phases. the first phase is the infection of the snail (the first intermediate host) via feces. they complete their gestation and hatch as cercariae. they leave their snail hosts and infect fish who are their second intermediate host. lastly, humans ingest the metacercariae in raw and undercooked fish. in humans, the metacercariae complete their life cycle and become full grown liver flukes. infections trematodes can cause disease in many types of vertebrates, including mammals, birds, reptiles, and fish. cattle and sheep can become infected by eating contaminated food. these infections lead to a reduction in milk or meat production, which can be of significant economic importance to the livestock industry. human trematode infections are most common in asia, africa and latin america. however, trematodes can be found anywhere where untreated human waste is used as fertilizer. humans can be infected by trematodes by immersion in or ingestion of contaminated water, or by consuming raw or undercooked contaminated animals or plants. albendazole can be used to treat clonorchiasis and opisthorchiasis. triclabendazole is often used to treat fasciolosis, and may also be useful in the treatment of paragonimiasis and dicrocoeliasis. praziquantel is effective in the treatment of all diseases caused by flukes (clonorchiasis, dicrocoeliasis, echinostomiasis, fasciolopsiasis, fasciolosis, gastrodiscoidiasis, heterophyiasis, metagonimiasis, opisthorchiasis, paragonimiasis, and schistosomiasis).