Clinical Parasitology- RA3

Question 1

Parasitism

Answer 1

One organism benefits at the expense of another

Question 2

Symbiosis/ Mutualism

Answer 2

Both partners benefit from each other

Question 3

Commensalism

Answer 3

One partner benefits, the other is unaffected

Question 4

Ectoparasite

Answer 4

Lives on surface of the host (e.g. arthropods)

Question 5

Endoparasite

Answer 5

Lives within the host (e.g. protozoa & helminths)

Question 6

Obligate parasite

Answer 6

Must spend at least part of the lifecycle associated with host

Question 7

Faculative parasite

Answer 7

Capable of living a free & parasitic existence

Question 8

Vector

Answer 8

Insect that transmits infectious agent

Question 9

Protozoa

Answer 9

Uunicellular eukaryotic microbe

Question 10

Helminth

Answer 10

Worm

Question 11

Namatode

Answer 11

Roundworm

Question 12

Cestode

Answer 12

Tapeworm

Question 13

Trematode

Answer 13

Fluke (flatworm)

Question 14

Describe the prevalence of parasitic diseases worldwide & especially in developing/under-developed countries.

Answer 14

“Parasitic infections currently account for greater morbidity & mortality than any other class of infectious agent in developing or under-developed countries.”

Question 15

List the characteristics of protozoa.

Answer 15

• Single celled eukaryotes
• Nucleated
• Contain organelles
• Many encyst themselves

Question 16

List the characteristics of helminths.

Answer 16

• Multicellular
• Elongated appearance
• Covered by a thick membranous coating called a cuticle

Question 17

How are protozoa classified?

Answer 17

Based on locomotion

Question 18

What are the four classes of protozoa?

Answer 18

Ameba
Flagellates
Sporozoa
Ciliates

Question 19

Ameba

Answer 19

Pseudopodia

Question 20

Flagellates

Answer 20

Flagella

Question 21

Sporozoa

Answer 21

Gliding

Question 22

Ciliates

Answer 22

Cilia

Question 23

What is special about the reproductive mechanism of the sporozoa?

Answer 23

Reproduction by schizogony

Question 24

What is Schizogony?

Answer 24

Multiple intracellular nuclear divisions prior to cytoplasmic divison

Question 25

How are Helminths classified?

Answer 25

Roundworm vs. Flatworm

Question 26

What group belongs to the roundworms?

Answer 26

Namatodes

Question 27

What groups belong to the flatworms?

Answer 27

Cestodes & Trematodes

Question 28

What is the difference between Cestodes & Trematodes?

Answer 28

Cestodes= Tapeworm that is segmented & lacks a digestive tract Trematode= non-segmented "Fluke"

Question 29

List the modes of parasitic transmission.

Answer 29

- Ingestion - Direct penetration of skin - Inoculation by vectors - Congenital transmission - Transmission by transfusion or transplantation

Question 30

What are the mechanisms of parasitic disease?

Answer 30

- Mechanical damage - Damage caused by parasitic products - Damage caused by the immune response to the parasite

Question 31

How does the immune response to protozoa differ from the response to helminths?

Answer 31

Protozoa= typical response similar to what would be seen against virus or bacteria Helminths= IgE & eosinophil dominated

Question 32

How do parasites evade the immune system?

Answer 32

- Size = often too large to be phagocytosed - Anatomical Location= residence in the gut makes it difficult for immune system to reach them - Intracellular sequestration - Formation of a cyst - Avoidance of phago-lysosomal destruction - Antigenic variation - Antigenic masking - Immunosuppression

Question 33

What is the major challenge to chemotherapeutic & immunological interventions to parasitic disease?

Answer 33

- Parasitic organisms are eukaryotic cells & are very similar to human cells - Thus, treatment often results in toxicity to the host - Differential toxicity is achieved by using drugs that are metabolically altered only by the parasite

Question 34

What are the two major drug groups used in treating parasitic infections?

Answer 34

- Anti-protozoals= target rapidly proliferating, metabolically active cells - Anti-helminths= Affect the neuromuscular system, carbohydrate metabolism, or egg production of adult worms