Website last accessed on 14.04.2023 Food-borne trematode infections are zoonotic, and their pathogens can be transmitted to humans only after the completion of a complex life cycle, some stages of which take place in the body of an intermediate animal host. The first intermediate hosts of all trematode species are freshwater snails. The second host varies depending on the species: in the case of clonorchiasis and opisthorchiasis it is freshwater fish, and in the case of paragonimiasis it is crustaceans.