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What is Rabbit Calicivirus (RHD) and how do I protect my rabbit from it?
Rabbit Calicivirus causes Rabbit Haemorrhagic Disease (RHD) which is very serious, usually causing death in non-immune rabbits. The virus, known as RHDV1, 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 RHDV1, making it less effective. An effective vaccine, Cylap® has been used by many owners to protect their pet rabbit against this disease.
However, given that the RHDV1 virus in recent years has been having little impact on wild rabbit populations, Australian scientists have been working on a new RHDV1 strain known as RHDV1 K5, which is due to be released in Spring 2016. This new strain will cause disease in wild and unvaccinated pet rabbits. It is believed that the Cylap® vaccine currently being used will provide protection against the RHDV1 K5 strain, so it is essential that pet owners continue to follow the recommended vaccination program for their rabbits.
Over the past year, a new RHD virus strain, known as RHDV2 has caused deaths in wild and domesticated rabbits in NSW, ACT, Victoria and South Australia, . It is a different virus to RHDV1 & RHDV1 K5 but still causes the same type of disease and death. The RHDV2 virus first emerged in 2015 with the source of the infection unknown. The most important thing to know is that the Cylap® vaccine has less protection against RHDV2, so even vaccinated pet rabbits 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.
RHDV2 vaccine is being used overseas and does appear to provide full protection but it may not be available in Australia for some time. The other complicating factor is that some of the overseas strains are different to the strain found in Australia, so this vaccine may not be effective against the Australian strain of RHDV2. Unfortunately, once RHDV2 is found in a local population of wild rabbits, it is very difficult to prevent infection in pet rabbits. However, vaccinating more often and at a younger age may improve protection.
Overview of RHDV strains
*Based on the results from a pilot study done in New South Wales that showed that all vaccinated rabbits survived infection whereas all unvaccinated rabbits died
# Based on the results from a pilot study done on a similar RHDV2 strain in New South Wales that showed 70-80% vaccinated rabbits survived infection and reports of high deaths in vaccinated rabbits from outbreaks in ACT, NSW and Victoria
What are the symptoms of RHDV?
RHDV damages internal organs such as the liver and intestines and may cause bleeding. For rabbits who are not vaccinated, 70-100% will die once signs of the disease are seen. 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 RHDV1 K5 after its controlled release?
If your rabbit is not yet protected against RHDV1, you should contact your vet and arrange vaccination. It is recommended that the current vaccination program be maintained using Cylap® vaccine, i.e. vaccinate rabbits at 10-12 weeks of age with a follow-up annual booster.
How can I protect my pet rabbit against RHDV2?
If you know that RHDV2 has been detected in your local area or you wish to take extra precautions, vaccinating at a younger age and more often may provide more protection. Contact your local veterinarian and see Australian Veterinary Association advice.
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:
The most important thing is to keep vaccination up to date and if you see signs of illness in your rabbit, contact your veterinarian as quickly as possible.
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