Cystoisosporiasis is infection with Cystoisospora (Isospora) belli; cyclosporiasis is infection with Cyclospora cayetanensis. Both organisms are coccidian protozoa. Symptoms include watery diarrhea with GI and systemic symptoms. Diagnosis is by detection of characteristic oocysts in stool or intestinal biopsy specimens. Treatment is usually with trimethoprim/sulfamethoxazole.
The life cycles of Cystoisospora belli and Cyclospora cayetanensis are similar to that of Cryptosporidium, except that oocysts must sporulate before becoming infective. Human cystoisosporiasis and cyclosporiasis are most common in tropical and subtropical climates. Transmission is by the fecal-oral route via contaminated food or drink. In North America, outbreaks of C. cayetanensis have been caused by ingestion of raspberries imported from Guatemala.
Symptoms and Signs
The primary symptom is sudden, nonbloody, watery diarrhea, with fever, abdominal cramps, nausea, anorexia, malaise, and weight loss. In immunocompetent patients, the illness usually resolves spontaneously but can last weeks.
In hosts with depressed cell-mediated immunity as occurs in AIDS, cystoisosporiasis and cyclosporiasis may cause severe, intractable, voluminous diarrhea resembling cryptosporidiosis. Extraintestinal disease in patients with AIDS may include cholecystitis and disseminated infection.
Diagnosis is by detection of oocysts via microscopic examination of the stool. Detection is facilitated by staining stool samples with modified acid-fast stain. Multiple stool specimens may be needed because cyst secretion may be intermittent. Diagnosis is sometimes made only when intracellular parasite stages are detected in biopsies of intestinal tissue. In cystoisosporiasis, cysts autofluoresce when ultraviolet microscopy is used; the stool may contain Charcot-Leyden crystals (hexagonal, double-pointed, and often needlelike crystals) derived from eosinophils. Unlike other protozoan infections, cystoisosporiasis may result in peripheral blood eosinophilia.
Treatment of choice for both cystoisosporiasis and cyclosporiasis is double-strength trimethoprim/sulfamethoxazole (TMP/SMX): 160 mg TMP and 800 mg SMX po bid for 10 days for cystoisosporiasis or for 7 to 10 days for cyclosporiasis. Children are given 5 mg/kg TMP (and 25 mg/kg SMX) po bid for the same number of days.
In patients with AIDS, higher doses and longer duration may be needed, and treatment of acute infection is usually followed by long-term suppressive therapy.
Ciprofloxacin 500 mg po bid for 7 days has also been used to treat cystoisosporiasis and cyclosporiasis but appears to be less effective than TMP/SMX.
Prevention is as for cryptosporidiosis.
Last full review/revision December 2009 by Richard D. Pearson, MD