Echinococcus Species - Echinococcosis Infection

Echinococcosis infection is a zoonosis caused in humans by the larval stage of cestodes belonging to the genus Echinococcus.Imaging techniques, such as CT scans, ultrasonography, and MRIs, are used to detect cysts, suggestive of cystic echinococcosis. After a cyst has been detected, serologic tests may be used to confirm the diagnosis.

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Clinical Overview

Diagnosis

Indications for Testing

Patient from endemic area with abdominal pain
Clinical evidence by magnetic resonance imaging (MRI)/ultrasound (US) may provide support for testing

Laboratory Testing

Diagnosis of Echinococcosis infection (CDC)
Serum antibody screening – ELISA, IFA, hemagglutination, latex agglutination
- ELISA and IFA – most sensitive testing methods
- Positive antibody response occurs in 90% of liver cysts but only in 50% of lung cysts
Diagnosis recommended prior to any surgery
- Aspiration of cysts for diagnosis is discouraged – may result in fluid leakage and dissemination

Imaging Studies

MRI/US – valuable in cyst detection

Differential Diagnosis

Hepatic mass
- Infection
  - Entamoeba histolytica
  - Hepatic abscess
  - Mycobacterium tuberculosis
  - Intra-abdominal sepsis
  - Schistosoma spp
- Hepatic cyst
- Hepatocellular carcinoma
- Budd-Chiari syndrome
- Hemangioma
Pulmonary mass
- Infection – lung abscess
- Lung tumor
- Mycobacterium tuberculosis
Central nervous system (CNS) mass
- Brain tumor
- Brain abscess
- Taenia solium

Background

Epidemiology

Incidence
- Cystic disease
  - 1-200/100,000
  - Endemic in Eurasia, South America, and Africa
  - In North America, most cases occur in immigrants from endemic countries
- Alveolar disease
  - 0.03-1.2/100,000
  - Restricted to northern hemisphere, particularly regions of China, Russian Federation, continental Europe, and North America
Transmission – fecal-oral route

Organism

4 species in humans – E. granulosus, E. multilocularis, E. vogeli, E. oligarthus
- E. granulosus (cystic) and E. multilocularis (alveolar) most common
Minute tapeworm, E. granulosus, develops in the intestine of dogs and other Canidae
- Prevalent where livestock raised in association with dogs
- Adult worm present only in dogs
Larval stage (hydatid cyst) – found in many mammals (eg, cattle, sheep, hogs, humans) when the eggs are ingested
Cysts develop in intermediate hosts (eg, humans, sheep, cattle, goats)
Hydatid cysts may form in any organ or tissue in humans – most commonly seen in liver, lung, and central nervous system (CNS)
- In humans, the embryo develops slowly into hydatid cysts
- Cysts vary considerably in size, depending on their age and location
  - May reach a diameter of 1 cm in ~5 years
  - May contain liters of fluid after ≥10 years
  - May or may not be able to expand freely depending on location in body
  - In some cases, even a modest growth results in serious impairment to function of vital structures or death

Clinical Presentation

Initial phase – asymptomatic
Classic presentation – cysts in various organs
- Symptoms depend on cyst location(s)
- Almost exclusively pulmonary and hepatic cysts (extrahepatic disease rare with E. multilocularis)
- Hepatic disease – most common presentation
  - May present as abdominal pain or a palpable right upper quadrant mass
  - Significant symptoms unusual until cyst grows >10 cm
- Lungs – second most common presentation
  - Cough, chest pain, hemoptysis
- Other organs – heart, CNS, kidney, bone, ocular cysts
Rupture of cysts leads to multifocal dissemination – patients may suffer fatal hypersensitivity reactions

ARUP Lab Tests

Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Echinococcus Antibody, IgG 2007220
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Recommended Use

Adjunct to other diagnostic tests (eg, imaging) for echinococcosis

Patient's travel history is necessary to aid in test interpretation

Seroconversion between acute and convalescent sera considered strong evidence of recent infection

Best evidence for infection is a significant change on 2 appropriately timed specimens when both tests are performed in same laboratory at same time

Limitations

Collagen vascular diseases, hepatic cirrhosis, schistosomiasis, and other parasitic infections can produce false-positive results

Strong cross-reaction between echinococcosis and cysticercosis positive sera

Medical Experts

Couturier, Marc Roger, PhD, D(ABMM), Medical Director, Microbial Immunology, Parasitology and Fecal Testing, and Infectious Disease Antigen Testing at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

Slev, Patricia R., PhD, Laboratory Section Chief, Immunology, at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah

References

Guidelines

Brunetti E, Kern P, le 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. PubMed

General References

Brunetti E, Junghanss T. Update on cystic hydatid disease. Curr Opin Infect Dis. 2009; 22(5): 497-502. PubMed

Carmena D, Benito A, Eraso E. The immunodiagnosis of Echinococcus multilocularis infection. Clin Microbiol Infect. 2007; 13(5): 460-75. PubMed

Filippou D, Tselepis D, Filippou G, Papadopoulos V. Advances in liver echinococcosis: diagnosis and treatment. Clin Gastroenterol Hepatol. 2007; 5(2): 152-9. PubMed

Ito A, Nakao M, Sako Y. Echinococcosis: serological detection of patients and molecular identification of parasites. Future Microbiol. 2007; 2(4): 439-49. PubMed

McManus DP, Gray DJ, Zhang W, Yang Y. Diagnosis, treatment, and management of echinococcosis. BMJ. 2012; 344: e3866. PubMed

Last Update: July 2018