Species of Echinostoma often accidentally infect humans.

Echinostomatidae Final , , with aquatic habits: adults in intestine Second Intermediate host, First Intermediate, Lymnaeidae e.g., , tadpoles, clams, snails: sporocyst, redia; etc.: metacercariae. ceracariae released Fasciolidae–Giant Liver flukes Adults in bile ducts of ruminants Sporocyst, rediae, ceracriae in Lymnaeid snails. Metacercariae in aquatic vegetation.

Fasciola hepatica Sources of human : watercress, lettuce, etc from areas where there are infected livestock. Pathogenesis

• Metacercariae penetrate gut to peritoneum. Penetrate Glisson’s capsule (outer covering of liver) and make their way through liver parenchyma to bile duct: • Cause cirrhosis (proline Excretion elicits collagen deposition); edema, thickening of bile ducts, jaundice, even Other Fasciolidae

• buski: human intestine. Worms cause lesions where they feed; chronic diarrhea, obstruction, verminous toxicity. • Fascioloides magna: in , elk. • : ruminants of Africa, SE Asia Paramphistomatidae in rumen of ruminants. Harmless as adults (unless in very large numbers); migrating larvae cause disease. Paramphistomatidae: Rumen flukes: metacercariae hatch in small intestion, migrate forward through reticulum to rumen. Megalodiscus temperatus

• Colon of frogs. hominis

• Humans and swine: lower , upper colon. • SE Asia. • Involves Helicorbus snails, but life cycle not completely known. • Causes diarrhea Plagiorchiformes

• Diverse forms parasitizing all classes of vertebrates. Cercaria with stylet. Metacercariae in various invertebrates. • Often occur in highly terrestrial hosts Dicrocoelidae

• : in bile ducts of ruminants (sheep, deer, ) in Europe (introduced to some parts of Eastern North America). • Uses snails and as intermediate hosts. Life cycle of D. dendriticum

Pathogenesis: may involves 10,000+ worms. Biliary obstruction; liver degeneration, jaundice. Haematoloechus medioplexus

• Parasites in lungs of frogs and toads • Sporocysts in Planorbula snails release cercariae which encyst as metacercariae on dragonfly naiads (rectal gills) • Frogs access the parasites when feeding on metamorphosed dragonflies Prosthogonimus spp. • Oviduct of birds. • Sporocysts in snails release ceracriae which encysts as metacercariae in rectal gills of Odonates. • Birds acquire infections from feeding on infected metamorphosed odonates. • Can interfere with egg production Paragonimus spp. • Lung flukes in Carnivores; may accidentally occur in man • Sporocysts in Thieridae snails release short tailed cercariae • Metacercariae in freshwater crabs, crayfish • Final host infected when it eats infected crustacea Paragonimus in the final host

• Metacercariae penetrate intestine, migrate anterior to penetrate diaphragm and wait for mates in the lung pleura. Pairs enter lung parynchyma and encyst. • In humans metacercariae may wander in tissues and cause problems. Nanophyetus salmincola

• Parasites in intestinal crypts of eating mammals and birds. • Sporocysts in Oxytrema snails release short tailed cercariae. • Metacercariae in muscle of fish. Opisthorchiformes

• Adults in bile system of all classes of vertebrates. • , Opisthorchis spp. Metorchis spp. in humans

Heterophyes

• Heterophyes spp commonly infect man accidantally. • H. heterophyes: North Africa, Middle East, Far East. • Adults between villi. Can cause breakdown of mucosa, release eggs into as embolisms.