MSD Manual

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Chelsea Marie

, PhD, University of Virginia;

William A. Petri, Jr

, MD, PhD, University of Virginia School of Medicine

Reviewed/Revised Oct 2022

Microsporidiosis is infection caused by Microsporidia, which are parasitic fungi. Symptoms depend on the organs infected, but infections can cause diarrhea, other intestinal symptoms, or eye symptoms.

Microsporidia may infect the intestine, liver, gallbladder, biliary tract (the tubes that connect the liver and gallbladder with the small intestine), eyes, sinuses, muscles, respiratory tract, urinary tract, and, occasionally, the brain. The infection may spread throughout the body.

Several species of Microsporidia can cause infection in people, but symptoms occur mainly in those with advanced AIDS Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and is treated with antiretroviral medications. If untreated, it can cause... read more Human Immunodeficiency Virus (HIV) Infection or other disorders that severely weaken the immune system. People with a healthy immune system may develop eye symptoms if microsporidia infect the cornea.

Microsporidia spread through spores, which can

  • Be ingested

  • Be inhaled

  • Enter through tissues around the eye

  • Be spread from person to person

  • Be spread through contact with an infected animal

Inside the body, microsporidia spores enter cells, where the spores develop, multiply, and form more spores. The infected cells eventually rupture, releasing the spores. The spores can then spread throughout the body, causing inflammation, or they can be excreted into the environment in the breath, stool, or urine.

Symptoms of Microsporidiosis

Symptoms of microsporidiosis vary depending on

  • Which species causes the infection

  • Which organs are affected

  • How well a person’s immune system is working

Other microsporidiosis symptoms may include abdominal pain, jaundice, fever, persistent cough, muscle aches and pain, headache, and eye inflammation with redness. Vision may be blurred. If infection of the eye is severe, blindness can result.

Diagnosis of Microsporidiosis

  • Examination of a sample of affected tissue, stool, urine, or other body fluids

To diagnose microsporidiosis, doctors examine a sample of the affected tissue (taken by biopsy) or a body fluid with a microscope, usually using special techniques to make the microsporidia more visible. For example, samples of stool, urine, blood, sputum, cerebrospinal fluid (taken by spinal tap Spinal Tap Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Imaging tests commonly used to diagnose nervous system (neurologic) disorders... read more Spinal Tap ), or the cornea (taken by scraping) may be examined.

Tests may also be done to identify the parasite's genetic material (DNA) in the sample.

Treatment of Microsporidiosis

  • Albendazole or fumagillin

  • For people with AIDS, also antiretroviral drugs

  • For eye infection, albendazole (taken by mouth) and fumagillin (as eye drops)

The antimicrobial treatment of microsporidiosis depends on which microsporidia species is causing the infection, whether the person's immune system is normal, and which organs are involved. Albendazole, taken by mouth, may help control diarrhea if the species causing the intestinal infection is susceptible to it. However, the drug does not eliminate the infection and has serious side effects, including bone marrow suppression (causing fewer blood cells to be made in bone marrow) and liver inflammation (hepatitis).

Albendazole is also used to treat microsporidiosis that affects the skin or muscle or that has spread throughout the body if the species causing the infection is susceptible.

Fumagillin tablets taken by mouth have been used to control diarrhea when the infecting microsporidia species is potentially susceptible, but it also may have serious side effects. Fumagillin tablets are not available in the United States.

Eye infections are treated with albendazole taken by mouth and fumagillin eye drops. Fluoroquinolone or voriconazole eye drops are sometimes useful. If these drugs do not relieve the symptoms, surgery to repair the cornea (keratoplasty) may be required.

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