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

Christopher Marston,Patrick Giraudoux

doi:10.3390/rs11010039

Abstract

(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.

Highlights

The parasitic tapeworm Echinococcus multilocularis (Em) is a highly effective pathogen of HumanAlveolar Echinococcosis (HAE), which is a chronic debilitating disease with >90% mortality in untreated patients 10 years after diagnosis [1,2,3]
Time-series Synthetic Aperture Radar (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
We address the following problems: (1) lack of information of the small mammal distributions, and landscape drivers thereof, of the species involved in the Em transmission cycle, which limits efficient targeting of control measures, (2) cloud-cover inhibiting optical remote sensing-based landscape-small mammal modelling, and (3) inaccuracies resulting from the influence of vegetation phenological dynamics for landscape-small mammal modelling

Summary

Introduction

The parasitic tapeworm Echinococcus multilocularis (Em) is a highly effective pathogen of HumanAlveolar Echinococcosis (HAE), which is a chronic debilitating disease with >90% mortality in untreated patients 10 years after diagnosis [1,2,3]. A neglected zoonotic disease, HAE is responsible for a significant burden of human disease across continental Asia, and is expanding in the prevalence and range in Europe, North America, and Asia [4,5,6]. In China and central Asia, HAE prevalence. [7,8,9]even eventhough thoughgeographical geographical patterns patterns are are highly variable, as humans can exceed as elsewhere in the world [10]. The reasons for this variability are unknown. Elsewhere in the world [10]

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Conclusion