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Ecology, management and conservation in natural and modified habitats
RESEARCH ARTICLE

Does a benign calicivirus reduce the effectiveness of rabbit haemorrhagic disease virus (RHDV) in Australia? Experimental evidence from field releases of RHDV on bait

Greg Mutze A C , Ron Sinclair A , David Peacock A , John Kovaliski A and Lorenzo Capucci B
+ Author Affiliations
- Author Affiliations

A Natural Resources Management Biosecurity Unit, Department of Water, Land and Biodiversity Conservation, GPO Box 2834, Adelaide, SA 5001, Australia.

B Istituto Zooprofilattico Sperimentale della Lombardia e dell’Emilia Romagna, Brescia, Italy.

C Corresponding author. Email: greg.mutze@sa.gov.au

Wildlife Research 37(4) 311-319 https://doi.org/10.1071/WR09162
Submitted: 20 November 2009  Accepted: 4 May 2010   Published: 28 June 2010

Abstract

Context. European rabbits are serious environmental and agricultural pests throughout their range in Australia. Rabbit haemorrhagic disease virus (RHDV) greatly reduced rabbit numbers in arid central Australia but had less impact in cooler, higher-rainfall areas. RHDV-like benign caliciviruses (bCVs) have been implicated in limiting the impact of RHDV in the higher-rainfall regions of Australia and also in Europe.

Aims. Experimental releases of RHDV on bait were tested as a means of initiating disease outbreaks. Serological evidence of antibodies to bCVs was examined to determine whether they reduce mortality rates and/or spread of the released RHDV, and how that might influence the effectiveness of future RHDV releases for rabbit management.

Methods. Four experimental releases were conducted in high-rainfall and coastal regions of southern Australia. Virus activity was implied from recapture rates and serological changes in marked rabbits, and genetic sequencing of virus recovered from dead rabbits. Changes in rabbit abundance were estimated from spotlight transect counts.

Key results. Release of RHDV on bait produced disease outbreaks that challenged almost all animals within the general release area and spread up to 4 km beyond the release sites. Recapture rates were high in marked rabbits that possessed antibodies from previous exposure to RHDV and extremely low amongst rabbits that lacked any detectable antibodies. Rabbits carrying antibodies classified as being due to previous infection with bCVs had recapture rates that were dependent on circulating antibody titre and were ~55% of recapture rates in rabbits with clear antibodies to RHDV.

Conclusions. This is the first quantified evidence that antibodies produced against bCVs provide significant protection against RHD outbreaks in field populations of rabbits.

Implications. bCVs can greatly reduce the impact of RHDV on wild-rabbit populations in Australia and presumably elsewhere. RHDV can be effectively released on bait although further releases are likely to be of minor or inconsistent benefit for controlling rabbit numbers where bCVs are common.

Additional keywords: benign calicivirus, biological control, ELISA, epidemiology, genetic sequencing, mark–recapture, myxomatosis, protective antibody, RHDV, survival.


Acknowledgements

We thank Peter and Vonnie Anderson, Echunga Golf Club, Lenswood Research Centre and the South Australian Department of Environment and Heritage for access to their properties, and acknowledge the assistance in field studies of Sue Burns, Jon Hardy, Ian Hopton, David Armstrong, Leigh Amey, Rob Coventry, Kate Thorn, Phil Crammond, Susie Warner, John Crocker and Bob Napier. Giulina Botti of Istituto Zooprofilattico Sperimentale, Brescia, prepared and checked all the ELISA reagents. All work was conducted in accordance with Primary Industries and Resources SA Animal Ethics experimental permit no. 09/03. Funding support was provided by the Natural Heritage Trust.


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