Creating better tomorrows for all pet rabbits
Rabbits and E. cuniculi (Encephalitozoon cuniculi)
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 the infection is most likely caught from the mother. The parasite can also be caught later in life, e.g. 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 tilt 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, dragging the back legs or complete 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. And where any are present, they are very unlikely to all be present at the same time.
EC testing is complicated. Blood tests, known as “titres”, may show positive for antibodies from past exposure. However, this doesn’t always mean there’s a current infection, just that the rabbit has been exposed to infection at some point, potentially months ago. High levels of antibodies can indicate 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 under general anaesthesia.
EC may lay dormant for months, and infection can flare up at any point, especially under stress or with another disease. Prevention and treatment involve the drug fenbendazole. (Sorry, we can’t give product names for legal reasons.)
Treatment is not always 100% effective. Whilst the drug kills the EC organism, the damage EC has done to the tissues will remain. In the kidneys, this can mean kidney failure. In the brain, this can mean the variety of neurological problems which are mentioned above. Ideally, prospective rabbits for pairing should each be tested before mixing, and if EC is detected, they should be treated (for 28 days). If both are negative, then treatment is not required.
Alternatively, to reduce the time and costs 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 commercial treatment for EC is an oral paste ‘wormer for rabbits’ which contains the active ingredient Fenbendazole. You can get a rabbit version of this. This product is also used to rid your rabbit of intestinal worms, which are less common. It’s given orally, once a day, for a 28-day period when EC is suspected.
Prevention?
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 from 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. New rabbits should be treated, or ideally tested, and treated if positive before admission and bonding. It is vital that during this 28-day period, you avoid re-infection. Because EC is spread via urine, this will mean regular, ideally daily, cleaning of all litter trays or any latrine areas. Be aware that EC can live in the grass so avoid putting the rabbits on any grass areas which may be infected. It is extremely difficult, if not impossible, to say how long grass or earth are infective for, and they are difficult to disinfect thoroughly due to their porous and variable nature. Wild rabbits have not been shown to carry EC.
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 infection. Speak to your doctor if you are concerned about the risk of infection.
Guinea pigs have been shown to develop clinical problems when infected with EC, but this has not been explored in as much detail as it has in rabbits. It is, however, another reason not to keep these two species together.
Most 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.
References:
Abu-Akkada SS, Oda SS (2016)
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Doboși AA, Bel LV, Paștiu AI, Pusta DL. A Review of Encephalitozoon cuniculi in Domestic Rabbits (Oryctolagus cuniculus)-Biology, Clinical Signs, Diagnostic Techniques, Treatment, and Prevention. Pathogens. 2022 Dec 7;11(12):1486. doi: 10.3390/pathogens11121486. PMID: 36558820; PMCID: PMC9785705.
Sieg, Jessica & Hein, Jutta & Jass, Ariane & Sauter-Louis, Carola & Hartmann, Katrin & Fischer, Andrea. (2012). Clinical evaluation of therapeutic success in rabbits with suspected encephalitozoonosis. Veterinary parasitology. 187. 328-32. 10.1016/j.vetpar.2011.12.014.
Latney LV, Bradley CW, Wyre NR. Encephalitozoon cuniculi in pet rabbits: diagnosis and optimal management. Vet Med (Auckl). 2014 Nov 6;5:169-180. doi: 10.2147/VMRR.S49842. PMID: 32670857; PMCID: PMC7337189.
Liatis, T, Makri, N, Czopowicz, M, Richardson, J, Nuttall, T & Sunol Iniesta, A 2024, ‘Otitis media/interna and encephalitozoonosis are the most common causes of head tilt in pet rabbits in the UK: 73 cases (2009- 2020).’, Veterinary Record, vol. 195, no. 1, e4267, pp. 1-10. https://doi.org/10.1002/vetr.4267
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