Rabbit Calicivirus, also known as Rabbit Viral Hemorrhagic Disease (VHD) is a highly contagious viral disease which affects only rabbits of the Oryctolagus cuniculus species – the wild and domesticated European rabbits, ancestors of our own domestic house rabbits. North American native rabbits and hares, such as our cottontails, snowshoe hares and jackrabbits are not susceptible to the calicivirus that causes VHD; humans and other mammals are not affected by VHD.
Symptoms of VHD may include loss of appetite, lethargy, depression, high fever, muscle spasms and sudden death with little to no warning. Some bleeding from the nose or mouth may occur, or rabbits may die without showing any symptoms at all. Any sudden rabbit death is suspicious and should be reported to your veterinarian or to the State Veterinarian as a possible case of VHD.
This is a hardy virus which can remain stable for about 3 ½ months at room temperature and for nearly 8 months at 39 degrees Fahrenheit; it even resists freezing. The incubation period is very short and the disease progresses rapidly; up to 90% of all rabbits may die within 48 hours of exposure to the virus. Rabbits surviving the virus are carriers; they will shed the virus for 6 weeks or longer.
Ironically, some countries deliberately introduce the deadly virus into the environment periodically to kill feral rabbits. Australia deliberately released the virus into the environment in the fifties to kill off feral rabbits and has continued to do so to this day; Australia plans to apply the virus - in solution - to chopped carrots in late March of 2013 to kill off wild rabbits in that country. Nice.
The virus is highly contagious and can be transmitted from contact with infected rabbits, their urine or feces, rabbit meat and rabbit fur. Insects and rodents can transmit the virus from infected rabbits to uninfected rabbits, and the virus can also be spread via contaminated items such as cages, food and water dishes, or caregivers’ clothing or shoes.
There is no known cure for VHD, although a killed-virus vaccination is available in countries where the disease is endemic (thus far it is not considered endemic in the United States; as a result there is no vaccine currently available here). This vaccine is used to protect domestic rabbits in Australia, New Zealand and Europe.
No one can pinpoint the exact origins of calicivirus, but it was first seen in China in 1984, and has since spread to Mexico, Continental Europe, Israel, the UK, Australia and New Zealand, with a couple of isolated outbreaks occurring in the U.S. Since the first known instance of VHD in China, the disease is now endemic to most of Europe and countries in Asia and Africa. The disease has been endemic in Cuba since 1993 and is suspected to exist in Bolivia. In Mexico, an outbreak occurred in 1988 with the disease eradicated by 1992. In 1995, a laboratory accident in southern Australia allowed the virus to escape and kill 10 million rabbits in 8 weeks.
The first reported occurrence of VHD in the U.S. was confirmed on April 7, 2000, and occurred in a backyard rabbitry of 27 pet rabbits in west central Iowa. The origin of that outbreak is unknown. 25 rabbits passed away and the remaining two were euthanized.
In February 2010, an outbreak of VHD was confirmed in Pine County, Minnesota, at a location which supplies rabbits to a wildlife center as food for predator animals. 25 domestic rabbits died of the disease; the outbreak appears to have been limited to that single incident at that single location. It was theorized that contaminated feed was the source of the disease.
Knowing about the existence of the diseases that can threaten the health of your rabbits is the first step in protecting them.
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Reference: Rabbit haemorrhagic disease: the new scourge of Oryctolagus cuniculus
David Chasey, Department of Virology, Central Veterinary Laboratory, Addlestone, Surrey KT153NB, UK
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Next: How to protect your rabbit from VHD
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