infections
Fluke Infections of the Liver
Introduction
Certain species of flukes cause infections of the liver. People are infected when they swallow cysts containing fluke larvae in raw, undercooked, dried, salt-cured, or pickled freshwater fish or on contaminated watercress. Depending on the infecting species and intensity of infection, people may have fever, chills, abdominal discomfort or pain, jaundice, itching, diarrhea, and weight loss. Doctors diagnose the infection when they see fluke eggs in a person's stool or in the contents of the intestine. Depending on the type of fluke, drugs such aspraziquantel,albendazole, ortriclabendazolecan eliminate them. Overview of Fluke Infections are parasitic flatworms. There are many species of flukes. Different species tend to infect different parts of the body. Liver fluke infections occur in Europe, Africa, eastern and central Asia, and South America but are rare in the United States. (See also Flukes that cause infections of the liver include Clonorchis sinensis(Chinese or oriental liver fluke), which causes clonorchiasis Opisthorchis viverrini(Southeast Asian liver fluke) andO. felineus(cat liver fluke), which cause an infection that resembles clonorchiasis Fasciola hepatica(the common liver fluke or sheep liver fluke), which causes fascioliasis and typically infects sheep and cattle The life cycle of flukes is complex. People can get liver fluke infections when they swallow cysts containing immature flukes (larvae) of the following: Clonorchis sinensisandOpisthorchisin raw, undercooked, dried, salt-cured, or pickled freshwater fish;Clonorchis sinensisalso sometimes in freshwater shrimp Fasciola hepaticaorFasciola giganticain cysts on watercress or other water plants growing in water contaminated by eggs in sheep or cattle dung are swallowed, the larvae leave the cysts in the intestines and travel back up the intestine and enter the Overview of the Liver and Gallbladder (the tube that carries bile from the liver and gallbladder to the intestine). Then they go up the bile duct into the liver or sometimes the gallbladder. There, they develop into adults and produce eggs. Adults can live 20 to 30 years if untreated. Eggs are passed in the stool and ingested by snails. Infected snails release immature flukes that can swim (called cercariae). Cercariae released from infected snails form cysts in various freshwater fish or shrimp. After the cysts ofFasciola hepaticaorFasciola giganticaare swallowed, they reach the intestine and release immature larvae. The larvae move through the wall of the intestine into the abdominal cavity and liver, then to the bile ducts. There, they develop into adult flukes, which produce eggs. Eggs are passed in stool. In water, the eggs release larvae, which penetrate snails. Infected snails release immature flukes (cercariae), which form cysts on watercress and other water plants. See also theWorld Health Organization (WHO)andCenters for Disease Control and Prevention (CDC)information on clonorchiasis and theWHOandCDCinformation on fascioliasis. 