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.
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
- Infection
- 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
- Cystic disease
- 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 Laboratory Tests
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
Collagen vascular diseases, hepatic cirrhosis, schistosomiasis, and other parasitic infections can produce false-positive results
Strong cross-reaction between echinococcosis and cysticercosis positive sera
Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Medical Experts
Couturier

Slev

References
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Brunetti E, Kern P, le Vuitton DA, et al. Expert consensus for the diagnosis and treatment of cystic and alveolar echinococcosis in humans. Acta Trop. 2010;114(1):1-16.
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McManus DP, Gray DJ, Zhang W, et al. Diagnosis, treatment, and management of echinococcosis. BMJ. 2012; 344:e3866.