The vector competence of Culex annulirostris, Aedes sagax and Aedes alboannulatus for Murray Valley encephalitis virus at different temperatures

Abstract

Culex annulirostris Skuse, colonized from Brisbane, Queensland, and Mildura, Victoria, Australia, were effective vectors of Murray Valley encephalitis virus at 20, 27 and 32-35 degrees C with full extrinsic incubation periods of 15, 10 and 4 days respectively. At 20 degrees C, 7-11 days post-infection, transmission by the Mildura colony (0-20%) was less efficient than the Brisbane colony (30-70%) but both were capable of 75-100% transmission after longer extrinsic incubation periods. Discriminant analysis of body and salivary gland titres showed that these were not satisfactory indicators of transmission. Wild-caught Aedes sagax (Skuse) and Cx annulirostris from the Murray Valley showed equal competence, but Aedes alboannulatus (Macquart) was a poor vector. The results provide data on rural amplification of Murray Valley encephalitis virus during spring and suggest that further work on the potential of Ae. sagax as a natural vector is warranted.