Echinococcosis

Background

• 2 most important forms are cystic and alveolar caused by E. granulosus and E. multilocularis
• Humans are accidental immediate hosts by ingesting parasitic eggs from contaminated food, soil, water, or direct contact with definitive hosts
• Usual intermediate hosts-sheep, goat, swine, cattle, rodents and camel
• Definitive hosts-dogs, cats, fox, and wolves
• Ingested eggs then hatch, penetrate intestinal mucosa, and spread hematogenously to final destination to form cysts

Clinical Features

• Asymptomatic for many years
• Abdominal cysts- pain, distension, nausea and vomiting
• Alveolar abscess-chest pain, shortness of breath, chronic cough
• Musculoskeletal pain, blindness, headache, and stroke like symptoms if involving muscles, bones, eyes or brain

Differential Diagnosis

• Neurocysticercosis

Hepatic abscess

• Pyogenic abscess
  • Aerobic: Escherichia coli, Klebsiella, Pseudomonas
  • Anaerobic: Enterococcus, bacteroides, anaerobic streptococci
• Echinococcosis
• Amebiasis
• Benign cysts/malignancy
• Tuberculosis
• Mycosis

Evaluation

Work-up

• Abdominal Ultrasound (most widely used)
• CT
• MRI
• ELISA-sensitivity inversely related to antigen sequestration in cysts
• Percutaneous aspiration

Management

• Tissue stage/hydatid disease: albendazole 400mg BID x 28 days, repeat as needed every 2 weeks x 3 cycles
• Surgical removal
  • Do not aspirate cysts (risk of seeding disease or anaphylactoid reaction from spillage of hydatid sand which contains antigenic proteins)
  • PAIR (Percutaneous aspiration, injection, reaspiration)
    • Inject with 95% ethanol or hypertonic saline, leave in for 15 minutes, then reaspirate

Disposition

• Discharge (if no significant clinical complications)

See Also

• Tapeworm
• Helminth infections
• Travel medicine
• Parasitic diseases

References

Authors

Silas Chiu, Ross Donaldson, Michael Holtz, Daniel Ostermayer, Neil Young