Zoonotic concern: Encephalitozoonosis in European Rabbits

Key Points

  • Many rabbits are asymptomatic carriers of the microsporidian, E. cuniculi.
  • Encephalitozoon may be spread through contact with rabbit urine.
  • The immunocompromised are at risk for encephalitozoonosis.
  • Clinical disease in humans varies.
  • Avoid contact with the urine of infected or health rabbits, and always utilized good sanitation practices.


The physical and psychological benefits of pet ownership have been well established (4), however close contact with pets is not without risks including the potential for transmission of zoonotic disease. There are no serious zoonotic diseases that can be spread from rabbits to healthy humans (11), but rabbits can carry a number of potential pathogens including Encephalitozoon cuniculi (Fig 1).

Bunny cuddle Alex FCC

Figure 1. Pet rabbits can carry a number of potential pathogens, including Encephalitozoon cuniculi. Photo credit: Alex via Flickr Creative Commons.


Asymptomatic carriers

Encephalitozoon cuniculi is an obligatory intracellular microsporidian parasite that can infect a wide range of mammals, including humans (5,13). The primary host for this primitive fungus is the rabbit. Infections in rabbits are typically subclinical (5.9).



Transmission of E. cuniculi is urine-oral in rabbits (9,13). Humans are exposed to spores through contact with rabbit urine. Spores are excreted in the urine, feces, or sputum and are very resistant in the environment. Exposure to rabbit secretions as well as ingestion of contaminated food or water are possible sources of human infection (3,13). Another route of infection, although less frequent, is inhalation of spores (13). 


Who is at risk?

Little is known about the prevalence or importance of infection with Encephalitozoon spp. in immunocompetent individuals (6,7,13). Serological studies suggest that human exposure to microsporidia may be common but without clinical significance (15).

Although E. cuniculi is a rare cause of infection in human patients, microsporidiosis is considered an emerging, opportunistic infection in AIDS patients and other immunocompromised individuals (9,13), such as organ transplant recipients, young children, the elderly. Complications due to E. cuniculi infection have been reported in severely immunocompromised patients (2,3,8,10). Contact lens wearers are also at increased risk of clinical disease (2).


Disease in humans

Clinical symptoms in humans include fever, headache, nausea, vomiting, diarrhea, breathlessness and other respiratory signs, as well as weakness (13).  Clinical reports of E. cuniculi infection have described a wide range of organ involvement, including peritonitis, hepatitis, granulomatous liver necrosis, renal failure, pneumonia, sinusitis, rhinitis, myalgia, otitis media, keratoconjunctivitis, cerebral and disseminated microsporidiosis, and seizure disorder (2,3,6,10,16).


Prevention and control

Avoid contact with the urine of infected or healthy rabbits, and always practice good sanitation when handling animals (12).




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  2. Didier ES, Didier PJ, Snowden KF, Shadduck JA. Microsporidiosis in mammals. Microbes Infect. 2000;2(6):709-20. doi: 10.1016/s1286-4579(00)00354-3. PMID: 10884622.
  3. Fournier S, Liguory O, Sarfati C, et al. Disseminated infection due to Encephalitozoon cuniculi in a patient with AIDS: case report and review. HIV Med. 2000;1(3):155-61. doi: 10.1046/j.1468-1293.2000.00022.x. PMID: 11737344.
  4. Friedmann E, Son H. The human-companion animal bond: how humans benefit. Vet Clin North Am Small Anim Pract. 2009; 39(2):293-326. doi: 10.1016/j.cvsm.2008.10.015. PMID: 19185195.
  5. Han B, Weiss LM. Microsporidia: obligate intracellular pathogens within the fungal kingdom. Microbiol Spectr. 2017;5(2):10.1128/microbiolspec.FUNK-0018-2016. doi: 10.1128/microbiolspec.FUNK-0018-2016. PMID: 28944750; PMCID: PMC5613672.
  6. Khan IA, Moretto M, Weiss LM. Immune response to Encephalitozoon cuniculi infection. Microbes Infect. 2001;3(5):401-5. doi: 10.1016/s1286-4579(01)01397-1. PMID: 11369277; PMCID: PMC3109655.
  7. Kicia M, Wesolowska M, Kopacz Z, et al. Disseminated infection of Encephalitozoon cuniculi associated with osteolysis of hip periprosthetic tissue. Clin Infect Dis. 2018;67(8):1228-1234. doi: 10.1093/cid/ciy256. PMID: 29659738.
  8. Kodjikian L, Garweg JG, Nguyen M, et al. Intraocular microsporidiosis due to Encephalitozoon cuniculi in a patient with idiopathic CD4+ T-lymphocytopenia. Int J Med Microbiol. 2005;294(8):529-33. doi: 10.1016/j.ijmm.2004.09.013. PMID: 15790298.
  9. Künzel F, Joachim A. Encephalitozoonosis in rabbits. Parasitol Res. 2010;106(2):299-309. doi: 10.1007/s00436-009-1679-3. Epub 2009 Nov 17. PMID: 19921257.
  10. Mathis A, Weber R, Deplazes P. Zoonotic potential of the microsporidia. Clin Microbiol Rev. 2005;18(3):423-45. doi: 10.1128/CMR.18.3.423-445.2005. PMID: 16020683; PMCID: PMC1195965.
  11. Mitchell MA, Tully TN. Zoonotic diseases associated with small mammals. In: Quesenberry KE, Orcutt CJ, Mans C, Carpenter JW (eds). Ferrets, Rabbits, and Rodents: Clinical Medicine and Surgery, 4th ed. St Louis, MO: Elsevier, 2021. p. 618.
  12. Ozkan O, Ozkan AT, Zafer K. Encephalitozoonosis in New Zealand rabbits and potential transmission risk. Vet Parasitol. 2011 Jun 30;179(1-3):234-7. doi: 10.1016/j.vetpar.2011.02.007. Epub 2011 Feb 15. PMID: 21377801.
  13. Santaniello A, Cimmino I, Dipineto L, et al. Zoonotic risk of Encephalitozoon cuniculi in animal-assisted interventions: laboratory strategies for the diagnosis of infections in humans and animals. Int J Environ Res Public Health. 2021;18(17):9333. doi: 10.3390/ijerph18179333. PMID: 34501921; PMCID: PMC8430659.
  14. Tsokana CN, Sokos C, Giannakopoulos A, et al. European Brown hare (Lepus europaeus) as a source of emerging and re-emerging pathogens of Public Health importance: A review. Vet Med Sci. 2020;6(3):550-564. doi: 10.1002/vms3.248. Epub 2020 Feb 23. PMID: 32088933; PMCID: PMC7397891.
  15. van Gool T, Biderre C, Delbac F, Wentink-Bonnema E, Peek R, Vivarès CP. Serodiagnostic studies in an immunocompetent individual infected with Encephalitozoon cuniculi. J Infect Dis. 2004;189(12):2243-9. doi: 10.1086/421117. Epub 2004 May 26. PMID: 15181572.
  16. Weber R, Deplazes P, Flepp M, et al. Cerebral microsporidiosis due to Encephalitozoon cuniculi in a patient with human immunodeficiency virus infection. N Engl J Med. 1997 Feb 13;336(7):474-8. doi: 10.1056/NEJM199702133360704. PMID: 9017940.
To cite this page:

Pollock C. Zoonotic concern: Encephalitozoonosis in European rabbits. August 18, 2011. LafeberVet Web site. Available at https://lafeber.com/vet/zoonotic-concern-encephalitozoonosis-in-european-rabbits/