Microbiology & infectious diseases
Parasites-gastrointestinal (not liver)
Hymenolepis nana
Author: Haind Fadel, M.D.
Last author update: 1 January 2015
Last staff update: 5 October 2020
Copyright: 2003-2024, PathologyOutlines.com, Inc.
PubMed Search: Hymenolepis nana[TI] full text[sb]
Table of Contents
Definition / general | Diagrams / tables | Life cycle | Clinical features | Diagnosis | Case reports | Treatment | Clinical images | Cytology description | Cytology images | Differential diagnosis | Additional referencesCite this page: Fadel H. Hymenolepis nana. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/parasitologyhymenolepisnana.html. Accessed December 24th, 2024.
Definition / general
- Dwarf tapeworm (nanos means dwarf), up to 40 mm long; among the smallest and most common intestinal parasitic infections causing a public health threat worldwide, particularly among children
- Most frequently recovered cestode species in US
Diagrams / tables
Images hosted on other servers:
Life cycle: Hymenolepis nana
Life cycle
- Direct life cycle: through ingestion of infectious eggs
- Eggs may be passed directly from person to person, usually by children
- Eggs may be ingested in food, especially grain products contaminated by rodent droppings (parasite is common in mice)
- Indirect life cycle: through ingestion of intermediate hosts (usually grain beetles) containing cysticercoid larvae; less common
- After human ingestion, eggs hatch in intestine and embryos penetrate the mucosa, where they mature as cysticercoid larvae
- Larvae subsequently emerge and reattach to the intestinal wall to complete their development into adult tapeworms in 2 - 3 weeks
- Internal autoinfection: if eggs hatch shortly after being discharged from worm and rapidly invade the intestinal wall without leaving the body
Clinical features
- Symptoms develop if large number of worms
- May include abdominal pain, diarrhea, anorexia, irritability
Diagnosis
- Recovery of oval, thin shelled, colorless eggs, 30 - 47 μm, from stool
- Scolex has an armed rostellum
- Proglottids have all of their genital pores located on same side of strobila
Case reports
- 44 year old man with heavy Hymenolepis nana infection, possibly through organic foods (Korean J Parasitol 2014;52:85)
- Finding in a concentrated stool specimen (Pritt: Creepy Dreadful Wonderful Parasites Blog - Case of the Week 539 [Accessed 18 April 2019])
Treatment
- Praziquantel
Clinical images
Images hosted on other servers:
Large number of adult worms in colon
Adults
Cytology description
- Egg has a thin inner membrane surrounding a hooked oncosphere from which polar filaments arise (Pritt: Creepy Dreadful Wonderful Parasites Blog - Answer to Case 539 [Accessed 18 April 2019])
- Polar filaments arise from opposite poles of the inner membrane and spread out into the space between the inner and outer membranes
Cytology images
Contributed by Bobbi Pritt, M.D.
H. nana egg in stool specimen
H. nana and H. diminuta eggs
Images hosted on other servers:
Morphological characteristics
Eggs, various images
Proglottids, various images
Adults
Differential diagnosis
- Other cestode worms
- Hymenolepis diminuta: has no polar filaments (Pritt: Creepy Dreadful Wonderful Parasites Blog - Answer to Case 539 [Accessed 18 April 2019])
- Plant material: see Pritt: Creepy Dreadful Wonderful Parasites Blog - Answer to Case 534 [Accessed 23 August 2019]
Additional references
