The isolation of bluetongue virus from field populations of the Obsoletus Complex in central Italy.

: Between July and September 2002, bluetongue (BT) virus (BTV) serotypes 2 and 9 caused mortalities amongst sheep in the communities of San Gregorio Magno (Salerno, Campania), Laviano (Salerno, Campania) and Carpino (Foggia, Puglia), central Italy. On three of the affected farms, approximately 10,000 specimens of Culicoides were captured, representing fifteen species. Not a single specimen of the classical Afro-Asiatic BT vector, C. imicola Kieffer, was found; species of the Obsoletus Complex dominated the light-trap collections (90%) and included C. obsoletus (Meigen), C. scoticus Downes and Kettle and C. dewulfi Goetghebuer. Fifty-eight pools of the Obsoletus Complex (excluding C. dewulfi), each numbering 100 individuals per pool, and containing only parous and gravid females, were assayed for virus. BTV serotype 2 (BTV-2) was isolated from three pools (San Gregorio and Carpino) and BTV-9 from one (Laviano). These results indicate clearly that a species other than C. imicola is involved in the current re-emergence of BT in the Mediterranean Basin, but whether this is only C. obsoletus sensu stricto, or only C. scoticus, or both together, has yet to be established.