What is E. cuniculi (Encephalitozoon cuniculi) in Rabbits?

Obtaining an early, quick and reliable diagnosis in most diseases is more likely to lead to a positive outcome for the patient. Effective treatment can be started as soon as possible, making the patient feel better, and minimising any secondary effects on an animal’s body. This is especially important in cases of Encephalitozoon cuniculi, as the disease progress can be quick and occurring ‘silently’ before a rabbit shows signs of illness.

What is Encephalitozoon cuniculi?

Encephalitozoon cuniculi is a protozoal parasite that can cause disease in domestic rabbits. It can be carried by some individuals who show no clinical signs, and will occasionally cause disease in other species, including humans. Although it is a zoonosis (a disease that can be spread between animals and people), the risk to healthy individuals who observe basic hygiene is very low.

How is E. cuniculi spread?

  1. cuniculi spores are spread in urine, with transmission occurring following ingestion of contaminated food or water. It can also be spread from a mother rabbit to her kits through the placenta.

Most common clinical signs associated with E cuniculi infection.

Some rabbits can be carriers of E. cuniculi, meaning that they can be clinically healthy, never showing any signs of disease, but they can still shed spores in their urine and pass disease on to others (up to 52% of domestic clinically healthy rabbits in the UK are thought to carry this disease).

A rabbit that develops clinical signs may have had only recent exposure to the pathogen, or they may have been infected with the dormant organism for months, or years, prior to developing any signs of disease. Clinical signs of illness may then occur in an apparently healthy individual secondary to an underlying stressor (e.g. a new cage mate, change of housing etc) or other condition leading to compromise of their immune system.

When clinical signs associated with E. cuniculi become apparent, they most commonly affect either the nervous system or the kidneys, however, less commonly, both body systems are involved. The clinical signs are caused by the body’s inflammatory reaction which leads to swelling and rupture of affected cells with subsequent destruction of the tissues involved.

Some of the most common clinical signs include hind limb weakness or paralysis, a head tilt, seizures, loss of balance, collapse, urinary incontinence or scalding and renal failure. Signs of renal failure include increased thirst and urination, a decreased appetite and weight loss. Unfortunately, once clinical signs are severe, recovery from this disease is unlikely.

If E. cuniculi is passed through the placenta, it can infect the eyes of unborn kits, causing destruction of the lens which can lead to cataract formation, most commonly between 6 months and 2 years of age. Early diagnosis and medical treatment can save the eye.

E cuniculi diagnosis

  1. cuniculi infection can be diagnosed in two ways.

A blood sample can be tested to measure the antibodies that are produced by the body at different times during the disease process. High IgM antibody titres reflect acute infection, or reactivation of a latent infection, increasing from 0-35 days post exposure, and can remain high for up to 18 weeks. However, raised IgG antibodies reflect exposure and chronic infection and doesn’t necessarily warrant treatment, unless concurrent clinical signs are present.

E cuniculi testing by PALS Vet Lab

PALS now provides express immunofluorescence antibody testing (IFAT) for E cuniculi, with a rapid turnaround time of 24 hours. A quick diagnosis is incredibly important in these cases, to reduce the damage caused by this pathogen by minimising the time it is active and therefore reducing associated clinical signs. Getting a quick diagnosis and being able to start an effective treatment regime is also important to stop the parasite being shed in the urine of an affected animal and therefore reducing the likelihood of transmission, either to in contact rabbits, or other animals, and potentially immunocompromised owners.

PCR testing can also be carried out on urine with same day results. This test looks for E cuniculi DNA. This test is most useful in acute cases as spore excretion will gradually decrease over time and may only be shed intermittently after the first three months following infection. If clinical signs are not being exhibited, it is less likely that an individual will be shedding spores into their urine.

Treating E cuniculi

The treatment that is currently available is aimed at slowing down, or stopping, the rate of reproduction of the protozoal spores to reduce the inflammation and subsequent tissue damage associated with disease. Unfortunately, there is no treatment that will reverse any damage that has already been caused by an active E cuniculi infection. Fenbendazole is used as a treatment to reduce the number of active spores within the body. It can also be used as a preventative measure, giving the treatment for a shorter course every 3 months, however, this will only reduce the number of active spores and won’t eradicate any that are in their latent form. Re-activation of the infection, or re-infection from environmental spores, are both possible at any point following a course of treatment for E. cuniculi.

Treatment can improve clinical signs to a point where the rabbit is clinically normal. However, often infected animals will have clinical signs that do not improve but that they can learn to adapt and live with that won’t affect their quality of life, e.g. a head tilt. There are some cases that do not improve despite treatment and supportive care. If clinical signs are debilitating and negatively affect the rabbit’s quality of life, euthanasia may be the kindest option.

Generally speaking, if diagnosis is prompt and treatment started as soon as possible to prevent further tissue damage being caused by the parasite, many rabbits can go on to live happily.

Preventing E. cuniculi

The most important way to prevent E cuniculi infection in your rabbit is by making sure that they don’t come in to contact with any rabbit that is known to be infected with the disease. Good hygiene is also important as environmental spores can easily be killed with contact for only 30 seconds with a 1-10% bleach solution.

If your rabbit is a known carrier, preventing reactivation of clinical signs involves minimising stress and concurrent disease, and possibly carrying out a routine treatment every 3-6 months. Only housing with other E cuniculi positive rabbits helps to prevent spread to naive individuals.


A quick, early and reliable diagnosis allows treatment to be initiated as early as possible when clinical signs start to be shown. This can minimise any tissue damage caused by this E cuniculi, leading to a happier, healthier and longer life for your rabbit.

Leave a Reply

Your email address will not be published.

This field is required.

You may use these <abbr title="HyperText Markup Language">html</abbr> tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

*This field is required.