Category: infectious-diseases-rabbits

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.

Myxomatosis is an infectious disease caused by the myxoma virus which is spread by biting flies or fleas and by mechanical vectors such as non-biting insects, bedding and food. The virus causes cells of the epidermis (the outermost layer of the skin) to die, and an accumulation of fluid beneath the dermis (the layer of skin below the epidermis).

The virus is usually introduced by biting insects, which causes local skin trauma, the introduction of the virus into the bloodstream and multiple skin eruptions (a rash).

Myxomatosis is widespread throughout the UK and has a higher seasonal prevalence in late summer, autumn and early winter. Both sexes and all breeds of rabbit can be affected with myxomatosis.

The main form of transmission is via insects like the rabbit flea (Spilopsyllus cuniculi) and mosquitoes. Dog and cat fleas can also carry the virus. The virus is also found in discharges, and transmission by mechanical vectors such as non-biting insects, bedding and food also occurs.

The virus can remain in the blood of the insect for many months and the ability of the bacteria to cause the disease can vary from year to year.

Signs of disease usually show within 8 days of transmission and the duration of illness usually lasts between 11 and 18 days. Death usually occurs within 14 days of infection from an overwhelming bacterial infection or acute respiratory infection.

The most obvious signs of infection are swelling of the lips, eyelids and genitals; infected rabbits can also suffer from a high temperature (pyrexia), depression, localised skin nodules (lumps) and noisy, laboured breathing.

There are two forms of myxomatosis, acute (sudden onset) and chronic (long-term).

Acute

• Initially your rabbit will appear bright but may develop swelling around the lips, eyelids and genitals.
• Your rabbit may become lethargic and develop a temperature with swollen eyelids causing blindness, but will still try to eat and can be hand fed.
• Because rabbits breathe through their nose swelling of the nose can lead to suffocation.
• These in turn may lead to lung infection and death.

Chronic

• Your rabbit will develop skin swellings, called myxomas or ‘pseudotumours’, which develop after 10-15 days, mainly on the ears, nose and paws.
• The swellings, which heal to leave scabs, soon disappear.
• 50% of rabbits can survive this form of myxomatosis so this is the form that can be treated.

Wild rabbits tend not to survive as long as domestic rabbits, as blindness and debility make them susceptible to predation from foxes and road accidents. Pet rabbits however, can survive longer with nursing care, but are usually put to sleep on humane grounds to prevent unnecessary suffering.

Fifty percent of rabbits usually survive the chronic nodular form; those affected with the chronic form may survive following infection; but the acute form is fatal and affected rabbits usually die within 2 weeks. Vaccinated rabbits can also be affected but show less severe signs and are more often than not possible to nurse through the disease, although nursing care can be intensive and take many weeks if not months.

Medical treatment usually involves eye drops, antibiotics and gastrointestinal stimulants, with hand-feeding/syringe feeding, as well as general nursing to keep the rabbit clean, dry and warm.

Myxomatosis is very common in wild rabbits but is also seen in pet rabbits, so make sure your rabbits hutch isn’t sited near wild rabbit populations. If you are unsure of the status of wild rabbits in your area, contact your local farmer, as they are often able to give an indication of current disease in a geographical area.

The virus is resistant to dryness and cold but not to heat and light, so the use of disinfectants such as bleach or caustic soda is extremely beneficial, although ensure that your rabbit’s hutch is thoroughly dry before returning your rabbit to it and bowls, bottles, etc are rinsed before using them again.

A combined vaccination is available for myxomatosis which also vaccinates against viral haemorrhagic disease 1 (VHD1). Immunity develops within 21 days of vaccination; your vet will examine your rabbit to ensure they are healthy at the time of vaccination, since rabbits already fighting illness may not respond to vaccination.

Vaccination can be started at 5 weeks of age and is best given in May or June before the peak myxomatosis season in late summer and autumn. The vaccine is not recommended in pregnant does or bucks used for breeding. An annual booster is sufficient to protect against both myxomatosis and VHD1. Your rabbit will require a separate vaccination to protect against VHD2.

If you live in a high-risk area, also consider hanging insect repellent strips and mosquito netting over your rabbit’s hutch to prevent him coming into contact with myxomatosis 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; this will prevent your rabbit coming into contact with wild rabbits that may be 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 products available from your veterinary surgery.

During the active stage of the disease, herpes virus replication within cells causes development of tissue lesions in the affected area. Many strains of the herpes virus produce external blisters and sores on the skin and these are highly contagious and can be transmittable between species. Some species of herpes virus can be transmitted between humans and animals but transmission from animals to humans is rare.

Rabbits can acquire a handful of different herpes viruses, but for pet rabbits, the most common infections are caused by Herpes simplex virus 1 (HSV-1), Herpes cuniculi (LHV-4), Herpes cuniculi (LHV-2) and Herpes sylvilagus (LHV-1/LHV-3).

Herpes simplex virus 1 (HSV-1)

A form of the virus that is thought to be specific to humans, but the external lesions make it easily transmittable to other species, including pet rabbits. One of the most common ways HSV-1 can affect rabbits is by infecting the eyes. Signs of this condition can include watery eyes, squinting, conjunctivitis (redness around the eyelids), ulceration of the cornea and blindness. It is a condition that can come and go as the virus re-emerges after periods of dormancy. Exposure of the HSV-1 strain to pet rabbits has also rarely resulted in brain lesions. This condition leads to seizures, coma and death.

Herpes cuniculi (LHV-4)

A form of the virus specific to domestic rabbits and is the most common naturally acquired strain of herpes virus in pet rabbits. It has also been seen occasionally in wild rabbits. This strain has mostly been seen in North America, and is usually found when larger colonies have been infected. It is highly contagious and young females seem more likely to be infected. The most common signs include wounds and blisters on the face, back, eyes and genitals, but other more serious signs can occur, including a swollen face, discharge from the nose and eyes, respiratory distress, anorexia and sudden death.

Herpes cuniculi (LHV-2)

Indigenous to domestic rabbits, but causes no signs of disease, so is difficult to detect.

Herpes sylvilagus (LHV-1/LHV-3)

Indigenous to wild cottontail rabbits, and is not known to infect domestic rabbits. It causes lesions in the throat, lymph nodes, liver, kidney and spleen.

Diagnosis varies depending on the strain of the disease. For mild or common strains, the veterinarian can diagnose the disease by observing clinical signs or taking blood or tissue samples and sending them to the laboratory for analysis.

For some tests, general anaesthesia may be required.

As with all viruses, treatment is aimed at supporting the animal until the virus can be largely controlled by the animal’s immune system. Since herpes viruses cannot be cured, there is no treatment that will eliminate the disease, but when the virus is active and signs of disease are seen, supportive treatment can be provided. For mild cases, this may mean giving pain relief, helping to minimise secondary bacterial infection by keeping wounds clean and administering nutrition and fluid support to help the animal recover faster. In some cases, the veterinarian may prescribe anti-viral medications to help the immune system combat the virus.

When the virus is active, the animal may be able to shed the virus to other animals, and possibly even humans, so the rabbit must be isolated from other animals and excellent hygiene adhered to at all times. Once the virus returns to a dormant phase, the animal will still be a carrier and may shed the disease to other animals so it should be housed to ensure that cross-contamination with other animals does not occur. Outbreaks of the disease can occur at any time, especially during seasonal changes or throughout periods of stress.