Concept Questions

Take some time to write answers to these questions. If you can answer them, you have a good grasp of the material!

1. As a review, compare the four major groups of protozoa according to overall cell structure, locomotion, infective state, and mode of transmission.

2. What are the primary functions of the trophozoite and the cyst in the life cycle? In which diseases is a cyst stage an important part of the infection cycle?

3. Why does Entamoeba require healthy carriers to complete its life cycle? What is the role of night soil in transmission of amebiasis? What is the basic pathology of amebiasis? How and where does it invade? Why are so many cases asymptomatic?

4. Briefly describe how primary amebic meningoencephalitis is acquired and its outcome.

5. Compare trichomoniasis and amebiasis with respect to transmission, life cycle, and relative hardiness.

6. Name ways in which giardiasis and amebic dysentery are similar. How are they different?

7. Compare the infective stages and means of vector transfer in the two types of trypanosomiasis and leishmaniasis. Are there any stages in the life cycle of the blood flagellates that occur in all three species? Which phase or phases is/are not ever infective to humans? (Hint: Look at table 23.3.)

8. What factors cause the symptoms in trypanosomiasis? In leishmaniasis?

9. What is the name of the infective stage of the malaria parasite in humans? In mosquitos? How many times must a female mosquito feed before the parasite can complete the whole cycle? Where in the human does development take place, and what are the results? What stage of development is the ring form? Which events cause the symptoms of malaria?

10. Describe the life cycle and host range of Toxoplasma gondii. How are humans infected? What are the most serious outcomes of infection?

11. Briefly describe the transmission cycle of Cryptosporidium, Sarcocystis, and Babesia.

12. In what ways are helminths different from other parasites, and why are there so many parasitic worm infections worldwide? What is the nature of human defenses against them?

13. Outline the five general cycles, and give examples of helminths that exhibit each cycle. What are the main portals of entry in worm infestations? How is damage done by parasites?

14. What are some ways that worms adapt to parasitism, and how are these adaptations beneficial to them?

15. How are nematodes, trematodes, and cestodes different from one another?

16. Where in the body do the helminth adults ultimately reside and produce fertile eggs?

17. How do adult Ascaris get into the intestine? How do adult hookworms get into the intestine? How do microfilariae get into the blood?

18. In what ways is trichinosis different from other worm infections?

19. Which worms can be found in the eye? Which worm can cause blindness?

20. What are the stages in Schistosoma development? Which organs are affected by schistosomiasis? What other organs can be invaded by flukes?

21. Describe the structure of a tapeworm. Name several ways in which tapeworms are spread to humans.

22. Which helminths are zoonotic? Which are strictly human parasites? Which are borne by vectors? Which can be STDs? Which cause intestinal symptoms?

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