Myxomatosis occurs in wild and domestic rabbits and is caused by a Myxoma virus, (a type of pox virus). In South America where the disease originally came from it only causes a mild disease in the indigenous rabbit population. In European rabbits it results in nearly 100% mortality. If wild rabbits regularly visit your garden your pet rabbit may be more at risk of this disease.
Myxomatosis has an incubation period of between 2-8 days following infection. The initial signs of the disease are usually a swelling of the eyelids, a sticky (purulent) discharge from the eyes and conjunctivitis; other swellings on the head, neck and genitals soon follow. The swellings on the head and eyelids may become so severe that the rabbit is blinded because the eyes are unable to open. Surprisingly the rabbit's appetite will often remain normal throughout all this. This acute form of the disease is usually fatal with death occurring about 2 weeks after the onset of signs. Treatment of the acute form of the disease is unlikely to be successful and rabbits tend to die from respiratory complications even with excellent nursing care. Therefore it is usually kindest to put the rabbit to sleep if this form of the disease is diagnosed.
Occasionally rabbits may develop the chronic form of the disease. Swellings called pseudotumours ("false tumours") appear about 12 days after infection with the myxoma virus. These swellings are usually seen on the nose, paws and ears. The pseudotumours can resolve spontaneously leaving scabs which then disappear. There is a 50% chance of survival if your rabbit develops this form of myxomatosis. If your rabbit develops the chronic form of the disease it is worth attempting to treat it using antibiotics to prevent secondary infections in conjunction with excellent nursing care. Occasionally the disease can present as a respiratory disease and in this situation it is very difficult to tell it apart from other respiratory diseases of rabbits, e.g. Pasteurellosis.
Myxomatosis is spread between rabbits by direct contact, indirect contact and by insect vectors (carriers). The most important source of infection being the rabbit flea Spilopsyllus cuniculi and mosquitoes. The myxoma virus is able to survive for long periods inside these insect vectors. Therefore if this disease is to be prevented from spreading these insects must be controlled. The best way to do this is to practice good standards of hygiene and use a product such as Advantage to control rabbit fleas. Advantage is a "spot on" flea preparation and will be readily available from your vet. To prevent other routes of transmission of this disease keep affected animals in isolation and disinfect areas where sick rabbits have been in order to kill the virus. Ensure that any disinfectant used will not be harmful to your rabbits.
It is best to prevent this disease in rabbits by vaccinating them since there is currently no treatment available for viral infections in animals. The vaccine generally given to prevent myxomatosis is a live vaccine containing Shope's Fibroma Virus. This does not cause disease in the rabbit but induces a cross immunity for the myxoma virus. This vaccine can be given to rabbits over 6 weeks of age. Immunity develops after 14 days. The vaccine against myxomatosis is usually given annually except in areas where there is a high risk of disease in which case it is given every 6 months. The vaccine should not be given within 2 weeks of the vaccine for Viral Haemorrhagic disease.