Rabbit Calicivirus Disease (RCD)
Rabbit Calicivirus disease (RCD) is caused by a naturally occurring virus, specific to the European rabbit.
It was first reported in China in 1984, and arrived in Europe in 1986. Soon it spread over the continent killing millions of rabbits.
The virus was imported into Australia under quarantine as a possible biological control agent for wild rabbits. Release of the virus was originally scheduled for 1997 or 1998, however the virus escaped to the Australian mainland from its quarantine field trails (on Wardang Island, South Australia) in October 1995.
In August 1997, the calicivirus was identified in dead rabbits found in the Otago region of the South Island, New Zealand. It has subsequently been found in rabbits in Canterbury. Its spread is attributed to man's intervention.
Kiwi and the native bats were not affected after being exposed to RCD in tests early this year (1997). MAF's report on RCD says chances are very low that it will kill other species, although little is known about the disease.
Disease Symptoms in Rabbits...
- Blood clots form in major organs such as the lungs, heart and kidneys.
- No obvious physical change in appearance.
- Rabbits appear listless
- Death occurs within 30 to 40 hours.
Infected rabbits show no obvious sign of distress. It should be noted that the process by which the virus causes these fatal blood clots is unknown.
Spread of the Disease
Rabbit calicivirus Disease is very infectious.
It is spread:
- By contact between infected and susceptible rabbits.
- Passively by rabbit fleas and mosquitos.
- By bush flies and blowflies. Mechanically by birds that feed on infected rabbits (NZ Falcon, Australasian Harrier).
- By rabbit droppings.
- By feed contaminated by urine from infected rabbits.
Study of the spread of the rabbit caliicivirus across Australia to date shows a seasonal pattern, with greater activity in spring and autumn.
Rabbits less than 10 weeks old may not die of the disease. If young rabbits are exposed to the virus they develop antibodies, become immune and survive to the next breeding population.
Protecting Pets and Commercial Rabbit Farms
Commercial rabbit farms and pet rabbit owners should take the same precautions against RCD as they should already be taking to prevent myxomatosis.
Prevent contact with wild rabbits:
- Don't feed grass or hay that may be contaminated by wild rabbits.
- Insect-proof all rabbit housing.
- Control flies, mosquitos and other insects.
- Vaccinate breeding stock and any pet rabbits over six weeks old.
Damage by Rabbits
Rabbits cause massive environmental damage and agricultural loss.
- Rabbits destroy native plants, especially seedlings.
- They prevent bush regenerating by killing new shoots as they begin to sprout.
- Females (does) can have up to seven litters per year of five or more young (kittens).
- Rabbit populations very quickly build up to plague proportions.
- Rabbits also eat crops, particularly the growing points of legumes such as lupins.
- Rabbits eat pastures.
- Rabbits contribute to soil erosion by destroying ground cover.
- Rabbits invade and take over the habitat of some native animals (braided river beds)