Use of high spatial resolution satellite imagery to characterize landscapes at risk for bluetongue

Abstract

-The recent and rapid spread in the Mediterranean Basin of bluetongue, a viral disease of ruminants transmitted by some species of Culicoides (biting midges), highlights the necessity of determining the conditions of its emergence. This study uses high spatial resolution satellite imagery and methods from landscape ecology science to identify environmental parameters related to bluetongue occurrence in Corsica, a French Mediterranean island where the disease occurred for the first time in 2000. A set of environmental variables recorded in the neighborhood of 80 sheep farms were related to case occurrence through a logistic regression model computed within three subsequent buffer distances of 0.5, 1 and 2 km. The results reveal the role of landscape metrics, particularly those characterizing land-use units such as prairies and woodlands, as well as farm type, latitude and sunshine to explain the presence of bluetongue. Internal and external validation both indicate that the best results are obtained with the 1 km buffer size model (area under Receiver Operating Characteristic curve = 0.9 for internal validation and 0.81 for external validation). The results show that high spatial resolution remote sensing (i.e. 10 m pixels) and landscape ecology approaches contribute to improving the understanding of bluetongue epidemiology.epidemiology / bluetongue / remote sensing / geographic information systems / landscape ecology

Predictive Modeling of West Nile Virus Transmission Risk in the Mediterranean Basin: How Far from Landing?

“…In particular, bird species richness was shown to be linked to landscape heterogeneity [66]. Similarly, landscape metrics have been linked to the abundance of Bluetongue vectors ( Culicoides imicola ) [67] and to the risk of Bluetongue clinical cases or seroprevalence [68,69]. …”

Anatomy of Bluetongue virus Serotype 8 Epizootic Wave, France, 2007–2008

“…These landscape indices are increased when the interweaving of land cover themes increases because landscape is complex and fragmented. Fragmentation indices have been linked to abundance of vectors of BTV ( C. imicola midges in southern France) ( 24 ), and the local density of forest and pasture edges have been linked to bluetongue disease risk in Corsica ( 25 ). More generally, ecotones are places where vegetal and animal species of different ecosystems meet and mix and thus where contact rates are increased.…”

Importance of Wetlands Management for West Nile Virus Circulation Risk, Camargue, Southern France

“…However, if the spatial dependence in the response variable is completely explained by the pattern in the exposure variable, no spatial autocorrelation should be present in the regression residuals and regression will produce correct effect estimates and confidence intervals [22]. Any not-accounted-for spatial correlation in the residuals of the logistic model was identified by applying the described Monte Carlo method [24] used in previous studies [25]. Goodness-of-fit of the final model was assessed by computing the area under the curve (AUC) of the receiver operating characteristic plots.…”