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Cyclospora: a newly identified intestinal pathogen of humans

R Wurtz1

  • 1Division of Infectious Disease, Cook County Hospital, Chicago, Illinois 60612.

Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America
|April 1, 1994
PubMed

Insights

Cyclospora cayetanensis, a newly identified coccidian protozoan, causes prolonged diarrhea in humans. This waterborne pathogen, resembling Cryptosporidium, affects various populations and may respond to trimethoprim-sulfamethoxazole.

Area of Science:

  • Medical Parasitology
  • Infectious Diseases
  • Gastroenterology

Background:

  • A previously unidentified acid-fast organism has been linked to prolonged human diarrhea.
  • Initial classification as a cyanobacterium was incorrect; it is now identified as a coccidian protozoan, Cyclospora cayetanensis.
  • This pathogen has been found globally in various human populations, including children, immunocompetent adults, and HIV-seropositive individuals.

Purpose of the Study:

  • To identify and characterize a novel protozoan pathogen causing prolonged diarrhea.
  • To describe the morphology, transmission, clinical presentation, and potential treatment of Cyclospora cayetanensis infections.

Main Methods:

  • Microscopic examination of stool samples (wet mounts, ultraviolet illumination).
  • Staining techniques, including modified carbolfuchsin (acid-fast staining).
  • Clinical observation of patient symptoms and response to treatment.

Main Results:

  • The organism, Cyclospora cayetanensis, is a wrinkled sphere (8-9 microns) with distinct walls and internal material, fluorescing under UV light.
  • Formalin-preserved oocysts show variable acid-fastness.
  • Clinical syndrome includes watery diarrhea, nausea, anorexia, cramping, fatigue, and weight loss, typically occurring in summer months.
  • Diarrhea is self-limiting in immunocompetent individuals but prolonged in advanced HIV infection.
  • Trimethoprim-sulfamethoxazole showed efficacy in a small number of treated patients.

Conclusions:

  • Cyclospora cayetanensis is a newly identified waterborne protozoan pathogen causing significant gastrointestinal illness.
  • The clinical course varies based on host immune status, with prolonged illness in immunocompromised individuals.
  • Further research is needed to fully understand this emerging pathogen and its management.

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