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

• Pyogenic abscess
• Amebiasis
• Benign cysts/malignancy
• Tuberculosis
• Mycosis
• Cysticercosis (brain)

Workup

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

Management

• Tissue stage/hydatid disease: albendazole 400 mg 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

• Home if no complications

Sources

• McManus DP, Zhang W, Li J, Bartley PB. Echinococcosis. Lancet. 2003 Oct 18;362(9392):1295-304.
• Moro P, Schantz P. Echinoccococis: A Review. International Journal of Infectious Disease. (2009) 13, 125-133.
• WHO factsheet Echinococccosis updated March 2014 http://www.who.int/mediacentre/factsheets/fs377/en/