The discussion covers the class of helminth parasites belonging to the class known as Trematoda or Digenea. Commonly known as the flukes, these parasites vary in egg, larva, and adult morphology and reproduction processes. The trematodes (another name for the parasites that belong to Trematoda) can be divided into two groups, the hermaphroditic (self-fertilizing) flukes that
infect organs and are foodborne, and the blood flukes or schistosomes that are dioecious (parasites that reproduce via separate sexes) and infect by direct penetration. Common to all trematodes
is their complex life cycles, which almost always include mollusks (snails) as an intermediate host. -Zeibig