Rabbit calicivirus in Australia
There are a number of RHDV strains present in Australia;
- RHDV 1 - Original virus released in 1995
- RHDV1A - Variant of type 1 isolated in Sydney in 2014
- RHDV1 - K5 Variant (release planned in March 2017)
- RHDV 2 - First recorded in mid 2015 in Australia, 2010 in Europe
- RCV - A1 Non pathogenic virus present in wild population
There has been some confusion between the new variant of RHDV1 (K5) and the discovery in 2015 of RHDV2 in wild and pet rabbits in the ACT and subsequently NSW, Victoria, SA, NT, Tasmania and WA. This new virus is called RHDV2, but is a different virus to RHDV1 and K5.
The pathogenic strains of the virus (RHDV1, RHDV1 K5 variant and RHDV2) are considered contagious and can be transmitted via; direct contact with infected rabbits, fomites, transmission via equipment and clothing, transmission by vectors including flies. Use of a parvovirus type cleaning protocol is recommended after suspicious cases.
30 January 2017: Korean strain (K5) of Rabbit Haemorrhagic Disease Virus (RHDV)
During the first week of March 2017, a planned national release of RHDV1 K5, will go ahead.
In April 2016, RHDV1 K5 was approved as a Restricted Chemical Product by the Australian Pesticides and Veterinary Medicine Authority (APVMA).
RHDV1 K5 is a variant of the (RHDV1) virus released in 1996. Based on scientific evidence to date, the existing RHDV1 vaccine (known as Cylap®) is effective against RHDV1 K5. This evidence is based on a small pilot study undertaken by NSW Department of Primary Industries.
It is recommended that all domestic rabbit owners be reminded to vaccinate their rabbits prior to the release of RHDV1 K5 and/or ensure their animals’ vaccinations are up-to-date.
The Department of Primary Industries recommend that rabbit owners take the following extra precautions:
- Prevent direct and indirect contact between domestic and wild rabbits.
- Avoid cutting grass and feeding it to rabbits if there is the risk of contamination from wild rabbits.
- Wash hands, with warm soapy water between handling rabbits.
- Good insect control is also important and will help reduce the risks of introduction of both RHDV and myxomatosis. Insect control could include insect proofing the hutch or keeping the rabbits indoors.
- Infected rabbits should be isolated and disposed of in a manner that will minimise environmental contamination.
- All cages and equipment should be thoroughly cleaned and disinfected. Disinfectants that can be used to decontaminate any equipment include 10 % bleach, 10 % sodium hydroxide, or parvocide disinfectants. If using disinfectants material safety data sheets must be available and consulted, prior to use. Autoclaving will also kill the virus.
RHDV1 K5 is not a new virus; it is a Korean variant of the existing (Czech) virus already widespread in Australia.
RHDV1 K5 will be released across more than 600 sites within Australia and is being coordinated through the State and Territory Governments (see further below for contacts).
Scientists do not expect to see population reductions like those seen with the release of Czech strain of RHDV1 in 1996/97. Since RHDV1 K5 is not being released into a naïve population like that in 1996, knockdowns are expected to be conservative, depending on location and susceptibility of the rabbit population to RHDV1 K5.
Each State and Territory has a contact lead – see below. If you have any concerns or questions, you can direct your enquiries to these contacts.
Local Land Services 1300 795 299
Dept. of Primary Industries 02 6391 3834
Quentin Hart (DPI) email@example.com
Dept. of Agriculture and Fisheries 13 25 23
Peter Elsworth Peter.Elsworth@daf.qld.gov.au
Dept. of Economic Development, Jobs, Transport and Resources 136 186
John Matthews firstname.lastname@example.org
Primary Industry and Regions South Australia
Greg Mutze Greg.Mutze@sa.gov.au
Dept. of Primary Industries, Parks, Water and Environment 1300 368 550
Michael Askey-Doran email@example.com
Dept. of Agriculture and Food 1800 084 881
Susan Campbell firstname.lastname@example.org
Dept. of Primary Industry and Fisheries 1800 084 881
Peter Saville Peter.Saville@nt.gov.au
Transport Canberra and City Services 13 22 81
Oliver Orgill email@example.com
RHDV2 does not pose a risk to human health and is not a notifiable livestock disease. However, the impact on pet rabbits and rabbit farms is high and it can cause death in young kittens (3-4 weeks) and a proportion of vaccinated adults. This new virus strain is distinct from RHD
V1, which was released in Australia in 1996 for the control of wild rabbits. It affects rabbits and hares only.
RHDV2 was first reported in France in 2010 and has been found in several other European countries. It was first detected in Australia in the Canberra area in May 2015.
Clinical signs of RHDV2 differ from the type 1 virus. RHDV2 affects kittens at a younger age (from 3-4 weeks) and clinical signs may be over 3-5 days before death. This is significant in general practice where unwell rabbits may present for vague clinical signs including; lethargy, inappetence, pyrexia and gut stasis. These rabbits will be infectious to other rabbits.
Clinical signs can include;
- significant increases in liver and kidney enzymes
The current vaccine for rabbit calcivirus (Cylap RCD) is not fully protective against RHDV2. However, there is evidence of some cross protection between type 1 and type 2 viruses. Keeping domestic or pet rabbits’ vaccinations up to date is recommended to provide the maximum possible protection against this new strain. While an updated vaccine has been developed in Europe it is not currently available in Australia.
Until a specific vaccine is available for RHDV2, a revised vaccination protocol using the vaccine currently available in Australia has been suggested, though it is not known to what extent this will confer protection.
Current Vaccination recommendations follow and will be regularly updated.
Current vaccination recommendations
The AVA recommends regular vaccination. For the RHDV1, 1A and RHDV1-K5 viruses 12 monthly vaccination is recommended. For the variant that emerged in parts of Australia in 2015 called RHDV2 there is no specific vaccination available in Australia. The AVA suggests the following protocols, this should be followed in consultation with your local veterinarian.
Kittens: 4, 8, 12 weeks of age, then every 6 months.
Adults: 2 vaccinations 2-4 weeks apart, then every 6 months.
This protocol is off-label. Cylap is not registered for use against RHDV2 or for 6 monthly use.
Based on studies conducted so far, giving the vaccine at more frequent intervals does not have negative health effects. Veterinarians need to advise owners that this protocol is off label.
Vaccination should always be administered to healthy animals, and a risk/benefit discussion with an owner is strongly recommended before vaccination of animals with chronic illness. Young animals are anecdotally more likely to show post-vaccination lethargy and inappetence. It is common to get a local reaction to the vaccine, especially if vaccination is not performed with a new needle, or if the vaccine is inadvertently given intradermally.
Note that any benefit of earlier and more frequent vaccination of kittens has to be balanced against the increased likelihood of any adverse event from the vaccine. The suggested off-label regime has not yet been validated in terms of increased protection or risk of adverse events, and feedback from veterinarians would be most welcome while we work to determine the most appropriate way to handle this situation.
Owners of pet rabbits and breeding stock are urged to implement strict biosecurity measures to protect their animals from infection, and talk to their vets about how best to achieve this.
Any veterinarian in NSW or ACT who suspects a domestic rabbit may have RHDV2 should submit a fresh frozen 1g liver sample (not formalin-fixed) to the State Diagnostic Veterinary Laboratory at the EMAI.
Alternatively, please collect and freeze a liver sample and contact Robyn Hall (02 6246 4245) or Ros Mourant (02 6246 4294) at CSIRO to request a sampling kit for submission.
See the August Biosecurity Bulletin link below for further information about submitting samples. Contact your Department of Agriculture in other states.
The Invasive Animals CRC, along with its partners, has a strengthened National RHDV Monitoring Program in place, which incorporates the monitoring of all RHDV viruses in Australia, including RHDV2.
For further information about rabbit biocontrol initiatives in Australia please visit the PestSmart website.
Vaccine product page
Vaccine material safety data sheet
NSW and ACT Biosecurity Bulletin on RHDV2 – 10 July 2015
NSW and ACT Biosecurity Bulletin on RHDV2 – 25 August 2015
Measures to minimise RHDV1 infection in pet 'domestic' rabbits – February 2017
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You must be a member of the Australian Veterinary Association to join. Join online or contact AVA national office on 1300 137 309 to join the AVA or add UPAV to your membership.
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Figure 1: The RHDV1 K5 release sites across Australia.