Species of the subgenus Avaritia including Culicoides obsoletus
Biting midges of the genus Culicoides include vector species for orbiviral diseases, such as bluetongue (BT) and African horse sickness (AHS). Although the Afro-Asiatic species Culicoides imicola is the major vector of BT in the Mediterranean Basin, recent outbreaks in regions where C. imicola is absent has incriminated other Culicoides including those belonging to the Obsoletus Complex of the subgenus Avaritia Fox, 1955. The classical taxonomy of this species complex is unclear and this stimulated the molecular analysis of 20 Culicoides populations sampled from 18 localities across Italy. Ribosomal ITS2 sequences were used to characterise the intra- and inter-specific variation between Italian members of the Obsoletus Complex and related species, by means of AMOVA and phylogenetic analyses. Although morphological differentiation is often extremely difficult, the molecular analysis clearly demonstrated a high degree of divergence between most of the species. The study shows that at least seven species of the subgenus Avaritia occur in Italy; these are C. obsoletus, C. scoticus, C. montanus, C. dewulfi, C. imicola and two species which could not be identified with certainty but one of which is similiar to C. chiopterus. Finally, a simple PCR assay was developed which rapidly discriminates between four members of the Obsoletus Complex in Italy, a prerequisite for vector identification.