Encephalitozoon Cuniculi & Seizures

Written by sarah goodwin-nguyen
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Encephalitozoon Cuniculi & Seizures
Rabbits with E. cuniculi may suffer from seizures. (floppy eared rabbits image by Ken Marshall from Fotolia.com)

Encephalitozoon cuniculi is a devastating and frightening disease for rabbit owners. Easy to contract and difficult to diagnose and treat, E. cuniculi may cause loss of balance, hind leg paralysis or seizures. Though it was first recognised as a disease in 1922, little else was known about E. cuniculi. In recent years, with the growing popularity of rabbits as indoor pets, rabbit veterinary medicine has grown. New information about E. cuniculi allows for better diagnosis and treatment.


Encephalitozoon cuniculi is a protozoan parasite that can be ingested or passed from another rabbit through urine. Many rabbits have some E. cuniculi and never show symptoms, until something triggers an overgrowth. The parasite is passed through spores in the urine, from mother to baby rabbit via placenta or milk, or the organism may become airborne. According to Molly Varga of Ashleigh Veterinary Practice, mice are a major carrier of E. cuniculi, so rabbit owners should be careful of shielding rabbits, hay and food from possible contamination by mice.

Methods of Attack

The E. cuniculi parasites are ingested or inhaled. From the gastrointestinal tract they travel in the bloodstream to the kidneys and other high-blood-flow organs, such as the brain, liver and eyes. It is only while the E. cuniculi are in the kidneys that the infected rabbit is contagious (except from mother to babies.) The parasites multiply within the rabbit's cells, eventually causing the cell to burst, enabling them to spread to adjacent cells. A well-functioning immune system will normally rid the animal of the parasites. If the rabbit's immune system is overworked due to illness, infection, injury, malnourishment or stress, however, the E. cuniculi will flourish.


A rabbit with an E. cuniculi overgrowth may display symptoms such as excessive urination, loss of balance, rolling, head tilt, seizures or hind-body paralysis. Renal failure, convulsions, incontinence, and nystagmus (eye twitching) are other possible symptoms. Rabbits infected before they are born may develop lesions around the eyes or visible white spots in the eyes. Seizures, paralysis and convulsions, the most extreme manifestations of the parasite, are caused when the parasites reach the brain. Neural damage may or may not be permanent.


A titre test, which detects the level of the antibody to an organism in the blood, can be used to show that the rabbit has been exposed to this parasite at some point in his life. Performing two titre tests with a generous interval of time in between and comparing the results can determine if the rabbit is building an immune response to an active infection rather than that he was previously infected. It may be helpful to rule out other possibilities for symptoms. For example, according to Teresa Lightfoot D.V.M., rabbit seizures may be caused by inner ear infection, heat stroke or head injury.


A rabbit-savvy vet will prescribe a dewormer, usually fenbendazole (Panacur), often combined with the bunny-safe antibiotic Baytril. Sometimes cousins of fenbendazole known as Albendazole and Oxibendazole may be used, but they are more likely to cause side effects. Explains Marinell Harriman in her article on Encephalitozoon cuniculi on the House Rabbit Society website, E. cuniculi are protozoa and do not respond to antibiotics like bacteria. However, antibiotics are useful for strengthening the rabbit's immune system and may help alleviate symptoms.

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