Diphyllobothriasis is defined as infection with the cestode Diphyllobothrium latum or other Diphyllobothrium species. It is endemic in areas where humans frequently consume raw or pickled fish. Diphyllobothriasis is a worldwide disease that affects people near fresh water and appropriate intermediate hosts. D latum commonly infects persons residing in Europe, Africa, and the Far East. Areas where consumption of raw or precooked fish is popular tend to have endemicity. Most persons with diphyllobothriasis are asymptomatic.
Sometimes when symptomatic the most common symptoms are abdominal pain, indigestion or dyspepsia, passage of proglottids. Other less common symptoms that are associated with this disease include fatigue, diarrhea, dizziness, numbness of extremities, and sensation of hunger. The actual results of infestation are not well studied; megaloblastic anemia is known to be a possible consequence. Diphyllobothriasis can also lead to cysticercosis whereby larval cysts infiltrate the lung, liver, eye or brain.
This results in inflammation leading to clinical features such as blindness, and neurological symptoms. In some countries (eg, Peru and Mexico) neurocysticercosis accounts for 30% of seizures making it an important cause of morbidity and mortality worldwide. 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. 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. No significant cases are reported in Mexico. D
Diphyllobothriasis is treated by pharmacologic means; surgical treatment is not required unless otherwise indicated. Even in the face of decreased vitamin B-12 levels, less than 2% of patients with diphyllobothriasis develop anemia. Vitamin supplementation may be required in severe cases. Praziquantel is considered the drug of choice for D latum infection, with niclosamide as an alternative. Resistant or advanced cases of diphyllobothriasis may require consultation with a gastroenterologist and an infectious disease specialist. The neurologic and hematologic manifestations of vitamin B-12 deficiency respond well to supplementation.