These parasites are part of the phylum Platyhelminthes and the class Trematoda.
They are are considered digenes because this parasite has more then one host. The most common vertebrate host of the parasite is the sheep.
There are some people that believe that this parasite is able to manipulate their hosts. This would be very hard to prove but it still an interesting idea. For instance it is believed that when an ant is infected with the parasite the extended phenotype of the parasite will force the ant to go to the top of a blade of grass and become paralized as they clamp on to the tip of the grass. This increases the probabilty of the ant to be eatten tby the sheep, cattle, or human.
The eggs are found in the feces of cattle, sheep, and man where land snails feed. The land snails then injest the eggs where they develop into miradidium. Those then develop into daughter sporocysts. The sporocyst are then left on the surface of vegetation by the slime ball left by the snail.
The ant then eats the cercariae in the slim ball and metacercaria encyst in the ant.
Cattle, Sheep, Humans:
When the cattle eat the grass they will also eat the ant that has the parasite encysted in them. The metacercaria then develops into the adult form in the liver. Eggs are then in the feces and deficated.