Abstract:
Following the emerging bluetongue virus transmission in European temperate regions, we
question the vector competence of the abundant Culicoides austropalpalis Lee and Reye in
South‑East temperate Australia. Field collected Culicoides midges were membrane fed with
a bluetongue virus serotype 1 (BTV‑1). The average feeding rate was 50%. After 13 days,
survival rate was 25% and virus RNA presence was checked by quantitative PCR targeting
viral genome segment 10. Virus RNA was found in 7.4% of individually tested females with
relative viral RNA load values lower than freshly fed females, indicating that viral replication
was low or null. A second qPCR targeting viral genome segment 1 confirmed the presence
of virus RNA in only four out of 29 previously positive specimens. After 10 days culture
on Culicoides cells, none of these four confimed positive samples did show subsequent
cytopathogenic effect on Vero cells or BTV antigen detection by ELISA. As control for this
virus activity detection, 12 days after microinjection of BTV‑1, Culex annulirostris mosquitoes
showed, after culture on Kc cells, cytopathogenic effect on Vero cells, with ELISA‑confirmed
infection. Despite its abundance in farm environment of the temperate Australian regions,
the results of this study make C. austropalpalis of unlikely epidemiological importance in the
transmission of BTV in Australia.
