Tools to investigate the capacity of Australian Culicoides as vectors of bluetongue viruses

Abstract

Bluetongue Virus (BTV, Reoviridae, Sedoreoviridae, Orbivirus) is the type species of the genus Orbivirus, and is responsible for the potentially devastating disease known as bluetongue disease (BT). Some 26 serotypes of BTV are recognised globally and are transmitted by haematophagous Culicoides midges. A total of 9 real time PCR (qPCR) assays were developed and evaluated to study the host feeding preference of Culicoides biting midges. These were used to test nearly 1400 individual blood fed Culicoides from Australia, Indonesia and the Republic of Korea. The second theme presented in this thesis was the development of a laboratory model to enable the infection of Culicoides with BTVs without the use of ruminants. Several different methods for blood feeding Culicoides were evaluated, including the use of a membrane feeder, cotton wool pads and embryonated chicken eggs (ECEs). The ECE method was chosen as the preferred method, refined, and then used to study the infection of different populations of Culicoides with BTVs including four species from the Northern Territory (NT), and one species from New South Wales (NSW). The third phase of experimentation presented in this thesis involved the evaluation of molecular methods for identification and quantification of Culicoides collected as part of surveillance programs. Overall the tools and techniques developed in this thesis have the potential to increase the efficiency of surveillance for BTVs and their vectors in Australia to maintain trade access.