Food-borne trematode infections of humans in the United States of America

Abstract

This review examines the literature on imported (allochthonous) and local (autochthonous) cases of food-borne trematode (FBT) infections in the United States of America (USA) from 1890 to 2009. Most of the literature is concerned with imported cases of the opisthorchiids Clonorchis sinensis and Opisthorchis viverrini. These flukes cause serious pathology in the liver and biliary system of humans. Chronic cases may induce liver (hepatocarcinoma) and bile duct (cholangiocarcinoma) cancers in humans. Clonorchiasis and opithorchiasis are preventable diseases that can be avoided by eating properly cooked freshwater fish products. Several species of lung flukes in the genus Paragonimus are local or imported FBT in the USA. The endemic cycle occurs in the USA with various local snails and crustaceans serving as intermediate hosts. Paragonimids are acquired when humans eat raw or improperly cooked freshwater crustaceans containing metacercarial cysts. Infection can cause severe lung disease and the symptoms of paragonimiasis often mimic those of tuberculosis and other non-helminthic diseases. Paragonimiasis can be avoided by not eating raw or improperly cooked shellfish. The liver fluke Fasciola hepatica can be acquired by eating raw or uncooked vegetation. The cycle exists in the USA involving local snails and aquatic vegetation. Although some cases are local, most are imported by travelers or immigrants. Fascioliasis can cause serious liver and biliary diseases in humans and consumption of tainted vegetation should be avoided. Lesser known FBT have been reported in the USA including species of Alaria, echinostomids, heterophyids, troglotrematids, and a self-induced infection of Plagiorchis. Treatment of the FBT mentioned in this review consists of various regimens of praziquantel, except for F. hepatica where the drug of choice is triclabendazole.