Myxomatosis in Rabbits

What is Myxomatosis in Rabbits?

Myxomatosis is caused by the Myxoma virus, a member of the Pox Virus family, like Chicken pox in people. Myxomatosis is a lethal disease of domestic and wild European rabbits with a 99% mortality rate. It is endemic (regularly occurring) in jungle rabbits in Central and South America and in bush rabbits in California. The Myxoma virus in rabbits is also found in Australia and Europe but is a different, often less severe strain than in the Americas.

Myxomatosis in pet rabbits has been reported in Oregon, California, and Mexico typically during June-October and January-February. The entire disease process can take between 8-21 days after infection.

Myxomatosis is a notifiable disease under the Animal and Plant Health Inspection Service.

U.S. Department of Agriculture. If you believe your rabbit has myxomatosis please contact your veterinarian so that your rabbit can be seen immediately and can be reported to the USDA by your veterinarian.

Symptoms of Myxomatosis in Rabbits

Early signs of myxomatosis include:

• Swelling and redness of eyelids and ear margins, and genitals

• White eye and nasal discharge

• Ear droop

• Purple/blue spots on the skin

• Skin nodules/lumps up to 1 cm in diameter, often on eyelids, face, nose, ears, and genitals, which can scab

Severe signs of myxomatosis include:

• Fever

• Lethargy

• Anorexia

• Difficulty breathing

• Skin hemorrhage

• Seizures

• Secondary bacterial infections, pneumonia

• Septicemia within 10-14 days of infection

• Acute death in 5-7 days of infection

Causes of Myxomatosis in Rabbits

The Myxoma virus is primarily transmitted through black fleas, fur mites, fleas, and mosquitos. The virus can be transmitted indirectly if a rabbit comes into contact with items an infected rabbit has touched, like food, bedding, water bottles, etc., but this is less common. This disease can also be transmitted directly from infected rabbits' eyes or nasal discharge to another rabbit.

How Veterinarians Diagnose Myxomatosis in Rabbits

Diagnosis is usually based on clinical signs, history, and bloodwork and is confirmed via histopathology or serology. On physical exam, rabbits often will have the above signs, swollen lymph nodes, and a fever of 106 degrees Fahrenheit.

On bloodwork, such as a complete blood count that looks at platelets, white blood cells, and red blood cells, a white blood cell called neutrophils is often elevated. Serology testing can be used to confirm the Myxoma virus, which tests for virus antibodies made by the body.

A biopsy of any lumps can be sent to a pathologist to confirm the virus via histopathology and isolate the virus in the tissue.

Treatment of Myxomatosis in Rabbits

Myxomatosis can be aggressive and is often fatal, with a 99% mortality rate, so most veterinarians will recommend euthanasia. If you are concerned that your rabbit might have myxomatosis, separate them from other rabbits in your home and take them immediately to a veterinarian.

There is currently no effective treatment other than supportive care. If treatment is elected, it is essential to have your rabbit examined daily by a veterinarian. The following often will be provided and prescribed:

• Fluid therapy: subcutaneous or intravenous fluids to help maintain hydration

• Non-steroidal anti-inflammatories like Metacam to help with pain and inflammation

• Antibiotics to prevent any secondary bacterial infections

• Nutritional support in the form of supplemental feedings recovery formulas like Critical Care or Emerald

Recovery and Management of Myxomatosis in Rabbits

Rabbits infected with less severe strains can show mild signs and recover over 3-5 weeks, but many have a moth-eaten appearance around ears and face from lesions. Myxomatosis can lead to secondary bacterial infections, pneumonia, septicemia or blood poisoning, and death. It is essential to follow your veterinarian’s care instructions closely and notify them of any changes.

Prevention of Myxomatosis in Rabbits

If you live in an area where myxomatosis is prevalent, keep your rabbit indoors. If they cannot be kept indoors, it is essential to use flea prevention like Revolution, use mosquito nets and screens, and do not let your rabbit come into contact with wild rabbits. If you come into contact with and touch wild rabbits, washing your hands thoroughly and changing clothes before interacting with your rabbit is essential.

A vaccine for the myxomatosis virus is unavailable for rabbits in the United States. The vaccine is available in Europe and the UK but has not been approved by the USDA. It is also unknown if this vaccine would be effective against the more severe California strain. Myxomatosis in Europe and Australia often has only a 50% mortality rate compared to the 99% mortality rate in the United States.

If you elect treatment, keep your rabbit with myxomatosis away from other rabbits in your home. Wash hands and change clothes before and after interacting with that rabbit to prevent the spread to your other rabbits. It is also essential to quarantine any new rabbits you acquire before introducing them to your rabbit per your veterinarian’s instructions.