En prenant de la hauteur et en offrant une vue élargie des territoires, les images satellite et les photographies aériennes permettent d’appréhender les facteurs environnementaux qui peuvent conditionner la santé des populations. Depuis l’essor de la télédétection satellite à partir des années 1970, son usage dans le domaine de la santé a connu des succès modérés. Si son potentiel a été largement évoqué dans la littérature jusqu’aux années 2000, son apport opérationnel ne s’est pas imposé. Ce n’est que récemment que les applications en santé se sont enrichies et multipliées par le développement d’approches interdisciplinaires. Cet article vise à questionner les usages de la télédétection appliquée aux questions de santé selon les aspects techniques, historiques, et thématiques afin d’identifier les verrous. Il propose tout d’abord une vue didactique des principes théoriques, des données disponibles et des usages possibles. A travers une étude bibliographique, il offre un regard rétrospectif sur l’évolution de sa mise en œuvre dans le domaine la santé, qui permet de synthétiser les contributions actuelles : pour la cartographie opérationnelle, pour la surveillance et l’analyse des dynamiques des maladies infectieuses ou, dans une moindre de mesure, pour appréhender les vulnérabilités des populations comme les difficultés d’accès aux soins. Enfin, l’article conclut sur les limites, les recommandations et les perspectives pour optimiser ces usages dont les verrous sont souvent techniques et structurels mais pour lesquels des méthodologies doivent encore être développées.
Observed variations in dolphin acoustic signals may be associated with behavior, social composition, and local differences in habitat features. This study aims at characterizing whistles emitted by the spinner dolphin population occurring in the waters of the main island of the Archipelago of Comoros (Mozambique Channel, Indian Ocean) and to assess factors possibly influencing the acoustic structure of signals. All parameters examined on 953 whistles significantly differed in relation to environmental conditions, group size, and behavior. By mixed model analysis, it was found that only habitat characteristics play a role in the variation of frequency parameters, and exerted on the acoustic structure of whistles stronger influence than socio-behavioral factors. Spinner dolphins occurring in the Comoros archipelago use higher frequencies and show longer signal duration compared to those from the Pacific and the Atlantic. Results suggest that frequency parameters are distinctive of the local population and reflect the habitat use of the species in the area. In conclusion, acoustic measurements may be crucial elements to be included in monitoring programs to identify local peculiarities of dolphins' populations.
Many small islands are located in the southwestern Indian Ocean. These islands have their own environmental specificities and very fragmented landscapes. Generic land use products developed from low and medium resolution satellite images are not suitable for studying these small territories. This is why we have developed a land use/land cover product, called Homisland-IO, based on remote sensing processing on high spatial resolution satellite images acquired by SPOT 5 satellite between December 2012 and July 2014. This product has been produced using an object-based classification process. The overall accuracy of the product is 86%. Homisland-IO is freely accessible through a web portal and is thus available for future use. Dataset: 10.5281/zenodo.2585747 (https://zenodo.org/record/2585747) Dataset License: CC BY 4.0
The world distribution of dwarf and pygmy sperm whales (Cetacea: Kogiidae) [Kogia spp.] is poorly known, and derived mostly from records of stranded animals. At sea, both species are elusive and difficult to identify. We photo-documented the presence of dwarf sperm whale (Kogia sima) in the waters of the Union of the Comoros. All three occurrences were sightings of apparently healthy animals from 2011 to 2013 in and near Itsandra Bay, off the island of Grande Comore. We discuss the importance of the Mozambique Channel and the Agulhas Current Large Marine Ecosystem for the species in the Western Indian Ocean.
Malaria has long been endemic in the Union of Comoros reaching an incidence of 15,045 cases for 100,000 inhabitants in 2010 (103,670 cases). Since then, strengthened control actions based on the distribution of Long-Lasting Insecticidal mosquito Nets and mass treatment have reduced malaria to a low level. However, it persists more specifically in Grande Comore, where 82% of cases were diagnosed between 2010 and 2016. This situation remains a challenge for health authorities seeking to eliminate malaria, by targeting transmission sites more precisely. In this context, this study aimed at mapping malaria at the finest scale, in order to describe its spatial distribution and identify possible environmental indicators. The National Malaria Control Program provided the 2016 data, the only year that could be mapped at the level of localities. This mapping revealed spatial autocorrelation between localities, especially in the east of the island with a major cluster around Itsinkoudi (using the Kulldorff’s spatial scan test). Secondary clusters showed that malaria remains present throughout the island in both rural and urban areas. We also analyzed satellite images (SPOT 5) with remote sensing techniques (Object-Based Image Analysis) to look for environmental indicators. Landscape analysis shows that malaria incidence is correlated across the island with low altitudes, and a larger proportion of grasslands or a fewer proportion of forested areas nearby (at less than 1km around villages). More locally in the east, malaria is linked to larger shrub areas. These relationships could be associated with the fact that lower altitude localities are more interconnected, such facilitating malaria transmission. In 2016, malaria persists in Grande Comore, showing new patterns with more cases in the eastern part of the island and the possibility of high incidences during the dry season. Precise mapping of epidemiological data and landscape analysis allow the identification of clusters and active transmission foci. They are important tools for health surveillance in order to optimize control actions on key transmission locations.
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