Trichinella – Serology

Testing Indications

This page provides routine serology (antibody) testing information for trichinellosis (also known as trichinosis or trichiniasis) at Public Health Ontario (PHO). The causative agents of trichinellosis include Trichinella spiralis (worldwide), T. pseudospiralis (worldwide), T. nativa (arctic and subarctic regions), T. nelsoni (Africa), T. britovi (Europe, western Asia, Africa), T. murelli (North America, Japan), and T. papuae (Papua New Guinea, Thailand, Cambodia, Taiwan).

The test information described below is limited to serologic testing. For muscle biopsy microscopy, please refer to the following link:

Indications:
Serology is the main non-invasive diagnostic test method available, with muscle biopsy microscopy reserved in cases of diagnostic uncertainty in the parenteral phase. Molecular testing is currently not routinely available in clinical laboratories.

Testing can be considered in patients with relevant risk factors (e.g., exposure to inadequately cooked meat) and development of symptoms within the appropriate incubation period. Trichinellosis usually develops as two phases: an enteral phase (gastrointestinal symptoms 1-7 days after exposure) followed by a parenteral phase (fever, myositis, periorbital edema, eosinophilia, and/or other visceral involvement between 2-8 weeks after exposure).

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.

Test updates (as of November 1, 2022):
Specimens are now routinely forwarded to the National Reference Centre for Parasitology (NRCP) for testing due to the discontinuation of the commercially available serology assay previously used in-house at PHO.

Specimen Collection and Handling

Specimen Requirements

Test Requested Required Requisition(s) Specimen Type Minimum Volume Collection Kit

Trichinella serology 

Serum

5.0 ml blood or 1.0 ml serum

Clotted vacutainer blood tubes (SST)

Submission and Collection Notes

1

Complete all fields of the General Test Requisition Form including:

  1. Test(s) requested and indication for testing
  2. Exposure history (including source of ingested undercooked meat)
  3. Travel history (if applicable)
  4. Clinical information including symptom onset date
  5. Patient setting/population
2

Label the specimen container 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.

Limitations

Haemolysed, icteric, lipemic or microbial contaminated sera are not recommended for testing.

The NRCP reports a sensitivity of 85% and specificity of 93% for their Trichinella serology assay. Serology may be negative in the first two weeks of illness. Serology may remain positive years after resolution of clinical symptoms and may not be able to distinguish active, resolved, or recurrent infection. Serology does not provide speciation of Trichinella species.

Preparation Prior to Transport

Centrifuge tube if using serum separator tube (SST). Place specimen in biohazard bag and seal.

Specimens should be stored at 2-8°C following collection and shipped to the PHO’s laboratory on ice packs as soon as possible.

Special Instructions

An acute (collected early after the onset of symptoms) and a convalescent (collected 4-12 weeks later) may be required for laboratory diagnosis.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Trichinella serology testing is referred out to the NRCP. Testing is performed once per week at the NRCP.

Turnaround time is up to 10 days from receipt at PHO’s laboratory.

Reporting

Results are reported to the ordering physician or health care provider as indicated on the requisition.

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

Test Methods

Trichinella serology is performed at the NRCP using a commercial indirect enzyme immunoassay (ELISA) kit for the detection of antibodies to Trichinella larvae.

Interpretation

Optical Density

Result Interpretation

OD <0.25

Negative

OD ≥0.25 and <0.35

Equivocal

OD ≥0.35 and <1.20

Low Positive

OD ≥1.20

High Positive

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.

Mis à jour le 11 nov. 2022