3. RCD as a Biocontrol Agent in New Zealand
The CVO’s report sets out the criteria that an ideal biological control agent should meet. It would be remarkable if an ideal candidate was found. Less than ideal candidates need to be assessed in terms of the criteria on which they fall short of the ideal.
Predicting how the RCD virus will behave in New Zealand is dependent upon evaluating knowledge of its behaviours in other countries. Notwithstanding that the virus has now been recorded in more than 40 countries, the records of its impact relate to domesticated rabbits and very little is written about its behaviour in wild rabbitpopulations. Apart from some anecdotal information from the UK, we are dependant on records from Spain and Australia. The CVO’s report summarises this experience.
The data received from Australia in April 1997 gives little confidence that
- spread of the virus can be reliably attributed to any particular mechanism or mechanisms;
- virus can be manipulated by man to achieve a control objective;
- virus will be effective in New Zealand in the absence (or relative absence) of vectors suspected to be implicated in the spread of the disease in Australia.
While there has been extensive natural spread of the disease throughout Australia, the mechanisms are still subject to speculation. In general, man-made infections have met with little success.
| Two modes of action of RCD have been considered by the Applicant Group and others: | ||
| (a) | as a biological control agent which persists in the environment and periodically induces epidemics. This appears to be the mode of action in the semi-arid (<300mm rain) areas of Australia but not in wetter areas; | |
| (b) | as a biocide killing exposed rabbits and those in their immediate contact but not persisting in the long term. There has been no convincing demonstration of this mode of action. | |
Thus a convincing answer to the question of whether RCD can effectively replace or supplement existing control measures in New Zealand can not be given at this time. Iconsider that optimism shown by the Applicant Group for the effectiveness of RCD can not be justified by experience in Australia.
This may be a function of not knowing how to manage the virus to achieve optimum results.
Over time, it is probable that the rabbit and the RCD virus will co-evolve and the virulence of the virus will decline. This phenomenon appears to be well accepted.
While individuals and welfare organisations highlighted some concerns in terms of the impact of the disease on infected rabbits and on the fate of orphaned kits in burrows, there were few unfavourable reactions on welfare grounds to the use of RCD as a control agent.
Contact for Enquiries
Manager, Strategic Science Team
MAF Biosecurity New Zealand
PO Box 2526
Wellington
NEW ZEALAND
Phone: +64 4 894 0115
Fax: +64 4 894 0731
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