Fasciola hepatica- Common liver fluke or Sheep liver fluke


Fasciola hepatica is a parasitic flatworm that belongs to the class Trematoda and the phylum Platyhelminthes. It is also known as the common liver fluke or the sheep liver fluke, because it mainly infects the livers of sheep and cattle, as well as other herbivorous mammals . Humans can also become infected by ingesting contaminated water plants or water containing the larval stage of the parasite .

Fasciola hepatica has a worldwide distribution, especially in temperate regions where sheep and cattle are raised. It is estimated that up to 17 million people are infected and that another 180 million are at risk of infection . Fascioliasis, the disease caused by F. hepatica, can cause significant economic losses in livestock production and serious health problems in humans .

Fasciola hepatica has a complex life cycle that involves two hosts: a definitive host (usually a herbivore) and an intermediate host (a freshwater snail of the family Lymnaeidae). The adult worms live in the bile ducts of the definitive host and produce eggs that are passed in the feces. The eggs hatch in freshwater and release miracidia, which infect the snails. Inside the snails, the miracidia develop into sporocysts, rediae, and cercariae. The cercariae emerge from the snails and encyst on aquatic plants or water as metacercariae. The metacercariae are the infective stage for the definitive host, which acquires them by eating the plants or drinking the water. The metacercariae excyst in the intestine of the definitive host and migrate through the abdominal cavity and the liver tissue to reach the bile ducts, where they mature into adult worms .

Fasciola hepatica can cause different clinical manifestations depending on the stage of infection and the number of parasites. The acute phase occurs during the migration of the larvae through the liver and is characterized by fever, abdominal pain, hepatomegaly, eosinophilia, and sometimes vomiting, diarrhea, urticaria, anemia, or jaundice. The chronic phase occurs when the adult worms settle in the bile ducts and is characterized by biliary obstruction, inflammation, fibrosis, cirrhosis, cholangitis, cholecystitis, or cholangiocarcinoma. Ectopic infections can also occur when the larvae migrate to other organs such as the lungs, brain, eyes, or skin .

The diagnosis of fascioliasis is based on the detection of eggs in stool or bile samples, serological tests for antibodies or antigens, molecular methods for parasite DNA, or imaging techniques for liver lesions. The treatment of choice is triclabendazole, which is effective against both immature and mature worms. Other drugs such as bithionol or nitazoxanide can be used as alternatives. The prevention of fascioliasis relies on health education, sanitation, control of snail populations, disinfection of water plants or water sources, and treatment of infected animals or humans .