Myxomatosis in rabbits

Myxomatosis, also called rabbit plague, is one of the viral diseases to which countless rabbits fall victim every year. Predominantly wild rabbits are affected by myxomatosis, in rare cases also hares. However, through different transmission routes, the viruses often enough find access to our domestic rabbits.

Myxomatosis – a virus for population control

The causative agent of myxomatosis is a virus from the family of poxviruses with the euphonious name Leporipoxvirus myxomatosis. Originally, the virus originated in South America, but it was not until the experiments of the French physician Paul-Félix Armand-Delille in the 1950s that it came to our continent.

Actually, the physician only wanted to get the rabbit population on his country estate under control with biological means. Without further ado, he infected two captured long ears with the virus and set them free again. Armand-Delille had a resounding success with this method, but he had neither secured his attempt nor thought it through further.

The myxomatosis virus spread all over Europe, even outside his country home. This is due to the simple transmission route via direct contact with the pathogen from rabbit to rabbit, but also by blood-sucking insects such as mosquitoes and fleas. Accordingly, the denser the rabbit population, the faster and more efficiently the virus can spread, which it does mainly during the warm, humid months of the year.

While the virus is still highly virulent at the beginning of the “disease season”, resulting in a mortality rate of 100 percent, the pathogen weakens as it spreads. Thus, although the myxomatosis virus can prevent a population explosion, it cannot eradicate rabbits!

At about the same time as the physician’s experiments, the Australians also used the myxomatosis virus to control the enormous rabbit population on their continent. To a certain extent, the plan works; once the rabbit density has shrunk to a tolerable level, the epidemic comes to a halt of its own accord.

Transmission and spread

The pathogen can be transmitted through direct physical contact with infected animals, as well as through grazing. However, the main route of transmission of myxomatosis is via mosquitoes and fleas. This also explains the seasonal nature of the disease, which usually begins in the spring and reaches its peak in July and August, when mosquitoes and other insects find particularly favorable living conditions. The epidemic then subsides again in the winter. The survivability of the virus within a mosquito is enormous with several months!

By the way, the myxomatosis virus is not dangerous for humans and other domestic animals. However, not only domestic rabbits that are allowed to nibble fresh greenery in the garden and are thus exposed to the danger of a mosquito bite are at risk. Rabbits that are kept exclusively indoors can also fall ill. The transmission route here is also possible through mosquitoes or fleas, but also through collected green fodder or by introducing the viruses through humans (shoes).

Symptoms of myxomatosis

A few days after the rabbit is infected with the myxomatosis virus, the first symptoms appear. One speaks of an incubation period of 3 to 5 days, in some cases also up to 9 days.

Typical for myxomatosis is an inflammation of the eyes, which initially can easily be mistaken for conjunctivitis. However, then there is a severe swelling of the eyelids with discharge of pus and adhesion of the eyelids, the rabbit goes blind after a short time. Similarly, swelling of the mouth and nose, as well as the ears and genital organs can be observed. Often, nodular changes are now added to the lips, eye rims, ears and genital area.

In the final phase, around 8 – 10 days after infection, the rabbit refuses all food and water intake, is apathetic and dies.

In the milder form of myxomatosis, the typical swelling and inflammation do not occur, but only pockmarked changes.

Treatment of myxomatosis in rabbits

A spontaneous cure of myxomatosis is possible, although very rare. Usually, affected animals die unless they are put down first. The veterinarian is also unlikely to be able to help with myxomatosis, as treatment is aimed only at alleviating symptoms. There is no drug that cures myxomatosis.

Preventing myxomatosis in rabbits

The best prevention to protect rabbits from myxomatosis is built on several pillars. The most important pillar is a vaccination against myxomatosis. This must be refreshed at regular intervals to maintain protection. However, myxomatosis vaccination does not protect 100% against myxomatosis. Even vaccinated rabbits can become infected with the virus. In most cases, however, the course of myxomatosis is much milder and the rabbits survive the disease.

Another pillar of prevention against myxomatosis is protection against fleas and mosquitoes. Where there is no bite, there is no transmission of the virus!

Also important is the avoidance of endangered areas. Walking in a park affected by myxomatosis greatly increases the risk to the rabbit living at home from introduced viruses (shoes). Gathering green fodder should also be avoided in regions affected by or at risk of myxomatosis. Short-term freezing of green fodder collected in nature offers a certain security against introduced mosquitoes.