Clonorchiasis

Clonorchiasis is an infection of the bile ducts caused by the Chinese liver fluke, Clonorchis sinensis. This chronic disease sometime lasts 30 years or longer but is rarely fatal. Clonorchiasis is widely found throughout China except in the northwestern region. It also occurs in Japan, Korea, Cambodia, and Vietnam. When found in other parts of Asia, it has typically been brought in from other areas, often via shipments of dried, pickled, or fresh fish imported from endemic areas. In most endemic areas, clonorchiasis commonly occurs in adults over age 30.

Causes

The Chinese liver fluke is found in humans, cats, dogs, swine, rats, and other animals. People are commonly infected by eating raw or undercooked freshwater fish that contain C. sinensis larvae housed in cysts. When the person digests the fish, the larvae are released from the cysts and migrate through the common bile duct. Eggs deposited in the bile passages are expelled in human stool. Snails then ingest the fully developed miracidia (ciliated larvae of a parasitic fluke that hatch from an egg). The miracidia produce more larvae, which are deposited into the water. In the water, the C. sinensis larvae penetrate a host fish and the cycle begins again. The life cycle from person to snail to fish to person takes at least 3 months to complete. Infection is not directly transmitted from person to person.

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