Parasite
Echinococcus granulosus
Hydatid cyst tapeworm of dogs and sheep
eh-kye-noh-KOK-us gran-yoo-LOH-sus
High-yield clue
Dog is the definitive host and sheep the intermediate host; humans ingest eggs and develop slow-growing hydatid cysts, often in the liver.
Overview
A tiny dog tapeworm whose larval stage forms large fluid-filled hydatid cysts in intermediate hosts, the classic study model for cystic echinococcosis.
Classification
- Cestode (tapeworm)
- Tiny adult in canine definitive host
- Sheep/livestock intermediate host
- Larval hydatid cyst in humans
Lab & identification clues
- Hydatid cyst with daughter cysts on imaging vocabulary
- Protoscoleces / 'hydatid sand' concept
- Serology for cyst antigens
Associations
- Dog-sheep cycle, egg ingestion from canine feces
- Liver and lung hydatid cysts
- Risk of anaphylaxis if a cyst ruptures (teaching point)
- Sheep-raising region epidemiology
Commonly confused with
- Taenia species
- Diphyllobothrium latum
Your notes
Original student-study summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment, dosing, or specimen-handling guidance.