Schistosoma (Schistosomiasis) – Microscopy, Antibody, and Antigen

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 testing information for schistosomiasis at Public Health Ontario (PHO). The causative agents of schistosomiasis include the parasitic blood trematodes (“flukes”) Schistosoma mansoni (Africa and South America), S. japonicum (East Asia), S. mekongi (Southeast Asia), S. haematobium (Africa and the Middle East), S. intercalatum (West and Central Africa), S. guineensis (West and Central Africa), and rarely hybrid species.

For information regarding other testing options, refer to the following webpage: Enteric Helminths (Nematodes, Trematodes, Cestodes, Acanthocephalans) and Balantioides – Microscopy.

Updates
This webpage has been consolidated with the Schistosoma- Serology and Schistosoma haematobium- Urine testing webpages. It has been updated to include antigen testing availability, background, testing indications, acceptance criteria, performance and limitations, interpretations, and expected turnaround times, which are now expressed in calendar days instead of business days.

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

Testing Indications

Microscopy and serology are indicated for the diagnosis of individuals with compatible clinical and epidemiological evidence of subacute to chronic schistosomiasis (e.g., travel to endemic areas with systemic urticarial oviposition hypersensitivity or “Katayama” fever, chronic periportal granulomatous hypertension, chronic granulomatous hematuria, unexplained hepatocellular or bladder carcinoma, ectopic granulomatous lesions).

Antigen testing is not routinely offered in Ontario and is only available upon approval by a PHO microbiologist in the context of positive microscopy and/or positive serology findings to appraise the likelihood of residually active live adult worm infection.

Note: There are currently no PCR tests available at PHO for Schistosoma. Also, there are no tests available at PHO for acute cercarial dermatitis (“swimmer’s itch”) due to either the human Schistosoma species listed above, or the zoonotic Schistosoma species present worldwide.

Acceptance/Rejection Criteria

Testing will only be accepted when both of the following documented on the requisition:

Travel/migration from endemic area (specify which)
Signs or symptoms compatible with subacute or chronic schistosomiasis

Enteric specimens received without sodium acetate, acetic acid, and formalin (SAF) preservation are ineligible and will be cancelled.
If multiple enteric or urinary specimens with the same collection date are submitted, only one will be tested. If multiple specimens are collected, they should be separated at least 1 to 2 days apart for all to be eligible for testing.
Antigen testing will only be accepted upon approval by a PHO microbiologist; if needed, contact PHO Laboratory Customer Service at 416-235-6556 or 1-877-604-4567 prior to sample submission.
Specimens are only accepted if originating from human sources. Specimens submitted from animal sources (e.g. pets) or environmental sources (e.g. water) will be rejected.

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Schistosoma - Microscopy	General Test Requisition	Enteric specimens (e.g., stool, intestinal biopsy / aspirate, gallbladder stones)	1.0 ml	SAF vial
Schistosoma - Microscopy	General Test Requisition	Other body fluid or tissue specimens (e.g. urine, aspirates, biopsies)	1.0 ml (fluid)	SAF or empty sterile vial
Schistosoma - Antibody	General Test Requisition	Blood or serum	5.0 ml blood or 1.0 ml serum	Blood, clotted – vacutainer tubes (SST)
Schistosoma - Antigen	General Test Requisition	Blood or serum	5.0 ml blood or 1.0 ml serum	Blood, clotted – vacutainer tubes (SST)

Submission and Collection Notes

Complete all fields on the requisition form.

Important: Specify both of the following testing indications on the requisition. Failure to provide this information may result in rejection:

Travel/migration from an endemic area (specify which)
Signs or symptoms compatible with subacute or chronic schistosomiasis

Important: Mix the enteric specimen thoroughly with SAF preservative immediately after collection to ensure proper preservation.

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. For additional information see: Criteria for Acceptance of Patient Specimens. Failure to provide this information may result in rejection or testing delay.

Timing of Specimen Collection

For enteric and urinary specimens: Microscopy may be negative within the first 2 months post-exposure (i.e. prepatent period), including during the early subacute systemic “Katayama” fever phase. For urine samples, collection around noon (12:00 PM ± 2 hours) be preferrable due to the circadian periodicity of urinary egg shedding; exercise prior to collection is not required but bedbound individuals or nighttime workers may have variable excretion rates.

Limitations

For serology and antigen testing: Grossly haemolysed, lipemic, contaminated specimens, and specimens containing anti-coagulant are unsuitable for testing.

Storage and Transport

Place specimen container in a biohazard bag and properly seal the bag. Centrifuge tube if using SST for serum specimens.

SAF specimens can be stored at room temperature (or alternatively 2-8°C) and shipped to PHO within 48 hours of collection. Other unpreserved specimens and serum specimens should be stored at 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 is performed daily from Monday to Friday at PHO’s Toronto, Peterborough, Ottawa, and London sites. Turnaround time is up to 7 calendar days from receipt at PHO.

Serology is performed once weekly at PHO’s laboratory-Toronto site. Turnaround time is up to 10 calendar days from receipt at PHO.

If approved, antigen testing is forwarded to the Leiden University Medical Center (LUMC) in the Netherlands. Turnaround time is up to 42 calendar days from receipt at PHO.

Test Methods

Microscopy on enteric specimens is performed at PHO using diphasic sedimentation by formalin and ethyl acetate (FEA). Microscopy on other specimens is performed using standard sedimentation.

Serology is performed at PHO using the commercial EUROIMMUN Anti-Schistosoma IgG enzyme-linked immunosorbent assay (ELISA) based on antibody capture using Schistosoma mansoni soluble egg antigens (SmSEA).

Antigen testing is performed using the laboratory-developed up-converting phosphor reporter particle-labeled lateral flow (UCP-LF) immunoassay targeting the circulating anodic antigen (CAA) regurgitated by live adult Schistosoma mansoni worms.

Performance and Limitations:
Microscopy is usually negative during the prepatent acute (cercarial dermatitis) or early subacute (“Katayama fever”) phases of infection. During the late subacute or chronic phases, sensitivity of a single enteric or urinary specimen ranges from 15-70% depending on the intensity of infection and intermittent shedding patterns. Therefore, a single negative microscopy result does not rule out infection. Multiple (e.g., 2 or 3) specimens may be collected to increase sensitivity. Inadequate specimen volume or delayed mixing of the enteric specimen and SAF fluid in the vial may lead to poor preservation of organism morphology and uninterpretable results. Microscopy at PHO can distinguish between the main clinical species of Schistosoma but does not readily differentiate active from inactive (or “nonviable”) eggs. Rectal biopsy has similar sensitivity as serial stool microscopic examinations; therefore, it is not routinely recommended.^1-14

For serology, sensitivity may be below 50% in the early subacute (“Katayama fever”) phase of infection. During the late subacute or chronic phases, sensitivity ranges from 70-98% and specificity ranges from 65-95%. Reported seropositivity most commonly appears 6-12 weeks after initial exposure but there have been occasional reports of late seroconversion up to 20-24 weeks post-exposure. Serology may remain positive for years after praziquantel therapy and may not be able to distinguish between active, resolved, or recurrent infection. This assay does not provide species identification. Sensitivity by species has not been established, however inter-species cross-reactivity has been described for other SmSEA-based assays with S. japonicum and S. mekongi; there may be lower sensitivity reported for S. haematobium. Serology may also be positive in mono-sexual infections in the absence of tissue-invading egg production. Cross-reactivity has been reported with other helminths (e.g., Strongyloides, hookworms, Trichinella, Trichuris, filarial nematodes, Fasciola, Opisthorchis, or Echinococcus).^7-12,15-20

For antigen testing, sensitivity ranges from 80-97% and specificity ranges from 95-100% for active Schistosoma infection. Reported antigen levels most commonly appear 3-8 weeks after initial exposure. Antigen levels usually decrease within 5-10 weeks after treatment. Antigen testing performance appears comparable for Schistosoma mansoni, S. haematobium, S. japonicum, and S. mekongi infection, and potentially for hybrid species as well. This assay does not provide species identification.^9-14

Interpretation

Microscopy:

Helminth Microscopy	Interpretation
*Helminth(s) found: Schistosoma* species**	The species name(s) and stage(s) will be reported.
No helminths found	No evidence of Schistosoma ova. Due to the limited test sensitivity, testing of additional specimens may be considered if clinically indicated.

Serology:

ELISA Ratio Value	Interpretation	Comments
≥ 1.1	Reactive	Schistosoma antibodies detected. Does not distinguish current from resolved or past infection. Cross-reactivity may occur with other infections. Clinical correlation required.
0.8 to 1.1	Indeterminate	Inconclusive results. Repeat collection if clinically indicated.
< 0.8	Non-reactive	Schistosoma antibodies NOT detected.

Antigen:

Result	Interpretation
Positive	Evidence of Schistosoma circulating anodic antigens (CAA). May represent active infection. Clinical/exposure correlation is required.
Negative	No evidence of Schistosoma circulating anodic antigens (CAA). May represent inactive or past infection. Clinical/exposure correlation is required.

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

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