Recent analysis suggests that the exotic variant RHDV2 (in Australia since 2015) is replacing RHDV1 class biocontrol agents in Australian rabbit populations as the dominant RHDV field strain. This has strategic implications both in terms of the risk associated with the long-term persistence and effectiveness of the RHDV1 K5 released in March 2017, offset by the strategic benefit of implementing a synergised rabbit biocontrol regime based on a combination of RHDV1 and RHDV2 biocontrol agents.
This project aims to explore the potential of RHDV2 to complement existing biocontrol agents through a series of experimental studies. This project plays a vital role in the Centre for Invasive Species Solutions 20 years rabbit biocontrol pipeline and aims to understand the potential use of this virus as a future rabbit biocontrol agent.
February 2019 update:
This project is supporting research into the potential registration of RHDV2 as a biological agent for control of wild rabbits. It is unclear how the survival of rabbits is influenced by previous infections by one or more strains of RHDV. Understanding these interactions will inform which RHDV strains may be best suited for release at different times of the year and in different parts of Australia. A component of this work has commenced that experimentally assesses the ability of different virus strains to overcome pre-existing immunity to other strains in wild rabbits.
Another component of this project, the development of a prototype monovalent vaccine for RHDV2 is progressing well.
August 2019 update:
Assessment of the virulence and welfare impacts of RHDV2 in both adult and young rabbits is almost complete. 100% case fatality rate has been observed in laboratory rabbits, with a short illness duration.
Another project aspect is investigating the effect of maternal immunity on the ability of young rabbits to get infected with RHDV2 – a critical piece of information that will inform the timing of any future applications of RHDV2 as an additional biocide.
Wild rabbits which have been trapped and challenged with different strains of calicivirus in box trials, with different survival rates. Two further box trials will take place in Orange, NSW, pending ethics approval.
A prototype vaccine for RHDV2 is currently under review with the APVMA, and a multivalent vaccine is also in progress.