L3: Intestinal and Luminal Amoeba and Flagellates of man

Question 1

What is the phylogeny of E. Histolytica

Answer 1

Phylum- Sarcomastigophora
Sub Phylum- Sarcodina 
Class- Rhizopoda 
Order- Amoebida
Order- Schizopyrenida

Question 2

What is the phylogeny of Giardia intestinalis

Answer 2

Phylum- Sarcomastigophora
Sub-Phylum - Mastigophora 
Class- Zoomastigophora 
Order- Diplomonadida 
Order- Trichomonadida

Question 3

Which commensal appears similar to E.histolytica

Answer 3

E.dispar

Question 4

Which parts of the human body are infected by E. histolytica

Answer 4

Intestines and extraintestines

Question 5

How do we identify E. histolytica

Answer 5

Only amoeba which feeds on red blood cells in humans

Question 6

Describe the nucleus of the trophozoite of E. histolytica

Answer 6

Cartwheel arrangement of chromatin

Question 7

What is the trophozoite phase of the entamoeba lifecycle called

Answer 7

A feeding animule/ feeding stage

Question 8

What is the cyst phase of the entamoeba lifecycle called

Answer 8

The infectious stage

Question 9

Describe the physical structure of an entamoeba cyst

Answer 9

Mature cysts have four nuclei with RNA associated to them, it is round and has a fibrous cell wall.
Immature cysts have a dark stained oval shaped structure known as a chromotoidal structure containing crystalline RNA

Question 10

What is the average size of the ent cyst

Answer 10

10-12 um

Question 11

How many fatalities are due to e hist

Answer 11

70k-100k

Question 12

E hist is the ___ most common cause of parasitic death in the world

Answer 12

Third

Question 13

Which groups are at risk for E. hist

Answer 13

• Male homosexuals
• Travelers
• Immigrants
• Institutionalized persons Eg prisoners

Question 14

Where might mature cysts of E hist be found

Answer 14

Fecally contaminated water, vegetables, through flies

Question 15

Describe the lifecycle of E hist in humans

Answer 15

Mature cyst ingested
Fibrous wall broken down by stomach acid causing excystation
In the large intestine the parasite forms ulcers in the small intestine wall which cause parasites to get into the blood supply. These parasites travel to the liver, brain and lungs. They do not produce cysts
Cysts are produced by commensals. When the colon absorbs water it causes trophozoites in that area to become cysts. These cysts develop to maturity and are produced in feces.

Question 16

What type of parasite is E histolytica

Answer 16

Luminal and Intestinal

Question 17

What are the three possible stages of pathogenisis

Answer 17

Benign- no invasive
Invasive- Ulcers
Extra Intestinal

Question 18

What is the purpose of the muscularis mucosa

Answer 18

Provides a physical barrier for the ulcer and prevents extra intestinal spread of trophozoites

Question 19

How is an ulcer formed

Answer 19

Proteolytic enzymes secreted by the trophozoites will erode the mucosa forming ulcers in the colon and appendix

Question 20

What is an amoeboma

Answer 20

A pseudo tumor formed as an immune response to a tumor in the colon. It may obstruct the intestine

Question 21

What is dysentery

Answer 21

Bloody diarrhea and soft mucusy stool, frequent visits to the bathroom and dehydration

Question 22

Explain the ways in which extra intestinal infection may lead to death

Answer 22

Cerebral amoebiosis

Perforated colon leads to bacteria flowing into the body cavity causing a sepsis

Question 23

What is the main mode of transmission of E.hist

Answer 23

Contact with fecal contaminated materials

Phoretic Commensalism

Question 24

What test may be used to distinguish E hist from E dispar

Answer 24

PCR based methods

Question 25

How does E hist avoid the immune system

Answer 25

• Secrete proteases which degrade antibodies (proteins)
  They have a cytolyitc capacity which allows them to degrade host tissue thus decreasing the immune response to trophozoites
  Secretions of the parasites may decrease the energy of T cells causing immunosuppresion

Question 26

Which drugs treat E hist and what do they do

Answer 26

Iodoquinol- Asymptomatic Infections

Metronidozole- Both asymtomatic and symptomatic infections

Question 27

Give an example for a freeliving ameoba which is a facultative parasite

Answer 27

Acanthamoeba spp - Opportunistic infection

Question 28

Describe the trophozoite of Giardia Intestinalis

Answer 28

Pear shaped, 10-18 um in length with 4 pairs of flagella, paired nuclei and median bodies
Mitosomes not mitochondria

Question 29

Describe Giardia cyst

Answer 29

Has a wall around it with 4 nuclei and remnants of flagella

10-12 microns

Question 30

Describe the Giardia Lifecycle

Answer 30

Enters through mouth
Acid bath breaks down cell wall
Small intestine parasite

Question 31

What are the two ways Giardia may manifest

Answer 31

Acute
- Incubates 5-6 days 
- Lasts 1-3 weeks 
- Diahrrea, abdominal pain, bloating, vomitting 
-Self limiting infection 
Chronic 
-Malabsorption of fats and B12 
- Recurrent symptoms 
- Gross discomfort 
- Not fatal

Question 32

This amoebic infection is family associated

Answer 32

Giardia intestinalis

Question 33

How does giardia evade the immune system

Answer 33

By having variation of antigens

Question 34

Which drug is used to treat giardia

Answer 34

Metranitrozole

Question 35

How is Giardia tested for

Answer 35

Identification of cysts or trophozoites in feces

Question 36

This amoebic parasite has no cysts in its lifecycle

Answer 36

Trichomonas vaginalis

Question 37

What is the primary mode of transmission of T.vaginalis

Answer 37

Sexual contact

Question 38

Describe the structure of t vaginalis

Answer 38

4 flagella
single nucleus
two axostyles which are asymmetric
5-18 microns

Question 39

What is an over the counter treatment for T vag

Answer 39

Vinegar douches