Hepatic Fasciola

• Hepatic Flukes


  Parasites found in the bile ducts, not the liver parenchyma
• Hepatic Fluke species


  • Fasciola hepatica
  • Fasciola gigantica
  • Clonorchis sinensis
  • Opisthorchis felineus
  • Opisthorchis viverrini
• Life cycle of Fasciola species

  1. Adult worms in biliary ducts

  2. Eggs released in bile, drained in duodenum, found in feces

  3. Unembryonated eggs hatch in water to release miracidium

  4. Miracidium infects snail, transforms to sporocyst, rediae, and cercariae

  5. Cercariae encyst as metacercariae on aquatic plants

  6. Humans ingest metacercariae on raw aquatic plants
• Fasciola species


  • Unembryonated eggs discharged in feces is the diagnostic stage
  • Humans are the definitive host
• Lophocercous cercariae


  Cercariae of Fasciola species have a long tail
• Fasciola hepatica infects sheep, Fasciola gigantica infects cows
• Diagnostic stage


  Unembryonated ovum
• Second intermediate host


  Aquatic plant
• Mode of transmission


  Eating raw aquatic plants, drinking water with metacercariae
• F. gigantica is larger than F. hepatica
• Fasciola species


  • Found in bile ducts, can appear in liver parenchyma with severe infection
• Fasciola hepatica


  Aka Sheep liver fluke or Temperate liver fluke
• Fasciola gigantica


  Aka Giant liver fluke or Tropical liver fluke
• Distinguishing Fasciola and Paragonimus

  • Fasciola has a cephalic cone, Paragonimus is coffee bean shaped with ventral sucker in midline
• Distinguishing Fasciola hepatica and Fasciola gigantica


  • F. hepatica has a more prominent shoulder
• Parts of Fasciola worm

  • Oral sucker
  • Pharynx
  • Branched intestine
  • Ventral sucker
  • Uterus
  • Branched single ovary
  • Branched pair testes
  • Vitellaria from shoulder to posterior end
• Key identification features of Fasciola

  • Oral sucker
  • Ventral sucker
  • Branched/dendritic testes
  • Vitellaria
  • Pharynx
  • Branched intestine
  • Uterus
  • Single branched ovary
• Unique characteristics of Fasciola

  • Only fluke with cephalic cone, shoulder, and branched intestine
• All trematodes lay embryonated eggs except Paragonimus, Echinostoma, Fasciola, and Fasciolopsis
• Fasciola hepatica ovum


  Similar to Paragonimus but without thickened posterior end, large, ovoid, operculated, yellowish-brown, unembryonated when laid, embryonates in water
• Fasciola ovum is hard to distinguish from Echinostoma and Fasciolopsis ova
• First intermediate host of Fasciola


  Snail of the genus Lymnaea
• Second intermediate host of Fasciola

  Aquatic plants like Ipomea obscura (kangkong) and Nasturtium officinale (watercress)
• Cercariae of Fasciola can also encyst in water without needing second intermediate host
• Human infection with Fasciola


  1. Ingestion of metacercariae

  2. Metacercariae penetrate intestinal wall

  3. Migrate to liver capsule and parenchyma

  4. Access bile ducts
• Acute/invasive phase of fascioliasis


  Early stage of infection with tissue invasion by immature flukes
• Migration of Fasciola metacercariae

  1. Penetrate intestinal wall

  2. Enter peritoneal cavity

  3. Migrate to Glisson's capsule

  4. Enter hepatic parenchyma

  5. Access bile ducts
• Fascioliasis


  Infection caused by Fasciola species
• Acute or invasive phase of fascioliasis

  1. Early stage of infection

  2. Invasion of tissues by immature fluke or metacercariae

  3. Penetration of metacercariae through intestinal wall

  4. Asymptomatic in peritoneal cavity

  5. Symptomatic when entering Glisson's capsule and hepatic tissue

  6. Human ingests metacercariae encysted in raw water plants

  7. Immature flukes migrate through intestinal wall, peritoneal cavity, liver capsule, hepatic tissue, to bile ducts
• Names for acute/invasive phase of fascioliasis

  • Migratory phase
  • Invasive phase
  • Hepatic phase
  • Parenchymal phase
  • Larval phase
• Acute/invasive phase symptoms


  • High fever
  • Hepatomegaly
  • Marked eosinophilia
• Larval migration can result in tissue destruction, inflammation, toxic/allergic reactions, and internal bleeding
• Some patients present with urticaria and anemia
• Chronic or latent phase of fascioliasis

  1. Reached bile duct

  2. Asymptomatic

  3. Adult worms cause obstruction, inflammation, fibrosis

  4. Worms re-enter liver parenchyma and cause abscess

  5. Immature larvae mature into adults in bile ducts

  6. Eggs passed in feces

  7. Peripheral eosinophilia
• Reason for lack of symptoms in chronic phase is downregulation of immune responses due to IL-10 production
• Fasciola adult


  Hepatic fluke with cephalic cone
• Halzoun


  Pharyngeal fascioliasis caused by adult worms temporarily lodged in pharynx
• Halzoun causes edematous congestion of pharynx, larynx, nasal fossae, and Eustachian tube, leading to dyspnea, dysphagia, deafness, and asphyxiation
• False fascioliasis


  Ingestion of raw liver containing Fasciola eggs, not an actual infection
• Ectopic fascioliasis


  Metacercariae pierce intestinal wall and infect organs other than the liver