Other genera within the Family include the liver flukes Platynosomum (in cats in several areas of the world but not Canada), and Eurytrema (in ruminants in Asia and South America).
Eggs of D. dendriticum are approximately 40 µm in length, and not quite oval with a thick, yellow-brown, smooth shell and an operculum. When passed each contains a miracidium. Eggs of D. dendriticum are very different from those of the other flukes of ruminants in North America, F. hepatica and F. magna, which are very similar to each other.
Host range and geographic distribution
Life cycle - indirect
The hermaphrodite adult D. dendriticum live in the biliary system. Eggs are passed in the feces and are swallowed by a suitable snail first intermediate host. Egg hatching occurs in the gut of the snail, and the miracidium released from each egg penetrates into the tissues of the snail and develops through two generations of sporocysts (but not rediae) and then cercariae. Cercarial development requires approximately three months.
The cercariae emerge from the snail in "slime balls" (each containing 200-400 cercariae) released from the respiratory pore of the snail and are eaten by an ant second intermediate host, in which the metacercariae develop and encyst. This phase of the life cycle requires up to two months. The metacercaria(e) in the ant’s nerve ganglion alter its behaviour – using their mouthparts, they attach to the upper portions of pasture grasses and other vegetation during the night and are then available to grazing animals early in the day, thereby enhancing transmission to the definitive host. Following ingestion of the ants by a definitive host, the metacercariae develop into immature flukes which migrate directly from the intestinal lumen into the biliary system. The pre-patent period is approximately eight weeks. Thus Dicrocoelium dendriticum can increase its numbers in its mammalian and molluscan, but not arthropod, hosts.
Life Cycle: Dicrocoelium dendriticum