Important update on Rabbit Calicivirus

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Canterbury Veterinary Clinic and Hospital
721 Canterbury Rd
Surrey Hills
Vic 3127

Phone:
03 9836 2708

Brendan Carmel
February 4, 2016

Rabbit Haemorrhagic Viral Disease - Type 2 (RHDV2)

You may have heard about a new type of calicivirus affecting rabbits in Australia. The newest virus called RHVD type 2 (or RHDV2) has been confirmed in Wangaratta, New South Wales, ACT and South Australia. It has recently (January 2016) been confirmed in metropolitan Melbourne. RHVD2 was first diagnosed in Europe in 2010.  As well as this new virus, the government has been readying the release of a variant of the calicivirus already in the wild population,  the K5 variant, also called the Chinese strain. A further variant of calicivirus has been isolated around Sydney, RHDV1A, which has not yet been reported elsewhere in Australia. 

There are now four types of Calicivirus with significance for pet rabbits in Australia;

  • RHVD1 (the original virus released in 1995)
  • RHVD1A (not in Victoria)
  • RHVD1 - K5 variant (release planned in Autumn 2016)
  • RHVD2 

We have one type of calicivirus vaccine available in Australia. It is called Cylap RCD and is what your vet will have used to vaccinate your rabbit. There is evidence that the current calicivirus vaccine provides some immunity to RHVD1 and the K5 variant. As with all vaccines we do not always have complete immunity or total protection. This may be because your rabbit has other illnesses preventing the development of protective antibodies. We do not know how well our current vaccine provides immunity for RHVD2. However, information from Europe and unpublished testing in Australia indicates partial protection for RHVD2 from the Cylap vaccination. We do not know how long the immunity from the vaccination lasts. Europe now has a vaccination available for RHVD2, but unfortunately this is not currently available in Australia.

This virus can act very quickly and, as for the calicivirus present in Australia since 1995 (RHVD1), there may be no sign of an unwell rabbit - the rabbit is simply found dead. The RHDV2 virus can present similarly, but may also act slower with rabbits being unwell, quiet or showing signs of gut stasis (not eating or defecating). It has been reported in the UK that some rabbits do not develop clinical signs, recover and develop immunity. These rabbits may continue to be infectious for a month or more and can infect other rabbits. RHVD2 can also affect kittens as young as 4 weeks. Sudden death is not always due to calicivirus; in fact it is often another disease process. It is important that diagnosis of calicivirus is based on a post mortem examination, and confirmed with viral testing. Contact your vet to discuss. Calicivirus cannot be diagnosed in a live animal, there is no blood test for calicivirus. 

It is always a difficult time when a bunny passes away. We would encourage owners to consider allowing a veterinarian to perform a post mortem examination, especially if calicivirus is suspected. This information has the potential to help us understand more about calicivirus and learn how to help protect other bunnies. 

There has been a lot of concern about this new virus among rabbit owners (and I am one of them!). While acknowledging this new calicivirus is significant, it is important to remember that this virus has been present in other regions for a while. During this time it has caused local outbreaks, particularly in groups of rabbits (farmed or show rabbits). It has not decimated the pet bunny population in these regions. In the UK it is suspected to be less virulent than RHVD1. It can and will cause unexpected deaths in pet rabbits, and it has the potential to affect all of our bunnies. 

Exotic vets across Australia have discussed an alternative vaccination protocol to help minimize the risk to your rabbit. Increasing the frequency of vaccinations may help reduce the number of cases. This is based on the observation of exotic veterinarians, the NSW DPI and information from Europe. It is the best information we currently have.  Decisions regarding vaccination will have to be made through conversations between you and your Vet. . This vaccination schedule is ‘off label’: we are using the vaccination outside of the labelled recommendations. We will discuss this important point when we see you and your bunny. When we get more information we may change our recommendations. We are trying to prevent a disease that has no treatment and high likelihood of death.

The Calicivirus vaccination schedule currently recommended by the Warranwood Veterinary Clinic and The Rabbit Doctor is:

  • Young Rabbits
    • Vaccinate from 4 weeks of age, repeat doses at 8 and 12 weeks
  • Adult rabbits
    • Vaccinate every 6 months
  • Unvaccinated adults, or overdue adults vaccinate twice 1 month apart, then every 6 months

What can you do to minimize the risk to your rabbits?

  • Vaccinate your rabbit every 6 months or as directed by your veterinarian
  • Keep rabbits indoors where possible
  • Screen outdoor rabbits from insects using mosquito netting
  • Keep indoor/outdoor rabbits inside at high risk times of day; dawn and dusk
  • Quarantine (keep separate) new rabbits for at least a week before introducing them to your current rabbits 
  • Take unwell rabbits to your rabbit savvy vet
  • Calicivirus lives in the environment for a long time (up to 3 or 4 months)
  • Calicivirus can be transmitted by insects, urine, faeces, saliva, bedding and by people and other animals moving between rabbits

Much of this information is summarized from the following sources;

  • www.ava.com.au/rabbit-calicivirus
  • www.idt-animal-health.com
  • www.petsmart.org.au 
  • www.harcourt-brown.co.uk 

Notes by Dr Lizzie Selby (Goldstraw) BVSc BSc MANZCVS (Unusual and Exotic Pets) with consultation from Dr Brendan Carmel and Dr Gerry Skinner.