Fascioliasis is a parasitic disease caused by the liver fluke Fasciola hepatica or Fasciola gigantica. This disease is endemic in more than 51 countries including those in Europe, Africa, Asia, the Americas, and Oceania, with more than 17 million people infected worldwide. The World Health Organization (WHO) has identified fascioliasis as an important human parasitic disease.

Acute infection is acquired by consuming watercress, water lettuce, or other greens contaminated with metacercariae (infective larvae form). The larvae excyst in the duodenum, migrate through the bowel wall into the peritoneal cavity, and penetrate the Glisson's capsule. The classic triad of the acute infection consists of hypereosinophilia, right upper quadrant pain (Murphy's sign), and fever, each of which is related to the migration of the larvae through the peritoneal cavity and liver. As the larvae migrate through the liver, they may cause severe damage to the liver, including subcapsular hematoma, hepatic rupture, multiple hepatic abscesses, and hepatic necrosis. Approximately 20%-25% of patients will experience urticaria and/or pruritus during the acute phase. The acute period of the disease lasts between 3 and 5 months. Finally, the larvae reach the large hepatic and common bile ducts.

The chronic stage develops when mature flukes reside in the bile ducts. Adult flukes produce eggs, and they reach the environment through the stools. The clinical picture of a chronic infection includes recurrent abdominal right upper quadrant pain, biliary colic pain (not associated with food), nausea, vomiting, recurrent or intermittent jaundice, and urticaria.

Some populations in endemic areas such as school-aged children, farmers, and vegetarians are at increased risk for acquiring the infection. Travelers may occasionally acquire the infection if they consume contaminated raw vegetables during a trip to endemic countries.  

Liver fibrosis can occasionally occur in heavily infected patients or in those with comorbidities (hepatitis C, hepatitis B, alcohol use disorder, etc).