Pour une médecine globale, préventive et écologique…: For a global, preventive and ecological medicine...

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On the Synergistic Use of Optical and SAR Time-Series Satellite Data for Small Mammal Disease Host Mapping

International audience(1) Background: Echinococcus multilocularis (Em), a highly pathogenic parasitic tapeworm, is responsible for a significant burden of human disease. In this study, optical and time-series Synthetic Aperture Radar (SAR) data is used synergistically to model key land cover characteristics driving the spatial distributions of two small mammal intermediate host species, Ellobius tancrei and Microtus gregalis, which facilitate Em transmission in a highly endemic area of Kyrgyzstan. (2) Methods: A series of land cover maps are derived from (a) single-date Landsat Operational Land Imager (OLI) imagery, (b) time-series Sentinel-1 SAR data, and (c) Landsat OLI and time-series Sentinel-1 SAR data in combination. Small mammal distributions are analyzed in relation to the surrounding land cover class coverage using random forests, before being applied predictively over broader areas. A comparison of models derived from the three land cover maps are made, assessing their potential for use in cloud-prone areas. (3) Results: Classification accuracies demonstrated the combined OLI-SAR classification to be of highest accuracy, with the single-date OLI and time-series SAR derived classifications of equivalent quality. Random forest analysis identified statistically significant positive relationships between E. tancrei density and agricultural land, and between M. gregalis density and water and bushes. Predictive application of random forest models identified hotspots of high relative density of E. tancrei and M. gregalis across the broader study area. (4) Conclusions: This offers valuable information to improve the targeting of limited-resource disease control activities to disrupt disease transmission in this area. Time-series SAR derived land cover maps are shown to be of equivalent quality to those generated from single-date optical imagery, which enables application of these methods in cloud-affected areas where, previously, this was not possible due to the sparsity of cloud-free optical imagery

Vegetation phenology and habitat discrimination : impacts for E.multilocularis transmission host modelling

Echinococcus multilocularis (Em), a parasitic tapeworm, is responsible for a significant burden of human disease across continental Asia. Here, we use a time-series of MODIS 16-day 250 m Enhanced Vegetation Index (EVI) satellite data to quantify the seasonal vegetation dynamics across a study area in Serxu County, Sichuan Province, China, in relation to the presence of the Em intermediate host Ochotona curzoniae (plateau pika) and Ochotona cansus (Gansu pika) (here merged to Ochotona spp.). A series of derived phenological metrics are analysed using the random forests statistical method to determine the relative importance of seasonal vegetation characteristics. Results indicate negative relationships between Ochotona spp. presence and EVI showing a preference for low-biomass habitats. However, EVI values during green-up and senescence periods are also shown to be important, potentially resulting from improved detectability of low-biomass grassland habitats at these times. Improved detection of Ochotona spp. preferred habitats via time-series EVI imagery offers better understanding of the distributions of this Em host, and the potential for monitoring the changes in Ochotona spp. optimal habitat distributions resulting from landscape change. This could aid the identification of villages at increased risk of infection, enabling preventive strategies to be adopted

Interactions between landscape changes and host communities can regulate echinococcus multilocularis transmission

An area close to the Qinghai-Tibet plateau region and subject to intensive deforestation contains a large focus of human alveolar echinococcosis while sporadic human cases occur in the Doubs region of eastern France. The current review analyses and compares epidemiological and ecological results obtained in both regions. Analysis of rodent species assemblages within quantified rural landscapes in central China and eastern France shows a significant association between host species for the pathogenic helminth Echinococcus multilocularis, with prevalences of human alveolar echinococcosis and with land area under shrubland or grassland. This suggests that at the regional scale landscape can affect human disease distribution through interaction with small mammal communities and their population dynamics. Lidicker's ROMPA hypothesis helps to explain this association and provides a novel explanation of how landscape changes may result in increased risk of a rodent-borne zoonotic disease

Ecohealth and the GDRI EHEDE. What’s up ?

International audienceThe integration of eco-epidemiology in the concept of one-health, the success achieved by systems approach in other science areas (e.g. rodent pest control, conservation biology, etc.) and the fact that disease transmission is increasingly thought to be the result of the (socio-eco) systemic integration of links between the health of all species and that of their environment, the difficult definition of "health" as a general concept, leave open a very fertile field of research.This field of research and application is being popularized in the term "Ecohealth". A basic tenet is that health and well-being cannot be sustained in a resource depleted, polluted and socially unstable planet. This is why Ecohealth scholars and practitioners engage in integrated systems approach to health that sustain ecosystem health services, foster social stability and promote the peaceful interdependence, coexistence and evolution of humans, animals, plants and their environments (see https://ecohealth.net).To do so, it is essential to develop parallel paths, bridges and sustainable long-term interactions, between disciplines that can contribute to these studies. Created in 2013, labeled by the CNRS, this is typically the goal of the GDRI EHEDE. Here we briefly introduce the main research issues of the GDRI EHEDE, and how different lab share experience for a better understanding of environmental issues linked to human, animal and ecosystem health:• Ecology of Cestode transmission in Asia, Europe and North America. The life-cycle of those metazoan parasites ranges from merely sylvatic to merely domestic and offers unique opportunities to understand, in a systems approach, how anthropogenic human disturbance of ecosystems leads to transmission re-enforcement, sustained stability or to extinction in various conditions.• Wildlife ecology and ecosystem health. Here we focus on (1) wildlife human conflicts such as those triggered by small mammal population surges (potentially resulting in increased parasite transmission) as a consequence of landscape and agricultural practice alterations, (2) conservation of the black and white snub-nosed monkey in a context of global warming and increasing agricultural encroachment in high altitude forests (3) management of increasing populations of wild Asian elephants in a mosaic of forest and intensive agriculture.• Permanent workshop on adaptive monitoring, data management and modelling. Here we share experience in long term multi-disciplinary study design and adaptive monitoring in the field of ecosystem health and environmental disease ecology. Moreover, the GDRI EHEDE focusing on integrated systems approaches to health and their practical applications has a special concern about spatially explicit and multiscale modelling

Pasture Types and Echinococcus multilocularis, Tibetan Communities

Our study showed that open pastures had more small mammal burrows than fenced pastures in Tibetan pastoralist communities in 2003. This characteristic was linked to a higher prevalence of Echinococcus multilocularis in dogs and indicates that pasture type may affect E. multilocularis transmission

Les "vagues voyageuses" du campagnol terrestre en Franche-Comté

Dans les prairies d'altitude, les dégâts provoqués par le campagnol terrestre posent un problème économique et agricole récurrent depuis le début des années 70. Dans la lutte contre cette peste agricole, l'utilisation croissante d'un anticoagulant rodenticide, la bromadiolone, a en plus considérablement augmenté la mortalité de nombreuses espèces animales, notamment de rapaces (légalement protégés), de renards et de sangliers. Dès le début du siècle, les recherches sur les variations de populations de rongeurs ont montré que la densité de certaines espèces de petits mammifères (lemmings, campagnols, etc.) fluctue de manière plus ou moins cyclique