Studies surveying the prevalence and biodiversity of mosquito-borne viruses in northern Australia was carried out using a novel, ELISA-based broad-spectrum virus screening system, based on the detection of long double-stranded RNA in inoculated mosquito cell cultures (MAVRIC). RNA was extracted for generic RT-PCR screening. MAVRIC-positive and RT-PCR negative pools were further characterised by deep sequencing, electron microscopy, vertebrate cell infection assays, microneutralisation assays and serological cross-reactivity studies.
Using MAVRIC, a novel orbivirus (family: Reovirdae), tentatively named Parry’s Lagoon virus (PLV) was detected and isolated from a pool of Culex annulirostris mosquitoes. PLV was shown to be phylogenetically and antigenically related to Corriparta virus (CORV), but failed to replicate in mammalian and avian cell lines, a fundamental difference to CORV. This striking phenotypic difference suggests that PLV has evolved to have a very restricted host range, indicative of a mosquito-only life cycle.
Fundamental differences between CORV and PLV warrant PLV’s classification as a separate species within the CORV serocomplex. The discovery and characterisation of additional mosquito-associated orbiviruses will provide valuable insights into genetic divergence, extending and enhancing our understanding of the mosquito virome.