Home

About Medical Parasitology

New Infections

Ova & Parasite (O&P) Exams

CPT Codes 2016

Quizzes

Review Tests

FAQ

Information Tables

Organism Index (A-Z)

Cyclospora cayetanensis (Pathogen)

Organism:
This organism belongs to the coccidia, is a true pathogen, and causes cyclosporiasis.  The round oocysts measure 8-10 µm (twice the size of Cryptosporidium spp.) and are found in fecal specimens.

cyclo1 cyclo2 cyclo3 cyclo4
Autofluorescence        Modified Acid-Fast Stains (Acid-Fast Variable)          Safranin Stain
Low Magnification

Life Cycle:
Intestine, oocysts passed in feces, are NOT immediately infectious, survive in the environment, and are transmitted via contaminated food and/or water. 

Acquired:
Fecal-oral transmission via oocyst form; outbreaks linked to contaminated water and various types of fresh produce (raspberries, basil, baby lettuce leaves, snow peas) have been reported.

Epidemiology:
Worldwide, primarily human-to-human transmission, animal-to-human transmission not documented

Clinical Features:
Intestinal: Nausea, low-grade fever, fatigue, anorexia, up to 7 bowel movements per day; relapses common.  Developmental stages of C. cayetanensis usually occur within epithelial cells of the jejunum and lower portion of the duodenum.  Cyclospora infection reveals characteristics of a small bowel pathogen, including upper gastrointestinal symptoms, malabsorption of D‑xylose, weight loss, and moderate to marked erythema of the distal duodenum. Histopathology in small bowel biopsy specimens reveals acute and chronic inflammation, partial villous atrophy, and crypt hyperplasia. In patients with AIDS, symptoms may persist for as long as 12 weeks; biliary disease has also been reported in this group. 

Clinical Specimen:
Intestinal:  Stool

Laboratory Diagnosis:
Intestinal:  Ova and Parasite examination (concentration ONLY); from concentrate sediment, (500 x g for 10 min) modified acid-fast stains are performed.  Some oocysts stain deep red with a mottled appearance but no internal organization, while unstained organisms appear as glassy, wrinkled spheres.  Oocysts are considered acid-fast variable, with colors ranging from clear to deep red; this is unlike Cryptosporidium where almost all the oocysts stain using modified acid-fast stains.  In order to maintain color in Cyclospora, use only a 1-3% acid decolorizer (1% recommended) for good staining of all the coccidia (Cryptosporidium, Cyclospora, Cystoisospora).  These oocysts also autofluoresce green (450to 490 DM excitation filter) or blue (365 DM excitation filter).
Tissue:  Found at all levels of the intestinal tract, with the jejunum being the most heavily infected site.  Routine H&E staining is sufficient to demonstrate the organisms.  Under regular light microscopy, the organisms are visible within a vacuole at the luminal end of the enterocyte rather than at the brush border like Cryptosporidium.

Organism Description:
Oocyst:  Round oocysts, containing no internal structure (immature when passed – not infectious). 
Tissue:   Organisms are visible within a vacuole at the luminal end of the enterocyte rather than at the brush border like Cryptosporidium.

Laboratory Report:
Cyclospora cayetanensis oocysts

Treatment: 
Garcia, L.S. 2007.  Diagnostic Medical Parasitology, 5th ed., ASM Press, Washington, D.C.
Disease self-limiting with weeks, but trimethoprim-sulfamethoxazole drug of choice.

Control:
Improved hygiene, adequate disposal of fecal waste, adequate washing of contaminated fruits and vegetables; primary food sources identified have been fresh berries (imported from Guatemala), basil, baby lettuce leaves as salad (mesclun)