Myxomatosis in Rabbits
Learn about this highly infectious killer disease here
The following information is taken verbatim from the the Intervet leaflet 'Myxomatosis and its Control'. It is reproduced with permission from Intervet (UK) Ltd.
What causes myxomatosis?
The disease myxomatosis in rabbits is caused by a virus. The virus is a type of pox virus which grows best in the skin of rabbits. Like all viruses the organism is minute and can only be seen under the electron microscope.
What are the signs of myxomatosis?
The very first signs we can see are puffy swellings around the head and face. 'Sleepy eyes' are a classic sign along with swollen lips, tiny swellings on the inside of the ear and puffy swelling around the anus and genitalia. Within a day or so, these swellins can become so severe as to cause blindness and the may be some distortion around the face, mouth, ears and nose.
Which rabbits are susceptible to myxomatosis?
In this country, the European rabbit (Oryctolagus) is highly susceptible to the disease. The European brown hare is sometimes, but rarely, affected with myxomatosis.
What breeds of rabbit are affected?
All breeds of rabbit are affected, including our wild rabbits found in the country, all breeds of pet and show rabbits including Dwarf rabbits, Lop Eared rabbits and Exotics. There is little evidence that one breed is more susceptible than another.
Where did myxomatosis come from?
Originally, myxomatosis was imported from brazil (where it was first discovered in the 1930's) to Australia in 1950. This was control the massive populations of rabbits in that subcontinent. In Brazil, the Cotton Tailed rabbit (Sylvilagus) is affected by the disease to a minor degree as only tiny lumps are produced by this self-limiting disease. However, in Australia the disease was devastating and markedly reduced the rabbit population.
How did the disease get to Britian?
The diseas was transmitted from Australia by French Physician, Dr A Delille, who wished to control the rabbit population on his country estate near Paris. The disease rapidly spread into the wild population in france and then was brought, entirely by accident, from France in 1953. there is no evidence that the disease was intentionally brought into Britain but there is no doubt that some farmers moved the disease around using diseased rabbits to contro the population of the rabbits locally.
How is the disease spread?
Myxomatosis is spread by blood sucking insects. A major insect parasite which transmits the disease in this country is the rabbit flea which is frequently found on wild rabbits although is less common on pet rabbits. In other countries, including some European countries, it is known that mosquitoes are a major insect vector of myxomatosis. Although this has never been proved in Britain, there is strong circumstantial evidence that mosquitoes transmit myxomatosis in the United Kingdom.
Incidently, myxomatosis is not easily spread by simple contact from one rabbit to another. For instance if a myxomatosis-infected rabbit is placed in the same hutch as a healthy rabbit and neither rabbit is parasitised by fleas or mosquitoes, the disease is virtually never transmitted by contact.. Myxomatosis virus can remain alive in the blood of fleas for many months and it is probably by over wintering of fleas in rabbit burrows that the disease is transmitted from year to year.
What happens when myxomatosis-infected flea bites a susceptible rabbit?
As the mosquito or flea bites the rabbit a small amount of the live virus is placed in the skin of the rabbitas the insect sucks blood. Within a few days the virus is transmitted to the local lymph nodeabd then passes into the blood of the rabbit which enables it to be moved around to several sites. the virus mainly multiples in the skin around the eyes, the nose, the face, the soft skin inside the ears and also the skin around the anus and genitals of the rabbit.
What is the incubation period of myxomatosis?
The incubation period varies slightly from one animal to another but can be as short as five days and as long as fourteen days (incubation period is the time from the point of introduction of the virus into the animal to the first time that clinical signs of illness are seen).
After infection how long do rabbits usually survive?
This also varies. Some animals may survive for weeks or monthd after infection but, if an infection is severe in a susceptible rabbit, death occurs within 12 days.
How does the disease progress?
Within a short space of time, affected rabbits become blind because of the swelling around the eyes and for this reason feeding and drinking is often difficult. However, one can sometimes see wild rabbits suffering from myxomatosis quietly grazing. of course, at this stage many rabbits become prey to animals such as foxes and other predators. Other rabbits may well become injured or killed on roads but the common cause of death is secondary lung infection which often occurs around day eight after the initial incubation of the disease. In pet rabbits, the disease often progresses more slowly and death is not so rapid because of the care which the owner gives the rabbit.
Do all affected rabbits die?
Not all affected rabbits die. Although recovery is rare in the wild (probably less than 10% of wild rabbits eventually recover from myxomatosis) recovery may be more common in pet rabbits with intensive nursing. (If care is taken with feeding, making sure that water is available and medical care to combat pneumonia is given, then recovery rates in pet rabbits are higher than in the wild but are variable depending on the severity of the disease.)
However, a word of warning - myxomatosis can be very protracted disease and affected animal may take weeks or months to recover. Even then there may be severe scaling, scabbing and scarring on the head and body.
How can the disease be controlled?
The disease can be controlled by two main methods:
- Control of insect parasites.
- Use of vaccines.
Controlling insects
Flea control is important and may involve not only keeping wild rabbits away from pet animals but also use of flea control measures such as sprays, dips and insect repellent strips. Incidently, there is some evidence that the domestic cat, which can often be affected with rabbit fleas, may be a secondary transmitter of the rabbit flea. Obviously, isolating pet rabbits from possible close contact with wild rabbits is sensible.
Do not forget to control mosquitoes - it may be possible to use mosquito nets and insect repellent strips. Care should be taken that the bedding of animals is kept dry and that pet rebbits are not kept in moist conditions which favour mosquito activity.
Your veterinary surgeon will be able to give advice on flea and mosquito control.
Use of vaccine against myxomatosis
In the UK a lincensed vaccine for the control of myxomatosis is available (Nobivac Myxo). This vaccine utilises a virus called the Shope Fibroma Virus which is closely related to the myxomatosis virus but does not cause the disease. occasionally, it is possible to see a tiny swelling at the site of vaccination but usually no signs are obvious after vaccination. this virus induces a degree of protection against myxomatosis.
It is not a new principle to use a similar virus to control disease. For instance, Edward Jenner made the first successful vaccination in 1796 against smallpox by immunising a patient with cowpox virus. there are several other examples of related viruses being used to control diseases in animals and man. Is the vaccine live or dead?
Nobivac Myxo is a live vaccine containing the Shope Fibroma Virus. However, the virus does not readily spread from one animal to another and all rabbits in a group should be individually vaccinated.
Does the vaccine cause disease?
No. Nobivac Myxo does not cause illness in vaccinated rabbits. The only clinical signs that may be seen are sometimes a slight lump at the site of vaccination. This is a good sign as it shows that the virus has actually caused a swelling in the skin and should confer a strong protection against myxomatosis.
Does vaccination guarentee protection against disease?
No, vaccination can never guarentee protection against any disease but Nobivac Myxo when properly used, offers the best available chance of producing immunity against myxomatosis.
Rabbits that that are exposed to myxomatosis, but have a degree of immunity, do not usually develop the diseasemyxomatosis. However, they mey develop a form of myxomatosis (atypical myxomatosis) which presents as small skin lumps/nodules which resolve over a period of time. Extreme care must be taken to avoid stress and other ailments. It must always be remembered that rabbits are very susceptible to stress.
Rabbits also suffer from common ailments which can prove fatal, one of which is pasteurellosis. Pasteurella bacteria are present in the majority of raabbits usually without making their presence known, but at times of stress or illness, can cause signs of disease - most commonly respiratory disease. This organism is the cause of 'snuffles' in rabbits.
What is the vaccination schedule?
- A single vaccination should be given to rabbits over six weeks of age.
- Rabbits should not be vaccinated during pregnancy.
- Only healthy rabbits should be vaccinated. the vaccine may not be effective in rabbits incubating the disease at the time of vaccination.
- Following initial vaccination rabbits should not be exposed to infection for at least 14 days.
- Some animals may be immunologically incompetent and fail to respond to vaccination. Are boosters necessary?
Boosters are suggested annually for rabbits which are not under a heavy challenge from disease. however, animals which are likely to be heavily challenged by disease e.g.
- Rabbits in a rabbit sanctuary, rabbits close to wild rabbits with myxomatosis.
- Rabbits with a heavy flea population.
- Rabbits in an area where myxomatosis is rife are best vaccinated twice a year.
Incidentally, most myxomatosis in the UK occurs in the late summer, autumn and early winter months. If giving a single annual vaccination it is probably best to vaccinate in May or June so that animals have the best protection during the autumn and early winter months. However, do remember that myxomatosis can affect animals during any month of the year so two vaccinations given six months apart may well be the most appropriate regime.
