Oral Presentation 8th Australasian Virology Society Meeting and 11th Annual Meeting of the Australian Centre for Hepatitis & HIV Virology Meeting 2015

Discovery and characterisation of a new non-pathogenic New Zealand rabbit calicivirus strain (#41)

Leila Nicholson 1 2 , Janine Duckworth 2 3 , Tanja Strive 3 4 , Jackie Mahar 4 5 , Edward Holmes 5 , Vernon Ward 1
  1. Department of Microbiology & Immunology, Otago School of Medical Sciences, University of Otago, Dunedin, New Zealand
  2. Wildlife Ecology and Management Group, Landcare Research, Lincoln, New Zealand
  3. Invasive Animals Cooperative Research Centre, University of Canberra, Bruce, ACT, Australia
  4. Health and Biosecurity, Commonwealth Scientific and Industrial Research Organisation, Black Mountain, Canberra, ACT, Australia
  5. Marie Bashir Institute for Infectious Disease and Biosecurity, Charles Perkins Centre, School of Biological Sciences and Sydney Medical School, The University of Sydney, Sydney, NSW, Australia

Since 1997 rabbit haemorrhagic disease virus (RHDV) has been used in New Zealand as a biological control agent to reduce pest rabbit populations but the effectiveness of RHDV is waning. One contributing factor is the increasing number of rabbits acquiring immunity to RHDV early in life. In other countries, RHDV immunity is influenced by the presence of benign rabbit caliciviruses (RCVs) which can confer a degree of cross protection against the pathogenic RHDV.  Antibodies that reacted against RHDV were found in wild rabbits sampled before 1997, suggesting benign RCVs were present in New Zealand prior to the arrival of RHDV.  Early attempts to isolate NZ RCV failed.  In the present study serological and molecular tools were used to screen for caliciviruses in samples from over 400 wild New Zealand rabbits. A specific RCV blocking ELISA [1] was used to study the RCV antibody prevalence across different geographical regions. Antibody profiles indicate that RCV infection is acquired early in life.  A universal lagovirus PCR test [2] identified a novel RCV strain from the duodenum of healthy wild rabbits. Sequencing and phylogenetic analysis of the capsid region revealed the virus shares a most recent common ancestor with Australian RCV strains but, with 88% nucleotide similarity, is distinctly different. The characteristics of NZ RCV were examined in laboratory rabbits (n=18) by measuring tissue viral loads and virus shedding for up to 28 days post infection. Results indicate the virus is non-pathogenic.  Prior to the discovery of the NZ RCV strain, 10 wild rabbits with pre-existing RCV antibodies were challenged with RHDV.  Results suggest the NZ RCV strain may provide a degree of cross-protection against RHDV but this needs to be confirmed in more comprehensive studies. The knowledge gained from this study will assist understanding virus-host/virus-virus interactions and ultimately aid future rabbit biocontrol efforts.

  1. Liu, J., P.J. Kerr, and T. Strive, A sensitive and specific blocking ELISA for the detection of rabbit calicivirus RCV-A1 antibodies. Virology Journal, 2012. 9(1): p. 182-186.
  2. Strive, T., J.D. Wright, and A.J. Robinson, Identification and partial characterisation of a new lagovirus in Australian wild rabbits. Virology, 2009. 384(1): p. 97-105.