|Description:||Magnified 125X, this photomicrograph revealed the presence of two trematode eggs, a Fasciolopsis buski egg on the right, and an Echinostoma sp. egg seen of the left, which were found in an unstained formalin-preserved stool sample. Note how much larger the F. buski is compared to that of the Echinostoma sp. egg. F. buski trematodes are the largest intestinal flukes found parasitizing human beings. These flukes inhabit Asia and the Indian subcontinent, especially in areas where humans raise pigs, and consume freshwater plants.|
See PHIL 3393 for a diagram illustrating the following:
Immature eggs are discharged into the intestine and stool (1). Eggs become embryonated in water (2), eggs release miracidia (3), which invade a suitable snail intermediate host (4). In the snail the parasites undergo several developmental stages (sporocysts (4a), rediae (4b), and cercariae (4c)). The cercariae are released from the snail (5)and encyst as metacercariae on aquatic plants (6). The mammalian hosts become infected by ingesting metacercariae on the aquatic plants. After ingestion, the metacercariae excyst in the duodenum (7)and attach to the intestinal wall. There they develop into adult flukes (20 to 75 mm by 8 to 20 mm) in approximately 3 months, attached to the intestinal wall of the mammalian hosts (humans and pigs) (8). The adults have a life span of about one year.