Which disease is produced by chronic infection with Clonorchis sinensis?

• A. Clonorchiasis
• B. Ascariasis
• C. Schistosomiasis
• D. Filariasis

Answer: (A)

The concept being tested is recognizing the disease caused by a chronic liver fluke infection. Clonorchis sinensis, the Chinese liver fluke, establishes long-term residence in the bile ducts after ingestion of metacercariae in undercooked freshwater fish. Over time this causes chronic inflammation of the biliary tree (cholangitis) and can lead to biliary obstruction and other complications, including an increased risk of cholangiocarcinoma. That long-standing biliary involvement is what defines the disease clonorchiasis.

Other options reflect infections from different parasites with distinct targets and manifestations: an intestinal nematode causes ascariasis, a blood fluke causes schistosomiasis, and a filarial parasite causes filariasis.