Cystoisospora,Cyclospora, andSarcocystis

Abstract

“Cystoisospora, Cyclospora, and Sarcocystis” provides an overview of the life cycles, pathogenesis, diagnosis, and treatment of these important parasites. These coccidial parasites have an environmentally resistant oocyst stage in their life cycles. They remain an important cause of diarrhea in patients in developing countries, and foodborne outbreaks still occur in developed countries. Humans are the only definitive hosts for Cystoisospora belli and Cyclospora cayetanensis and pass unsporulated oocysts in their stools. Sarcocystis requires two hosts. Humans are definitive hosts for S. hominis and S. suihominis and become infected after ingesting undercooked meat of bovids (cattle, buffalo) and pigs, respectively. Humans pass sporulated oocysts and sporocysts in their stools. Humans are also accidental intermediate hosts for one or more Sarcocystis species, and most cases are observed in Southeast Asia. Muscle sarcocysts are associated with fever and muscle pain. Diagnosis of Cystoisospora, Cyclospora, and Sarcocystis is based on microscopic examination of stool samples using acid-fast-stained slides or with UV microscopy. PCR-based methods of stool examination for oocysts have been developed. There are currently no serologic tests available to detect antibodies to these parasites and aid in their diagnosis. Combination antiretroviral therapy (cART) is associated with a better prognosis in AIDS patients, but clinical episodes still occur even in some patients on cART. Treatments for acute Cystoisospora and Cyclospora infections are available and effective. Apparent drug failures are most likely related to poor drug absorption or distribution rather than to true drug resistance.