Lecture 4: Protozoan Parasites

Question 1

what is a protozoa?

Answer 1

usually defined as protists that are more animal like than plant like

most of them are motile, although they don’t photosynthesize.

they can live in different areas of the body (different hosts).

• the gut, liver, spleen, heart, eyes, etc

Question 2

protozoa are divided into 4 main groups, what are they?

Answer 2

1. amoeba
2. flagellates
3. cilliates
4. sporozoa

Question 3

from the point of view of functional and physiological complexity, a protozoan is more like an animal or single cell?

Answer 3

more like an animal than a single cell

Question 4

what is niche selection

Answer 4

selected to live in a specific essential niche defined by anatomical, physiological and biochemical features of the site.

Question 5

what are two types of stages in the complex life cycle of parasites?

Answer 5

• asexual and sexual reproduction
• resistant cyst stage (not all) (protection stage)

Question 6

describe motility in amoebas

Answer 6

1. Extension (the formation of long actin filaments at the leading edge extends the lamellipodium)
2. Adhesion
3. Translocation (rearrangement of the actin cytoskeleton in other regions of the cell causes the cell to be pulled toward the leading edge.
4. De-adhesion

Question 7

flagellum vs cilia movement?

Answer 7

cilia: back and forth beating
you will see multiple around exterior

flagellum: propeller-like motion
only a few

there will always be a basal body (anchor).

Question 8

how do sporozoa move?

Answer 8

• NO FLAGELLA, CILLIA OR PSEUDOPOD
  
  • They have an actin-myosin that attach to the surface that move unidirectionally.

Question 9

how do protozoa reproduce asexually (2)

Answer 9

• binary fission and multiple fission

they are variations on mitotic division

Question 10

how do protozoa reproduce sexually?

Answer 10

by gamete fusion

Question 11

Apicomplexan life cycle

Answer 11

• You have one part of it that is the sexual stage
• Haploid stage and diploid stage.

Question 12

define sporogony

Answer 12

multiple fission of a zygote

Question 13

define sporozoite

Answer 13

daughter cell resulting from sporogony

Question 14

define schizogony

Answer 14

fission of sporozoites where multiple mitoses take place followed by simultaneous cytokineses, resulting in many daughter cells all at once.

Question 15

define Gametogony

Answer 15

production of gametes

Question 16

define zygote

Answer 16

fusion of gametes (meiosis may occur after fusion).

Question 17

what is the apical complex?

Answer 17

• For the invasion of the parasite into the host.
  
  • Has a few different structures belonging to it.
  • At the apical end of the cell
  • Contains rhoptries , micronemes, dense granules, polar rings and a conoid
  • Reason why the group is called apicomplexa parasites is because they form apical complex: which helps the organism invade the host.
    Apical complex feeds the host cell with many substances to ruin the integrity of cell membrane.

Question 18

Why do Apicoplast have 4 membranes?

Answer 18

• One ancestral cell takes up a bacteria and if this new organism now takes up another organism
  
  • So this is a product of primary and secondary endosymbiosis.

Question 19

oocysts vs sporozoites?

Answer 19

oocysts: released into the environment with diarrhea (infective stage)

sporozoites: what causes pathology/diarrhea

Question 20

how are you infected with oocytes?

Answer 20

• Sporulated oocysts will infect you. You can take them up when drinking contaminated water. Sometimes can be food sources.
  Zoonotic transmission will occur with cryptosporidium because they ae not host specific and can live in animals and humans.

Question 21

The emergence of sporozoite

Answer 21

• Sporozoite will enter small intestine and enter a cell
  
  • Develop into tropozoite where it has an asexual life cycle (Type I meront)
  • Several merozoites will be leaving the asexual cycle.
    ○ Some merozoite will differentiate into type II. Merozoite will break up into gamont.
    ○ Differentiate into micro and macrogamont (male and female) for sexual reproduction.
    You can reinfect yourself again and again.

Question 22

How many sporozoites within an oocyte?

Answer 22

• Oocyte wall is unique with a suture at the end
  -The suture dissolves during excystation, opening the wall to 4 sporozoites.

Question 23

How many oocysts to initiate infection?

Answer 23

• Ingest 30 oocytes within drinking water
  They are highly infective.

Question 24

How do you get infected?

Answer 24

• Fecal oral route
  
  • If animals are in the environment that release this into the environment with their feces, you can get infected as well.
    Cryptosporidium is not host specific.

Question 25

Who is at risk to getting infected with cryptosporidium

Answer 25

- Workers ○ Veterinarians, farmers, medical personnel, day-care centers - Social factors ○ Family, children, pet owners, travelers, drinking non-filtered water. Immuno-deficient people

Question 26

What are the symptoms of cryptosporidium infection

Answer 26

- Some individuals can be asymptomatic (releasing the parasite into the environment unknowingly) - Symptoms last 1-2 weeks. - Symptoms include: Stomach cramps, pain, watery diarrhea, dehydration, weight loss, vomiting, fever.

Question 27

What is the cryptosporidium pathology?

Answer 27

-cryptosporidium resides at the apical surface of intestinal epithelial cells and does not invade deeper layers of the human gastrointestinal mucosa -metabolites are secreted by cryptosporidium - inflammation and disruption of salt-water balance of the intestinal epithelium as the parasite replicates - mucosal inflammation with the presence of macrophages and neutrophils at the site of infection - classical immune response to infectious agents

Question 28

How to diagnose / treat someone with cryptosporidium infection?

Answer 28

- Microscopy test to diagnose - No treatment. Immuno-competent individuals will recover. - Difficult to manage for AIDS patients Because there is no treatment.

Question 29

How to prevent or control crypto?

Answer 29

- You usually get infected by taking in water The crypto oocyst is resistant to chemical disinfectants but is susceptible to drying (no longer in moist area) and UV rays.

Question 30

Prevention and control of crypto

Answer 30

- Water purification and filtration. Even if you think water is clean, you can filter to ensure no oocytes.