Microsporidiosis causes symptoms mainly in people with a weakened immune system Overview of Immunodeficiency Disorders Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual. Immunodeficiency... read more , such as people with 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
.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.
Drugs can control but not eliminate the infection.
(See also Overview of Parasitic Infections Overview of Parasitic Infections A parasite is an organism that lives on or inside another organism (the host) and benefits (for example, by getting nutrients) from the host at the host's expense. Although this definition actually... read more .)
Microsporidia used to be classified as protozoa but are now considered fungi Overview of Fungal Infections Fungi are living organisms, but they are not plants or animals. All living things are divided into categories called kingdoms, and fungi have their own kingdom. Some fungi cause infections in... read more . 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 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 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
People with a normal immune system typically have no symptoms, but in people with 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 or other conditions that weaken the immune system Overview of Immunodeficiency Disorders Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual. Immunodeficiency... read more , 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 Overview of Malabsorption Malabsorption syndrome refers to a number of disorders in which nutrients from food are not absorbed properly in the small intestine. Certain disorders, infections, and surgical procedures can... read more ) 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 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 
), 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)
If the immune system Overview of the Immune System The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more is normal, mild cases of microsporidiosis usually resolve without treatment.
In people with 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 , it is very important to treat the HIV infection Antiretroviral Treatment of Human Immunodeficiency Virus (HIV) Infection Antiretroviral medications used to treat human immunodeficiency virus (HIV) infection aim to do the following: Reduce the amount of HIV RNA (viral load) in the blood to an undetectable amount... read more as effectively as possible with antiretroviral drugs. 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.
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.
Drugs Mentioned In This Article
| Generic Name | Select Brand Names |
|---|---|
albendazole |
Albenza |
voriconazole |
VFEND |
