Encephalitozoon Cuniculi

What is E. Cuniculi?

E. Cuniculi is a microscopic protozoan parasite that causes disease in rabbits. It colonises in the rabbit’s brain, eyes and kidneys. Rabbits are infected by ingesting or inhaling spores which are excreted in the urine or faeces of infected animals – it can live in infected areas for several weeks. E. Cuniculi can potentially be transferred to humans but appears not to affect healthy humans. severely immunocompromised people should avoid animals confirmed or suspected with carrying the parasite.

What are the clinical signs?

Clinical signs can be non specific, but some of the following signs may be noted:

Nervous signs

  • Head tilt/neck twisting
  • Paralysis
  • Weakness of the hind legs
  • Eventually leading to tremors/fits and then a coma

Eye disease

  • Cataracts and blindness

Kidney disease

  •  Increased drinking and urination
  •  Urinary incontinence/scalding
  • Kidney failure

Heart disease

Myocarditis (inflammation of the heart muscle) can be a cause of sudden death

How is it diagnosed?

If your rabbit is showing clinical signs that point towards E. Cunicili then the vet may suggest doing a blood test which will show if they have been exposed to the parasite. If the result comes back negative this is generally conclusive and E. Cunicili can be ruled out; unless the sample is taken very early on in infection and the immune system is too weak to allow antibodies to be produced. A positive result isn’t quite as easy to interpret. A high result, together with clinical signs is usually enough to confirm the diagnosis, but a low positive result can be a problem as many rabbits carry the parasite without symptoms (asymptomatic). In this case the blood sample is repeated a few weeks later, and if the levels have risen this indicates an active infection.

How is it treated?

If E. Cuniculi is diagnosed or suspected then a 28 day course of Fenbendazole is recommended. This is available in a paste form which is given by mouth, on a daily basis. Anti-inflammatory drugs can also be given. Supportive therapy is sometimes needed depending on the severity of clinical signs, as some rabbits with severe head tilt are unable to move around or feed themselves adequately. In some cases the treatment does not improve clinical signs – usually if it is going to work, an improvement will be seen in the first week of treatment. For those rabbits who aren’t responding then euthanasia may be the only option if the rabbit has no quality of life.

What is the prognosis?

The prognosis depends on the severity of clinical signs, the response to treatment and the frequency and severity of any flare ups. The main thing to bear in mind is your rabbit’s quality of life, which you should discuss with your vet.

Can I stop my rabbit from getting E. Cuniculi?

First of all, you need to be 100% sure that your rabbit isn’t already a carrier of the parasite – so speak to your vet about having a blood test for E. Cuniculi. If the result comes back as negative, then the best way of preventing your rabbit being infected is by preventing contact with other rabbits – domestic or wild. Bearing in mind the parasite is primarily passed on from infected urine, good hygiene is vital – routine disinfectants should kill the spores. Other measures like raising food and water bowls off the ground to prevent urine contamination may be helpful.

Written by Laura Sullivan MRCVS

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