Not Found

Find information on medical topics, symptoms, drugs, procedures, news and more, written in everyday language.


By Richard D. Pearson, MD, Emeritus Professor of Medicine, University of Virginia School of Medicine

Microsporidiosis is infection caused by Microsporidia protozoa. Symptoms depend on the organs infected, but the infection commonly causes diarrhea, other intestinal symptoms, or eye symptoms.

  • This infection causes symptoms mainly in people with a weakened immune system, such as people with AIDS.

  • Symptoms vary but include chronic diarrhea, abdominal pain, fever, weight loss, and eye inflammation.

  • Doctors diagnose the infection by identifying the protozoa in a sample of the infected tissue.

  • Antiparasitic drugs can control but not eliminate the infection.

Several species of Microsporidia cause infection in people, but symptoms occur mainly in those with AIDS or other disorders that weaken the immune system. These protozoa may infect the intestine, biliary tract, cornea, muscles, respiratory tract, urinary tract, and, occasionally, the brain. The infection may spread throughout the body.

Microsporidia spread through spores, which can be ingested or inhaled or enter through the eye. They may spread from person to person or through contact with an animal. Inside the body, the spores pierce a cell and inject it with material that becomes spores. The cell eventually ruptures, releasing the spores. The spores then spread throughout the body, causing inflammation, or are excreted 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

People with a normal immune system typically have no symptoms, but microsporidiosis can cause chronic diarrhea in people with AIDS. Other microsporidiosis symptoms may include abdominal pain, jaundice, fever, weight loss, a persistent cough, pain in the side (flank), muscle aches, headache, and eye inflammation with redness. Vision may be blurred. If infection is severe, blindness may result.

Diagnosis of Microsporidiosis

  • Examination of a sample of the affected tissue under a microscope

To diagnose microsporidiosis, doctors examine a sample of the affected tissue under a microscope, usually using special techniques to make the protozoa more visible. Samples of stool, urine, blood, sputum, cerebrospinal fluid (taken by spinal tap), cornea (taken by scraping), or other tissue (taken by biopsy) may be needed.

Special tests are also used to identify the parasite's genetic material (DNA) in the sample.

Treatment of Microsporidiosis

  • For persistent diarrhea, albendazole (a drug usually used to treat worm infections—an antihelminthic drug)

If the immune system is normal, microsporidiosis treatment is rarely needed.

For persistent diarrhea, albendazole, taken by mouth, may help control symptoms if the species causing the infection is susceptible to it. However, the drug does not eliminate the infection.

If people have AIDS, it is also very important that the HIV infection is treated as effectively as possible. Such treatment can strengthen the weakened immune system and thus usually helps control the diarrhea.

Eye drops containing albendazole and fumagillin may relieve eye symptoms. If they do not, surgery to repair the cornea (keratoplasty) may be required.