Diphyllobothriasis

Diphyllobothriasis occurs in areas where lakes and rivers coexist with human consumption of raw or undercooked freshwater fish. Such areas are found in the Northern Hemisphere (Europe, newly independent states of the former Soviet Union (NIS), North America, Asia) (particularly in Japan (because of Sushi or Sashimi)), Uganda, Peru (because of Ceviche) Chile.
Around the middle of the 20th century in Japan, before advancements in refrigeration, many sushi/sashimi connoisseurs suffered great morbidity and mortality from Diphyllobothrium after eating unrefrigerated sashimi. Through research in parasitology, scientists came to realise that the primary cause was the relatively-favourable parasite-breeding conditions that raw fish offered.
The disease is rare in the United States, however it was once more common and was referred to as "Jewish housewife's disease" because Jewish housewives preparing the traditional "gefilte fish" frequently tasted the fish before it was cooked

Praziquantel and niclosamide are historical treatments that should no longer be used as first line therapy in developed countries; they result in destruction and disintegration of the worm which may make it impossible to confirm that the scolex (head of the worm) has been passed (the only way to confirm cure). Praziquantel or niclosamide should only be used in situations when endoscopy is not available or is not possible.
The preferred treatment for all tapeworm infections is injection of diatrizoic acid into the duodenum, which causes the worm to detach and be passed whole.