Cystoisospora (Cystoisosporiasis) – Microscopy

Consistent with O. Reg. 671/92 of the French Language Services Act, laboratory testing information on this page is only available in English because it is scientific or technical in nature and is for use only by qualified health care providers and not by members of the public.

Background
This page provides microscopy testing information for cystoisosporiasis at Public Health Ontario (PHO). The causative agent of cystoisosporiasis is the parasitic apicomplexan Cystoisospora (syn. Isospora) belli.

For information on other protozoan testing options—excluding Cystoisospora —please refer to the following test information sheet: Enteric Protozoa (Cryptosporidium, Cyclospora, Dientamoeba, Entamoeba, and Giardia) - PCR.

Updates
This webpage has been updated to include background information, testing indications, acceptance criteria, performance characteristics and limitations, result interpretations, and expected turnaround times based on calendar days instead of business days.

*Uncontrolled print copy. Valid only on day of print: 17 Dec 2025.

Testing Indications

Microscopy is recommended for the diagnosis of individuals with clinical and epidemiological evidence suggestive of cystoisosporiasis, such as persistent malabsorptive enteritis following travel to or residence in subtropical or tropical regions. While severe or chronic disease is more commonly observed in individuals with impaired immunity, cases have also been reported in immunocompetent individuals .^1-2

Note: Currently, PCR and serological (antibody) testing for Cytoisospora are not available at PHO.

Acceptance/Rejection Criteria

To ensure your specimens are processed without delay, please review the following requirements before submission:

Clinical and Exposure Information Required
Specimens must be accompanied by relevant clinical and exposure details on the requisition. Submissions without this information may be rejected or testing may be delayed.
Proper Specimen Preservation Required
Enteric specimens received without sodium acetate, acetic acid, and formalin (SAF) preservation are ineligible and will be cancelled.
Specimen Collection Timing
If submitting more than one specimen, ensure that each specimen is collected at least 1 to 2 days apart. If multiple specimens collected on the same date are received, only one specimen will be tested.
Human Specimens Only
Only human-derived specimens are accepted. Specimens from animals (e.g. pets) or environmental sources (e.g. food, water) will be rejected.

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Cystoisospora or Apicomplexan – Microscopy	General Test Requisition	Enteric specimens (e.g., feces, intestinal biopsy / aspirate / scraping, Entero-Test)	1.0 ml	SAF vial

Submission and Collection Notes

Complete all fields of the requisition form.

Important: make sure that the specimen and SAF fluid is mixed thoroughly as soon as collection occurs to preserve the specimen fully.

Label the specimen container(s) with the patient’s first and last name, date of collection, and one other unique identifier such as the patient’s date of birth or Health Card Number. Failure to provide this information may result in rejection or testing delay.

If the patient is part of a cluster/outbreak investigation, contact PHO Laboratory Customer Service at 416-235-6556/1-877-604-4567 prior to sample submission.

Limitations

Avoid antacids or antimicrobials at least 2-3 weeks before collection as it can alter the intestinal microbiome. Avoid laxatives/enemas (e.g. mineral/castor oil), nonabsorbable antidiarrheal preparations (e.g. bismuth), and kaolin at least 7-10 days before collection as it can affect the staining process. Avoid contrast dyes (e.g. barium) at least 3 weeks before collection as it can affect the staining process. Avoid contact between feces and urine or water during collection.

Storage and Transport

Place specimen container in a biohazard bag and properly seal the bag. SAF specimens can be stored at room temperature (or alternatively 2-8°C) and shipped to PHO within 48 hours of collection. All specimens must be shipped in accordance with the Transportation of Dangerous Good Act.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Microscopy on enteric specimens is performed daily from Monday to Friday at PHO’s laboratory -Toronto, Peterborough, Ottawa, and London sites. Turnaround time is up to 7 calendar days from receipt at PHO.

Test Methods

Microscopy is performed at PHO using acid-fast staining technique.

Performance and Limitations:
Microscopy sensitivity for detection of Cystoisospora is unknown and likely low. Infections are often persistent and may intermittently shed in feces, therefore multiple (e.g., 2 or 3) specimens may be collected to increase sensitivity. Inadequate specimen volume or delayed mixing of the specimen and SAF fluid in the vial may lead to poor preservation of organism morphology and uninterpretable results.^1-2

Interpretation

Apicomplexan Microscopy	Interpretation
Apicomplexan(s) found: Cystoisospora belli	The organism stage(s) will be reported.
No apicomplexans found	No evidence of Cystoisospora organisms. Due to the limited test sensitivity, testing of additional specimens may be considered if clinically indicated.

Reporting

Results are reported to the physician, authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.

References

Dubey JP, Almeria S. Cystoisospora belli infections in humans: the past 100 years. Parasitology. 2019 Oct;146(12):1490-1527. doi: 10.1017/S0031182019000957. Epub 2019 Aug 9. PMID: 31303182.
Lindsay DS, Dubey JP, Blagburn BL. Biology of Isospora spp. from humans, nonhuman primates, and domestic animals. Clin Microbiol Rev. 1997 Jan;10(1):19-34. doi: 10.1128/CMR.10.1.19. PMID: 8993857; PMCID: PMC172913.