Trichinella (Trichinellosis) – Antibody and 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 antibody (serology) and microscopy testing information for trichinellosis (also known as trichinosis) at Public Health Ontario (PHO). The causative agent of trichinellosis is the parasitic larval nematode Trichinella. Infections occur worldwide following ingestion of undercooked meat (particularly wild meat). Trichinellosis manifestations include acute gastrointestinal illness (e.g., watery diarrhea, abdominal pain, nausea) followed a few days later by muscular and visceral eosinophilic inflammation (fever, urticaria, myositis, periorbital edema, suffusion, splinter hemorrhage, pneumonitis, pleuritis, myocarditis, encephalitis).

Updates

Updated to consolidate microscopy and antibody (serology) testing information into a single test information webpage.

*Uncontrolled print copy. Valid only on day of print: 19 Oct 2026.

Testing Indications

Serology may be considered for the diagnosis of individuals with compatible exposure history and clinical presentation for trichinellosis. The larvae may also be retrieved from body fluids or tissues, particularly muscle biopsies, but is usually reserved in cases of diagnostic uncertainty during the extraintestinal phase.

Note: Trichinella PCR is not available at PHO.

As a Disease of Public Health Significance (DOPHS) under the Health Protection and Promotion Act (HPPA), additional testing recommendations for public health management of trichinellosis are stated in the Ontario Ministry of Health Infectious Diseases Protocol Appendix 1 for Trichinosis.

Acceptance/Rejection Criteria

Testing will only be performed when all the following criteria are documented on the requisition form:

Exposure to undercooked meat
Clinical signs or symptoms consistent with trichinellosis
Eosinophilia, eosinophilic pleocytosis, or ocular lesion(s)

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Trichinella – Antibody	General Test Requisition	Serum	1.0 ml	Red top (clotted) tube or serum separator tube (SST)
Trichinella – Microscopy	General Test Requisition	Body fluid or tissue specimen (e.g. muscle biopsy)	1.0ml (fluid) or 0.2mg (tissue)	Sterile container

Submission and Collection Notes

Complete all fields of the requisition form.

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

Exposure to undercooked meat
Clinical signs or symptoms consistent with trichinellosis
Eosinophilia, eosinophilic pleocytosis, or ocular lesion(s)

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 test cancellation or testing delay.

CSF antibodies may be detectable in patients with encephalitis, but it is not a validated specimen type for this test and requires approval. If needed, contact PHO’s customer service for information.

Timing of Specimen Collection

For serology: If a recent infection is suspected following exposure, repeat collection of a convalescent (3-12 weeks later) serum sample may be beneficial since serology may be negative during the acute phase of illness.

Limitations

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

Storage and Transport

For serology: Centrifuge tube if using serum separator tube (SST).

Place specimen container in a biohazard bag and properly seal the bag. Specimens should be stored at 2-8°C and shipped to PHO on ice packs within 48 hours of collection.

All clinical specimens must be shipped in accordance to the Transportation of Dangerous Good Act.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Trichinella antibody testing is referred out to the National Reference Centre for Parasitology (NRCP) in Montreal. Turnaround time for antibody testing is up to 20 calendar days from receipt at PHO.

Trichinella microscopy is performed daily from Monday to Friday at PHO’s laboratory-Toronto. Turnaround time for microscopy is up to 3 calendar days from receipt at PHO.

Test Methods

Trichinella antibody testing is performed at the NRCP using an enzyme-linked immunosorbent assay (ELISA) from purified Trichinella spiralis larval excretory-secretory (ES) antigens. Trichinella microscopy is performed at PHO using direct wet mount, including the “squashed” compression method for muscle biopsies.

Performance and Limitations:
Trichinella antibody testing performance is reported to have 85% sensitivity and 93.8% specificity by the NRCP. In other antibody assays, sensitivity has been reported to range from 70-99% and specificity from 90-96%, with cross-reactivity reported with other helminth infections. Test performance may vary by Trichinella species, inoculation dose, and clinical presentation (e.g. acute gastrointestinal phase versus extraintestinal phase). Serology may be negative in the first two weeks of illness. In clinical cases where there is strong clinical suspicion for trichinellosis and the results are equivocal or low positive, convalescent serum samples demonstrating a significant rise in antibody level over time may be useful to confirm active infection. The assay may remain positive for years after infection and may not be able to distinguish between active, resolved, or recurrent infection.^1-2

Trichinella microscopy sensitivity in muscle biopsies is not well documented in humans but may be under 50% in animal studies. Like serology, microscopy may be negative in the first two weeks of illness, including during the gastrointestinal phase, and may remain positive for years after infection. Detection yield may be higher in sites where the myositis manifestations are most prominent, or from striated muscles with minimal surrounding adipose tissue such as the deltoid, gastrocnemius, or biceps muscles. Otherwise, if tissue material is biopsied, organisms or indirect inflammatory basophilic transformation of muscle cells may be found by histopathology if locally available.^3-4

Interpretation

For Trichinella antibody testing (“Trichinella by EIA – Referred Out”):

Trichinosis Sample Value	Result	Interpretation
≥ 1.2	High Positive	Trichinella antibodies detected. Does not distinguish between species. Cross-reactivity may occur with other helminth infections. May not distinguish between active, resolved, or recurrent infection.
0.35-1.19	Low Positive	Trichinella antibodies detected. Does not distinguish between species. Cross-reactivity may occur with other helminth infections. May not distinguish between active, resolved, or recurrent infection.
0.25-0.34	Equivocal	Trichinella antibody status inconclusive. Clinical/exposure correlation required and repeat testing may be considered if clinically indicated.
< 0.25	Negative	Trichinella antibodies NOT detected. If recent infection is suspected, collection of a convalescent serum sample 3-12 weeks later is recommended to assess for seroconversion.

For Trichinella microscopy (“Parasite microscopy”):

Parasite microscopy	Interpretation
Parasite(s) found Trichinella species	Trichinella infection. Does not distinguish between species. May not distinguish between recent, remote, or recurrent infection.
Parasite(s) not detected	No evidence of Trichinella cysts by microscopy. Does not rule out infection.

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.

Specimens that are positive for Trichinella are reported to the Medical Officer of Health as per Health Protection and Promotion Act.

References

Sun GG, Song YY, Jiang P, Ren HN, Yan SW, Han Y, Liu RD, Zhang X, Wang ZQ, Cui J. Characterization of a Trichinella spiralis putative serine protease. Study of its potential as sero-diagnostic tool. PLoS Negl Trop Dis. 2018 May 14;12(5):e0006485. doi: 10.1371/journal.pntd.0006485. PMID: 29758030; PMCID: PMC5967804.
Yang Y, Cai YN, Tong MW, Sun N, Xuan YH, Kang YJ, Vallée I, Boireau P, Cheng SP, Liu MY. Serological tools for detection of Trichinella infection in animals and humans. One Health. 2016 Mar 4;2:25-30. doi: 10.1016/j.onehlt.2015.11.005. PMID: 28616474; PMCID: PMC5462648.
Barlow A, Roy K, Hawkins K, Ankarah AA, Rosenthal B. A review of testing and assurance methods for Trichinella surveillance programs. Food Waterborne Parasitol. 2021 Aug 9;24:e00129. doi: 10.1016/j.fawpar.2021.e00129. PMID: 34458599; PMCID: PMC8379475.
Gottstein B, Pozio E, Nöckler K. Epidemiology, diagnosis, treatment, and control of trichinellosis. Clin Microbiol Rev. 2009 Jan;22(1):127-45, Table of Contents. doi: 10.1128/CMR.00026-08. PMID: 19136437; PMCID: PMC2620635.