Fasciola Hepatica - Liver Fluke

Fasciola hepatica is a parasitic fluke that lives in the liver. 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. The cercaria exits and finds aquatic vegetation where it forms a cyst called metacercaria. A human eats the raw freshwater plant containing the cyst. The metacercaria excysts in the first part of the small intestine, duodenum. It then penetrates the intestinal wall and gets into the peritoneal cavity. It finds the liver and starts eating liver cells. This happens only a few days after the initial contact with the parasite. Usually the larva spends a few weeks just browsing and eating the liver. Then it relocates to the bile duct where it begins its final stage and becomes an adult. It takes about three months for the metacercaria to develop into an adult. Adults are about 3 cm long and 1 cm wide. Adult females can produce up to 25000 eggs per day.

In the chronic phase of fascioliasis adults in the large biliary ducts cause liver inflammation and obstruction of the biliary fluid. During the migration of the larvae (this acute phase of the disease lasts many weeks) symptoms include:

• diarrhea
• eosinophilia (high number of white blood cells)
• fever
• nausea
• stomach ache
• vomiting.

Fasciola hepatica is found in areas where cattle and sheep are raised.

Fasciola hepatica is identified from eggs in a stool sample. The eggs are very similar to those of Fasciolopsis buski. Early stage of the infection can be diagnosed from a blood sample, if antibodies are found. Fascioliasis is treated with triclabendazole drug.

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