Lapis ISSN 2398-2969

Encephalitozoon cuniculi

Synonym(s): Microsporidia

Contributor(s): Vetstream Ltd, Emma Keeble, Molly Varga




  • Phylum: Microspora.
  • Order: Microsporidia.
  • Genus:Encephalitozoon.
  • Species:cuniculi.


  • Gk:kephale- head, andenkephalos- brain.
  • Gk:zoion- animal.
  • L:cuniculus- rabbit; underground passage.

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Clinical Effects



  • Obligate intracellular parasite.
  • Multiplies in peritoneal macrophages, and can latently infect kidneys and central nervous system.
  • Spores are present in the environment.


  • Infection usually by ingestion of spores, but also possible by inhalation.
  • Parasite then undergoes schizogony and sporogony in peritoneal macrophages, kidney and brain cells, also lung, liver and heart.
  • Spores are passed in the urine of the host.
  • Transplacental infection may also be possible.


  • Probably via urine contamination and ingestion.
  • Possible also by inhalation.
  • Vertical transmission has been suggested from experimental work.

Pathological effects

  • Serum antibodies can be detected.
  • Simultaneous detection of IgM and IgG indicates recent infection.
  • IgM indicates recent infection but will be absent after day 38 from intiation of infection. IgG increases variably over the course of infection and levels can fluctuate during a chronic infection.
  • Severe disease occurs in immunocompromised animals of many species.
  • Cell-mediated immunity appears to be important - protective immunity is T-cell dependent.
  • The clinical signs ascribed to microsporidiosis   Encephalitozoonosis  in the rabbit vary, and can be mild or severe. However they are often chronic and subclinical, being diagnosed on post-mortem.
  • Signs include abdominal distension and renal failure   Kidney: renal failure  , urinary incontinence   Urinary incontinence  , paralysis, head tilt   Head tilt  , retarded growth, cataracts   Eye: cataract  , tremors, torticollis, hindlimb paresis   Paresis / paralysis: limb  , convulsions and death.
  • The parasite multiplies in peritoneal macrophages. Initial target organs are those with high blood flow (lung, liver, heart and kidneys) which are infected in the first few weeks post-ingestion. In the chronic form the parasite replicates in the brain.
  • Multiplication of the parasite results in granulomatous inflammation. This can cause granulomatous interstitial pneumonitis, focal interstitial granulomatous hepatitis, meningoencephalitis and phacoclastic uveitis.

Other Host Effects

  • Latent subclinical infections are common in rabbits.


Control via animal

  • Symptomatic therapy may be attempted.
  • Infected animals should be isolated.

Control via chemotherapies

  • Treatment is directed at the inflammation caused by the rupture of cells.
  • Prednisolone   Prednisolone  may be successful in resolving nervous system signs since glucocorticoids suppress granulomatous inflammation, though corticosteroids should be used with caution in rabbits.
  • However,in vitrostudies indicate thatEncephalitozoonspp   Encephalitozoon cuniculi  are susceptible to benzimidazoles such as albendazole   Albendazole  , thiabendazole   Tiabendazole  and oxbendazole, and antibiotics   Therapeutics: antimicrobials  such as fumagallin. Albendazole   Albendazole   is teratogenic and embryotoxic.
  • Ocular infection in a person resolved following itraconazole treatment, althoughin vitrotests found this to be ineffective.
  • Treatment with 20 mg/kg fenbendazole   Fenbendazole  by mouth daily for 4 weeks has been found to be effectivein vivoin control of infection and in resolution of clinical signs.

Control via environment

  • Good hygiene may reduce the spread of the parasite.
  • Screen and isolate infected animals.
  • Prevent urine contamination of food and water.
  • Seroconversion precedes renal shedding. Identify infected animals before excretion in an outbreak situation.
  • Retest monthly.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Hein J, Flock U, Sauter-Louis C et al (2014) Encephalitozoon cuniculi in rabbits in Germany: prevalence and sensitivity of antibody testing. Vet Rec 174 (14), 350 PubMed.
  • Varga M (2014) Questions around Encephalitozoon cuniculi in rabbits. Vet Rec 174 (14), 347-348 PubMed.
  • Wright I (2011) Encephalitozoon cuniculi: Infecting the rabbit next door. UK Vet: Companion Animal 16, 49-50 VetMedResource
  • Furuya K, Asakura T, Igarashi M et al (2009) Microsporidian Encephalitozoon cuniculi antibodies in rabbit urine samples. Vet Rec 165 (3), 85-86 PubMed.
  • Reusch B, Murray J K, Papasouliotis K et al (2009) Urinary protein:creatinine ratio in rabbits in relation to their serological status to Encephalitozoon cuniculiVet Rec 164 (10), 293-295 PubMed.
  • Keeble E J & Shaw D J (2006) Seroprevalence of antibodies to Encephalitozoon cuniculi in domestic rabbits in the United Kingdom. Vet Rec 158 (16), 539-544 PubMed.
  • Harcourt-Brown F M & Holloway H K R (2003) Encephalitozoon cuniculi infection in pet rabbits. Vet Rec 152 (14), 427-431 PubMed.
  • Boot R, Hansen A K, Hansen C K et al (2000) Comparison of assays for antibodies to Encephalitozoon cuniculi in rabbits. Lab Anim 34 (3), 281-289 PubMed.
  • Feaga W P (1997) Wry neck in rabbits. JAVMA 210 (4), 480 PubMed.
  • Levkut M, Horváth M, Bálent P et al (1997) Catecholamines and encephalitozoonosis in rabbits. Vet Parasitol 73 (1-2), 173-176 PubMed.
  • Stiles J, Didier E, Ritchie B et al (1997) Encephalitozoon cuniculi in the lens of a rabbit with phacoclastic uveitis - confirmation and treatment. Vet Comp Ophthal (4), 233-238 VetMedResource.
  • Thomas C, Finn M, Twigg L et al (1997) Microsporidia (Encephalitozoon cuniculi) in wild rabbits in Australia. Austr Vet J 75 (11), 808-810 PubMed.
  • Nast R, Middleton D M & Wheler C L (1996) Generalized encephalitozoonosis in a Jersey wooly rabbit. Can Vet J 37 (5), 303-305 PubMed.
  • Wesonga H O & Munda M (1992) Rabbit encephalitozoonosis in Kenya. Lab Anim 26 (3), 219-221 PubMed.
  • Greenstein G, Drozdowicz C K, Garcia F G et al (1991) The incidence of Encephalitozoon cuniculi in a commercial barrier-maintained rabbit breeding colony. Lab Anim 25 (4), 287-290 PubMed.
  • Cox J C & Ross J (1980) A serological survey of Encephalitozoon cuniculi infection in the wild rabbit in England and Scotland. Res Vet Sci 28 (3), 396 PubMed.
  • Gannon J (1980) A survey of Encephalitozoon cuniculi in laboratory animal colonies in the United Kingdom. Lab Anim 14 (2), 91-94 PubMed.