Cystoisosporiasis is infection with the parasite Cystoisospora (Isospora) belli. The main symptoms are watery diarrhea with abdominal cramping and nausea.
People can become infected with Cystoisospora by consuming food or water contaminated with the parasite.
Cystoisosporiasis symptoms are more severe and prolonged in people with a weakened immune system, such as people with AIDS.
Symptoms vary but include watery diarrhea, abdominal cramping, fever, and weight loss.
Doctors usually diagnose the infection by identifying Cystoisospora in a sample of stool.
(See also Overview of Parasitic Infections.)
Cystoisosporiasis is most common in tropical and subtropical climates. When encountered in the United States, it is usually in immigrants or travelers with exposure in endemic areas.
Image from the Centers for Disease Control and Prevention Image Library.
Symptoms of Cystoisosporiasis
The primary symptom of cystoisosporiasis is sudden, nonbloody, watery diarrhea. Other symptoms include fever, abdominal cramps, nausea, fatigue, and weight loss. Symptoms in people with a normal immune system usually last weeks, then subside.
In people with a weakened immune system, including people with AIDS, cystoisosporiasis may cause severe diarrhea that may persist for a long time.
Diagnosis of Cystoisosporiasis
Stool tests
To diagnose cystoisosporiasis, a stool sample is examined under a microscope for Cystoisospora eggs. Specialized techniques can be used to increase the chances of identifying the eggs.
When stool analysis does not identify a cause for persistent diarrhea, doctors may use a flexible viewing tube (endoscope) to examine the upper part of digestive tract. Doctors may use this procedure to obtain a sample of tissue to be examined and analyzed (biopsied). Cystoisospora, if present, can be seen in a biopsy sample from the intestine.
Prevention of Cystoisosporiasis
When traveling to tropical and subtropical areas where the infection is common, people should avoid eating uncooked foods, including salads and vegetables, and should avoid consuming potentially contaminated water and ice. Hand washing with soap and water is important. Drinking water that has been boiled is safe. Filtering water through a 0.1 or 0.4 micron filter can remove cysts of Cystoisospora and other parasites, as well as bacteria that cause diseases.
Treatment of Cystoisosporiasis
In people with AIDS, it is very important to treat HIV infection as effectively as possible with antiretroviral drugs. Such treatment can strengthen the weakened immune system, which usually helps control the diarrhea and other symptoms. People with AIDS may need a higher dose of TMP/SMX and a longer course of treatment. Sometimes long-term TMP/SMX maintenance therapy is needed in people with HIV/AIDS.
