Note: this article was originally written in early 2016, and will be amended with notes as further developments occur. This article was last updated January 2019.
Calicivirus (Rabbit Haemorrhagic Disease Virus, or RHDV) is one of two viruses present in Australia in order to control the wild population of rabbits. The first strain of RHDV was introduced in the mid-90s from the Czech Republic (this was RHDV1 V351), and since its original introduction has been diversifying and evolving in the wild. As a result many wild rabbits have immunity to calicivirus, and there are a number of non-disease causing (non-pathogenic) strains, and as such the Australian government is investigating further strains of the virus which may be more effective in controlling wild rabbits.
In Australia we are able to vaccinate against RHDV1 with the CYLAP vaccine, however our vaccination protocols are forever evolving to allow us to use new evidence to provide the best protection from the virus for our patients. As calicivirus presents as sudden death in rabbits there is often much fear when an apparently healthy rabbit dies, particularly if they had been vaccinated. In order to prevent fear and worry and enable our clients to make the best decisions for protecting your bunny friends we would like to keep you informed of recent developments in calicivirus in Australia.
What is the Korean strain (RHDV K5)?
In 2014 the Australian government investigated a number of strains of calicivirus not present in Australia in the hope of finding one which would be effective against wild rabbits that have immunity to Australian strains, particularly a non-pathogenic strain called RCV-A1. This non-pathogenic strain provides protection to wild rabbits from the strains of calicivirus required for population control. They found that the most effective was the Korean strain.
Currently the government is planning on releasing the Korean strain in various areas of Australia. This has caused worry in the bunny owning community that their pets may not be protected with the current CYLAP vaccine. Evidence suggests that CYLAP provides adequate protection for the Korean strain, provided vaccinations are kept up to date (as is the case with older strains of calicivirus).
What is RHDV2?
In recent years there has been the discovery of RHDV2 (a calicivirus-like virus) in Europe, which is significantly different from previously known strains of calicivirus, including those known in Australia at the time. This European form has been found to cause death in a low percentage of rabbits exposed to the virus who had been previously vaccinated with the CYLAP vaccine. It is also able to infect younger rabbits (as young as four weeks old) and some rabbits experience a more prolonged form of the disease rather than the sudden death seen in previous forms of calicivirus. It has also been found to cause liver disease in hares. Based on this information the European RHDV2 strain was rejected by the government for use against Australian wild bunnies.
Though the government has not introduced the European strain there has recently been an Australian strain of RHDV2 discovered in wild and farmed rabbits in Australia. This has not yet been well studied, and it is unknown if it is the same as the European strain or just a relative. As such we are not yet sure of how it affects vaccinated rabbits.
The Australian RHDV2 has been detected in northern Victoria (on the border of NSW), the ACT, NSW, and in two cases in SA. MRC has corresponded with research and health organisations, which report that he total number of confirmed cases in the country is 10-15, and these have all been wild rabbits or farmed rabbits. As of the time of writing MRC has not heard of any cases of pet rabbits reporting positive for RHDV2 in Australia.
(2018 update: a small number of confirmed cases of RHDV2 have been reported in domestic rabbits in Australia in the years since the release of K5, however as of this time there are no published studies assessing associated risk factors and there appears to be a wide range of vaccination statuses associated with these animals. At this time there have been no confirmed cases at Melbourne Rabbit Clinic, even in rabbits passing away with ‘calici-like’ symptoms).
What is the best way to protect my bunny?
Vaccination is still the best way to protect pet rabbits from all forms of calicivirus. While there have been no studies yet in using the CYLAP vaccine to protect from RHDV2 it is recommended that vaccination protocol is as follows:
- Young rabbits be vaccinated at 4, 8 and 12 weeks, alternatively at 10-12 weeks with a booster vaccination between two and four weeks following this
- Adult rabbits be vaccinated every 6-12 months (see here for discussion and information on six monthly vaccinations), or every 10 months if they did not have a booster vaccination with their initial course
- Adult rabbits undergo a vaccination and subsequent booster again if they have not been vaccinated in the last 12 months
- Breeding does be vaccinated every 6 months to maintain high maternal immunity to pass on to kittens
House rabbits are also at lower risk of contracting the virus, and it is highly recommended that you keep your rabbits inside, particularly if they are not up to date with their vaccinations. Insect-proofing of outdoor enclosures will decrease risk, however it is not 100% effective as RHDV can be airborne.
My bunny passed away suddenly, what can I do to find out if it was calicivirus?
Unfortunately the only way to confirm that a rabbit has died from calicivirus is to collect fresh liver samples during a post-mortem examination. These liver samples must be frozen and assessed by a government laboratory. If you are concerned that your rabbit has passed away from possible calicivirus please contact us or your local vet for direction on submitting samples.
Welcome to 2016!
Happy new year to all our friends, from Melbourne Rabbit Clinic! 2016 is going to be a big year at MRC, with us moving very soon to our own new clinic home. The new clinic is only a short drive from where we are now and is located off Dorset Road, on the corner of Alma Avenue and Austin Street. We are currently painting and decorating and will be moving our equipment across over the next month, so stay tuned for more updates as they develop.
The holidays may be over but our sales continue at Melbourne Rabbit Clinic. Our cubes are still half price ($20 for 16 sides), meaning it’s now super cheap to build your furry friends a new house for the holidays. Cubes are super versatile building materials for indoor enclosures, check www.boingonline.com or google search ‘bunny condos’ for inspiration and advice.
Also on sale are our Fun Links, brightly coloured plastic links for throwing and shaking, and we have a whole bunch of exciting Oxbow dried herb mixes in stock (new to Australia!). Drop in to check out our fun ranges!