INFECTION OF CULICOIDES-BREVITARSIS AND C-WADAI (DIPTERA, CERATOPOGONIDAE) WITH 4 AUSTRALIAN SEROTYPES OF BLUETONGUE VIRUS

Field collected Culicoides brevitarsis Kieffer and C. wadai Yitaoka were fed on sheep that had been artificially infected with a field-isolate of either bluetongue virus serotype 3 (BLU3), BLU9, BLU16, or BLU23. Feeding rates averaged 11.9% but were variable. Survival of midges during incubation tended to be enhanced by the addition of antibiotics and fungicide to the diet. Attempts to transmit virus to sheep by the bite of these two species were unsuccessful. Both C. brevitarsis and C. wadai had infection rates of between 1.3 and 1.5% for BLU16 and BLU23. The infection rate for BLU3 in C. wadai was low at 0.07% whereas those for BLU3 in C. brevitarsis and BLU9 in both species could not be calculated because of insufficient virus isolations. The relatively high infection rates for BLU16 and BLU23 suggest that both C. brevitarsis and C. wadai are capable of circulating these viruses in the field.