Chapter 5: The Protozoa

Question 1

What are the two methods for tissue and organ infection by protozoa?

Answer 1

1. As intracellular parasites, obtaining nutrients by direct uptake or ingestion of cytoplasm
2. As extracellular parasites in the blood, intestine or genitourinary system, obtain nutrients by direct uptake or ingestion of host cells

Question 2

What are three important characteristics of protozoa?

Answer 2

1. single-celled, eukaryotic cells, ranging in size from 2-100 nm
2. most are free-living, but others are important parasites of humans
3. multiply in their host until controlled by its immune response or by treatment

Question 3

Which protozoa parasite presents the most severe global problem?

Answer 3

malaria kills approximately 500,000 people per year, mostly young children

Question 4

What is the mode of reproduction of protozoa? What is an exception to the typical mode?

Answer 4

In humans, reproduction is usually asexual, by binary or multiple division of growing stages (trophozoites)
Sexual reproduction is normally absent or occurs in the insect vector phase of the life cycle, where present
-Cryptosporidium is exception in undergoing both asexual and sexual reproduction in humans

Question 5

Which intestinal parasite produces cysts as part of its life cycle and is commonly contracted when drinking unfiltered mountain water?

Answer 5

Giardia lamblia

Question 6

What are the protozoal classes based on mode of locomotion?

Answer 6

Amoeboids (pseudopodia), ciliates (cilia), sporozoa (non-motile), flagellates (flagella)

Question 7

What three examples were shown of extracellular protozoa evading immune recognition by the host?

Answer 7

1. trypanosomes undergo antigenic variation of surface antigens
2. malaria parasites show polymorphisms in dominant surface antigens
3. . amoebae can consume complement at the cell surface

Question 8

How can intracelular protozoa evade host defense mechanisms?

Answer 8

A variety of devices evade or inactivate the harmful effect of intracellular enzymes or reactive oxygen and nitrogen metabolites

Question 9

What are some issues that could arise from the host immune response and antimalarial treatment?

Answer 9

antigenic variation, anemia, toxic by-products