- Microsporidiosis is a disease that is caused by small parasites called microsporidia.
- Generally, microsporidia do not cause disease in healthy people but rather in people with immune system deficiency.
- Microsporidiosis can cause chronic diarrhea, kidney disease, and infection of the sinuses and eyes.
- Diagnosing microsporidiosis requires laboratory testing.
- Treatment of microsporidiosis requires medications and supportive care.
What is microsporidiosis? What causes the disease?
Microsporidiosis is a disease caused by infection with microscopic organisms called microsporidia. Microsporidia are eukaryotic parasites that must live within other host cells in which they can produce infective spores. These spores cause microsporidiosis, a disease that is primarily seen in individuals infected with human immunodeficiency virus (HIV), although it can rarely also cause disease in individuals with a normal immune system. Microsporidia are found worldwide, and there are numerous vertebrates and invertebrates that can serve as hosts for this parasite.
Microsporidiosis can cause infection of the intestine, lung, kidney, brain, sinuses, muscles, and eyes. Although there are over 1,200 species of microsporidia, there are 15 species that have been identified as causing disease in humans.
What are risk factors for microsporidiosis?
The main risk factor associated with acquiring microsporidiosis is immunodeficiency. The vast majority of cases of microsporidiosis occur in individuals with a compromised immune system, primarily in people with HIV/AIDS-related immunosuppression. It can also affect immunocompromised individuals such as organ-transplant recipients, people with diabetes, cancer patients, and those who are chronically on steroids. Rarely, microsporidiosis can occur in healthy people with a normal immune system.
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Is microsporidiosis contagious?
Though the route of spread is poorly understood, studies have suggested that humans may possibly contract microsporidia via sexual transmission with an infected individual. Transmission from human to human may also possibly occur via the fecal-oral route or through direct contact with ocular secretions from infected individuals.
What is the incubation period for microsporidiosis?
The exact incubation period for microsporidiosis in humans has not been definitively established for all species.
How are microsporidia transmitted?
Microsporidia spores are released from the stool, respiratory secretions, and urine of infected animals. A number of animals, including insects, birds, and mammals, can serve as reservoirs of infection for microsporidia. Transmission of these spores is thought to occur primarily via ingestion or inhalation by humans, though the process is not perfectly understood. Studies have also suggested that water-borne and food-borne transmission may be possible.
Once within a cell, the microsporidia develop and multiply, producing more spores. The infective spores are then released when the cell expands and bursts.
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What symptoms does microsporidiosis cause?
Although microsporidiosis can occur in people with normal immune systems, it is very uncommon. The symptoms of microsporidiosis primarily occur in people with immune-system deficiency, such as HIV-infected individuals and organ-transplant recipients. Microsporidiosis can cause intestinal, lung, kidney, brain, sinus, muscle, or eye disease.
Intestinal symptoms that are caused by microsporidia infection include chronic diarrhea, wasting, malabsorption, and gallbladder disease. In patients with AIDS, the chronic diarrhea may be extremely debilitating and carries a significant mortality (death) risk. The majority of cases of intestinal microsporidiosis in AIDS patients are caused by Enterocytozoon bieneusi.
Lung symptoms may include a cough and difficult, labored breathing. A chest X-ray may show signs of inflammation, fluid, or cavities in the lungs.
Microsporidiosis can cause infection in the urinary tract, kidney failure, bladder inflammation, and bowel perforation. Microsporidia can also spread throughout the body (disseminate) to cause inflammation in the brain, pancreas, sinuses, and muscle tissue.
Eye infection with microsporidia can cause inflammation of the cornea and conjunctiva (keratoconjunctivitis). Symptoms of ocular microsporidiosis may include eye pain, eye redness, or blurry vision.
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How do health-care professionals diagnose microsporidiosis?
There are several tests available to diagnose microsporidia infection. Microscopic examination of stained samples of body fluids, primarily fecal samples, allows for rapid diagnosis, although the exact species of microsporidia may not be identified. Urine samples can also be used to detect spores when the kidney and/or bladder are involved.
A powerful microscope, called a transmission electron microscope, is needed to identify the exact species of microsporidia. However, this form of testing is expensive, and it is not available for routine use in all laboratories.
Other methods, such as immunofluorescence assays and polymerase chain reaction (PCR) testing, can also identify microsporidia infection in the research-laboratory setting.
Finally, blood tests and imaging studies can also assist in detecting microsporidiosis.
What types of specialists treat microsporidiosis?
Microsporidiosis is generally treated primarily by an infectious-disease specialist. Other specialists may be consulted depending on the site of infection, such as an ophthalmologist for eye involvement.
What is the treatment for microsporidiosis?
The treatment of microsporidiosis is generally achieved with medications and supportive care. Depending on the site of infection and the microsporidia species involved, different medications are utilized. The most commonly used medications for microsporidiosis include albendazole (Albenza) and fumagillin.
For patients with diarrhea and dehydration, intravenous fluid administration and electrolyte repletion may be necessary. Dietary and nutritional regimens may also assist with chronic diarrhea. Finally, improvement of immune system function with antiretroviral therapy in HIV-infected individuals may also lead to improvement of symptoms.
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What is the prognosis of microsporidiosis?
In general, the prognosis of microsporidiosis in healthy individuals with a normal immune system is good. However, immunocompromised individuals who develop microsporidiosis have a more guarded prognosis, with the outcome determined by the site of infection, the severity of infection, and the time elapsed to seek prompt medical treatment. Microsporidiosis in these individuals can sometimes be fatal.
Is it possible to prevent microsporidiosis?
For patients with HIV infection, microsporidiosis may be prevented by maintaining an intact immune system through the use of antiretroviral medications. Frequent hand washing and limiting exposure to potential sources of infection are also recommended. Because of the possibility of sexual transmission, safe sexual practices are an important preventive step. At this time, there is no vaccine available to prevent microsporidiosis.
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Didier, E.S., and L.M. Weiss. "Microsporidiosis: current status." Current Opinion in Infectious Diseases 19 (2006): 485-492.
United States. Centers for Disease Control and Prevention. "Microsporidiosis." Sept. 14, 2015. <http://www.cdc.gov/dpdx/microsporidiosis/index.html>.