New Calicivirus – Important information for rabbit owners

According to the Australian Veterinary Associations (AVA) web site, plans are currently underway for a controlled release of a new variant of RHDV1 (Rabbit Haemorrhagic Disease Virus 1) (previously known as Calicivirus) to control wild rabbits. The timing of the release is dependent on approvals, but it is planned for some time in 2016, likely Autumn.

Lop-Ear RabbitThere has been some confusion between this new variant of RHDV1 which is called K5 and the discovery in 2015 of RHDV2 in wild and pet rabbits in the ACT and subsequently NSW, Victoria and SA. This completely new virus is called RHDV2 because the mode of death is the same as RHDV1, but in fact they are two totally different viruses.

The original Czech strain of RHDV1 was released in Australia in 1996, however it has become less effective over time and it is the hope that the K5 variant will boost the impact of current rabbit biocontrol methods.

Prior to registering K5 for use in wild rabbit biocontrol, the NSW Department of Primary Industries examined the current RHDV (Calicivirus) vaccine for suitability in protecting domestic and production rabbits from the new strain, K5.  All of the rabbits vaccinated with the currently available vaccine survived the infection with K5 whilst none of the unvaccinated rabbits survived.

This experiment indicates that the current vaccine is likely to continue to protect pet rabbits against this disease after release of K5, provided that the correct vaccination protocols are followed.

The AVA recommends that rabbits are vaccinated against RHDV (calicivirus) at 10-12 weeks of age and then given an annual booster and health check. Occasionally in the face of an outbreak, rabbits may be vaccinated earlier than 10 weeks, in which case a booster is recommended 4 weeks later.

Whilst the current vaccination protocol is appropriate for the K5 strain that will be released later this year (2016) we need to adopt a new protocol for the newly discovered virus – RHDV2. This European virus, RHDV2, (Rabbit Haemorrhagic Disease Virus 2) has recently been identified in wild and pet rabbits in the ACT and surrounds. It is not known how this new virus entered Australia.

RHDV2 can cause death in young rabbits (3-4 weeks) and a proportion of vaccinated adult rabbits. It is known that the currently available vaccine does not protect all rabbits against disease from RHDV2. While an updated vaccine is being developed for RHDV2 in Europe, a revised vaccination protocol may be warranted, using the vaccine currently available in Australia. The suggested regime is: vaccinate baby rabbits at 4 weeks, then at 8 weeks, and again at 12 weeks or later, followed by yearly vaccinations. For breeding adults, a six monthly booster is recommended.