Summary
Culicoides brevitarsis Kieffer is the main vector of bluetongue and Akabane viruses in Australia. Its threat to animal health and livestock exports requires that areas free of the vector and viruses be defined clearly. In New South Wales, survival of the vector over winter is limited to the northern coastal plains. C. brevitarsis therefore has to reinfest areas outside the endemic area each year. Models have been developed to predict the extent and nature of its movements. It can move at different rates and this is partly due to significant delays of movement due to the barrier formed by the altitude of the Great Dividing Range. C. brevitarsis subsequently retains a coastal distribution in most years. At the end of the season, the times when activity would effectively cease can be estimated from temperature data. These data allow evidenced-based conclusions on zonal and seasonal freedom to be made in combination with light trap monitoring.

Keywords
Altitude, Australia, Bluetongue, Culicoides brevitarsis, Dispersal, Models, Vector freedom.