Diphyllobothrium is a genus of tapeworm which can cause Diphyllobothriasis in humans through consumption of raw or undercooked fish. The principal species causing diphyllobothriosis is Diphyllobothrium latum, known as the broad or fish tapeworm, or broad fish tapeworm. D. latum is a pseudophyllid cestode that infects fish and mammals. D. latum is native to Scandinavia, western Russia, and the Baltics, though it is now also present in North America, especially the Pacific Northwest. In Far East Russia, D. klebanovskii, having Pacific salmon as its second intermediate host, was identified. Other members of the genus Diphyllobothrium include Diphyllobothrium dendriticum (the salmon tapeworm), which has a much larger range (the whole northern hemisphere), D. pacificum, D. cordatum, D. ursi, D. lanceolatum, D. dalliae, and D. yonagoensis, all of which infect humans only infrequently. Diphyllobothriasis occurs in areas where lakes and rivers coexist with human consumption of raw or undercooked freshwater fish. Such areas are found in Europe, newly independent states of the former Soviet Union, North America, Asia, Uganda, Peru, and Chile. It is particularly common in Japan, because of sushi or sashimi. 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 realize that the primary cause was the relatively favorable parasite-breeding conditions that raw fish offered. The disease is rare in the United States. It was, however, 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.
People at high risk for infection have traditionally been those who regularly consume raw fish. Many regional cuisines include raw or undercooked food, including sushi and sashimi in Japanese cuisine, carpaccio di persico in Italian, tartare maison in French-speaking populations, ceviche in Latin American cuisine and marinated herring in Scandinavia. With emigration and globalization, the practice of eating raw fish in these and other dishes has brought diphyllobothriasis to new parts of the world and created new endemic foci of disease. The standard treatment for diphyllobothriasis, as well as many other tapeworm infections is a single dose of Praziquantel, 5–10 mg/kg PO once for both adults and children.
An alternative treatment is Niclosamide, 2 g PO once for adults or 50 mg/kg PO once. One should note that Praziquantel is not FDA approved for this indication and Niclosamide is not available for human use in the United States. One treatment for sparganosis is praziquantel, administered at a dose of 120 to 150 mg/kg body weight over 2 days; however, praziquantel has had limited success. In general, infestation by one or a few sparganum larvae is often best treated by surgical removal. DNA analysis of rare worms removed surgically can provide genome information to identify and characterise each parasite; treatments for the more common tapeworms can be cross-checked to see whether they are also likely to be effective against the species in question.