Fasciola, commonly known as the liver fluke, is a genus of parasitic Trematoda. There are three species within the genus Fasciola: Fasciola nyanzae, Fasciola hepatica and Fasciola gigantica. Fasciola hepatica and F. gigantica are known to form hybrids. Both F. hepatica and F. gigantica and their hybrids infect the liver tissue of a wide variety of mammals, including humans, in a condition known as Fasciolosis. F. hepatica measures up to 30 mm by 15 mm, while F. gigantica measures up to 75 mm by 15 mm.
Species
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Fasciola nyanzae Leiper, 1910
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Fasciola hepatica Carl Linnaeus, 1758
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Fasciola gigantica Cobbold, 1855
- Also published separately as:
- Abstract published as:
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Hybrid or Introgression populations of Fasciola gigantica × Fasciola hepatica
[Young N. D., Jex A. R., Cantacessi C., Hall R. S., Campbell B. E. et al. (2011). "A Portrait of the Transcriptome of the Neglected Trematode, Fasciola gigantica—Biological and Biotechnological Implications". PLoS Neglected Tropical Diseases 5(2): e1004. .]
Life cycle
Fasciola pass through five phases in their egg, miracidium, cercaria, metacercaria, and adult fluke.
The eggs are passed in the feces of mammalian hosts and, if they enter freshwater, the eggs hatch into miracidia. Miracidia are free-swimming. The miracidia then infect
Gastropoda intermediate hosts and develop into cercariae, which erupt from the body of the snail host and find and attach to aquatic plants.
The cercariae then develop into metacercarial cysts. When these cysts are ingested along with the aquatic plants by a mammalian host, they mature into adult flukes and migrate to the bile ducts.
The adults can live for 5–10 years in a mammalian host.
Animal hosts
The intermediate hosts, where
Fasciola reproduce asexually, are
Gastropoda from the family
Lymnaeidae, also known as pond snails.
A wide variety of mammals can be , where Fasciola reach adulthood and reproduce, including pigs, rodents, , and humans.
Geographic distribution
Fasciola are widespread and inhabit 70 countries and parts of all continents except for Antarctica. It is most common in areas with sheep and cattle are raised.
The regions most impacted by
Fasciola are the northern
Andes and the Mediterranean region.
History and discovery
Evidence of fascioliasis in humans exists dating back to Egyptian mummies that have been found there are with Fasciola eggs.
Cercariae of
F. hepatica in a snail and flukes infecting sheep were first observed in 1379 by Jehan De Brie.
The life cycle and hatching of an egg were first described in 1803 by Zeder.
Prevention and treatment
Fascioliasis is treated with
triclabendazole. There is no vaccine for
Fasciola currently available.
In severe cases of biliary tract obstruction, surgery is an option to remove adult flukes.
The most common way that humans are infected is through the consumption of undercooked vegetables, often watercress, that are contaminated with metacercariae.
One prevention method is to kill off the snail hosts in a water body using molluscicides.
