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[Clonorchis sinensis]

Clonorchis sinensis The small knob at the abopercular end is visible in this image.

Clonorchis sinensis egg the small knob at the abopercular end is visible in this image.

C. sinensis adult.

C. sinensis adult.

Causal Agents

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

Life Cycle

Life cycle of Clonorchis sinensis

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 5 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.

Geographic Distribution

Endemic areas are in Asia including Korea, China, Taiwan, and Vietnam. Clonorchiasis has been reported in non endemic areas (including the United States). In such cases, the infection is found in Asian immigrants, or following ingestion of imported, undercooked or pickled freshwater fish containing metacercariae.

Clinical Presentation

Most pathologic manifestations result from inflammation and intermittent obstruction of the biliary ducts. In the acute phase, abdominal pain, nausea, diarrhea, and eosinophilia can occur. In long-standing infections, cholangitis, cholelithiasis, pancreatitis, and cholangiocarcinoma can develop, which may be fatal.

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  • Page last reviewed November 29, 2013
  • Page last updated November 29, 2013
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
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