Diphyllobothriasis Associated with Eating Raw Pacific Salmon

The incidence of human infection with the broad tapeworm Diphyllobothrium nihonkaiense has been increasing in urban areas of Japan and in European countries. D. nihonkaiense is morphologically similar to but genetically distinct from D. latum and exploits anadromous wild Pacific salmon as its second intermediate host. Clinical signs in humans include diarrhea and discharge of the strobila, which can be as long as 12 m. The natural life history and the geographic range of the tapeworm remain to be elucidated, but recent studies have indicated that the brown bear in the northern territories of the Pacific coast region is its natural final host. A recent surge of clinical cases highlights a change in the epidemiologic trend of this tapeworm disease from one of rural populations to a disease of urban populations worldwide who eat seafood as part of a healthy diet.