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eFigure 35–29. Life cycle of Clonorchis sinensis (Chinese liver fluke). Ingestion of raw fish infected with viable metacercariae is followed by development of mature flukes in hepatic bile ducts and then passage of fluke eggs in feces with access to water in which the appropriate snail hosts (Parafossarulus) are found. A suitable freshwater fish host such as the carp then becomes infected with metacercariae. 1–10: After excystation (1) in the human duodenum of cysts ingested with raw or undercooked freshwater fish, an adult fluke (2) in the bile duct (3) lays eggs (4) in bile that pass to the intestine and are deposited with stool into a fishpond. Feces are eaten by a snail, and the ingested egg hatches within the snail, releasing a miracidium (5) that penetrates snail tissues and forms a mother sporocyst (6) which produces a number of rediae (7). The rediae proceed through successive generations, ultimately filling much of the snail. The final redial generation produces numbers of large-tailed cercariae (8) that leave the snail, swim to a fish, crawl between its scales (9), and encyst in the tissues (10) to be eaten by another human or piscivorous mammalian reservoir host to sustain the cycle. (Reproduced, with permission, from Goldsmith R, Heyneman D [editors]. Tropical Medicine and Parasitology. Originally published by Appleton & Lange. Copyright © 1989 by The McGraw-Hill Companies, Inc.)

Current Medical Diagnosis & Treatment 2018 > Protozoal & Helminthic Infections

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