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The trematode Dicrocoelium dendriticum, the lanceolate fluke.
Ruminants are the usual definitive hosts for Dicrocoelium dendricitum, although other herbivorous animals, carnivores, and humans can serve as definitive hosts. Embryonated eggs are shed in feces . The eggs are ingested by a snail . Many species of snail may serve as the first intermediate host, including Zebrina spp. and Cionella spp. When the miracidia hatch , they migrate through the gut wall and settle into the adjacent vascular connective tissue, where they become mother sporocysts . The sporocysts migrate to the digestive gland where they give rise to several daughter sporocysts. Inside each daughter sporocyst, cercariae are produced . The cercariae migrate to the respiration chamber where they are shed in slime ball from the snail . After a slime ball is ingested by an ant, the cercariae become free in the intestine and migrate to the hemocoel where they become metacercariae . Many ants may serve as the second intermediate host, especially members of the genus, Formica. After an ant is eaten by the definitive host , the metacercariae excyst in the small intestine. The worms migrate to the bile duct where they mature into adults . Humans can serve as definitive hosts after accidentally ingesting infected ants .
Europe, northern Asia, America and northern Africa.
Most infections are light and asymptomatic. In heavier infections, symptoms may include cholecystitis, liver abscesses and upper abdominal pain.