Understanding RHDV2 interaction with other RHDVs and its potential as an additional rabbit biocontrol agent

Summary

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.

Status

Commenced

Objectives

  1. Assess RHDV2 based on an experimental virulence assessment in comparison to existing data for other control tools.
  2. Work with the APVMA about the information requirements and data needed to assess RHDV2 as a rabbit biocontrol agent.
  3. Support the development of a multivalent vaccine to protect pet and commercially bred rabbits

Project Leader



Dr Pat Taggart
Project Team
  • Dr Pat Taggart , NSW DPI
  • Dr Tarnya Cox, NSW DPI
  • Dr Peter Fleming, NSW DPI 
  • Quentin Hart, NSW DPI 
  • Dr Andrew Read, NSW DPI 
  • Dr Peter Kirkland, NSW DPI 
  • Trudy Sharp, NSW DPI  
  • Dr Tanja Strive, CSIRO 
  • Dr Robyn Hall, CSIRO 
  • Dr Peter Caley, CSIRO 
  • John Kovaliski, PIRSA 
  • Dr Brad Page, PIRSA 
  • Sammi Chong, CSIRO
  • Dr Sahra McFetridge, PIRSA
  • Dr Sahra McFetridge, PIRSA
Project Partners
  • NSW Department of Primary Industries (NSW DPI)
  • Commonwealth Scientific and Industrial Research Organisation (CSIRO) 
  • Primary Industry and Regions South Australia (PIRSA)
  • Australian Wool Innovation (AWI)
  • Meat and Livestock Australia (MLA)

The project receives funding from the Australian Government Department of Agriculture, Water and Environment

Outputs

February 2021 update:

Experiments have been undertaken to contribute data to understanding the interactions between the different genotypes of RHDV. The experiments involved studying the ‘protection’ afforded by both natural infection and maternal antibodies, as well as studies involving immunity induced by vaccination. These data confirm that; a) the challenge viruses cause extremely high mortality rates (approaching 100%) b) that RHDV2 has a very variable capacity to overcome immunity c) that the K5 strain of RHDV1 has the capacity to overcome immunity to RHDV2 strains in a moderate proportion of rabbits.

August 2020:

RHDV2 virulence trials in both adult and young domestic rabbits are complete, the results are currently being prepared for publication. Trials have commenced into how maternal antibodies protect young rabbits against RHDV2 infection. A humaneness assessment of RHDV2 infections was completed using an established welfare matrix scoring process. The updated welfare assessment will be made available through PestSmart.

Good progress is being made towards a multivalent vaccine and a research permit for use of a prototype monovalent RHDV2 vaccine has been submitted to the AVPMA and is awaiting approval.

February 2020 update:

A component of the RHDV2 registration package has been prepared for submission to the APVMA.

The virulence of RHDV2 has been assessed in both adult and young laboratory rabbits. Studies investigating the effects of maternal antibodies on RHDV2 infection have commenced in laboratory rabbits.

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.

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.  

Scientific articles:

  • Cox, T.E., Ramsey, D.S.L., Sawyers, E. et al (2019). The impact of RHDV-K5 on rabbit populations in Australia: an evaluation of citizen science surveys to monitor rabbit abundance. Sci Rep 9,15229 https://doi.org/10.1038/s41598-019-51847-w
  • Taggart, P. L., Hall, R. N., Cox, T. E., Kovaliski, J., McLeod, S. R., & Strive, T. (2021). Changes in virus transmission dynamics following the emergence of RHDV2 shed light on its competitive advantage over previously circulating variants. Transboundary and Emerging Diseases https://doi.org/10.1111/tbed.14071
  • Ramsey, D. S. L., Cox, T., Strive, T., Forsyth, D. M., I., S., Hall, R., . . . Campbell, S. (2020). Emerging RHDV2 suppresses the impact of endemic and novel strains of RHDV on wild rabbit populations. Journal of Applied Ecology. https://doi.org/10.1111/1365-2664.13548

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