Opisthorchiasis

Opisthorchiasis is a human parasitic infection caused by liver flukes of the genus Opisthorchis, primarily Opisthorchis viverrini and Opisthorchis felineus. These parasites inhabit the biliary ducts in the liver and biliary system, causing a range of hepatobiliary symptoms.

Infection occurs after ingesting raw or undercooked freshwater fish containing metacercariae. The flukes reside in the bile ducts; eggs are excreted in feces. Freshwater snails serve as the first intermediate hosts and fish as the second intermediate hosts, with humans as the definitive hosts.

Most infections are asymptomatic or mild. Heavy infections cause biliary inflammation, obstruction, abdominal pain, intermittent jaundice, and cholangitis. Chronic infection is associated with bile duct changes and an increased risk of cholangiocarcinoma, especially with Opisthorchis viverrini.

Diagnosis relies on stool examination for eggs; serology and imaging can aid in ambiguous cases. First-line treatment is praziquantel; alternatives include albendazole or nitazoxanide in some settings. Management may require treatment of biliary obstruction or complications.

Prevention focuses on avoiding raw or undercooked freshwater fish, proper cooking or freezing of fish, and control of the snail hosts. Public health measures in endemic areas include health education, safe water, and surveillance to reduce transmission and associated morbidity.