Echinococcus Species

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Patient from endemic area with abdominal pain
  • Clinical evidence by 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

Echinococcosis infection is a zoonosis caused in humans by the larval stage of cestodes belonging to the genus Echinococcus.

Epidemiology

  • Incidence – 1-200/100,000 for cystic disease; 0.03-1.2/100,000 for alveolar disease
    • Endemic in Eurasia, South America, and Africa
    • In North America, most cases occur in immigrants from endemic countries
  • Transmission – fecal-oral route

Organism

  • Four species in humans – E. granulosus, E. multilocularis, E. vogeli, E. oligarthus
    • E. granulosus and E. multilocularis 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 the liver, lung, central nervous system
    • 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
        • At the end of ≥10 years, may contain liters of fluid
      • May or may not be able to expand freely depending on the location in the body
      • In some cases, even a modest growth will result in serious impairment to the function of vital structures and even 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

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

Limitations

Patients with collagen vascular diseases, hepatic cirrhosis, schistosomiasis, and other parasitic infections may have false-positive results

Strong cross-reaction between echinococcosis and cysticercosis positive sera

Guidelines

Brunetti E, Kern P, le Vuitton DAngè, 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

Medical Reviewers

Last Update: June 2016