Seasonal Survival and Expectation of Infective Life of Culicoides Spp. (Diptera: Ceratopogonidae) in Israel, With Implications for Bluetongue Virus Transmission and a Comparison of the Parous Rate in C. Imicola from Israel and Zimbabwe1

Abstract

The vectorial potential of Culicoides imicola, Culicoides obsoletus, and Culicoides oxystoma with respect to bluetongue virus (BTV) in Israel in 1981–1982 was evaluated based upon their respective mean periods between blood meals, their estimated survival rates between blood meals, and their expectation of infective life. Culicoides imicola was identified as the species with the highest vectorial potential because of its seasonality, presence throughout the entire year, survival rate, and expectation of infective life. This species may serve as an overwintering agent for BTV. By the same criteria, C. obsoletus was ranked 2nd in vectorial potential. Its survival rate and expectation of infective life were more limited than in C. imicola, but it also appeared capable of serving as an overwintering agent for BTV. Culicoides oxystoma was ranked 3rd because of its small numbers, presence only from August to December, limited peak survival rate, and brief period of expected infective life. However, for a limited period the last 2 variables for the 3 species tested were highest in C. oxystoma. During the bluetongue season the mean period between blood meals is 3.3 to 4.6 days for C. imicola, 3.5 to 5.0 days for C. oxystoma, and 4.0 to 4.9 days for C. obsoletus. Comparison between C. imicola from Bet-Dagan, Israel, and C. imicola from Mt Hampden, Zimbabwe, shows that in both countries the parous rate in this species peaks from midsummer to the onset of winter, a period corresponding to the bluetongue season.