The correct answer is C, the appropriate snail intermediate host is not present in the United States.  These intermediate hosts are represented by hydrobiid snails that are found in China, Japan, Korea, Taiwan, and Vietnam.  Infection by Clonorchis sinensis is endemic in the cited countries that border the China Sea.

Click here to open a new window with a schematic diagram showing the life cycle of Clonorchis sinensis.  Close the new window to return to this page.