Causal Agent:
The trematode Dicrocoelium dendriticum, the lanceolate fluke.

Life Cycle:

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 .

Geographic Distribution:
Europe, northern Asia, America and northern Africa.