Pathology > Parasitology > 1. Intestinal Parasites


(answers at end of document)

1.This is a microscopic section of colon with invasive protozoan parasites. What species is likely to be involved, and what determines its pathogenic potential?

2.These are trophozoites of the protozoan shown on the previous slide, stained in two ways. What characteristics allow you to make a diagnosis?


3.This drawing illustrates most of the salient characteristics which would help make a diagnosis on the previous slide.

4.Several cysts of which ameba are shown here?

5.This drawing illustrates the diagnostic features of the cysts on the previous slide.

6. Which intestinal protozoan is shown here, and what is the significance of detecting this organism?

7.The diagnostic features of the trophozoite on the previous slide are illustrated in comparison to those of the pathogenic ameba shown earlier.

8. Photographs of two planes of focus of the same cysts are shown. Which organism is this?

9. The characteristics of the cysts of both ameba species are diagramed.

10.Which intestinal protozoan is shown, which stage of the life cycle and what is the pathophysiology of the disease?

11.The diagnostic features of Giardia are shown.

12. Which intestinal helminth is shown, in what part of the intestine does it reside, and how can it cause symptomatic disease?

13. Three forms of eggs of the helminth are shown. Why are they different?

14. Which helminth egg is shown, and how does the parasite cause disease?

15.What kind of specimen would be most likely to yield this egg, and what is the likely clinical setting.

16.Which egg is shown, how might you contract this infection, and what is the most important feature of the associated disease?

17.The diagnostic criteria of the egg on the previous slide is shown.

18.Compare the life cycles of these two nematodes. Why is it important to be able to distinguish these two larvae?

19.A pair of adult trematodes are shown. Where are they found in the infected host, and what is the pathophysiology of the disease associated with the infection?

20,21,22.The eggs on these slides come from different species of the trematode shown in slide 19. Where in the body are the eggs likely to be found, and what specimens might be taken to find them?

23. The characteristics of the eggs in the last three slides are diagramed.

24.The head and two views of the body of a tapeworm are shown. The egg is shown on the next slide (25).

25.Which tapeworm is this, and how is the infection contracted?

26.The features of the egg of the tapeworm of the previous two slides are diagramed.

27.Which helminth might this be? Why should you bother to find out?

28,29.What characteristics of the Taenia species shown the these slides allows you to differentiate them?


Entamoeba histolytica trophozoites


E. histolytica cysts


Entamoeba coli - fecal - oral contamination is suggested, look for other pathogens


Giardia lamblia


Ascaris - Embryonated eggs with and without coats and unembryonated






Hook worm


Hookworm, strongloides




Diphylobothryum latum - contracted through raw fish


Tapeworm, solium vs. saginata


Eggs the same, scolex differs