Lecture B1 - Introduction to the Biology of Parasitic Protozoa

Question 1

What is parasitic protozoa?

Answer 1

Microscopic, one celled organisms that are parasitic in nature and can multiply in humans and cause serious disease.

Question 2

What is the GPI-anchor?

Answer 2

Glycosyl-phosphatidyl-inositol anchor.

Question 3

What helped in establishing the structure of GPI-anchors?

Answer 3

Variant surface glycoprotein of Trypanosome Brucei.

Question 4

What is the archezoa hypothesis?

Answer 4

Nucleus was invented before the mitochondrion was acquired.
First eukaryotes were anaerobes.

Question 5

When would the archezoa hypothesis fall?

Answer 5

Archezoans branch among aerobic species with mitochondria.
Mitochondrial genes on archezoan genomes.
Mitochondrion derived organelles in archezoans.

Question 6

What are some unusual organelles from parasites?

Answer 6

Unusual mitochondria.
Highly reduced organelles often without mitDNA, hydrogenosomes and mitosomes.
Apical organelles of aplicomplexans essential for invasion of host cells.
The polar tube of microsporidia essential for invasion of host cells.
Glycosides in kinetåplastids.
Non-photosynthetic plastids in apicomplexa.

Question 7

What do most apicomplexa possess?

Answer 7

An apicoplast which is a secondary plastid.

Question 8

Name some common parasites that transmission route is via mucosal surfaces.

Answer 8

Toxoplasma gondi
Trichomonas vaginalis
Giardia limblia

Question 9

Name some parasites that transmitted through insects.

Answer 9

Trypanosoma
Leishmania

Question 10

What is symbiosis?

Answer 10

The association between organisms from different species - different types of association can be defined.

Question 11

What are the three main categories of symbiosis?

Answer 11

Mutalism
Commensalism
Parasitism

Question 12

Describe mutualism.

Answer 12

Both partners benefit from the interaction and they are co-dependent for thriving.

Question 13

Describe commensalism.

Answer 13

One partner benefits from the interaction whereas the other is neither harmed nor benefitted.

Question 14

Describe parasitism.

Answer 14

One partner relies on a host for nutrients and shelter and there is a potential cost to the host - it is as a potential pathogen causing pathologies to the host.

Question 15

What are obligate symbionts?

Answer 15

Require a host to complete their life cycle.

Question 16

What are facultative pathogens?

Answer 16

Don’t cause disease all the time, blurring the distinction between pathogens and commensals.

Question 17

What are opportunistic pathogens?

Answer 17

Cause pathologies when the host is compromised - example is AIDS, patient is immunodeficient so parasite can take over.

Question 18

What are 2 examples of free-living species as occasional/accidental pathogens?

Answer 18

Acanthamoeba spp.
Naegleria fowleri.
Extremely rare but gets in through your nose and kills within a week.

Question 19

Why are the best parasites ones that don’t kill?

Answer 19

Because if the host is killed then they can’t propagate and die too.
This leads to long term interactions between hosts and pathogens.

Question 20

What is a monoxenous parasite?

Answer 20

A parasite requiring a single host for completing their life cycle.

Question 21

What is a herexenous parasite?

Answer 21

A parasite requiring two or more hosts to complete their life cycle. Intermediate host(s) required for development and the definite host required for sexual maturity.

Question 22

What are human diseases caused by animal parasites called?

Answer 22

Zoonoses.

Question 23

What is the 3 modes of transmission of parasites?

Answer 23

Contact transmission
Vehicle dependent
Vector transmission

Question 24

Name some examples of parasites that inhabit the digestive tract.

Answer 24

Amoeba
Diplomonada
Parabasalia
Ciliates
Stramenopile
Apicomplexa
Microsporidia

Question 25

What are some decal-oral transmission factors?

Answer 25

Personal hygiene (food handling, institutions, children in day care)
Developing countries (highly endemic, poor sanitation, travellers diarrhoea)
Water-borne epidemics
Zoonoses

Question 26

What is the life cycle of microsporidia?

Answer 26

Invasion of new host cells via the polar tube
Amplification and differentiation into spores
Release of spores from infected host cells
Typically infects intestinal cells in mammals
Can invade other tissues

Question 27

What are the 2 common cryptosporidium species infecting humans?

Answer 27

C. parvum
C. hominis

Question 28

Describe toxoplasma gondi.

Answer 28

Has an immature host and a definitive host.
Cosmopolitan distribution.
Seropositive prevalence rates vary greatly.
Thought to generally cause being disease in immunocompetent adults.
Tissue cyst forming coccidia.
Usually doesn’t affect humans but if someone becomes immunocompromised it can cause problems.

Question 29

What are some important human pathogens that are transmitted by arthropods vectors?

Answer 29

Plasmodium falciparum P. vivax
Trypanosome Brucei
Leishmania spp