Echinococcus Species - Echinococcus

Indications for Testing

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

Laboratory Testing

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

Imaging Studies

MRI/US are valuable in cyst detection

Differential Diagnosis

Hepatic mass
- Entamoeba histolytica
- Hepatic cyst
- Inferior vena cava thrombosis
- Liver abscess
- Intra abdominal sepsis
- Budd-Chiari syndrome
- Hepatocellular carcinoma
- Schistosoma spp
Pulmonary mass
- Lung tumor
- Lung abscess
CNS mass
- Brain tumor
- Brain abscess
- Taenia solium

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

Three species – E. granulosus, E. multilocularis and E. vogeli
Minute tapeworm, E. granulosus, develops in the intestine of dogs and other Canidae; prevalent where livestock are raised in association with dogs
Larval stage (hydatid cyst) may be found in many mammals (cattle, sheep, hogs, man) when the eggs are ingested
Adult worm is present only in dogs
Cysts develop in intermediate hosts (human, sheep, cattle, goats)
Hydatid cysts may form in any organ or tissue in humans; most commonly seen in the liver, lung and central nervous system
- In humans, the embryo develops slowly into hydatid cysts, reaching a diameter of 1 cm in ~5 years; at the end of ≥10 years, may contain liters of fluid
- Cysts vary considerably in size, depending on their age and location
  - Cysts 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

Classic presentation is cysts in various organs (almost exclusively pulmonary and hepatic cysts)
Hepatic disease is the most common presentation and may present as abdominal pain or a palpable right upper quadrant mass (~2/3 of patients)
Lungs are the second most common site of cyst involvement
Rupture of cysts leads to multifocal dissemination

Treatment

Percutaneous aspiration, infusion of scolicidal agents with reaspiration, surgery

Prevention

Strict dog-control programs in endemic areas

Tests generally appear in the order most useful for common clinical situations

Test name: Echinococcus Antibody, IgG

ARUP #: 0050250

Methodology: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Use:

Confirm suspicion of Echinococcus parasite infection

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

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

The best evidence for infection is a significant change on two appropriately timed specimens where both tests are done in the same laboratory at the same time

Guidelines

Brunetti E, Kern P, Vuitton DA. Expert consensus for the diagnosis and treatment of cystic and alveolar echinococcosis in humans. Acta Trop. 2010; 114 (1) :1-16.PubMed

General

Hill, Harry R., MD. Group Medical Director, Laboratory of Immunology, ARUP Laboratories, and Executive Director of the ARUP Institute for Clinical and Experimental Pathology; Professor and Division Head, Pathology (Clinical), University of Utah

Comprehensive Review: July 2011
Last Update: July 2011

Central Nervous System Tumors

Hepatocellular Carcinoma

Schistosoma Species