Viral hemorrhagic disease (VHD)

There are several highly infectious and potentially fatal diseases that can affect your rabbit. Viral hemorrhagic disease (also known as VHD, rabbit haemorrhagic disease or RHD) is one of the most common, along with myxomatosis, which is discussed in a separate factsheet.

There are two strains of VHD (VHD1 and VHD2). VHD1 was first discovered in China in 1984 in rabbits that had been imported from Germany, and it arrived in the UK in 1992. VHD2 was first recognized in France in 2010 and soon after came to the UK.

To ensure your rabbit is protected against these diseases, vaccination is essential.

VHD is a viral condition which only affects rabbits, although a similar disease (European Brown Hare Syndrome) has been reported in hares, which is caused by a related virus, although it does not cross-infect. VHD is caused by a highly contagious virus called the calicivirus.

VHD1 is nearly always rapidly fatal the virus attacks the internal organs, particularly the liver, causing massive internal bleeding (haemorrhage). Death occurs in almost 100% of affected rabbits within less than 48 hours.

VHD2 has a slower onset of symptoms, which can be very non-specific. These may range from anorexia, lethargy, simply being off colour, to sudden and unexplained death. The mortality rate of VHD2 is between 7-20% of affected rabbits and death is over the course of several days. Unlike VHD1, rabbits under the age of 6 weeks seem to have no immunity to VHD2.

VHD and which strain is responsible can only be confirmed on post-mortem.

Both strains of VHD are transmitted by direct contact with the nasal secretions and saliva of infected rabbits. It can also be spread indirectly by aerosol exposure to contaminated fomites (objects) and mechanically via equipment and clothing. Insects, rodents and birds may also be able to carry the virus and infect isolated rabbits (such as pet rabbits). VHD can also survive the digestive tract of carnivores, so could be transmitted in faeces from foxes or dogs who have eaten infected wild rabbits.

VHD is very resilient to environmental changes and can survive freezing conditions.

If your rabbit is suffering from VHD you may notice symptoms such as a high fever (pyrexia), lethargy, collapse, convulsions, paralysis, breathing difficulties (dyspnoea) and loss of appetite. However, the symptoms of VHD2 can be very vague and some rabbits may not show any symptoms. With both strains, some rabbits can appear to be fine and then when seen several hours later be found dead or dying.

There are several forms which VHD1 may take:

• Rabbits under the age of 6 weeks are not affected by VHD1, although those between the ages of 4-6 weeks may show symptoms but survive.
• If the disease takes it severest form (hyperacute) then the infected rabbit will often be found dead 16 hours to 3 days after infection, with blood having come from the mouth, nose and possibly back end.
• Rabbits with an acute form of the disease will show lethargy and anorexia, followed by convulsions, epistaxis (bleeding from the nose) and death. All rabbits infected with this form will die.
• A small percentage of rabbits may develop a chronic form of the disease. These rabbits display symptoms of jaundice (yellow coloration to the skin and eyes), weight loss and lethargy and die 1-2 weeks after infection from liver failure.
• VHD2 appears less defined and as a relatively new strain of the virus information and knowledge is being gleaned all the time. It appears that VHD2 often has non-specific symptoms which can be put down to other diseases in rabbits.

Unfortunately, there is no cure for either strain of VHD disease, and VHD1 is almost always fatal, with most rabbits dying within a few days. Owners are often unaware that their rabbit is even ill as VHD can be fatal in a matter of hours. A percentage of VHD2 rabbits do survive, but the exact amount is still unclear.

Vaccination

Vaccination is essential!

Your rabbit can be vaccinated against VHD1 and VHD2 when it reaches 5 weeks of age. The vaccination that is now given to rabbits combines the VHD1 and VHD2, and myxomatosis vaccinations together. Fullest protection from the vaccine takes 3 weeks following administration.

Rabbits who have previously received a myxomatosis vaccination but not a VHD2 vaccination may not respond fully to all elements of the combined vaccination, so may need an alternative protocol prior to moving onto the new combined vaccination. You should discuss this with your veterinarian. Likewise, if there is a local outbreak of one of the diseases, your veterinarian may suggest using separate vaccinations in order to get a more rapid onset of protection.

The combined vaccination is licenced in the UK for use in pregnant does, but not recommended for use in breeding bucks due to its safety in these rabbits not having been tested.

Antibodies from a vaccinated doe may persist in her kits and may decrease the duration of activity of the vaccination in kits vaccinated below 7 weeks of age, so an early booster may be recommended by your veterinarian.

Your rabbit will require a booster injection every year to ensure continued protection against the disease.

Your veterinarian will be able to advise on their vaccination protocol and the available vaccine(s) they have in stock.

Other precautions

No vaccine is ever 100% guaranteed to prevent a disease, so other precautions can be taken to prevent your rabbit contracting VHD.

Don’t handle rabbits in pet shops or other similar environments and ensure you wash your hands thoroughly after coming into contact with other rabbits. All your rabbit’s bedding and food should be bought from reputable pet shops to ensure there is no contamination.

If you live in a high-risk area, consider hanging insect repellent strips and mosquito netting over your rabbit’s hutch to prevent them coming into contact with VHD vectors. You should also ensure that your rabbit’s bedding is kept clean and dry, to avoid attracting unwanted insects.

Make sure your garden is not accessible to wild rabbits and other wildlife; this will prevent your rabbits coming into contact with wild rabbit carrying the disease.

If you have other pets that come into contact with your rabbits, such as dogs or cats, make sure they are also regularly treated for fleas with a product from your veterinary surgery, as these are potent enough to ensure the fleas, larvae and eggs are all killed.