NL95) are recorded, which induces an increase of total rainfall. But, in the southern part of Ghana, there is a stable total rainfall due to an increase in NP95 compensated by a decrease in NL95.
Dans cette étude, on a fait appel à la télédétection et aux systèmes d'information géographiques (SIG) pour évaluer et cartographier l'érosion hydrique en utilisant l'équation universelle des pertes ...en sol USLE dans le bassin versant de l'Oued Mina en Algérie. Ce bassin est caractérisé par une grande irrégularité dans les précipitations, une forte pente, une lithologie essentiellement marneuse et une couverture végétale très faible ce qui le rend très vulnérable à l'érosion. L'USLE est la combinaison de six facteurs spécifiques qui décrivent les caractéristiques du bassin versant. Les données de télédétection multi-temporelles et les SIG sont utilisés pour évaluer et cartographier chaque facteur individuellement. L'intégration des cartes thématiques des facteurs du modèle USLE dans le SIG permet de cerner l'impact de chaque facteur dans les pertes en sol, de classer par importance relative les zones d'érosion, et de quantifier les pertes en sol dans le bassin.
Editeur Z.W. Kundzewicz
Citation Toumi, S., Meddi, M., Mahé, G., et Brou, Y.T., 2013. Cartographie de l'érosion dans le bassin versant de l'Oued Mina en Algérie par télédétection et SIG. Hydrological Sciences Journal 58 (7), 1542-1558.
Les pluies maximales journalières annuelles de 34 postes pluviométriques de la Côte d'Ivoire ont été analysées sur la période 1947-1995. Ensuite, elles ont été ajustées à une loi de valeur extrême ...sélectionnée parmi les lois lognormale et de Gumbel suivant le test d'Anderson. Cette étape permet d'identifier la zone d'application des deux lois et d'évaluer l'impact de l'utilisation exclusive de la loi de Gumbel lors des études de génie civil sur l'ensemble du territoire. La cartographie des quantiles de période de retour de 2-100 ans à l'aide du krigeage indique que la loi lognormale convient mieux aux séries des régimes climatiques de type équatorial de transition et équatorial de transition atténué, surtout dans les parties ouest et centrale du pays. La loi de Gumbel paraît bien adaptée aux régimes de montagne, équatorial de transition et équatorial de transition atténué surtout dans sa partie nord et une petite portion de sa zone sud.
Cette étude évalue les conséquences de la variabilité climatique sur la maïsiculture pluviale dans l'est Ivoirien. Les tests de stationnarité ont mis en évidence des ruptures dans les séries ...pluviométriques à la fin des années 1960. L'impact de ces décrochages sur les saisons culturales montre que, malgré sa réduction après les années 1970, la durée de la première saison culturale ne constitue pas un facteur restrictif pour la maïsiculture de cycle court. L'évolution des conditions hydriques de la maïsiculture et les potentiels de rendements induits ont été simulés sur la base des données climatiques et des résultats d'essais de longue durée. Les conditions hydriques ont été caractérisées en termes de déficit et d'excès d'eau par le modèle CROPWAT-FAO de simulation du bilan hydrique. La confrontation des résultats des simulations et des indicateurs descriptifs des tendances de production, montre que l'état actuel des conditions climatiques n'explique pas la dynamique d'ensemble de la maïsiculture dans l'est Ivoirien.
Citation Noufé, D., Lidon, B., Mahé, G., Servat, E., Brou, Y. T., Koli, Bi Z., & Chaléard, J.-L. (2011) Variabilité climatique et production de maïs en culture pluviale dans l'est Ivoirien. Hydrol. Sci. J.
56(1), 152-167.
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