What is “E cuniculi”?

E cuniculi (Ec) is a microscopic brain and kidney parasite that affects rabbits along with a small range of other species. Some rabbits can carry the parasite without ever becoming ill whilst others may show a range of symptoms.

Are my rabbits at risk?

Potentially, all rabbits are at risk as infection is most likely caught from the mother. The parasite can also be caught later in life eg after being introduced to an infected newcomer, or sharing a grazing area with a rabbit carrying the infection.

How do I know if my rabbits have been infected with Ec?

Typical signs of infection:

  • Head tilting to one side.
  • Eyes may track side to side or up and down.
  • Shuffling or weakness on one or both back legs – in some cases paralysis
  • Uncontrollable spinning or rolling
  • Unexplained changes including seizures, deafness, cataracts or behavioural changes
  • Drinking and urinating more than usual due to kidney failure.

However these symptoms are not guaranteed to be present in your rabbit.

Ec testing is complicated as blood tests, known as “titres”, may show positive for antibodies from any exposure. However, this doesn’t always mean there’s a current infection, just that the rabbit has been exposed to infection. High levels of antibodies indicates a current infection. Using microscopic tests or DNA fingerprinting, spores of the parasite may also be found in the urine. False negatives are possible and these may incorrectly convince you that there’s no current infection. A biopsy of affected tissues is possible, but this means a tissue sample would need to be taken from your rabbit.

Rabbits may carry diseases, which may be spread from one to another. One such disease, which may lay dormant for months and so may evade detection, not showing any signs, is called Encephalitizoon cuniculi (EC). It can both be tested for, and treated, although treatment is not always 100% effective. Ideally, prospective rabbits for pairing should each be tested before mixing, and, if EC detected, treatment started (It requires a 28 day treatment course). If both are negative, then treatment is not required.

Alternatively, to reduce the time and cost of testing, they may both be assumed to be positive, and treatment started prior to mixing, and continued for a total of 28 days”

How is Ec treated?

The two commercial treatments for Ec are Panacur and Lapizole, both containing the active ingredient, Fenbendazole. These products are also used for ridding your rabbit of intestinal worms. Both products are given orally for a 28 day period when Ec is suspected.


Ec is surprisingly widespread and it is almost impossible to be absolutely certain that any rabbit is infection-free. However, it should be stressed that despite approximately half of all pet rabbits carrying the infection, only a small proportion of these cases ever show any illness.

Technically, the only certain way of preventing your rabbit being infected would be to keep it away from other rabbits for its whole life. This is something we cannot recommend as the risks of Ec infection are far less significant than the misery your rabbit would suffer if it was kept alone. In most cases, keeping rabbits in a stable group is the next best thing.

We do not recommend routine worming to prevent Ec as, like any drug, it can be harmful and should only be used when necessary. This should be discussed with your vet before using preventatively.

Is Ec infectious to me or my other animals?

Humans with severely compromised immune systems (typically those with HIV/AIDS, or on chemotherapy) may be at risk of transmission. Speak to your doctor if you are concerned about the risk of infection.

Other species are not believed to be generally susceptible to the rabbit strain of Ec, although if they are immune suppressed, this is also possible.