Fasciola hepatica
Geographic Range
Liver flukes are found world-wide, especially in the U.S., Europe, Asia, and S. Africa. Basically they inhabit any region where mammals and snails are found.
- Biogeographic Regions
- nearctic
- palearctic
- oriental
- ethiopian
- neotropical
- australian
Habitat
The habitat of the liver fluke changes in relation to its current life stage.
- Terrestrial Biomes
- savanna or grassland
- forest
- rainforest
- scrub forest
- Aquatic Biomes
- lakes and ponds
- rivers and streams
Physical Description
- Other Physical Features
- ectothermic
- bilateral symmetry
Reproduction
Liver flukes reproduce both sexually and asexually. Adults are hermaphroditic, capable of both cross- and self-fertilization. The larvae stage known as sporocyst reproduces asexually with its offspring developing into rediae, which also multiply asexually. Adults live in the bile ducts of their mammalian host. Their eggs enter the host gut and are passed on with feces. They hatch to form free-living egg larvae or miracidia, which can live only a few hours in water. If a suitable snail host is entered, the miracidium develop into a sporocyst, which produce, either more rediae or another type of larvae called cercaria. The cercaria exit the snail via the pulmonary cavity, free-swim until attaching to grass or some other object, and develop into cyst-encased metacercaria. The metacercaria remain secure in their cysts until eaten by a mammal. If eaten, a metacercarium bores through to the mammal's liver and remains until it matures into an egg producing adult, at which time it settles in the bile ducts.
- Parental Investment
- no parental involvement
Behavior
Liver flukes have no distinguishing behavior traits or social systems. They can live solitarily or together in a host.
- Key Behaviors
- parasite
Food Habits
Adult liver flukes feed on liver tissue while in the mammal host. The larvae stage known as redia feed on the digestive gland or liver while in the snail host. The free-living miracidium and metacercarium stages are non-feeding.
Economic Importance for Humans: Positive
None.
Economic Importance for Humans: Negative
Liver flukes cause tremendous loss to farmers of cattle and sheep. They are responsible for such diseases as liver rot and black disease, which are detrimental to livestock. They are very hard to control in grazing animals. Though drugs will kill adults, they have no effect when the fluke is in a migratory stage. Vaccines given to livestock do not reduce infection. Grazing management reduces but does not eliminate infestation, probably because wild animals such as rabbits serve as reservoirs.
Contributors
Susan Stewart (author), University of Michigan-Ann Arbor.
Glossary
- Australian
-
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- Nearctic
-
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
- Neotropical
-
living in the southern part of the New World. In other words, Central and South America.
- Palearctic
-
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
- asexual
-
reproduction that is not sexual; that is, reproduction that does not include recombining the genotypes of two parents
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- ectothermic
-
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- oriental
-
found in the oriental region of the world. In other words, India and southeast Asia.
- parasite
-
an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death
- rainforest
-
rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.
- scrub forest
-
scrub forests develop in areas that experience dry seasons.
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- tropical savanna and grassland
-
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
- savanna
-
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
-
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
References
Olsen, Wilford O. 1962. Animal parasites: Their biology and lifecycles. Burgess Publishing Co.
<BR>
Pantelouris, E. M. 1965. The common liver fluke Fasciola hepatica L. Pergamon Press.