Echinococcosis – Serology

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Background
This document provides routine serology (antibody) testing information for echinococcosis (also known as hydatid disease) at Public Health Ontario’s (PHO) laboratory. The causative agent of cystic echinococcosis (CE) include E. granulosus complex (includes E. granulosus sensu stricto, E. equinus, E. ortleppi, and E. canadensis). The causative agent of alveolar echinococcosis (AE) is E. multilocularis. The causative agents of neotropical echinococcosis (NE) include E. vogeli and E. oligarthrus.

The test information described here is limited to serologic testing. For microscopy or PCR examination, please refer to our Echinococcus – Cyst webpage.

Update

As of May 1, 2023, Echinococcus granulosus (or species unspecified) requests are forwarded to the National Reference Centre for Parasitology (NRCP) due to the discontinued distribution of the commercial RIDASCREEN Echinococcus IgG ELISA. Turnaround time has been extended from 10 days to up to 15 days.

* Copie d'impression non contrôlée. Valide uniquement le jour de l'impression : 21 nov. 2024.

Testing Indications

Serologic testing is advised for individuals with compatible exposure history and clinical presentation for AE or CE. If cyst tissue samples are available, they should be additionally tested by microscopy for confirmation. Imaging and microscopy remains the primary modality for diagnosis of NE as test performance for NE cases is unknown.

CE is found worldwide and is acquired by ingestion of embryonated eggs from dogs (and less commonly fox, dingo, jackal, or hyena) or from the surrounding environment. It may present as a fluid-filled unilocular tissue cyst with concentric expansion and internal daughter cysts. AE is primarily found in North America and North/Central Eurasia and is acquired by ingestion of embryonated eggs from foxes (and frequently racoon dogs, dogs, or cats) or from the surrounding environment. It may present as a mucoid multilocular tissue cyst with excentric proliferation and metastases. NE is rarely reported in Central and South America and is acquired by ingestion of embryonated eggs from dogs or their surrounding environment. It may present as a fluid-filled multilocular tissue cyst with excentric proliferation (E. vogeli) or concentric expansion (E. oligarthrus).

AE is a Disease of Public Health Significance (DOPHS) under the Health Protection and Promotion Act (HPPA). Additional testing and management recommendations are stated in the Ontario Ministry of Health Infectious Disease Protocol Appendix 1 for Disease: Echinococcus multilocularis infection.

Acceptance/Rejection Criteria

E. granulosus (or species unspecified): All samples meeting the specimen collection instructions below will be accepted for testing.
E. multilocularis: Testing is only performed upon approval by PHO’s microbiologist. Contact PHO’s customer service (416-235-6556, 1-877-604-4567, or customerservicecentre@oahpp.ca) for approval.

Specimen Collection and Handling

Specimen Requirements

Test Requested	Required Requisition(s)	Specimen Type	Minimum Volume	Collection Kit
Echinococcus or hydatid serology	General Test Requisition	Serum	5.0 ml blood or 1.0 ml serum	Blood, clotted – vacutainer tubes (SST)
Echinococcus granulosus or cystic hydatid serology	General Test Requisition	Serum	5.0 ml blood or 1.0 ml serum	Blood, clotted – vacutainer tubes (SST)
Echinococcus multilocularis or alveolar hydatid serology	General Test Requisition	Serum	5.0 ml blood or 1.0 ml serum	Blood, clotted – vacutainer tubes (SST)

Submission and Collection Notes

Complete all fields of the General Test Requisition form, including:

Test(s) requested and indication for testing
Exposure history
Clinical information including symptom onset date or if asymptomatic
Patient setting/population

Where known, specify whether the patient is suspected of cystic (E. granulosus) or alveolar (E. multilocularis) hydatid disease,as the type of test differs (see Algorithm below).

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.

Storage and 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 on ice packs to PHO’s laboratory as soon as possible.

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

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Echinococcus granulosus (or species unspecified) serology testing is forwarded to the NRCP, where testing is performed once per week. Turnaround time is up to 15 days from receipt at PHO’s laboratory.

If approved by a PHO microbiologist, Echinococcus multilocularis serology testing is performed and forwarded to Institute for Infectious Diseases (IFIK) Parasitology Laboratory at the University of Berne, Switzerland. Turnaround time is up to 45 days from receipt at PHO’s laboratory.

Test Methods

Echinococcus granulosus serology is performed at the NRCP using a commercial indirect enzyme-linked immunosorbent assay (ELISA) kit for the detection of antibodies to Echinococcus species. The assay provides a semi-quantitative value based on the optical density of the assay signal.

Echinococcus multilocularis serology is referred out to the IFIK Parasitology Laboratory at the University of Berne, Switzerland. E. multilocularis testing at IFIK uses a two-step approach. First, a panel of three parallel laboratory-developed ELISAs are performed to screen for E. granulosus (EgHF-ELISA) and E. multilocularis (Em2-ELISA and recEm18-ELISA). If any are positive, confirmatory testing is performed by Western blot to further discriminate between E. granulosus and E. multilocularis.

Algorithm

If E. granulosus (or species unspecified) is requested, samples will be forwarded to NRCP for testing and results will be returned to PHO’s laboratory to be reported to the physician.

If E. multilocularis is requested, approval by a PHO microbiologist is required prior to testing. If approved, sample will be forwarded to the IFIK in Berne, Switzerland for testing.

Interpretation

For NRCP referred out testing results:

*Echinococcus* species ELISA Optical Density (OD) Ranges	Result
< 0.35	Negative
≥ 0.35 and < 0.45	Equivocal
≥ 0.45 and < 1.20	Low Positive
≥ 1.20	High Positive

For IFIK referred out testing result:

EgHF-ELISA	Em2-ELISA	recEm18-ELISA	EgHF-Westernblot	EmVF-Westernblot	Interpretation
Negative	Negative	Negative	Not performed	Not performed	No antibodies detectable against Echinococcus spp.
Positive	Negative or Positive	Negative or Positive	Positive	Negative	Antibodies detected indicate CE (cystic echinococcosis)
Positive	Negative or Positive	Negative or Positive	Negative	Negative	Non-specific antibody reaction
Negative or Positive	Positive	Negative or Positive	Negative	Positive	Antibodies detected indicate AE (alveolar echinococcosis)
Negative or Positive	Positive	Negative or Positive	Negative	Negative	Non-specific antibody reaction
Negative or Positive	Negative or Positive	Positive	Negative	Positive	Antibodies detected indicate AE (alveolar echinococcosis)
Negative or Positive	Negative or Positive	Positive	Negative	Negative	Non-specific antibody reaction

Test Performance
NRCP Echinococcus species ELISA: Performance has been primarily studied for E. granulosus hepatic cysts, with reported sensitivity of 75-85% for CE1 cysts, 89-97% for CE2 or CE3 cysts, and 33-57% for CE4 or CE5 cysts.^1,2 Sensitivity decreases to 50 to 60% for E. granulosus lung cysts.³ Sensitivity for other isolated cyst locations is not well established and varies depending on reported case series, e.g. about 80% for E. granulosus splenic cysts._^4-7 Overall specificity has been reported between 90.6% to 96%.¹ Test performance has not been well established for E. multilocularis. Although likely to cross-react, if E. multilocularis is specifically suspected, it must be specifically requested in order for ELISA testing to be performed using more accurate E. multilocularis-specific antigens (e.g. Em2 and recEm18).

IFIK E. multilocularis panel: The performance of the panel of assays is described by IFIK as 93% sensitivity and >98% specificity with overall 95% accurate speciation.

Test Limitations
NRCP Echinococcus species ELISA: Early, small, calcified, degenerative, or non-hepatic cysts may have lower sensitivity. Performance may be affected by immunosuppression. The assay does not distinguish between E. granulosus and E. multilocularis. The assay has not been evaluated for E. vogeli or E. oligarthrus and may be negative. Cross-reactivity has been described with other helminths including Taenia, Schistosoma, Strongyloides, and filarial nematodes. Serology may remain positive for years after therapy and may not be able to distinguish between active, resolved, or recurrent infection.

IFIK E. multilocularis panel: Performance may be affected by immunosuppression or treatment. The assay has not been evaluated for E. vogeli or E. oligarthrus and may be negative.

Reporting

Results are received back at PHO’s laboratory, and reports are forwarded to the ordering physician or authorized health care provider (General O. Reg 45/22, s.18), or submitter as indicated on the requisition.

Specimens that are positive for E. multilocularis are to be reported to the Medical Officer of Health as per the Ontario Health Protection and Promotion Act.

References

Tamarozzi F, Covini I, Mariconti M, Narra R, Tinelli C, De Silvestri A, et al. Comparison of the diagnostic accuracy of three rapid tests for the serodiagnosis of hepatic cystic Echinococcosis in humans. PLoS Negl Trop Dis. 2016;10(2):e0004444. Available from: https://doi.org/10.1371/journal.pntd.0004444
Tamarozzi F, Silva R, Fittipaldo VA, Buonfrate D, Gottstein B, Siles-Lucas M. Serology for the diagnosis of human hepatic cystic Echinococcosis and its relation with cyst staging: a systematic review of the literature with meta-analysis. PLoS Negl Trop Dis. 2021;15(4):e0009370. Available from: https://doi.org/10.1371/journal.pntd.0009370
Brunetti E, Kern P, Vuitton DA; Writing Panel for the WHO-IWGE. Expert consensus for the diagnosis and treatment of cystic and alveolar Echinococcosis in humans. Acta Trop. 2010;114(1):1-16. Available from: https://doi.org/10.1016/j.actatropica.2009.11.001
Mejri A, Arfaoui K, Ayadi MF, Aloui B, Yaakoubi J. Primitive isolated hydatid cyst of the spleen: total splenectomy versus spleen saving surgical modalities. BMC Surg. 2021;21(1):46. Available from: https://doi.org/10.1186/s12893-020-01036-8
Culafić DM, Kerkez MD, Mijac DD, Lekić NS, Ranković VI, Lekić DD, et al. Spleen cystic Echinococcosis: clinical manifestations and treatment. Scan J Gastroenterol. 2010;45(2):186-90. Available from: https://doi.org/10.3109/00365520903428598
Kalinova K, Stefanova O, Bosheva M. Surgery in children with hydatid disease of the spleen. J Pediatr Surg. 2006;41(7):1264-6. Available from: https://doi.org/10.1016/j.jpedsurg.2006.03.005
Ben Ameur H, Affes N, Abdelhedi C, Kchaou A, Boujelbene S, Beyrouit MI. Hydatid cyst of the spleen: Tunisian series of 21 cases. Indian J Surg. 2015;77(Suppl 2):515-9. Available from: https://doi.org/10.1007/s12262-013-0905-5

* Copie d'impression non contrôlée. Valide uniquement le jour de l'impression : 21 nov. 2024.

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Mis à jour le 4 mai 2023