Hydatid cysts are associated with which parasite type?

• A. Tapeworms
• B. Nematodes
• C. Trematodes
• D. Protozoa

Answer: (A)

Hydatid cysts are a result of infection with tapeworms (cestodes), specifically the Echinococcus species. In this life cycle, adult tapeworms reside in the intestines of a definitive host (like a dog or fox) and release eggs in the feces. When an intermediate host—or a person—ingests those eggs, the larvae hatch and form hydatid cysts in organs such as the liver or lungs. These cysts are fluid-filled and can contain many protoscolices, representing a larval stage of the tapeworm. Because hydatid cyst formation is tied to tapeworms rather than nematodes, trematodes, or protozoa, the correct association is with tapeworms.