Fasciola is a hermaphroditic trematode which causes the zoonotic disease Fascioliasis. Humans become infected with the disease by ingesting uncooked watercress and other aquatic vegetation on which metacercariae are encysted. Once inside the body, the metacercariae excyst in the small intestine and migrate into the peritoneal cavity through the intestinal wall. Larvae penetrate Glisson’s capsule, enter the liver and stay in the liver parenchyma for up to 9 weeks. Eventually, the larvae enter the bile ducts and mature into adult worms and produce eggs.

While in the body, pathological damage begins once the larvae enter the liver parenchyma. Hyperplasia of the bile ducts occurs, likely due to the toxins produced by the larvae. Once matured, the worms cause damage from metabolic by-products, mechanical irritation, and obstruction. Adult worms may be found elsewhere in the body besides the liver, for example in the gallbladder. The worms may also reenter the liver parenchyma and produce abscesses. Some patients may be symptomatic within the first few weeks of infection however, no eggs will be present in feces until the worms have matured, which takes 8 weeks. Symptoms include fever, anorexia, weight loss, anemia, diarrhea, and vomiting. Some patients will not experience any symptoms. If a patient is found to be seropositve for Fascioliasis, the patient will remain seropositve for several years and will be cross reactive with Schistosomiasis.

The life-cycle of Fasciola holds the key to preventing the spread infection. Adult worms within a host, in this case humans, produce eggs inside the body. These eggs are passed through the feces and enter the surrounding environment. The eggs are picked up by certain species of snails, which act as an intermediate host. From there, the cereariae encyst onto water vegetation. By stressing the dangers of eating uncooked water vegetation in endemic areas, the spread of infection could be reduced. Recent estimates report that as many as 2.4 million people are infected worldwide.