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Title: STUDIES ON OVERWINTERING OF BLUETONGUE VIRUSES IN INSECTS

Author
item WHITE, DAVID - FORMER 5410-10-0 EMPLOYEE
item Wilson, William
item BLAIR, CAROL - COLO STATE UNIV
item BEATY, BARRY - COLO STATE UNIV

Submitted to: Journal of General Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2004
Publication Date: 10/19/2004
Citation: White, D.M., Wilson, W.C., Blair, C.D., Beaty, B.J. Studies on overwintering of bluetongue viruses in insects. Journal of General Virology. (2005)86,453-462

Interpretive Summary: Bluetongue viruses (BTVs) are economically important insect-transmitted viruses that affect sheep and Cattle. How these viruses persist over winter in temperate climates has eluded researchers for many years. This paper presents evidence that suggest that BTVs could over winter in the insect vector.

Technical Abstract: Bluetongue viruses (BTVs) are economically important arboviruses that affect sheep and cattle. The overwintering mechanism of BTVs in temperate climates has eluded researchers for many years. Many arboviruses overwinter in their invertebrate vectors. To test the hypothesis that BTVs overwinter in their vertically infected insect vectors, Culicoides sonorensis larvae were collected from long-term study sites in northern Colorado, USA, and assayed for the presence of BTV RNA by nested RT-PCR. Sequences from BTV RNA segment 7 were detected in 30% (17/56) of pools composed of larvae and pupae collected in 1998 and in 10% (31/319) of pools composed of adults reared from larvae collected in 1996. BTV was not isolated from the insects. Additionally, Culicoides cell-culture lines derived from material collected at one of the sites, or derived from insect samples collected during a BTV outbreak, contained BTV RNA segment 7. In contrast, segment 2 RNA was detected at half the rate of segment 7 RNA in the field-collected larvae and was only detected in the Culicoides cell lines with one of two primer sets. These data suggest that BTVs could overwinter in the insect vector and that there is reduced expression of the outer capsid genes during persistent infection.