Microbiology & infectious diseases
Parasites-gastrointestinal (not liver)
Diphyllobothrium latum
Author: Haind Fadel, M.D.
Last author update: 1 January 2015
Last staff update: 5 October 2020
Copyright: 2003-2025, PathologyOutlines.com, Inc.
PubMed Search: Diphyllobothrium latum[TI] cestodes
Table of Contents
Definition / general | Epidemiology | Pathophysiology | Diagrams / tables | Clinical features | Diagnosis | Case reports | Treatment | Gross images | Microscopic (histologic) images | Differential diagnosisCite this page: Fadel H. Diphyllobothrium latum. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/parasitologydiphyllobothrium.html. Accessed January 21st, 2025.
Definition / general
- Humans may be infected by one of several species of the fish tapeworm Diphyllobothrium, which normally infect piscivorous mammals and possibly birds
- Although Diphyllobothrium latum is the most common species to infect humans, differentiation cannot be made based on morphology - molecular methods are required (Emerg Infect Dis 2014;20:1955)
Epidemiology
- Occurs in Northern Hemisphere (Europe, North America, Asia) and South America (Uruguay and Chile)
- Humans acquire larvae by ingesting raw or incompletely cooked fish that have spent at least part of their life in fresh water
Pathophysiology
- Cestode Diphyllobothrium latum (the fish or broad tapeworm) is largest human tapeworm
- Inhabits small intestine, grows to 10 meters or longer, can persist for years
Diagrams / tables
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Life cycle - Diphyllobothrium latum
Clinical features
- Adult worms mature and initiate egg production in ~1 month
- Infection may be asymptomatic, with passage of a length of strobila being the initial complaint (Korean J Parasitol 2007;45:219)
- In others, a variable degree of abdominal discomfort and diarrhea may be present
- Rarely, intestinal obstruction occurs
- In endemic areas in Northern Europe, a small percentage of patients develop vitamin B12 deficiency and associated megaloblastic anemia
Diagnosis
- Diagnosis made by finding the typical brown, oval, operculate eggs in feces using standard recovery techniques
- Eggs: measure 58 - 76 μm by 40 - 51 μm and in addition to the operculum, have a small round knob-like projection on the abopercular end
- Scolex: elongated; displays a pair of longitudinal grooves known as bothria, which replace the usual suckers
- Gravid proglottids: wider than long, have genital pores located midventrally, adjacent to centrally located, rosette shaped uterus
Case reports
- 20 and 50 year old men with Diphyllobothrium nihonkaiense infection (Korean J Parasitol 2014;52:197)
- Molecular detection of Diphyllobothrium nihonkaiense in humans (Emerg Infect Dis 2014;20:315)
Treatment
- Praziquantel: adults and children, one dose, 5 - 10 mg/kg orally
- Niclosamide: adults 2 gm orally once; children 50 mg/kg (maximum 2 gm) orally once
Gross images
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Proglottids
Microscopic (histologic) images
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Eggs in wet mount
Proglottids and scolex
Adults and eggs in tissue
Differential diagnosis
- Other intestinal cestodes
