Helminth

Echinococcosis

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Echinococcosis, Echinococcus Granulosus, Echinococcus, Hydatid Disease

  • See Also
  1. Alveolar Hydatid Disease
  2. Helminth
  3. Parasitic Infection
  • Epidemiology
  1. Endemic worldwide in sheep raising areas
    1. Mediterranean
    2. Prior Soviet Union block nations
    3. Australia
    4. South America
    5. Africa
  2. U.S. sources
    1. Immigrants to North America
    2. Western U.S. sheep farmers
    3. Southwestern Native Americans
    4. Native Inuits in Alaska and Canada (Caribou, wolves)
    5. Some cases along Mississippi
  • Pathophysiology
  1. Echinococcus Granulosus infection
    1. Infections in Human by ingestion of Tapeworm eggs
    2. Eggs hatch in the Intestine, releasing Tapeworm larvae
    3. Larvae invade across the intestinal wall, and metastasize throughout the body (see sites below)
    4. Larvae form single, round fluid-filled cysts (hydatid cysts) within infected tissue
      1. Similar cyst development to Taenia Solium (Cysticercosis)
      2. Larvae reproduce asexually within the cyst via asexual budding
      3. Smaller cysts (protoscolices) form within the original cyst
      4. Cysts grow at 1-5 cm per year, up to 5-10 cm and may cause mass-effect related findings
    5. Cyst contents are highly immunogenic
      1. Cyst rupture may cause severe Allergic Reactions and Anaphylaxis (may be fatal)
  2. Transmission
    1. Definitive Host: Dogs and other carnivores
    2. Intermediate host: Human, Sheep, Cattle
  3. Sites of involvement
    1. Liver (most common)
    2. Lung (second most common)
    3. Kidney
    4. Muscle
    5. Spleen
    6. Brain
    7. Bone
  • Symptoms
  1. Asymptomatic in 60% of cases (for 10-20 years)
  2. Cough
  3. Abdominal mass
  4. Hemoptysis
  5. Chest Pain
  • Complications
  1. Cyst rupture
    1. Anaphylactic reaction
    2. Pyopneumothorax
    3. Mediastinal erosion
  • Labs
  1. Complete Blood Count
    1. Eosinophilia may be present
  2. Skin test
    1. Casoni's Antigen
  3. Echinococcus serologic titer
    1. Test Sensitivity: 50% of lung infections
    2. EITB has highest sensitivity and Specificity
  4. Fine needle aspiration of cyst
    1. Tapeworm parts and Eosinophilic granules
  • Imaging
  1. Abdominal Ultrasound or CT: Liver or Kidney Cysts
  2. Chest XRay: Lung cysts
    1. Size: 1-10 cm in diameter
    2. Lower lobes and right side more commonly involved
    3. Consider CT Chest or MRI Chest
  • Management
  1. Surgical excision of cysts
    1. Pretreatment with Albendazole or Mebendazole may be recommended
    2. Avoidance of spilling cyst contents during surgery (may trigger life-threatening Allergic Reaction)
    3. Cysts may be aspirated, instilled with Ethanol (or similar) and then resected
  2. Inoperable cysts may undergo CT guided PAIR Treatment (in combination with antihelminth agents)
    1. Percutaneous aspiration
    2. Infusion of Ethanol
    3. Reaspiration
  3. Anti-Helminth agents (used concurrently with surgery)
    1. Albendazole (Albenza)
    2. Mebendazole (Vermox, Emverm)
  • Prevention
  • Education program in endemic areas
  1. Carefully wash fruits and vegetables before ingestion
  2. Avoid water potentially contaminated by dog feces
  3. Hand Washing after soil exposure
  4. Treat dogs frequently with worming formulations (e.g. niclosamide)
  5. Avoid feeding dogs the entrails of livestock
  • Prognosis
  1. Mortality as high as 4-5% in untreated patients
  • References
  1. Chrieki (2002) Am Fam Physician 66(5):817-20 [PubMed]