The liver fluke Fasciola hepatica is usually a parasite of sheep and cattle. "Liver rot" in sheep was described in a French work in 1379, and the first human case was described in 1760. The fluke's life cycle was discovered in 1881. Fascioliasis is a significant veterinary problem, but human infection is also fairly common. The fluke's life cycle is much like that of Fasciolopsis buski (see Fasciolopsiasis), with people or herbivores infected by eating raw watercress or other plants contaminated by the cysts of the fluke. Adult worms settle down in the bile ducts after a period of wandering in the liver. Mild infestations may cause little damage, but fever, jaundice, and right upper quadrant abdominal pain radiating to the shoulder blade are common symptoms. Bile ducts may become partially or totally obstructed, and liver destruction can be severe.

F. hepatica is cosmopolitan in distribution, with important foci of human infection in southern France, in Algeria, and in South America. Diagnosis is made by examining the feces of symptomatic patients with a microscope to find the eggs. Treatment is generally effective. Prevention is by treating sheep to keep them from perpetuating the cycle, controlling snail intermediate hosts, and keeping domestic animals away from ponds where watercress is grown.

K. David Patterson

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