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What is rabbit calicivirus and how do I protect my rabbit from rabbit haemorrhagic disease?
Rabbit Haemorrhagic Disease (RHD) is caused by the Rabbit Haemorrhagic Disease Virus (RHDV), which is a type of rabbit calicivirus, causing death in non-immune rabbits. The strain of RHDV, known as the Czech strain (belonging to the RHDV1 family), was released by the government in 1996 to help control wild populations of rabbits, in an effort to minimise environmental damage being caused. However, over time, wild rabbits have developed natural immunity to this strain, making it less efficient. An effective vaccine, Cylap® has been used by many owners to protect their rabbits against this strain of the virus.
However, in recent years the Czech strain has been having little impact on wild rabbit populations, so Australian scientists have evaluated a number of different RHDV variants for release. From this evaluation, a new strain was selected known as the Korean strain or K5 (belonging to the RHDV1a family), which is due to be released in Autumn 2017. This new strain, which was found to be more infectious than the Czech strain, also causes RHD and death in non-immune rabbits. Of concern is the lack of sufficient evidence to demonstrate that the Cylap® vaccine will provide adequate protection against K5 and that it is not currently registered to protect specifically against this strain. A small pilot study to evaluate the effectiveness of the Cylap® vaccine against K5 has indicated some protection but further trials need to be undertaken to obtain conclusive results. Thus, it is essential that rabbit owners do not rely on the Cylap® vaccine to safeguard their rabbits against K5.
Over the past eighteen months, a new variant of RHDV, known as RHDV2, has caused the same type of disease and deaths in wild and domesticated rabbits in NSW, ACT, Victoria, South Australia, Tasmania and Western Australia. The first confirmed report of the RHDV2 virus was in a wild rabbit in Canberra in 2015 with authorities unable to state the source of the infection. The most important thing to know is that no validated trials have been conducted to test the Cylap® vaccine against RHDV2 and there are many reports of vaccinated rabbits dying from infection with RHDV2. Thus, all domesticated rabbits, including those who are vaccinated, are at a high risk of becoming ill and dying from RHDV2 if they are exposed to the virus. Young rabbits (3-4 weeks of age) are particularly vulnerable.
Multiple RHDV2 vaccines being used overseas are not currently available in Australia. In addition, strains of RHDV2 which these vaccines protect against are different to the strain found in Australia, so these vaccines may not be effective here. Unfortunately, once RHDV2 is found in a local population of wild rabbits, it is very difficult to prevent infection in domesticated rabbits.
Overview of RHDV strains
* Note: A small pilot study done in New South Wales showed that all vaccinated rabbits survived infection whereas all unvaccinated rabbits died; however, these results have not been validated and should be considered with great caution
# Based on many reports of deaths in vaccinated rabbits from outbreaks in several states
What are the symptoms of RHDV?
RHDV damages internal organs such as the liver and intestines and may cause bleeding. Signs include fever, restlessness, lethargy and poor appetite with bleeding from the nose and/or blood on the floor where housed. Often infected rabbits will show no signs and die suddenly. If a pet rabbit is showing signs, a veterinarian should be contacted immediately.
How does RHDV spread?
All RHDV strains can spread easily from infected rabbits in droppings, urine, secretions from the eyes and nose, and at mating. Spread can also occur from contaminated objects such as food, clothing, cages, equipment, insects (especially flies), birds and rodents. The virus can survive in the environment for three and a half months over hotter periods but up to seven and a half months in moderate temperatures.
How can I protect my pet rabbit against K5 after its controlled release?
Until further trials are done to validate that Cylap® is fully protective against K5, owners are advised that vaccination may not provide protection. Therefore, owners are advised to take general precautions as outlined below.
How can I protect my pet rabbit against RHDV2?
No vaccine is available in Australia that specifically protects against RHDV2; vaccination using Cylap® vaccine is not considered to provide protection against RHDV2 strains.
Because the virus can remain in the environment for an extended period and it can be transmitted on objects, the following precautions may assist in minimising the risk of infection:
Vaccination using Cylap® will protect against the original strain of calcivirus released in 1996 so it is important to keep vaccination up to date and if you see signs of illness in your rabbit, contact your veterinarian as quickly as possible.
This website provides general information which must not be relied upon or regarded as a substitute for specific professional advice, including veterinary advice. We make no warranties that the website is accurate or suitable for a person's unique circumstances and provide the website on the basis that all persons accessing the website responsibly assess the relevance and accuracy of its content.