Challenge tests on seronegative sub-adult rabbits from 9 sites in south-eastern Australia showed that wild rabbits have developed resistance to infection with Czech strain 351 RHDV originally released in Australia. Differences in infection rates were observed between populations and in comparison with domestic rabbits used as an unselected reference population. Selection for resistance to infection appears to be highest in zones of intermediate rainfall rather than arid or high rainfall areas.
Resistance to RHDV infection may help to explain recent increases in rabbits in inland Victoria and South Australia and has implications for future rabbit control. Nevertheless, there is also a case to argue that RHDV has co-evolved to at least partly off-set the changes in rabbit resistance; wide-spread outbreaks of RHDV are still regularly observed in areas where resistance is high.
In practical terms we have identified those areas where resistance is highest and where more resources will be required in the future for addition rabbit control such as poisoning and warren destruction. Resistance has not reached such high levels that inoculating rabbits with a standard 0.5 ml of stock RHDV suspension no longer causes disease, however this may not be enough to initiate new RHD outbreaks if Czech strain virus is less able to infect resistant rabbits.
Understanding how RHDV coevolves as rabbits develop increasing genetic resistance will be important in assessing the long-term future of RHDV as a biological control agent. Research on the significance of genetic changes in the virus needs to be extended with direct studies on the virulence of viruses currently active in the field.
Final report prepared for Australian Wool Innovation and Meat and Livestock Australia as part of the Invasive Animals Co-operative Research Centre project 7.T.5 RHD: Genetic Resistance.
|Author||Cooke BD, Elsworth PG, Berman DMcK, McPhee S, Kovaliski J, Mutze GJ, Sinclair RG and Capucci L|
|Publisher||Invasive Animals CRC|
|Department||Invasive Animals Cooperative Research Centre|
|Control method||Biological Control|
|Region||Australia - national|
|Documents||Rabbit Haemorrhagic Disease: Wild rabbits show resistance to infection with Czech strain-351 RHDV initially released in Australia [341 kb PDF]|
|Links||PestSmart Toolkit for Rabbits: www.pestsmart.org.au/pestsmart/rabbits/|