Viral haemorrhagic disease (VHD)

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 what 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 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 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 colouration 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 and very successful. Your rabbit can be vaccinated against VHD1 when it reaches 5 weeks of age. The vaccination that is now given to rabbits combines the VHD1 and myxomatosis vaccination together.

Rabbits who have previously been vaccinated with any other brand of myxomatosis vaccine, other than the Nobivac Myxo vaccine, may fail to respond to the VHD element of the combined myxomatosis and VHD vaccination. If you feel your rabbit may be one of these, you should speak to your vet.

Pregnant does and bucks intended for breeding should not be vaccinated with the combined Myxo-RHD vaccination since safety of the vaccination in these groups has not been tested.

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

Vaccination for VHD2 is not included in the Nobivac Myxo-RHD vaccine, so your rabbit will require a further vaccination to help protect against VHD2. There is no UK-based vaccine for VHD2, but several vaccines from Europe have been given Special Import Certificates (SICs) from the Veterinary Medicines Directorate (VMD) to enable vets to order them and use them on rabbits in the UK.

Filavac VHD K C + V comes from France and is the most commonly used vaccine in the UK. The vaccine is given to rabbits over the age of 10 weeks and requires a single initial vaccine followed by a 6 monthly booster in areas where VHD2 cases have been confirmed, or an annual booster in low risk areas. The vaccine offers protection for both VHD1 and VHD2 strains. A two week gap must be left between giving Filavac and Nobivac Myxo-RHD vaccines as no clinical trials have been undertaken with the use of the two vaccines together.

Cunivak RHD from Germany is also obtained via an SIC from the VMD. This vaccine requires an initial vaccination from 4 weeks of age which is repeated after 3 weeks and then an annual booster; two weeks must be left between the vaccine and Nobivac Myxo-RHD. The vaccine covers both VHD1 and VHD2 strains.

Cunipravac RHD Variant from Spain is obtained via a Special Treatment Certificate. The vaccine is oil based so skin reactions are much more likely. The vaccine can be administered from 4 weeks of age and requires a further vaccine 6 weeks later with boosters every 6 months. As the vaccine only comes in multidose vials, it has currently not proven popular in the UK! It offers protection against VHD2 and two weeks must be left between the vaccine and Nobivac Myxo-RHD.

The only vaccine in the UK that currently offers protection against Myxomatosis is the Nobivac Myxo-RHD so it is imperative not to cease vaccinating with Nobivac, but to add in another vaccine to protect against VHD2.

Your vet 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 rabbits 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 rabbits hutch to prevent him coming into contact with VHD vectors. You should also ensure that your rabbits 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 rabbit coming into contact with wild rabbit carrying the disease.

If you have other pets that come into contact with your rabbit, 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.