subject: Fasciolidsis clinical features and management [print this page] Fasciolidsis clinical features and management
Aetiology and distribution The parasite measures 3 x 1.5cm. Eggs are released inthe biliary passages and pass to the exterior in the faeces.The miracidium hatches in fresh water and penetrates the tissues of a freshwater snail (Lymnaea species). After acycle lasting 4 months in the snail, cercariae are released.These encyst on the leaves of watercress and other typesof aquatic vegetation. Humans are infected by eating water cress with encysted metacercariae. Maturation to the adult stage in bile ducts takes about 4 months until egg laying starts. Sheep are the normal hosts of this infection,and human infections are likely wherever sheep are herdedin wet pasture lands.
Pathology There is hepatic parenchymal necrosis in the phase of migration through the liver. The liver tissue regenerates.The worm burden determines the severity of disease. In the bile ducts there is chronic inflammation, with regenerative hyperplasia of the epithelium and some degree of duct obstruction.
Clinical features Pain in the liver area, fever, chills, tender hepatomegaly and marked eosinophilia are usual features during the tissue migration phase. Upper abdominal discomfort and hepatomegaly are present in mild to moderate infections,whereas heavy infections may cause obstructive jaundice and cholangitis as well.
Diagnosis Eggs of the parasite are found in stools or duodenal aspirate,though they can be difficult to find in relatively lightinfections. Endoscopic retrograde cholangiopancreatography may show filling defects in the biliary tree and flukes may be extracted from ducts using a stone basket. Eosinophilia is usual and serological tests for this infectionare usually positive.
Management and prevention Triclabendazole, 10mg/kg b.d. x 1 day, or bithionol, 40mg/kg in 2 divided doses on alternate days for 15 dosagedays, are effective.Watercress production must be separate from sheeppastures. Wild watercress should not be sold for human consumption.
