Rabbit plague (tularemia) causes and prevention

Not only rodents can be affected by tularemia, the bacterial infection with the causative agent of hare plague can also take severe forms in humans. In this country, it is very rare for humans to contract rabbit plague.

This was not always the case, because the rabbit plague pathogen once served as a bioweapon. In the animal kingdom, rabbit plague is also not very common in our region. It is much more common in many other countries of the world, for example in the USA, Mexico, Canada, in Scandinavia, China or Russia, but also in Europe.

Although it sounds similar, rabbit plague should not be confused with rabbit plague (myxomatosis).

Bacterium triggers rabbit plague

The pathogen that leads to the clinical picture of rabbit plague is the bacterium Francisella tularensis from the Pasteurellaceae bacteria family. It belongs to the gram-negative rod-shaped bacteria that are immobile and do not form spores.

While the bacterium cannot tolerate conventional disinfectants and heat, it is highly resistant to cold. Even after three years, the rabbit plague pathogen can survive in infected frozen rabbit meat.
Francisella tularensis can be divided into two types:

The highly virulent type A, which is most common in North America.
The less virulent, but no less dangerous type B, which occurs worldwide.

The disease was first described in 1911. George W. Mc Coy found a sick squirrel and isolated the pathogen responsible for rabbit plague only one year later. He spent many years studying this pathogen and the disease itself, which he also gave its name, in reference to Tulare County, California.

Before the First World War, two scientists from the Soviet Union succeeded in developing a vaccine against rabbit plague. They henceforth named the bacterial genus Francisella – in honor of the American bacteriologist Edward Francis.

Origin of tularemia in rabbits

Tularemia is also known as lemming fever, Parinaud’s disease, or rodent or rabbit plague, the latter probably describing the disease most accurately.

Predominantly wild animals such as hares and rabbits as well as squirrels, mice and rats are infected by the bacterium.

The pathogen is highly virulent; just a few germs are sufficient to trigger the disease.

For comparison
To contract salmonellosis, half a million of the salmonella germs must be ingested; to contract tularemia, ingestion of 10 germs is sufficient.[/attentionbox ]

Ingestion of the rabbit plague pathogens can occur via numerous routes. Infection is possible through the environment (contaminated soil or water), direct contact with diseased animals, as well as through blood-sucking parasites such as ticks or mosquitoes.

The pathogen thus enters the organism through various ports of entry (respiratory tract, skin, digestive tract, blood) and is further distributed there via the bloodstream. Incidentally, the most common route of infection is through parasites, and less common is through contaminated feed or water.

Symptoms of rabbit plague in rabbits

The symptoms of rabbit plague vary greatly, since the pathogen spreads throughout the body after an incubation period of two to three days and can produce a variety of symptoms.

Initial general symptoms can indicate numerous diseases and hardly allow the conclusion of rabbit plague. Thus, fever, weakness and an increased respiratory rate are also found as symptoms in many other diseases.

In the nodular form of hare fever, skin abnormalities in the form of lymph gland infections and skin abscesses can also be observed.

Initial symptoms are then followed quite rapidly by emaciation due to poor appetite, unsteady gait and weakness, apathy and ultimately death.

Often the diagnosis of tularemia in rabbits can only be made after death due to the rapid progression of the disease. Postmortem examination then reveals massive tissue loss in various organs, an enlarged liver and spleen, and hemorrhages in the pleura and lungs.

Although the septicemic course of hare fever (in the form of blood poisoning) with correspondingly high mortality is the predominant form of the disease, mild forms of tularemia can also be observed. In this case, there is only a swelling of local lymph nodes and general symptoms of the disease with lack of appetite, possibly fever and weakness, which is overcome after a few days.
Treatment of rabbit plague

In many cases, treatment of rabbit plague comes too late and the patient dies. Because of the short incubation period and rapid progression of the disease, rapid intervention is often not possible, and the rabbit plague is not recognized as such.

An attempt at treatment should be made with an aminoglucoside antibiotic, for example, tetracycline, streptomycin, neomycin, etc., since it has a very broad spectrum of action on this genus of bacteria.

In addition, the immune system of the sick rabbit must be supported accordingly in order to be able to defend itself against the pathogen with its own forces. However, the prospects for treatment are rather poor.

Preventing rabbit plague

The probability of domestic rabbits contracting rabbit plague is very low. Nevertheless, a possible risk of infection should not be provoked.

In which areas tularemia occurs or in which counties rabbit plague cases can be detected, can be found out at the responsible state authorities. In Lower Saxony, for example, the State Office for Consumer Protection and Food Safety provides a distribution map on its homepage.

In endangered areas, a free run for domestic hoppers should be secured in such a way that contact with wild rodents (including mice!!) is not possible.

Likewise, feed should be safely protected from possible contamination.

Another major point of contamination are blood-sucking parasites, especially ticks and mosquitoes. Safe parasite protection is recommended here.

Incidentally, there is no vaccination against rabbit plague in rabbits.