Models for the dispersal in Australia of the arbovirus vector, Culicoides brevitarsis Kieffer (Diptera : Ceratopogonidae)

Culicoides brevitarsis is the main biting midge responsible for the transmi ssion of bluetongue and Akabane viruses to livestock in Australia. Models a re given for its dispersal after winter from endemic areas at the southern limit of its distribution in New South Wales (NSW); the models might also b e applicable elsewhere. Model 1 shows that dispersal can be explained by di stance from a key point just outside the endemic area in mid-northern/north ern coastal NSW. The model provides probability data for times of first occ urrence at sites within regions down the southern coastal plain or up the H unter Valley towards (but rarely reaching) the western slopes and tableland s. Model 2 shows that the movement depends on temperature and wind speed fr om northerly and easterly directions. Preliminary data also are given to su ggest a relationship between density in the endemic area and the maximum di stance that C. brevitarsis can travel in a given year. The models can be li nked to other information which in combination can provide probabilities fo r winter survival outside the endemic area, times of occurrence at sites wh ere it cannot survive winter and times when activity ceases naturally at th ese sites at the end of the season. This information can be used to predict the potential for virus transmission and indicate zones of seasonal freedo m from both vector and virus for the export of livestock. (C) 2000 Elsevier Science B.V. All rights reserved.