page_title: Fasciola hepatica
section_title: Life cycle
hierarchical_section_title: Fasciola hepatica / Life cycle
caption_attribution_description: English: Photo of apertural view of a shell of Galba truncatula.
context_page_description: Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic trematode of the class Trematoda, phylum Platyhelminthes. It infects the livers of various mammals, including humans. The disease caused by the fluke is called fasciolosis or fascioliasis, which is a type of helminthiasis and has been classified as a neglected tropical disease. Fasciolosis is currently classified as a plant/food-borne trematode infection, often acquired through eating the parasite's metacercariae encysted on plants. F. hepatica, which is distributed worldwide, has been known as an important parasite of sheep and cattle for decades and causes significant economic losses in these livestock species, up to £23 million in the UK alone. Because of its relatively large size and economic importance, it has been the subject of many scientific investigations and may be the best-known of any trematode species. F. hepatica's closest relative is Fasciola gigantica. These two flukes are sister species; they share many morphological features and can mate with each other.
context_section_description: Fasciola hepatica occurs in the liver of a definitive host and its lifecycle is indirect. Definitive hosts of the fluke are cattle, sheep, and buffaloes. Wild ruminants and other mammals, including humans, can act as definitive hosts as well. The life cycle of F. hepatica goes through the intermediate host and several environmental larval stages. Intermediate hosts of F. hepatica are air-breathing freshwater snails from the family Lymnaeidae. Although several lymnaeid species susceptible to F. hepatica have been described, the parasite develops only in one or two major species on each continent. Galba truncatula is the main snail host in Europe, partly in Asia, Africa, and South America. Lymnaea viator, L. neotropica, Pseudosuccinea columella, and L. cubensis are most common intermediate hosts in Central and South America. Several other lymnaeid snails may be naturally or experimentally infected with F. hepatica, but their role in transmission of the fluke is low. The list of lymnaeid snails that may serve as natural or experimental intermediate hosts of F. hepatica include:
  Austropeplea ollula
  Austropeplea tomentosa
  Austropeplea viridis
  Fossaria bulimoides
  Galba truncatula
  Lymnaea cousini
  Lymnaea cubensis
  Lymnaea diaphana
  Lymnaea humilis
  Lymnaea neotropica
  Lymnaea occulta
  Lymnaea stagnalis
  Lymnaea viatrix
  Omphiscola glabra
  Pseudosuccinea columella
  Radix auricularia
  Radix lagotis
  Radix natalensis
  Radix peregra
  Radix rubiginosa
  Stagnicola caperata
  Stagnicola fuscus
  Stagnicola palustris
  Stagnicola turricula
  The metacercariae are released from the freshwater snail as cercariae, and form cysts on various surfaces including aquatic vegetation. The mammalian host then eats this vegetation and can become infected. Humans can often acquire these infections through drinking contaminated water and eating freshwater plants such as watercress. Inside the duodenum of the mammalian host, the metacercariae are released from within their cysts. From the duodenum, they burrow through the lining of the intestine and into the peritoneal cavity. They then migrate through the intestines and liver, and into the bile ducts. Inside the bile ducts, they develop into an adult fluke. In humans, the time taken for F. hepatica to mature from metacercariae into an adult fluke is roughly 3 to 4 months. The adult flukes can then produce up to 25,000 eggs per fluke per day. These eggs are passed out via stools and into freshwater. Once in freshwater, the eggs become embryonated, allowing them to hatch as miracidia, which then find a suitable intermediate snail host of the Lymnaeidae family. Inside this snail, the miracidia develop into sporocysts, then to rediae, then to cercariae. The cercariae are released from the snail to form metacercariae and the life cycle begins again.
caption: Galba truncatula, an amphibious freshwater lymnaeid snail that serves as the main intermediate host of Fasciola hepatica in Europe
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