Clonorchis sinensis, or the human liver fluke, is in the class Trematoda and the phylum Platyhelminthes. The human liver fluke can infect the liver, gall bladder, and bile duct. This parasitic fluke is found mainly in Asia and when found outside of Asia, in immigrants from Asia. The parasite has been found in people outside of Asia who had ingested the parasitic cysts in undercooked, imported, or pickeled freshwater fish.
The eggs of Clonorchis sinesis are ingested by freshwater snails. The eggs hatch into miracidia, or a motile form of the parasite that is cilia covered and settles in the snail to create sporocysts. The sporocyst is a sac that can either create more sporocysts or rediae. The rediae is the larval form with an oral sucker that can then produce more rediae or cercariae. Then free swimming parasitic larvae (cercariae) hatches from the eggs that were ingested by the snail and encyst on the skin of a fresh water fish. The metacercariae is the cercariae encysted and resting on the skin of the fish, which is later ingested by the human host. The parasite excysts in the duodenum of the human host, turns into its adult stage in the bilary duct, and finally the embryonated eggs are passed through human feces into the external environment.
Clonorchis sinensis is a carcinogenic human liver fluke.
In recent years the drug Praziquantal has been used to treat clonorchiasis, but a new drug Tribendimidine is being studied for efficacy and saftey. Tribendimidine has an efficacy comparable to Praziquantal and has lead to fewer adverse effects and events than that of Praziquantal. Larger clinical trials are warranted.