Viral haemorrhagic disease (VHD) is a major killer of rabbits. It first occurred in 1992 in the UK having migrated from China where originated in 1984.
The first signs of VHD are often a dead rabbit in the cage. It may have been bright and normal just hours previously but the progression of this disease is so fast that they can die very quickly.
The incubation period (time between the rabbit encountering the virus and disease developing) is short between 12-36 hours. Signs of disease are sudden death, elevated temperature (>41C), not eating, dullness, lying flat on stomach, convulsions, paralysis, groans or cries, breathing difficulties and a bloody discharge from the nose. Several of these signs can occur at once but it is important to mention that these are not exclusive signs of VHD and some other diseases can have the same clinical signs. The per-acute and acute forms of the disease are characterised by sudden death with blood possibly being seen from the nostrils. Chronic disease can be seen in some rabbits (usually 5-10% of those infected) where the virus causes severe jaundice, weight loss and lethargy. These rabbits usually die 1-2 weeks later, usually of liver failure. As with any illness veterinary advice should be sought as soon as possible.
In an outbreak a high percentage of the rabbits in a group are usually affected with high levels of mortality. The disease only seems to occur in rabbits over 40-50 days old. Rabbits under this age can become infected but do not seem to suffer the disease. the reason for this is not know. If an outbreak is suspected veterinary advice should be obtained as soon as is possible.
The virus survives in the environment for a long time. There is research showing that it lasts at least 105 days dried on cloth, 48 hours at 60 degrees C (hotter than the hottest bath) and 225 days at 4 degrees C (fridge temperature)
The virus can be spread by direct rabbit-rabbit contact but also through vectors such as birds, insects or other objects e.g. car tyres. There is evidence of VHD being carried long distances by these methods, notably escaping from an island off the Australian coast to the mainland.
Prevention through vaccination is the most effective option. There is currently only one vaccine available in the UK and this is Cylap. Cylap is a killed vaccine available from vets, with a single dose primary course in animals over 10 weeks followed by an annual booster (for animals younger than 10 weeks consult your vet).
VHD tends to be under reported as the rabbits die suddenly unlike myxomatosis where they tend to linger for a number of days, giving owners time to take them to the vets.
To sum up: VHD is a fatal viral disease of rabbits. It spreads easily and kills most of those it infects. The virus can survive for a long time in the environment and vaccination forms the mainstay of prevention.