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. Author manuscript; available in PMC: 2018 Oct 1.
Published in final edited form as: Trends Parasitol. 2017 Jul 25;33(10):799–812. doi: 10.1016/j.pt.2017.06.002

Figure 1. Opisthorchis viverrini transmission cycle.

Figure 1

Human infection occurs when cyprinid fish bearing metacercariae in their tissues and organs are consumed raw or partially cooked (including smoked, pickled and salted). Metacercariae in the fish excyst in the duodenum and enter the bile ducts, where they mature sexually. The adult worms produce eggs which are passed out in faeces to the environment. When freshwater Bithynia snails ingest the eggs, miracidium hatch and develop into sporocysts which undergo asexual multiplication, and develop into rediae and cercariae. Upon release in the environment, free-swimming cercariae actively search for a fish host, most often from the cyprinidae family, to penetrate the tissues and skin and develop into metacercariae infective to humans and other fish-eating mammals.