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.
Microsporidiosis causes symptoms mainly in people with a weakened immune system, such as people with HIV.
Symptoms vary but include chronic diarrhea, abdominal pain, fever, weight loss, and eye inflammation.
Doctors diagnose the infection by identifying microsporidia in a sample of the infected tissue or in stool, urine, or other body fluids.
Medications can control but not eliminate the infection.
(See also Overview of Parasitic Infections.)
Microsporidia used to be classified as protozoa but are now considered fungi. These spore-forming parasitic fungi live inside infected cells.
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 HIV 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
Microsporidia transmission occurs mostly through food, including fish and crustaceans. Transmission also occurs through water including seawater, drinking water, and other environmental sources.
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
People with a normal immune system typically have no symptoms or mild diarrhea. Eye infections can also occur and have been increasingly reported in healthy individuals.
In people with HIV or other conditions that weaken the immune system, microsporidiosis can cause chronic diarrhea and various infections (such as hepatitis and sinusitis). If microsporidiosis affects the intestine, people may not absorb enough nutrients from food (called malabsorption), leading to weight loss.
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 sample of a body fluid. They examine the samples under 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), 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
For people with HIV, also antiretroviral medications
If the immune system is normal, mild cases of microsporidiosis usually resolve without treatment.
In people with HIV, it is very important to treat the HIV infection as effectively as possible with antiretroviral medications. Such treatment can strengthen the weakened immune system, which usually helps control the diarrhea and other symptoms. Likewise, it is important to reverse, if present, other causes of immune suppression.
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.
