Toxoplasmosis in rabbits

Toxoplasmosis is one of the infectious diseases and is often associated only with cats. Nevertheless, rabbits can also suffer from this parasitic disease, because a large proportion of our rabbits carry these parasites.

Often such an infection goes unnoticed, as it is without any symptoms. In a few rabbits, however, a toxoplasma infection does break out – and is then usually fatal.
Pathogen of toxoplasmosis – a parasite

The causative agent of toxoplasmosis is the protozoan Toxoplasma gondii. A protozoan, also called a primordial organism, is a fairly simple creature from the animal kingdom that makes the transition from plant to animal.

These protozoa are host-specific, meaning they have an end host in or with which they live. Toxoplasma gondii has chosen the cat as its final host, but undergoes some early developmental cycles in other, so-called intermediate hosts.

Almost all vertebrates can be considered as intermediate hosts, including humans.
Reproduction and spread of toxoplasmosis

Toxoplasma gondii is shed in feces by its definitive host in the form of contagious oocysts. Oocyst is composed of the ancient Greek word egg and bladder. This egg blister is only visible with a microscope and now adheres to food contaminated by cat feces, where it can survive for a long time.
Good to know:
When collecting green food in the park or when food comes into contact with the cat’s home litter box, the risk of serving Toxoplasma oocysts to the rabbit is thus quite high.

However, oocysts must mature for a few days to become infectious. This is done quickly and the so-called sporulation is completed after 2 to 4 days. Within each oocyst there are now 8 sporocytes. The rabbit therefore ingests the “mature” oocysts with the infectious contents and as soon as they reach the intestine, the oocyst bursts and releases the sporocytes.

They now travel throughout the body via blood and lymph, where asexual division takes place in a nucleated cell of the host. One mother cell becomes two daughter cells, a division process that continues until the host’s infected cell bursts open.

The “division products” now released are called tachyzoites. The process repeats until the host’s specific defenses kick in and fight this foreign reaction.

As a result, the division period becomes slower and slower; these are now referred to as bradyzoites. These are now enclosed in cysts and embedded in the tissue of the intermediate host. They are found mainly in the muscles, but also in the brain and within the retina of the eye.

If the intermediate host is now eaten by the cat, the transformation of the bradyzoites into oocysts takes place in its intestine, which in turn are excreted with the feces. For rabbits and other vertebrates that are not end hosts of Toxoplasma gondii, the parasite’s cycle ends with tissue deposition of the cysts.

Rabbits (humans as well) therefore do not excrete oocysts and are not carriers!

Symptoms of toxoplasmosis in rabbits

If the pathogen is only “present”, i.e. has been fought by the police of the organism through the defense system and has then encapsulated itself in its preferred tissues, it does not cause any problems for the long-eared rabbit and remains without symptoms.

However, a kind of overreaction of the immune system to Toxoplasma gondii may occur. What exactly leads to the outbreak of toxoplasmosis in rabbits has not been conclusively clarified.

It is suspected that especially immunocompromised animals do not progress to the stage of cyst formation during initial infection because the immune system does not adequately fight the pathogens and thus the division process and further progression of cyst formation does not occur. The division of the toxoplasmosis mother cells within the cells of the rabbit organism is thus not slowed down by antibody formation and destroys more and more endogenous cells of its host.

This leads to a whole series of symptoms, which, however, could also be indicative of other diseases, for example a cold or pneumonia.

The more or less typical symptoms of toxoplasmosis in rabbits include, for example, rapid shallow breathing with secretion from the eyes and nose with poor general condition, reluctance to eat and fever. In addition, movement disorders such as tremors, paralysis, which can sometimes occur on all legs at the same time, or a tilted head are among the symptoms of toxoplasmosis.

Treatment of toxoplasmosis in rabbits

The variety of symptoms does not necessarily make it easy for the rabbit owner to recognize a possible toxoplasmosis disease in his rabbit. This makes it all the more important to see a veterinarian promptly if any of the above symptoms occur.

However, even with early diagnosis, the prognosis is often rather poor. The veterinarian can consolidate a possible suspected diagnosis with the help of a detailed anamnesis, he will ask the owner for example about a possible cat contact, and a blood test. This is usually done by antibody detection, which, however, does not distinguish between infection already passed through and active infection and thus offers little help.

Direct pathogen detection is carried out in human medicine by means of pathogen cultivation and indicates an active infection – provided, however, that the technical quality is high and the findings are interpreted critically.

A blood test cannot confirm the diagnosis of toxoplasmosis in rabbits 100 percent, but it can exclude other infections with similar symptoms.

Therapeutically, an attempt can be made to counter Toxoplasma gondii with antibiotics designed to inhibit reproduction.

In most cases, however, saving the rabbit’s life is not possible and it must admit defeat in the fight against toxoplasmosis.

Preventing toxoplasmosis in rabbits

Infection with Toxoplasma gondii cannot be prevented with absolute certainty. The best prevention is a species-appropriate husbandry and nutrition of the rabbits to create an active and “awake” immune system and prevent toxoplasmosis.

However, since exactly this species-appropriate diet is a possible source of infection and cats do not mark their droppings with a sign, a minimum of hygiene and caution should be taken for granted when foraging in nature. Fresh greens should therefore always be washed thoroughly, preferably with hot water, before being placed in the rabbit bowl.

Freezing at – 21 degrees Celsius or heating at a minimum of 50 degrees Celsius for 20 minutes, which is usually not very practical in rabbit feeding, will also reliably kill Toxoplasma gondii.

For cat-keeping rabbit owners, a strict separation of litter box and rabbit food also applies. By the way, infected rabbits do not pose a danger to other rabbits or to humans; there is no risk of infection because they do not excrete pathogens with their feces.