Summary
A geographic information system (GIS) based on grids was developed by the National Reference Center for Veterinary Epidemiology at the Istituto Zooprofilattico Sperimentale dell’Abruzzo e del Molise ‘G. Caporale’ (IZS) in Teramo to identify potential infectious sites for bluetongue (BT) disease in Italy. Geographical and climatic variables were used to build a spatial process model (SPM); the different layers were combined by sequential addition. The final grids (with a cell size of 0.0387 decimal degrees) were generated for each season of the year, and the suitability of each cell for the presence of C. imicola given a value ranking from 0 to 10. While this model more accurately predicts the presence of C. imicola in the Basilicata and Sicily regions, it still over-predicted its presence in the Puglia region. This could be due to the occurrence of calcareous soils which dominate the Puglia landscape. The present SPM is an additive model that assigns an equal weight to each variable. However, the results suggest the existence of hitherto unconsidered variables that significantly influence the prevalence of C. imicola. To reflect their importance, these variables should be assigned a higher weighting in future models. However, the decision in regard to precisely what this weighting should be depends on a very thorough knowledge of the ecology of C. imicola.

Keywords
Bluetongue, Culicoides imicola, Geographic information system, Italy, Spatial model.