Preliminary analysis
Preliminary analysis has shown an observed reduction of up to 36% in rabbit numbers at Australian release sites following the release of RHDV1 K5 in March 2017.
Initial data is positive, however, long-term success will be measured and seen through environmental benefits and increased productivity for the agricultural sector. It is important to stress that not all sites where RHDV1 K5 was released did experience the same results and results are based on all data collected.
The outcomes of the community-led national RHDV1 K5 were published in 2019 and are available here.
Domestic pet rabbits and breeding stock
- Owners should seek advice from their veterinarian regarding vaccination.
- Owners should implement biosecurity measures to protect their animals from infection.
- Download this flyer for distribution.
Background
RHDV1 K5 is not a new virus. RHDV1 K5 is a naturally occurring Korean variant of the Rabbit Haemorrhagic Disease Virus (RHDV). Its release is expected to ‘boost’ current management and help slow down the increase in rabbit numbers.
RHDV1 K5 does not spread through the landscape as efficiently as the original strain of RHDV did in the mid-1990s. The RHDV1 K5 strain can be spread by insect vectors, direct rabbit-to-rabbit contact and other animals feeding on infected rabbit carcasses may also excrete the virus.
Domestic rabbit owners are advised to seek advice from their local veterinarian and use protective biosecurity measures to help keep their rabbits safe from infection.
You can help
Landholders are asked to help maximise outcomes from the virus release by undertaking follow-up conventional control, coordinating any future releases at a landscape level, report rabbit sightings, and submit samples from dead rabbits for testing.
RHDV1 K5 is now available as a commercial product to authorised users, however landholders are asked to wait for late Spring or Autumn before releasing the virus.
Training and virus distribution
Winter is not best practice period for release. The key factor informing when the virus can be deliberately released is the absence of breeding activity on the ground (i.e. avoiding periods when very young rabbits and heavily pregnant does are present).
The supply and use of RHDV1 K5 in WA to authorised users was enabled under the Biosecurity and Agriculture Management Regulations Amendment 2017 (Government Gazette Friday, 3 February 2017). Under the regulations, anyone who will be handling and mixing the liquid suspension virus must complete online training to become authorised users of RHDV. RHDV1-K5 Authorisation Training is available from DPIRD's Client Online Training website.
Coordinated, landscape-scale release of rabbit biological control viruses will maximise effectiveness and produce greater results than patchy, individual landholder releases. DPIRD recommends land managers contact their local biosecurity group before applying for the virus to coordinate a release or to determine if a release has already occurred within their area. To find out about your local biosecurity group details, contact TalkingRBG@dpird.wa.gov.au.
The commercially available rabbit biological control virus, RHDV1-K5, can be released by authorised users in Western Australia who have completed their training. Although DPIRD keeps a record of authorised individuals and their post code, we are not informed of when or where individual releases of the virus occur. DPIRD does not routinely undertake virus release for pest rabbit control. Under collaborative research programs, DPIRD has undertaken a few releases since the initial 2017 nationwide release of RHDV1-K5, at trial sites.
One vial of RHDV1-K5 will treat approximately 150 hectares of rabbit-prone land (less if rabbit density is high). However, due to the evident lack of long-distance transmission of the virus by vectors, other factors will influence the ability of the virus to spread among local rabbits. These include rabbit density, the extent of rabbit population fragmentation (how far apart groups of rabbits are in your area) and the presence of built and natural landscape features that may obstruct rabbit-to-rabbit contact.
In highly fragmented rabbit populations and where rabbit movements may be constrained, one vial of RHDV1-K5 is likely to treat much less than 150ha.
The virus is either mixed onto bait (oats or carrots), or can be directly injected into live rabbits. Both techniques require some pre-feeding to get rabbits to eat bait or to attract them into approved wire cages. Oats should be standard intact oats with husks attached and carrots should be good quality and freshly diced. One vial of reconstituted product (10 mL) diluted with an additional 90 mL of water (100 mL total volume) is sufficient to treat 10kg of freshly diced carrots OR 5kg of oats.
For information on the delivery of RHDV, see the PestSmart webpage. For more information about the cost of the virus, contact the NSW Department of Primary Industries (DPI) Virology labs (02) 4640 6337 or virology.enquiries@dpi.nsw.gov.au.
Submit reports and dead rabbit samples
RabbitScan is a free resource for landholders, Landcare groups, community groups, local Councils, professional pest controllers and biosecurity groups. It has been designed by landholders for communities, and it is very easy to use.
What to record
- rabbit activity (such as sightings and warrens)
- damage, such as soil erosion
- Control activities (such as warren ripping)
- disease in rabbit populations (such as RHDV)
Carry out integrated control
The release of RHDV1 K5 is part of a 20-year national biocontrol plan for rabbits. It will not result in a 90% reduction of pest rabbit populations, as seen with other biocontrol releases.
It is critical then that landholders undertake an integrated and complementary pest management approach, with conventional control measures put in place following release of the virus. This could include starting a conversation with neighbours with the aim of integrated best-practice rabbit control at a landscape scale.
Land managers must also consider concurrent control for predators such as foxes (potentially looking for alternative food sources in the absence of rabbits). A reminder to carry out Integrated Pest Management is included on the virus product label directions and in the online RHDV1 K5 training package.
A video series on best-practice rabbit control has been released by the Invasive Animals CRC to increase skills in control programs. The videos include instructional ‘how-to’ videos to demonstrate control procedures such as poison baiting, baiting with biocontrol agents, rabbit warren fumigation, rabbit warren ripping and harbour destruction. It also includes video instructions for the RabbitScan (FeralScan) app and information on the RHDV1 K5 release.
Why do we need a new biocontrol agent?
Rabbits are Australia’s most destructive agricultural pest animal, costing upwards of $200 million in lost agricultural production annually. Two rabbits can become 200 rabbits in just two years, and in another two years that could be 40,000. It is vital to keep on top of the problem with new interventions and new tools.
A Czech strain of Rabbit Haemorrhagic Disease Virus (RHDV) was first released in Australia in 1996 and proved extremely effective, knocking down up to 90% of the pest rabbit population in some parts of Australia.
However, in 2009 a native benign calicivirus, called RCV-A1, was identified as a factor for RHDV being less effective in cooler and wetter climates.
The release of RHDV1 K5 comes after more than five years of testing through the Invasive Animals Cooperative Research Centre (IACRC) RHD Boost project, with major financial and in-kind resources provided by the Australian government, state governments, and industry and non-government organisations.
After testing 38 variants of RHDV, this project noted that RHDV1 K5 should work better in the cool-wet regions of Australia where the current variant has not been so successful.
Animal welfare considerations
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Given the short disease time (between 24 and 72 hours after infection) and the sudden death from rapid organ failure, RHDV1 K5 is one of the most humane control methods for rabbits (even more so than the Czech strain).
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RHDV1 will only infect the European rabbit and will not harm humans, other pets or native species.
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Approval to use RHDV1 K5 included a stringent approval process by the Australian Pesticides and Veterinary Medicine Authority, including consideration of all information available on potential impacts to native animals.
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Even predatory animals that eat rabbits that have died from RHDV1 K5 do not develop an infection.
Protection measures for pet rabbits
Owners should seek advice from their veterinarian regarding vaccination.
Owners should implement biosecurity measures to protect their animals from infection.
RHDV can be spread by flies and biting insects, and direct rabbit-to-rabbit contact. Predators feeding on infected rabbit carcasses may excrete viable virus in their faeces.
The virus can also remain in the environment for an extended period and can be transmitted on objects including clothing, fodder and bedding material.
Pet rabbits that are already vaccinated for the existing strain of RHDV1 are likely to be covered for the new strain (K5) and all strains of RHDV1.
If unvaccinated, rabbit owners should talk to their local veterinarian about vaccination. Studies have shown that the existing RHDV1 vaccine is likely to be effective against the new K5 variant. A detailed summary of field and experimental data into the efficacy of RHDV vaccines can be found on the PestSmart website.
The AVA recommends that rabbits are vaccinated against RHDV (calicivirus) as follows:
- Kittens: 4, 8, 12 weeks of age, then 6 monthly for life
- Adults: 2 vaccinations 1 month apart, then 6 monthly for life
- This protocol is off-label. Cylap is not registered for 6 monthly use or for use against RHDV2.
Australian Veterinary Association advice on biosecurity measures
- If possible, keep rabbits inside for the next few weeks or until they can be vaccinated and your vet advises it is now safe for them to be outside.
- Prevent direct and indirect contact between domestic and wild rabbits. Rabbit-proof your backyard to prevent access by wild rabbits.
- Limit contact between and handling of unfamiliar pet rabbits.
- Avoid cutting grass and feeding it to rabbits if there is the risk of contamination from wild rabbits.
- Remove uneaten food on a daily basis.
- Wash hands with warm soapy water in between handling rabbits that are not normally in contact with each other.
- Good insect control is vitally important and will help reduce the risks of introduction of both RHDV and myxomatosis. Insect control should include insect proofing the hutch or keeping the rabbits indoors.
- Infected rabbits should be isolated and any dead rabbits should be disposed of in a manner that will minimise environmental contamination. Contact your local vet for more information.
- All cages and equipment should be thoroughly cleaned and disinfected. Disinfectants that can be used to decontaminate equipment include 10% bleach, 10% sodium hydroxide, or parvocide disinfectants. Autoclaving will also kill the virus.
Further information
RHDV1 K5 project updates
IACRC web pages healthierlandscapes.org.au