About Medical Parasitology

New Infections

Ova & Parasite (O&P) Exams

CPT Codes

Quizzes, General

Quizzes, Histology

Quizzes, Blood

Review Tests


Information Tables

Organism Index (A-Z)



***Reminder: Slides are copyrighted and cannot be copied for publication.

A 9-year-old female from a rural area presented to the pediatrics outpatient department with a chief complaint of intermittent abdominal pain, anal pruritus and nocturnal restlessness since for last 2-3 weeks. On physical examination, there were no positive clinical findings. Routine O&P examinations of the stool samples revealed the following images: spherical eggs 70 µm in diameter, yellow-colored, thick-shelled eggs that contained six central hooklets but no polar filaments.

The image on the left is from the direct saline mount, while the middle and right images were prepared using D’Antoni’s iodine in the wet mount from the concentration sediment.


  1. What organisms are suggested from the images shown above?

  2. What groups of parasites might be involved, and are these typical based on her history?

  3. Does the morphology provide an accurate identification? Why or why not?

  4. How common is this parasite worldwide and how likely is it that the patient might be asymptomatic?

(Scroll Down for Answers and Discussion)


The images presented in Diagnostic Quiz #78 are the following: ANSWERS TO QUESTIONS:

  1. The images certainly suggest a helminth egg; the overall appearance is that of a tapeworm egg (cestode), particularly with the presence of the six-hooked embryo (oncosphere).

  2. The history is relatively non-specific; in cases of this infection there may be nothing to suggest the infection and/or possible exposure route. Also, the patient may actually be asymptomatic.

  3. The presence of spherical eggs 70 µm in diameter, yellow-colored, thick-shelled eggs that contained six central hooklets but no polar filaments are suggestive of Hymenolepis diminuta eggs, the rat tapeworm. Although Hymenolepis nana (the dwarf tapeworm) is much more common, occasionally

    H. diminuta can be found, particularly in children. The H. diminuta eggs are characterized by having no polar filaments that lie between the oncosphere and the egg shell, while H. nana has the typical polar filaments (see images below).

  4. This infection is uncommon, but when found is often from children. Again, the patient may have vague mild symptoms or may be asymptomatic.


H. diminuta is a rodent parasite for which the arthropod acts as intermediate host. Rodents become infected by ingesting the arthropod containing cysticercoid larvae. Human beings, usually children, can be accidentally infected by the ingestion of infected arthropod (often grain beetles). In humans, infections with

H. nana are much more common than those by H. diminuta, as its transmission does not require any intermediate host. H. nana can be spread directly from person to person via the eggs. Although H. diminuta infection in humans is uncommon, a few hundred cases have been reported worldwide. The human form of H. diminuta infection is often asymptomatic, but abdominal pain, irritability, itching and eosinophilia have been reported.


The routine O&P examination is recommended for egg recovery and subsequent microscopic identification (10X and 40X power – low and high dry).


The images are very typical. Note the six-hooked oncosphere and no polar filaments in H. diminuta, while the polar filaments are present in H. nana (see arrows).

Hymenolepis diminuta Hymenolepis nana


Garcia, L.S. 2016. Diagnostic Medical Parasitology, 6th Ed., ASM Press, Washington, D.C.


Each Quiz has a two section format: the first section will present the Quiz topic and the second section will provide a discussion of the answer and/or various options in response to the Quiz situation presented to the user. In some situations, there may be more than one correct response.

The content within this site is made possible through the extensive contribution of Lynne S. Garcia, M.S., MT(ASCP), CLS(NCA), BLM(AAB), F(AAM), Director, Consultantation and Training Services (Diagnostic Medical Parasitology and Health Care Administration). For additional information, she can be contacted at LynneGarcia2@verizon.net.

Reference: Garcia, L.S. 2015. Diagnostic Medical Parasitology, 6th Ed., ASM Press, Washington, D.C.

Quiz 1 Quiz 2 Quiz 3
Quiz 4 Quiz 5 Quiz 6
Quiz 7 Quiz 8 Quiz 9
Quiz 10 Quiz 11 Quiz 12
Quiz 13 Quiz 14 Quiz 15
Quiz 16 Quiz 17 Quiz 18
Quiz 19 Quiz 20 Quiz 21
Quiz 22 Quiz 23 Quiz 24
Quiz 25 Quiz 26 Quiz 27
Quiz 28 Quiz 29 Quiz 30
Quiz 31 Quiz 32 Quiz 33
Quiz 34 Quiz 35 Quiz 36
Quiz 37 Quiz 38 Quiz 39
Quiz 40 Quiz 41 Quiz 42
Quiz 43 Quiz 44 Quiz 45
Quiz 46 Quiz 47 Quiz 48
Quiz 49 Quiz 50 Quiz 51
Quiz 52 Quiz 53 Quiz 54
Quiz 55 Quiz 56 Quiz 57
Quiz 58 Quiz 59 Quiz 60
Quiz 61 Quiz 62 Quiz 63
Quiz 64 Quiz 65 Quiz 66
Quiz 67 Quiz 68 Quiz 69
Quiz 70 Quiz 71 Quiz 72
Quiz 73 Quiz 74 Quiz 75
Quiz 76 Quiz 77 Quiz 78
Quiz 79 Quiz 80 Quiz 81
Quiz 82 Quiz 83 Quiz 84
Quiz 85 Quiz 86 Quiz 87
Quiz 88 Quiz 89