Fasciola (Fascioliasis) – Microscopy and Antibody
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 and antibody (serology) testing information for fascioliasis at Public Health Ontario (PHO). The causative agents of fascioliasis are the parasitic liver trematodes (“flukes”) Fasciola hepatica and Fasciola gigantica.
For identification of extracted worms or worm segments, refer to the following PHO webpage: Worm (Whole or Segment) – Identification.
Updates
This webpage has been merged with the Fasciola- Serology webpage and updated to include revisions to the background, testing indications, acceptance criteria, performance and limitations, interpretations, and expected turnaround times, which are now expressed in calendar days instead of business days.
Testing Indications
Microscopy and serology are indicated for the diagnosis of individuals with compatible clinical and epidemiological evidence of fascioliasis- such as hepatobiliary or ectopic manifestations following ingestion of undercooked aquatic plants from endemic regions.
Note: Currently, antigen detection and PCR-based testing for Fasciola species are not available at PHO.
Acceptance/Rejection Criteria
- Testing will only be accepted when both of the following are documented on the requisition:
- Aquatic plant ingestion (e.g. watercress)
- Signs or symptoms compatible with fascioliasis
- Enteric specimens received without sodium acetate, acetic acid, and formalin (SAF) preservation are ineligible and will be cancelled.
- If submitting multiple enteric specimens with the same collection date, only one will be tested. If multiple specimens are collected, these should be collected at least 1 to 2 days apart, for all to be eligible for testing.
- Specimens are only accepted if originating from human sources. Specimens submitted from animal sources (e.g. pets) or environmental sources (e.g. food) will be rejected.
Specimen Requirements
| Test Requested | Required Requisition(s) | Specimen Type | Minimum Volume | Collection Kit |
Fasciola - Microscopy |
Enteric specimens (e.g., stool, intestinal biopsy / aspirate) |
1.0 ml |
SAF vial |
|
Fasciola - Microscopy |
Other body fluid or tissue specimens (e.g. aspirates, biopsies) |
1.0 ml (fluids) |
SAF or empty sterile vial |
|
Fasciola - Antibody |
Blood or serum |
5.0 ml whole blood or 1.0 ml serum |
Blood, clotted – vacutainer tubes (SST) |
Submission and Collection Notes
Complete all fields of the requisition form.
Important: Specify both of the following testing indications on the requisition. Failure to provide this information may result in rejection:
- Aquatic plant ingestion
- Signs or symptoms compatible with fascioliasis
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 specimens: Microscopy may be negative within the first 2 months post-exposure due to the prepatent period, including the acute migratory hepatic phase of fascioliasis.
Limitations
For serology: 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.
Test Frequency and Turnaround Time (TAT)
Microscopy 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.
Serology is forwarded to the National Reference Centre for Parasitology (NRCP) in Montreal. Turnaround time is up to 42 calendar days from receipt at PHO.
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 the NRCP using a laboratory-developed enzyme-linked immunoassay (ELISA) based on antibody capture using the recombinant Fasciola hepatica immature and adult cathepsin L5 (FhCatL5 or FhCL5) excretory-secretory antigen.
Performance and Limitations:
Microscopy is usually negative during the prepatent acute migratory liver phase of infection. During the chronic biliary phase, sensitivity of a single enteric 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 cannot distinguish between species of the Fasciola genus; submission of the adult worm is needed to provide further species level identification. In some situations, ingestion of liver products containing Fasciola adults or eggs may lead to the non-pathogenic transient (or “spurious”) passage of Fasciola eggs in the gastrointestinal tract without infection. If the patient recently ingested liver products, clinical correlation and repeat testing several days after a liver-free diet may be advised to rule out spurious passage. 1-4
For serology, the NRCP reports a sensitivity and specificity of > 95% for F. hepatica infection. There is limited data on its performance in F. gigantica infection, although other assays using similar antigenic variants suggest potential cross-reactivity between both species. Cross-reactivity may occur with other infections (e.g. Toxocara, Trichinella). Serology may be negative very early in infection. There is also limited data on post-treatment serological response, but other assays in humans and animals have described decrease in antibody titres in most cases by 2 months.3-12
Interpretation
Microscopy:
| Helminth Microscopy |
Interpretation |
|---|---|
|
Helminth(s) found: |
The organism stage(s) will be reported. Species level identification cannot be made via the ova stage but only via the adult worms. If the patient recently ingested liver products, clinical correlation and repeat testing several days after a liver-free diet may be advised to rule out spurious passage. If a true infection is suspected, assessment of close contacts sharing a similar diet (e.g. household members) is recommended. |
|
No helminths found |
No evidence of Fasciola ova. Due to the limited test sensitivity, testing of additional specimens may be considered if clinically indicated. |
Serology:
| ELISA Optical Density (OD) Value |
Interpretation |
Comments |
|---|---|---|
|
≥ 0.50 |
Positive |
Fasciola antibodies detected. Does not distinguish current from resolved or past infection. Cross-reactivity may occur with other helminths. Clinical correlation required. If a true infection is suspected, assessment of close contacts sharing a similar diet (e.g. household members) is recommended. |
|
0.40 to 0.49 |
Equivocal |
Inconclusive results. Repeat collection if clinically indicated. |
|
< 0.40 |
Negative |
Fasciola antibodies NOT detected. |
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
- Cosme A, Ojeda E, Cilla G, Torrado J, Alzate L, Beristain X, Orive V, Arenas J. Fasciolasis hepatobiliar. Estudio de una serie de 37 pacientes [Fasciola hepatica. study of a series of 37 patients]. Gastroenterol Hepatol. 2001 Oct;24(8):375-80. Spanish. doi: 10.1016/s0210-5705(01)70204-x. PMID: 11674955.
- Sayasone S, Utzinger J, Akkhavong K, Odermatt P. Repeated stool sampling and use of multiple techniques enhance the sensitivity of helminth diagnosis: a cross-sectional survey in southern Lao People's Democratic Republic. Acta Trop. 2015 Jan;141(Pt B):315-21. doi: 10.1016/j.actatropica.2014.09.004. Epub 2014 Sep 16. PMID: 25225157.
- World Health Organization. Report of the WHO Informal Meeting on use of triclabendazole in fascioliasis control, WHO headquarters, Geneva, Switzerland, 17–18 October 2006. Available online at: https://www.who.int/publications/i/item/WHO-CDS-NTD-PCT-2007.1
- Nguyen Thu H, Dermauw V, Tran Huy T, Roucher C, Dorny P, Nguyen Thi H, Trung KH, Dao Van T, Do Nhu B, Nguyen Kim T. Diagnosing Human Fascioliasis Using ELISA Immunoassays at a Tertiary Referral Hospital in Hanoi: A Cross-Sectional Study. Trop Med Infect Dis. 2022 May 17;7(5):76. doi: 10.3390/tropicalmed7050076. PMID: 35622703; PMCID: PMC9147183.
- Drescher G, de Vasconcelos TCB, Belo VS, Pinto MMDG, Rosa JO, Morello LG, Figueiredo FB. Serological diagnosis of fasciolosis (Fasciola hepatica) in humans, cattle, and sheep: a meta-analysis. Front Vet Sci. 2023 Aug 31;10:1252454. doi: 10.3389/fvets.2023.1252454. PMID: 37736397; PMCID: PMC10509555.
- Cornelissen JB, Gaasenbeek CP, Borgsteede FH, Holland WG, Harmsen MM, Boersma WJ. Early immunodiagnosis of fasciolosis in ruminants using recombinant Fasciola hepatica cathepsin L-like protease. Int J Parasitol. 2001 May 15;31(7):728-37. doi: 10.1016/s0020-7519(01)00175-8. PMID: 11336755.
- Morphew RM, Wright HA, Lacourse EJ, Porter J, Barrett J, Woods DJ, Brophy PM. Towards delineating functions within the fasciola secreted cathepsin l protease family by integrating in vivo based sub-proteomics and phylogenetics. PLoS Negl Trop Dis. 2011 Jan 4;5(1):e937. doi: 10.1371/journal.pntd.0000937. PMID: 21245911; PMCID: PMC3014944.
- Martínez-Sernández V, Perteguer MJ, Hernández-González A, Mezo M, González-Warleta M, Orbegozo-Medina RA, Romarís F, Paniagua E, Gárate T, Ubeira FM. Comparison of recombinant cathepsins L1, L2, and L5 as ELISA targets for serodiagnosis of bovine and ovine fascioliasis. Parasitol Res. 2018 May;117(5):1521-1534. doi: 10.1007/s00436-018-5809-7. Epub 2018 Mar 21. PMID: 29564626; PMCID: PMC7088297.
- López Corrales J, Cwiklinski K, De Marco Verissimo C, Dorey A, Lalor R, Jewhurst H, McEvoy A, Diskin M, Duffy C, Cosby SL, Keane OM, Dalton JP. Diagnosis of sheep fasciolosis caused by Fasciola hepatica using cathepsin L enzyme-linked immunosorbent assays (ELISA). Vet Parasitol. 2021 Oct;298:109517. doi: 10.1016/j.vetpar.2021.109517. Epub 2021 Jul 6. PMID: 34271318.
- Hillyer GV, Soler de Galanes M. Identification of a 17-kilodalton Fasciola hepatica immunodiagnostic antigen by the enzyme-linked immunoelectrotransfer blot technique. J Clin Microbiol. 1988 Oct;26(10):2048-53. doi: 10.1128/jcm.26.10.2048-2053.1988. PMID: 3182993; PMCID: PMC266814.
- Apt W, Aguilera X, Vega F, Miranda C, Zulantay I, Perez C, Gabor M, Apt P. Treatment of human chronic fascioliasis with triclabendazole: drug efficacy and serologic response. Am J Trop Med Hyg. 1995 Jun;52(6):532-5. doi: 10.4269/ajtmh.1995.52.532. PMID: 7611560.
- Martínez-Moreno A, Jiménez V, Martínez-Cruz MS, Martínez-Moreno FJ, Becerra C, Hernández S. Triclabendazole treatment in experimental goat fasciolosis: anthelmintic efficacy and influence in antibody response and pathophysiology of the disease. Vet Parasitol. 1997 Jan;68(1-2):57-67. doi: 10.1016/s0304-4017(96)01067-9. PMID: 9066052.
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