At night, anal itching is common as the worm appears in the perianal region to lay eggs. Diagnosis can be done by applying a strip of sticky tape to the anus and checking for eggs on the tape by microscopy. Larvae excyst in the GI tract, then gain entry to the host circulatory system where they can again encyst in the muscles of the host. Liver flukes reside in the liver and cause liver tissue destruction, damage to host metabolism and impairment of bile production and drainage. Transmission is by ingestion of eggs in water or food, with development of larvae in the GI tract.
Larva develop into adults that reside in the liver tissue and bile ducts.
Clonorchis senensis is commonly known as the Chinese liver fluke, and infection by this fluke is common in Southeast Asia. Larva in infected water burrow through the skin of a host to gain entry to the host circulatory system. They then emerge in the GI tract, where they find their way up the bile ducts where they prefer to live. The male and female adult worms live in the bile ducts in a state of continuous copulation, producing eggs that traverse the bile ducts to pass with the feces to contaminate water for the infectious cycle to repeat with another unwary host. Anemia is common with heavy infection.