Cystoisosporiasis also known as Isosporiasis is an uncommon intestinal disease caused by parasitic infection of Cystoisospora belli. This disease is common in subtropical and tropical regions of the world. The parasite spreads by ingesting contaminated food or water, the most common symptom includes watery diarrhoea, which may be associated with abdominal pain, cramping, anorexia, nausea, vomiting, and low-grade fever. If untreated, people with weak immune systems, such as people with AIDS, may be at higher risk for severe or prolonged illness. The diagnosis of cystoisosporiasis is usually made by identifying oocysts in stool wet mounts or stained fecal smears.
Cystoisospora are uncommon in the United States, but can be acquired by travelers to endemic countries. In a study of more than 16,000 HIV-infected patients between 1985 and 1992 in Los Angeles County, the prevalence of Cystoisospora infections was highest in foreign-born patients, particularly those from Mexico and El Salvador, and among persons of Hispanic ethnicity.
Cystoisosporiasis can be treated with the sulfa drugs like trimethoprim-sulfamethoxazole. For adults, the daily dose of pyrimethamine is in the range of 50 to 75 mg. This dose is given orally, either once a day or divided into 2 separate doses. Clinical management includes fluid and electrolyte support for dehydrated patients and nutritional supplementation for malnourished patients. If symptoms worsen or persist despite approximately 5 to 7 days of TMP-SMX therapy, the possibilities of noncompliance, malabsorption, and concurrent infections/enteropathies should be considered; the TMP-SMX regimen (daily dose, duration, and mode of administration) also should be reevaluated.
Some of the major researches on Cystoisosporiasis are Molecular Diagnosis of Cystoisosporiasis Using Extended-Range PCR Screening, Ultrastructural aspects of Cystoisospora belli (syn. Isospora belli) in continuous cell lines.