A spatial assessment of Culicoides spp. distribution and bluetongue disease risk areas in Austria.

Bluetongue disease (BT) was introduced into Central Europe in the summer of 2006 and has since affected most European countries. In this study we analysed the distribution of the biting midge vector Culicoides spp. in Austria and modelled Bluetongue disease risk zones. Culicoides spp. abundance data was collected from weekly catches of 14 months from 54 trapping locations. The corresponding weather data mean temperature (p < 0.001), wind (p < 0.001), relative humidity (p = 0.019) and altitude (p = 0.059) were identified as predictors on Culicoides spp. distribution in a regression model (R 2.8.0). The majority of catches were detected at temperatures above 10 degrees C and at relative humidities between 65-80%. The point data of these parameters originating from 186 meteorological stations were interpolated using the Geostatistical Analyst Kriging tool (ESRI ArcGIS 9.3). To create seasonal risk maps we overlaid regions with optimal temperature and humidity conditions with domestic ruminants density data. Our results show that the summer season holds the greatest risk of a BT epidemic with 25.9% of the analysed area providing optimal conditions for vector abundance and 12.4% showing contact risk with ruminant hosts. This project (1) provides fundamental data on the Culicoides spp. distribution in Austria, (2) determines limiting climatic parameters on vector abundance and (3) identifies risk areas by including areas of possible host-parasite-interactions. These high-risk areas can subsequently be given special attention for precautionary monitoring and surveillance measures.