Fasciola hepatica, also known as the common liver fluke or sheep liver fluke, is a parasitic trematode (fluke or flatworm, a type of helminth) of the class Trematoda, phylum Platyhelminthes. It infects the livers of various mammals, including humans, and is transmitted by sheep and cattle to humans the world over. 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. Life cycle 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