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.
Tabs Content 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
Pulmonary mass
Infection – lung abscess Lung tumor Mycobacterium tuberculosis Central nervous system (CNS) mass
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
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
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, Section Chief, Immunology; Medical Director, Serologic Hepatitis and Retrovirus and Immunology Core Laboratory; Co-Medical Director, Microbial Immunology, at ARUP Laboratories; Associate Professor of Clinical Pathology, University of Utah
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
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