Microbiology & parasitology

Parasites-hepatobiliary

Fasciola



Topic Completed: 1 August 2015

Minor changes: 6 October 2020

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PubMed Search: Fasciola [title] colon

Elliot Weisenberg, M.D.
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Cite this page: Weisenberg E. Fasciola. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colonfasciola.html. Accessed October 15th, 2021.
Definition / general
  • Disease of the intestine caused by infection by the trematode (liver fluke) Fasciola hepatica
  • Infection by F. gigantica is often included in this category
Epidemiology
  • Disease is more common in animals; however, worldwide an estimated 2 million people are infected
  • Disease is uncommon in the continental United States and Canada
  • Disease is more common in Europe, Asia, Africa, the Caribbean, and South America
  • The highest rates of infection are in Bolivia and Peru in the Andean highlands
  • Disease has been reported in Hawaii
  • Infection may be endemic or imported
  • Disease related to infection of the colon is very rare
Etiology
  • Life cycle:
    • Adult hermaphroditic worms in mammalian bile ducts, usually sheep or cattle, pass immature eggs in feces in fresh water
    • The eggs hatch releasing miracidium that infect Lymnaeidae snail hosts
    • In 5 to 7 weeks the snails release cercariae that lose their tails and become metacercariae with a hard outer cyst wall that attach to plants and can survive for long periods
    • Cysts may also float on water
    • Human disease is relatively commonly caused by ingestion of raw watercress
    • The plants are eaten by cattle, sheep, or people
    • The metacercariae hatch in the duodenum, penetrate the intestinal wall, and migrate across the peritoneum to the liver
    • They burrow into the liver for 2-3 months, mature into adults, and enter bile ducts completing the cycle
    • Worms may live 10 years in bile ducts
    • Uncommonly, infection has occurred from ingestion of undercooked goat or sheep liver
Diagrams / tables

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Life cycle


Clinical features
  • Acute or invasive fascioloidiasis generally causes right upper quadrant pain and discomfort, fever, hepatomegaly, and eosinophilia
  • Less commonly immune mediated disease of the heart, lungs, or nervous system may occur
  • Chronic disease is associated with chronic biliary obstruction, ascending cholangitis, and jaundice
  • In contrast to acute disease, eosinophilia may be mild or absent
  • Cirrhosis or malignancy may ensue. Disease caused by ectopic flukes is uncommon, it has been reported in subcutaneous tissue, lymph nodes, epididymis, duodenum, appendix, stomach and colon
  • Only rare case reports of colonic disease exist - these patients have presented with abdominal pain and right sided colon masses
Diagnosis
  • In general, diagnosis is from identification of eggs in stool although serologic testing exists
  • In colonic cases the diagnosis has been made from identification of worms and eggs during tissue examination
Case reports
Treatment
  • Triclabendazole, available through the CDC under a special investigational protocol
  • Resistance has been reported (Emerg Infect Dis 2012;18:1028)
Gross description
  • In the colon, masses mimicking malignancy are described
  • Mechanical bowel obstruction has been reported
  • In bile ducts, the adult worm is leaf shaped and up to 2 cm in greatest dimension
Gross images

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Adult liver fluke

Microscopic (histologic) description
  • In the colon sinus tracts, eosinophilia, Charcot Leyden crystals, necrosis, fibrosis, granulomatous inflammation, lymphocytic and plasma cell infiltrates
Microscopic (histologic) images

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Egg with unshouldered operculum

Differential diagnosis
  • In the liver depending on the circumstance the differential diagnosis includes ascending cholangitis, cysts caused by bile duct dilation caused by other infections (other fasciola, clonorchiasis), non-paracytic cysts, primary biliary cirrhosis, and sarcoidosis
  • During parasitic exam F. hepatica must be distinguished from F. buski
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