Diphyllobothrium latum

Background

• Cestode also known as broad fish tapeworm
• Most common cause of diphyllobothriasis
• Other species in the family can also infect humans, including Dibothiocephalus nihonkaiense, Dibothriocephalus dendriticus, Diphyllobothrium stemmacephalum, Diphyllobothrium balaenopterae, and Adenocephalus pacificus

Epidemiology

• Life cycle starts with eggs that pass from the feces of the definitive hosts (fish-eating mammals and birds) into the water; they hatch into coracidia, which are ingested by intermediate host (crustaceans); coracidia develop into larvae in the crustacean, which is then eated by a second intermediate host (small fish); in the small fish, it develops into plerocercoid larvae; the infested fish is eaten by the definitive host (or a human), where it develops into its cestode form in the small intestine
• Relatively wide distribution, but most common in the circumpolar and arctic regions

Clinical Manifestations

• Infestations may be chronic, up to 25 years
• Mostly asymptomatic
• Can cause vitamin B12 deficiency
• Occasionally cause GI symptoms
• Occasionally cause cholecystitis or cholangitis due to migration of the proglottids

Diagnosis

• Identification of ova or proglottids in stool
• May be found incidentally during endoscopy

Management

• Praziquantel 5 to 10 mg/kg p.o. once
• Alternative: niclosamide 2 g p.o. (chewed or crushed) once