Myxomatosis is caused by the myxoma virus, a kind of pox virus. There are different strains of the virus which vary in their virulence (basically the ability to cause disease). The susceptibility of different rabbit species (e.g. domestic rabbits, vs hares, vs cottontails etc.) to the virus varies as well.
The virus is spread by biting insects (e.g. fleas, mosquitoes, mites, lice, and flies) as well as by direct contact (between rabbits), indirect contact (via items that such as food dishes or clothes that carry the virus from rabbit to rabbit), and by aerosols.
Myxomatosis can take several courses. Rabbits may suddenly become very ill with conjunctivitis (red, runny eyes), a high fever, loss of appetite and lethargy, and may die within 48 hours. Sometimes the illness lasts longer, and the mucous membranes and other tissues become swollen, including the eyes, nose, mouth, ears (which become droopy) and the genital and anal areas. The entire face may become very swollen, and thick pus may be discharged from the nose and the rabbit may have difficulty breathing. Most rabbits die within 14 days.
In more chronic cases (and depending on the strain of virus and immunity of the rabbit) lumps and nodules (myxomas) may develop over the body. Rabbits with this form may survive, and become immune to myxomatosis virus. This seems to be a less likely course of disease in domestic rabbits, however, with most suffering from the acute forms with eventual death.
