Illustrative guide of clinical signs of rabbits with E. cuniculi


Esther van Praag, Ph.D. is funded solely by the generosity of donors.

Every donation, no matter what the size, is appreciated and will aid in the continuing research of medical care and health of rabbits.

Thank you  


The protozoal parasite Encephalitozoon cuniculi lives in the nervous system and major organs of rabbits. A variety of clinical signs characterize the disease, yet they vary from one rabbit to another, rendering diagnosis of the disease difficult.

Damage is observed on organs, causing liver failure and kidney failure and calcification. These changes affect the biochemical parameters and can be measured during a complete blood test.

The behavior and general appearance of a rabbit can be affected. Main signs that are characteristic for an E. cuniculi infection are illustrated here. Limb weakness and pressure on the inner ear can lead to a loss of balance and hopping in circles.

In the end phase, seizure attack become usually more frequent and stronger, and the rabbit can become comatose and die.

More or less pronounced torticollis (commonly called head tilt or wry neck)

 Michel Gruaz

Ringo - anonymous

Hind limb weakness and paralysis



A rabbit that suffer hind limb weakness often stretched the affected limb to the front

Paralysis of the hindlimbs




Emma Staub

Typically, urination outside the litterbox is observed


Emma Staub

Phacoclastic uveitis, cataracts, nystagmus

Magdalena Stasiowska

Sandy Minshull

Renee Brennan

Renee Brennan

Video of Rudy, a rabbit presenting clinical signs of encephalitozoonosis: severe involuntary head tilt and rhythmic horizontal movement of the eyes.

Neurological signs such as seizure with convulsions, shuddering





Thanks are due to Dr. Magdalena Stasiowska (Przychodnia Weterynaryjna Wrocław, Poland), to Michel Gruaz, (Switzerland) and to Emma Staub (USA). Many thanks also to Renee Brennan for sharing the video of her head-tilted rabbit Rudy.

Further information

Biderre C, Mathis A, Deplazes P, Weber R, Metenier G, Vivares CP. Molecular karyotype diversity in the microsporidian Encephalitozoon cuniculi. Parasitology. 1999; 118 ( Pt 5):439-45.

Deplazes P, Mathis A, Baumgartner R, Tanner I, Weber R. Immunologic and molecular characteristics of Encephalitozoon-like microsporidia isolated from humans and rabbits indicate that Encephalitozoon cuniculi is a zoonotic parasite. Clin Infect Dis. 1996; 22(3):557-9.

Gomez-Bautista M, Rojo-Vazquez FA. Chemotherapy and chemoprophylaxis of hepatic coccidiosis with sulphadimethoxine and pyrimethamine. Res Vet Sci. 1986; 41(1):28-32.

Gray LC, Magdesian KG, Sturges BK, Madigan JE. Suspected protozoal myeloencephalitis in a two-month-old colt. Vet Rec. 2001; 149(9):269-73. 

Lindsay DS, Dubey JP. Determination of the activity of pyrimethamine, trimethoprim, sulfonamides, and combinations of pyrimethamine and sulfonamides against Sarcocystis neurona in cell cultures. Vet Parasitol. 1999; 82(3):205-10. 

Mrema JE, Rieckmann KH. A rabbit--in vitro system to evaluate drug action against Plasmodium falciparum. Trans R Soc Trop Med Hyg. 1983; 77(1):130-5. 

Mathis A, Akerstedt J, Tharaldsen J, Odegaard O, Deplazes P. Isolates of Encephalitozoon cuniculi from farmed blue foxes (Alopex lagopus) from Norway differ from isolates from Swiss domestic rabbits (Oryctolagus cuniculus). Parasitol Res. 1996; 82(8):727-30.

Mathis A, Michel M, Kuster H, Muller C, Weber R, Deplazes P. Two Encephalitozoon cuniculi strains of human origin are infectious to rabbits. Parasitology. 1997; 114 (Pt 1):29-35.

Moore LA, Johnson PJ, Messer NT, Kline KL, Crump LM, Knibb JR. Management of headshaking in three horses by treatment for protozoal myeloencephalitis. Vet Rec. 1997; 141(11):264-7. 

Peeters JE, Geeroms R, Halen P. Evolution of coccidial infection in commercial and domestic rabbits between 1982 and 1986. Vet Parasitol. 1988; 29(4):327-31. 

Peeters JE, Geeroms R, Froyman R, Halen P. Coccidiosis in rabbits: a field study. Res Vet Sci. 1981; 30(3):328-34. 

Suter C, Muller-Doblies UU, Hatt JM, Deplazes P. Prevention and treatment of Encephalitozoon cuniculi infection in rabbits with fenbendazole. Vet Rec. 2001; 148(15):478-80.

Sobottka I, Albrecht H, Visvesvara GS, Pieniazek NJ, Deplazes P, Schwartz DA, Laufs R, Elsner HA. Inter- and intra-species karyotype variations among microsporidia of the genus Encephalitozoon as determined by pulsed-field gel electrophoresis. Scand J Infect Dis. 1999; 31(6):555-8.

Thomas C, Finn M, Twigg L, Deplazes P, Thompson RC. Microsporidia (Encephalitozoon cuniculi) in wild rabbits in Australia. Aust Vet J. 1997; 75(11):808-10.

Tassignon MJ, Brihaye M, De Meuter F, Vercruysse A, Van Hoof F, De Wilde F. Efficacy of treatments in experimental toxoplasmosis Bull Soc Belge Ophtalmol. 1989; 230:59-72. French.