(RHDV2; GI.2) is a pathogenic calicivirus that affects European rabbits () and various hare () species. GI.2 was first detected in France in 2010 and subsequently caused epidemics in wild and domestic lagomorph populations throughout Europe. In May 2015 GI.2 was detected in Australia. Within 18 months of its initial detection GI.2 had spread to all Australian states and territories and rapidly became the dominant circulating strain, replacing (RHDV/GI.1) in mainland Australia. Reconstruction of the evolutionary history of 127 Australian GI.2 isolates revealed that the virus arrived in Australia at least several months before its initial description and likely circulated unnoticed in wild rabbit populations in the east of the continent prior to its detection. GI.2 sequences isolated from five hares clustered with sequences from sympatric rabbit populations sampled contemporaneously, indicating multiple spillover events into hares rather than an adaptation of the Australian GI.2 to a new host. Since the presence of GI.2 in Australia may have wide ranging consequences for rabbit biocontrol, particularly with the release of the novel biocontrol agent GI.1a/RHDVa-K5 in March 2017, ongoing surveillance is critical to understanding the interactions of the various lagoviruses in Australia, and their impact on host populations. This study describes the spread and distribution of (GI.2) in Australia since its first detection in May 2015. Within the first 18 months following its detection, RHDV2 spread from east to west across the continent and became the dominant strain in all mainland states of Australia. This has important implications for pest animal management and for owners of pet and farmed rabbits, as there is currently no effective vaccine available in Australia for GI.2. The closely related RHDV (GI.1) is used to control overabundant wild rabbits, a serious environmental and agricultural pest in this country, and it is currently unclear how widespread circulation of GI.2 will impact ongoing targeted wild rabbit management operations.

In mid-February 2015, a large number of deaths were observed in the sole extant population of an endangered species of freshwater snapping turtle, Myuchelys georgesi, in a coastal river in New South Wales, Australia. Mortalities continued for approximately 7 weeks and affected mostly adult animals. More than 400 dead or dying animals were observed and population surveys conducted after the outbreak had ceased indicated that only a very small proportion of the population had survived, severely threatening the viability of the wild population. At necropsy, animals were in poor body condition, had bilateral swollen eyelids and some animals had tan foci on the skin of the ventral thighs. Histological examination revealed peri-orbital, splenic and nephric inflammation and necrosis. A virus was isolated in cell culture from a range of tissues. Nucleic acid sequencing of the virus isolate has identified the entire genome and indicates that this is a novel nidovirus that has a low level of nucleotide similarity to recognised nidoviruses. Its closest relatives are nidoviruses that have recently been described in pythons and lizards, usually in association with respiratory disease. In contrast, in the affected turtles, the most significant pathological changes were in the kidneys. Real time PCR assays developed to detect this virus demonstrated very high virus loads in affected tissues. In situ hybridisation studies confirmed the presence of viral nucleic acid in tissues in association with pathological changes. Collectively these data suggest that this virus is the likely cause of the mortalities that now threaten the survival of this species. Bellinger River Virus is the name proposed for this new virus.

Rabbit haemorrhagic disease virus (RHDV, or GI.1) is a calicivirus in the genus Lagovirus that has been widely utilized in Australia as a biological control agent for the management of overabundant wild European rabbit (Oryctolagus cuniculus) populations since 1996. Recently, two exotic incursions of pathogenic lagoviruses have been reported in Australia; GI.1a-Aus, previously called RHDVa-Aus, is a GI.1a virus detected in January 2014, and the novel lagovirus GI.2 (previously known as RHDV2). Furthermore, an additional GI.1a strain, GI.1a-K5 (also known as 08Q712), was released nationwide in March 2017 as a supplementary tool for wild rabbit management. To discriminate between these lagoviruses, a highly sensitive strain-specific multiplex RT-PCR assay was developed, which allows fast, cost-effective and sensitive detection of the four pathogenic lagoviruses currently known to be circulating in Australia. In addition, we developed a universal RT-qPCR assay to be used in conjunction with the multiplex assay that broadly detects all four viruses and facilitates quantification of viral RNA load in samples. These assays enable rapid detection, identification and quantification of pathogenic lagoviruses in the Australian context. Using these assays, a novel recombinant lagovirus was detected in rabbit tissue samples, which contained the non-structural genes of GI.1a-Aus and the structural genes of GI.2. This variant was also recovered from the liver of a European brown hare (Lepus europaeus). The impact of this novel recombinant on Australian wild lagomorph populations and its competitiveness in relation to circulating field strains, particularly GI.2, requires further studies.

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