File:Opisthorchiasis.jpg

Opisthorchiasis

This illustration shows the life cycle of Opisthorchis felineus and O. viverrini, responsible for Opisthorchiasis.

The adult flukes deposit fully developed eggs that are passed in the faeces 1. After ingestion by a suitable snail (first intermediate host) 2, the eggs release miracidia 2a, which undergo in the snail several developmental stages (sporocysts 2b, rediae 2c, cercariae 2d).

Cercariae are released from the snail 3 and penetrate freshwater fish (second intermediate host), encysting as metacercariae in the muscles or under the scales 4.

The mammalian definitive host (cats, dogs, and various fish-eating mammals including humans) become infected by ingesting undercooked fish containing metacercariae.

After ingestion, the metacercariae excyst in the duodenum 5 and ascend through the ampulla of Vater into the biliary ducts, where they attach and develop into adults, which lay eggs after 3 to 4 weeks 6.

The adult flukes (O. viverrini: 5 mm to 10 mm by 1 mm to 2 mm; O. felineus: 7 mm to 12 mm by 2 mm to 3 mm) reside in the biliary and pancreatic ducts of the mammalian host, where they attach to the mucosa.

Links: CDC Opisthorchiasis

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