Rabbit calicivirus disease is caused by an organism that infects domestic rabbits primarily. Widespread throughout many regions of the world, it has been eradicated in the continental United States. While a threat to pets and laboratory animals, it has been introduced in some wild populations as a biocontrol measure.
Also known as rabbit hemorrhagic disease (RHD), calicivirus is highly contagious. It kills up to 90 percent of infected rabbits, typically within one to three days of infection. The virus itself is a member of the Lagovirus genus. Infection results in the rapid formation of blood clots in the brain, lungs and kidneys. It is spread primarily through contact with sick animals or with objects contaminated by the virus via body secretions. Animals that prey on rabbits, such as foxes, weasels, ferrets and predatory birds, may shed the virus in their feces even if it does not make them ill.
Members of the Oryctolagus cuniculus family, including show, laboratory and pet animals are most at risk. Most wild rabbits in the continental United States, such as the cottontail and jackrabbit, are not of this family and are thus immune. Exceptions are found wild rabbits of the Oryctolagus group on the San Juan Islands of Washington. The domestic breeds most affected in the U.S. have been the California Whites and Palominos. Rabbit kits under the age of eight weeks appear to be immune.
The disease was first reported in China in 1984, possibly as the result of a mutation in an endemic but harmless virus carried by angora rabbits from the former West Germany. By the late 1990s, the disease had spread to 40 countries, mostly in Europe, Australia, Cuba and New Zealand. Rabbit calicivirus remains endemic in most of Europe and Asia. The first case reported in the U.S. was in Iowa in 2000. Subsequent outbreaks occurred in Illinois, New York, Indiana and Utah. After 2005, the virus seems to have been eradicated in the U.S.
Rabbits infected with calicivirus seldom show any external symptoms. When they do occur, they may include squealing, fevers and a lapse into coma that precedes death, usually within 72 hours of initial infection. Those animals that have the virus and subsequently recover often display restlessness, excitement, loss of appetite, some degree of paralysis and eye irritation. Animals that seem to have recovered will often show signs of jaundice and digestive dysfunction that prove fatal within a few weeks.
As there is no known cure for calicivirus, control is essential. Rabbit carcasses should be buried and animals exposed to the virus should be quarantined or euthanized. Sanitizing objects that have come in contact with sick animals can be done more effectively by using bleach, a 10 percent solution of sodium hydroxide, or similar disinfectant. Neither chloroform or ether is effective.