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Biology

Causal Agent:

The trematode Clonorchis sinensis (Chinese or oriental liver fluke).

Life Cycle:

Life Cycle of Clonorchis

Embryonated eggs are discharged in the biliary ducts and in the stool The number 1. Eggs are ingested by a suitable snail intermediate host The number 2. Each egg releases a miracidia The number 2a, which go through several developmental stages (sporocysts The number 2b, rediae The number 2c, and cercariae The number 2d). The cercariae are released from the snail and after a short period of free-swimming time in water, they come in contact and penetrate the flesh of freshwater fish, where they encyst as metacercariae The number 3. Infection of humans occurs by ingestion of undercooked, salted, pickled, or smoked freshwater fish The number 4. After ingestion, the metacercariae excyst in the duodenum The number 6 and ascend the biliary tract through the ampulla of Vater The number 6. Maturation takes approximately 1 month. The adult flukes (measuring 10 to 25 mm by 3 to 5 mm) reside in small and medium sized biliary ducts. In addition to humans, carnivorous animals can serve as reservoir hosts.

Life cycle image and information courtesy of DPDx.

 
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