Boosting rabbit biocontrol: RHDV1 K5 in Victoria
RHD Boost is a 20 year national biological control project involving the release of a naturally occurring Korean variant of rabbit calicivirus called Rabbit Haemorrhagic Disease Virus K5 (RHDV1 K5).
RHDV1 K5 will boost existing biological control agents that are already in the environment. RHDV1 K5 will not kill every last rabbit. Land managers are encouraged to take advantage of the release of the virus and follow up with conventional control to remove remnant rabbits and destroy their warrens.
Rabbits are Australia's most destructive agricultural pest animal, costing $200 million in lost agricultural production every year, with a further $6 million expended on rabbit control measures. Rabbits also impact the environment, with less than one rabbit per hectare, enough to stop the growth and regeneration of some native species and negatively affect biodiversity. The draft threat abatement plan released by the Australian Government Department of the Environment in November 2015 found that rabbits are a significant threat to biodiversity, affecting 304 nationally threatened plant and animal species.
RHD Boost is about fine tuning and enhancing the effects of calicivirus. It is a national project to introduce a new variant of RHDV1 into Australia, to improve the control of rabbits, particularly in areas where calicivirus has had limited impact on rabbit populations.
RHDV1 K5 is not a new virus; it is a Korean variant of the existing virus already widespread in Australia. The RHD Boost project found that RHDV1 K5 should work better in the cool-wet regions of Australia where the current variant has not been so successful. RHDV1 K5 was selected out of 38 candidate variants because it can overcome the protective effects of a benign (harmless) calicivirus (RCV-A1) which naturally occurs in Australia's rabbit population. RHDV1 K5 is a naturally occurring variant of RHDV and has not been altered by humans in any way.
RHDV1 K5 kills more rabbits and causes more rapid death than the current variant of RHDV. This leads to improved animal welfare and humaneness outcomes, as well as helping to lessen the impacts of rabbits on biodiversity and production.
Do not expect to see population reductions like those seen with the release of calicivirus in 1996/97. RHDV1 K5 is not being released into a naïve population like that in 1996. Knockdowns are expected to be in the range of 0-40%, depending on the location of the rabbit population and susceptibility to RHDV1 K5. It will not kill every last rabbit. Land managers are encouraged to take advantage of the arrival of the virus and follow up with conventional control to remove remnant rabbits and destroy their warrens.
The release of RHDV1 K5 in conjunction with a community-led response, using best practice rabbit management principles, is an opportunity to mitigate rabbit damage and assist manage rabbits to low levels. Rabbits don't stop at fences and if RHDV1 K5 reduces rabbit populations, a coordinated community-led response is required to sustain a long term advantage. RHDV1 K5 offers a new opportunity to begin a conversation with neighbours with the aim of integrated best practice rabbit control at a landscape scale. Land management groups are encouraged to get their communities involved in rabbit management activities for the release.
Frequently asked questions
What is RHDV1 K5?
RHDV1 K5 is a variant of Rabbit Haemorrhagic Disease Virus (RHDV) or calicivirus that causes a fatal haemorrhagic disease in the European rabbit (Oryctolagus cuniculus). RHDV1 K5 is specific to the European rabbit, and once a rabbit shows symptoms, death is rapid. There is no treatment or cure for rabbit haemorrhagic disease (RHD); however, a vaccine for domestic and production rabbits is available.
Where will RHDV1 K5 work best?
RHDV1 K5 is expected to work in all areas where rabbits are found, with the greatest benefits in the cool-wet regions of the country. An endemic (naturally occurring) benign (harmless) variant of RHDV is found in the cool-wet regions of Australia and temporarily protects rabbits from RHDV1. RHDV1 K5 can overcome this protection, so it is likely that in these cool-wet regions we will see an improvement in RHDV biocontrol. Many parts of Victoria will potentially benefit from the release.
What type of knock-down will RHDV1 K5 achieve?
While exact knockdown figures are unknown, do not expect to see population reductions like those seen with the release of calicivirus in 1996/97. We are not releasing the virus into a naïve population like in 1996. Knockdowns are expected to be in the range of 0-40%, depending on location and susceptibility of the rabbit population to RHDV1 K5.
Is RHDV1 K5 safe? (people, pets, wildlife and livestock)
Yes. No variant of RHDV1 or RHDV1 K5 has ever been found to cause infection in any other animal except the European rabbit (Oryctolagus cuniculus). Even predatory animals that eat a rabbit which has died from RHDV1 do not develop an infection. RHDV is safe for people, pets, wildlife and livestock.
Is RHDV2 safe? (people, pets, wildlife and livestock)
RHDV2 is a different -virus to RHDV1 K5 and RHDV1. RHDV2 is the first ever reported RHDV that is not 100% species specific, and has been detected in hares. RHDV2 has been reported to infect certain sub-species of hares in Europe as well as rabbits. In June 2016 it was confirmed in a small number of European Brown Hares in Australia, the only hare species present here. It is currently unclear if these were rare spillover infections from rabbits to hares, or if RHDV2 actually spreads effectively between hares as it does between rabbits.
The existing RHDV1 vaccine has been shown to be effective against RHDV1 K5. However, the RHDV1 vaccine currently used in Australia may only provide partial protection against RHDV2.
Does RHDV1 K5 affect other animals?
No. RHDV1 K5 only causes infection in rabbits, and only the European rabbit (Oryctolagus cuniculus). No other animal has ever developed an infection from being exposed to RHDV1 K5.
If RHDV1 K5 takes 48 hours to kill the rabbit, doesn't the rabbit suffer during this time?
RHDV is one of the more humane methods of controlling wild rabbits. Essentially, the rabbits end up with 'cold-like' symptoms, become lethargic and then die quickly. Post-infection, there is a rise in body temperature lasting up to 24 hours, followed, in 70–90% of cases, by death up to 48 hours after the onset of a fever. The overall welfare impact prior to death has been assessed as low using the relative humaneness model developed under the Australian Animal Welfare Strategy.
I have a pet rabbit, is there a vaccine available?
Yes. There is a vaccine (Cylap®) for prevention of RHDV1 that has been available in Australia since 1996. This vaccine has been shown to be effective against RHDV1 K5, provided that the correct vaccination protocols are followed. Talk to your vet for further information on vaccinating your pet rabbits, and other measures to prevent disease.
Scientists are currently exploring options to develop an updated vaccine for domestic rabbits which will cover all known variants of rabbit haemorrhagic disease (including RHDV1 and RHDV2) in Australia. Scientists have a number of factors to work through to ensure an updated RHD vaccine is safe and effective for domestic rabbits and updates will be provided on the progress of this research as soon as they become available.
What are the costs of rabbits to agriculture?
Rabbits are estimated to cost over $200 million in lost agricultural production every year. Rabbits compete with stock for food, impact crops, horticulture and pastures, contribute to soil erosion and destabilise the structural integrity of the land, potentially leading to injury of livestock. Rabbits are also linked to the decline of native animals and plant species throughout their range. Rabbits are thought to have a negative impact on 304 threatened species in Australia.
Rabbits are a regional issue, why should I care?
Rabbits are not only a regional issue. Rabbits can cause significant damage in urban environments, such as gardens, parks, reserves, sports grounds, cemeteries, along railway tracks and in urban remnant bushland environments.
What is the cost of rabbits to the environment?
Currently there is no dollar value on the impact of rabbits on the environment; however, their impact is known to be significant. Rabbits continue to compete with native wildlife for food, contribute to soil erosion and subsequently desertification of the Australian environment. They severely limit the regenerative ability of many plants and plant communities including endangered species, and in some cases can support populations of introduced predators that also prey on native wildlife.
How is the RHDV1 K5 variant different to the current calicivirus released in 1996?
Both variants cause the same disease, however the RHDV1 K5 variant is better adapted to overcome the protective effects of the benign calicivirus found several years ago in Australian rabbits. These benign viruses can temporarily protect rabbits from infection with our current variant of RHDV. These benign viruses are predominantly found in the cool-wet regions of Australia, where typically RHDV1 has not worked as well as it has in more arid environments. The use of the RHDV1 K5 variant should improve the effectiveness of RHDV in these cool-wet regions and continue to suppress rabbit numbers throughout their distribution, particularly in conjunction with other forms of control.
How do rabbits with RHDV die?
Rabbits that are infected with RHDV first develop symptoms anywhere from 24-72 hours after infection and usually succumb within 6-36 hours after the first symptoms appear. Many infected animals show no signs of disease and die suddenly. Some animals may exhibit lethargy or excitement before death. Animals die from the rapid onset of multiple organ failure. Given the short disease time and the sudden death from rapid organ failure, RHDV continues to be one of the most humane control methods for rabbits.
How can I get involved in the release of RHDV1 K5?
The call for expressions of interest to be involved as a release site now closed and more than 600 sites around Australia have been selected to release the virus. This includes 150 sites selected for release in Victoria.
Those sites that were not selected as a release site can still be actively involved in the program by tracking the spread of the virus and collecting samples. For more information visit the Pestsmart website.
Will RHDV1 K5 be available after the initial release?
Yes, the commercial product will be available 2 months after the official RHDV1 K5 planned release.
Is there any advantage in community assisting spread?
Yes. Community assistance with the spread of RHDV1 K5 will help ensure that the virus reaches as many rabbit populations as possible and that as large a knockdown as possible is achieved. The community can then take advantage of this knockdown, by following up with conventional control tools such as baiting, ripping and fumigation to achieve sustainable long-term control.
Where are the release sites in Victoria?
Victoria has two specifically established paired release and monitoring sites to investigate the impact of RHDV1 K5 on Victorian rabbit populations. These sites are located around Avalon, Sunbury, Kerang and Pyramid Hill. Additionally 150 community release sites have been selected across Victoria.
When is the release planned for?
The release of RHDV1 K5 is planned for early 2017. The timing of the release of RHDV1 K5 will be dependent upon a number of factors. Releases should be undertaken under the ideal climatic conditions and when kittens are not or are less likely to be present.
How does RHDV spread naturally?
RHDV is spread by insect vectors, such as bushflies and blowflies. Direct contact between a rabbit and a rabbit carcass with RHDV is also an avenue of spread. Animals that predate on rabbit carcasses such as foxes, dogs and cats may also excrete the virus in their faeces.
What can community groups do to take advantage of the release of RHDV1 K5 and better manage rabbits?
There is a simple recipe for success around rabbit control, which is the accurate and timely application of a range of control techniques at best practice, based around destruction of warrens. This can achieve long term control of rabbits, which can be maintained at low cost and low effort. The sequence and timing of control effort is extremely important to achieve successful outcomes.
- Allow biological control and natural mortality to reduce the rabbit population.
- Bait to reduce numbers prior to ripping.
- Remove harbour and destroy warrens (i.e. ripping).
- Follow up with fumigation and further warren destruction.
- Be persistent, remain vigilant and monitor regularly.
Research has shown that to deviate from this basic recipe reduces the efficacy of the rabbit management program.
Landcare or community groups can plan now to maximise any impact that RHDV1 K5 may provide. Groups should begin with planning activities for pre and post release. Success requires high levels of participation in rabbit control at a landscape scale. For more information on best practice rabbit management visit PestSmart or our European rabbit page.