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