No special status Other Comments In countries that Fasciola gigantica is present, the prevalence of infected animals is extremely high. Sobhon, et al. Glossary living in sub-Saharan Africa south of 30 degrees north and Madagascar. Palearctic living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.
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Causal Agent The trematodes Fasciola hepatica also known as the common liver fluke or the sheep liver fluke and Fasciola gigantica are large liver flukes F. Although F. These forms usually have intermediate morphologic characteristics e.
Further research into the nature and origin of these forms is ongoing. Life Cycle Immature eggs are discharged in the biliary ducts and passed in the stool. In the snail, the parasites undergo several developmental stages sporocysts , rediae , and cercariae.
The cercariae are released from the snail and encyst as metacercariae on aquatic vegetation or other substrates. Humans and other mammals become infected by ingesting metacercariae-contaminated vegetation e. After ingestion, the metacercariae excyst in the duodenum and penetrate through the intestinal wall into the peritoneal cavity. The immature flukes then migrate through the liver parenchyma into biliary ducts, where they mature into adult flukes and produce eggs. In humans, maturation from metacercariae into adult flukes usually takes about 3—4 months; development of F.
Life cycle image and information courtesy of DPDx. Page last reviewed: December 31,
Fasciola Hepatica - Liver Fluke
In addition to humans it infects cows and sheep. It is known as the common liver fluke and causes a disease called fascioliasis. The life cycle of Fasciola hepatica starts when a female lays eggs in the liver of an infected human. Immature eggs are discharged in the biliary ducts and taken out in the feces. If landed in water, the eggs become embryonated and develop larvae called miracidia. A miracidium invades an aquatic snail and develops into cercaria, a larva that is capable of swimming with its large tail.
Distribution[ edit ] Fasciola gigantica causes outbreaks in tropical areas of southern Asia, Southeast Asia, and Africa. The geographical distribution of F. Infection is most prevalent in regions with intensive sheep and cattle production. In Egypt F. Intermediate hosts[ edit ] As with other trematodes, Fasciola develop in a molluscan intermediate host. Species of the freshwater snails from the family Lymnaeidae are well known for their role as intermediate hosts in the life cycle of Fasciola gigantica; however, throughout the years an increasing number of other molluscan intermediate hosts of F. The species of Fasciola can become adapted to new intermediate hosts under certain conditions at least based on laboratory trials.