Key Points
- Many rabbits are asymptomatic carriers of 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.
Introduction
The physical and psychological benefits of pet ownership have been well established (Friedman 2009), 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 (Mitchell 2005), but rabbits can carry a number of potential pathogens including Encephalitozoon cuniculi (Fig 1).
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. The primary host for E. cuniculi is the rabbit. Infections in rabbits are typically subclinical (Künzel 2010).
Transmission
Transmission of E. cuniculi is urine-oral in rabbits (Künzel 2010). Humans are exposed to spores through contact with rabbit urine.
Who is at risk?
Little is known about the prevalence or importance of infection with Encephalitozoon spp. in immunocompetent individuals (Khan 2001). Serological studies suggest that human exposure to microsporidia may be common but without clinical significance (Van Gool 2004).
Although E. cuniculi is a rare cause of infection in human patients, microsporidiosis is considered an emerging, opportunistic infection in AIDS patients. Complications due to E. cuniculi infection have been reported in severely immunocompromised patients including (Didler 2000, Fournier 2000, Mathis 2005, Kodjikian 2005):
- HIV-infected
- Organ transplant recipients
- Idiopathic CD4+ T-lymphocytopenia
- Young children and the elderly
- Contact lens wearers
Disease in humans
Clinical reports of E. cuniculi infection have described a wide range of organ involvement including (Didler 2000, Fournier 2000, Khan 2001, Mathis 2005)
- Peritonitis
- Hepatitis, granulomatous liver necrosis
- Renal failure
- Pneumonia, sinusitis, rhinitis
- Myalgia
- Otitis media
- Visual impairment, keratoconjunctivitis
- Seizure disorder
There is also a report of disseminated E. cuniculi infection in the brain of an AIDS patient (Weber 1997).
Prevention and control
Avoid contact with the urine of infected or healthy rabbits, and always practice good sanitation when handling animals.