On examination of a stool sample, eggs with a rounded operculum, prominently shouldered operculum, and a small knob at the abopercular end are seen. The patient reports eating freshwater fish in the Assam region. Which fluke is responsible?

• A Fasciola hepatica
• B Paragonimus westermani
• C Schistosoma mansoni
• D Clonorchis sinensis ✓

Explanation

Clonorchis sinensis (Chinese liver fluke) eggs are characterised by a prominent shoulder-like rim (shoulder operculum) and a small knob at the abopercular end — a combination unique among trematode eggs. Infection occurs by eating raw freshwater fish (second intermediate host). Clonorchis inhabits bile ducts and is associated with cholangiocarcinoma. Fasciola eggs are large, yellow-brown, and operculate without a knob. Paragonimus eggs are ovoid with a flattened operculum. Schistosoma mansoni eggs are non-operculate with a lateral spine. Treatment is praziquantel.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.