Myxomatosis or rabbit plague is a viral disease that occurs mainly in domestic and wild rabbits. Hares can fall ill with myxomatosis, but the symptoms of the disease are only mild. The virus is not dangerous for humans.

Worldwide

European wild rabbit, domestic rabbit, brown hare

The transmission of the pathogens occurs mainly in summer via stinging-sucking insects; directly from the sick to the healthy animal, indirectly via flies, humans, stable equipment.

3-9 days

Swelling, lumps and skin lesions appear on the head, particularly on the eyelids and in the genital and anal areas. The disease usually ends in death.

There is no specific treatment for myxomatosis. It cannot be cured, but antibiotics and other medications can be used to support the disease. The disease usually ends in the death of the affected animals.

Vaccination, hygiene and biosecurity measures

In Austria, among others, wild and domestic rabbits in the area of Vienna and Lower Austria were/are affected. More precise information on the geographical spread of myxomatosis in Austria cannot be given as the disease is not notifiable.

Myxomatosis or rabbit plague is a viral disease that occurs predominantly in domestic and wild rabbits(Oryctolagus cuniculus). The main hosts are the European wild rabbit(Oryctolagus cuniculus) and its breeding form, the domestic rabbit(Oryctolagus cuniculus forma domestica). The wild rabbits of South America(Sylvilagus brasiliensis) are considerably more resistant to the myxomatosis virus (mild or symptomless infection) than their European representatives. European wild rabbits(Oryctolagus cuniculus), which were introduced into Australia and are now a plague, have largely developed genetic resistance to the myxomatosis virus. Brown hares are largely insensitive to the myxomatosis virus. Even under high infection pressure, a maximum of 1 % of brown hares fall ill. Other animals or humans are not at risk from the myxomatosis virus.

The causative agent of myxomatosis belongs to the smallpox virus genus Leporipoxvirus (subfamily: Chordapoxvirinae) and is known as Myxoma virus. The genus of leporipoxviruses also includes the Hare fibroma virus (FIBV, causative agent of fibromatosis in hares), the Rabbit fibroma virus (RFV, causative agent of fibromatosis in rabbits) and the Squirrel fibroma virus (SQFV, causative agent of fibromatosis in squirrels). The leporipoxvirus is a brick-shaped DNA virus with a genome size of 160 kbp.

The spread of myxomatosis in Europe was triggered in 1952 by the release of diseased, infected rabbits in France. As a result, the myxomatosis virus spread rapidly in Europe and had an almost population-destroying effect. After the last outbreak of the disease was reported in Austria in 1955, cases in both wild and domestic rabbits became more frequent in autumn 2009 and 2010. Myxomatosis is widespread in Europe: outbreaks were reported in England (Leeds, Sussex, Essex, Cambridge etc.) in 2004/2005, in Switzerland in 2007, in Luxembourg in 2008, in Russia in 2009 and again in England (Wales) in 2009, in Greece in 2012, in Portugal and Spain in 2018 and in Finland in 2020. In Austria, wild rabbits and domestic rabbits in Vienna and Lower Austria were/are affected. No outbreaks were recorded by AGES in Austria in 2024.

Myxomatosis is listed in the WOAH Terrestrial Animal Health Code, meaning that member countries are obliged to report outbreaks of the disease.

The virus is mainly transmitted via blood-sucking insects such as mosquitoes or fleas, with the rabbit flea being the main vector. Transmission via mites, ticks and lice cannot be ruled out. The virus remains active in the insect for up to 3 months. An increased density of insects in warm, humid summers and in autumn leads to a higher incidence of the disease. Myxomatosis is known to occur in cycles of 4-5 years with highly virulent courses.

Other transmission routes are: direct contact between animals, indirectly via animate, inanimate and mechanical vectors. Humans can also act as indirect vectors through contact with infected animals. Working tools, stable clothing or stable accessories contaminated with the virus are also responsible for spreading the virus. Sick animals should not be touched with bare hands (hand washing, hand disinfection, gloves). The virus remains infectious in the environment for up to 7 months.

Symptoms

The mortality rate is 20 to 100 %. Highly virulent strains cause a mortality rate of almost 100 %. Attenuated strains cause milder and atypical courses.

The first symptoms appear after an incubation period of 3 to 9 days. The disease usually ends in death after approx. 10 to 14 days.

The most important symptoms are

• High fever
• Swelling around the head (eyes, nose, mouth, base of ears), anogenital area and extremities
• Lumps in the area of the head and extremities
• Eye and nasal discharge
• Difficulty swallowing
• Secondary bacterial pneumonia with dyspnoea is possible

Myxomatosis mainly manifests itself in three forms:

Acute course: Classically, there are swollen eyelids (conjunctivitis with purulent discharge), swelling in the head area (nose, ears, lips), followed by fever and oedema formation all over the body. As a result of the swelling and lump formation, the ears buckle under the weight. The head appears increasingly misshapen ("hippopotamus head", "lion's head", "big head disease"). Subcutaneous oedema is increasingly found in the area of the genitals, the anal area, the hind legs, the lower abdomen and on the back. At the beginning of the disease, the animals are still lively and eat. After 1-2 weeks, apathy and inappetence occur, followed by death.

Peracute course: The symptoms of the disease are less pronounced. Swelling of the eyelids with associated conjunctivitis is frequently observed. Nevertheless, the animals die within a few days.

Chronic course: Nodular and subcutaneous oedema formations are mainly observed in the head area and on the hind legs. Healing is possible in individual cases. Recovered animals can remain asymptomatic carriers.

A respiratory form of the disease without skin lesions has also been reported.

Therapy, control

There is no specific treatment for myxomatosis and it is not considered curable. Antibiotics and other medications can be used as supportive treatment. If an animal survives, it continues to excrete the virus for months. Latently infected rabbits also excrete myxomatosis viruses, meaning that the disease can spread within the herd via contact infections.

The myxomatosis virus has a high tenacity in the environment. Therefore, all objects or buildings with which diseased animals come into contact must be thoroughly cleaned and disinfected after the animals have died. The virus is relatively insensitive to a variety of chemicals such as potassium permanganate, sublimate, phenol and boric acid. The virus is not sensitive to cold, but is sensitive to heat.

Newly introduced rabbits should be quarantined for 14 days and vaccinated. As a preventative measure, a six-monthly vaccination with an attenuated live vaccine can provide protection against infection. There are authorised active substances in Austria and Germany. Detailed information on vaccinations can be obtained from your vet.

Further preventive measures:

• Effective insect protection (insect screens, repellents...)
• Preventing contact between domestic and wild rabbits
• General hygiene and biosecurity measures

Sample type:

live animals

• skin lesions and/or skin crusts

carcasses (dead)

• whole carcasses
• skin lesions and/or skin crusts

detection methods:

• pathomorphological examinations
• molecular biological methods (PCR)