Parasitic Protoza: Introduction

What are the characteristic feature of parasitic protozoans?

Single-celled eukaryotic parasites that rely on host metabolism for energy, have one nucleus, and posses organelles for movement.

How many protozoan species are parasitic?

10,000+ species

How many protozoan species are parasitic/commensal with humans?

25 species

List the five major phyla in Kingdom Protista?

1. Metamonada

2. Euglenozoa

3. Ciliophora

4. Apicomplexa

5. Amoebozoa

List examples of parasitic protozoa in phylum Metamonada.

Giardia spp. (beaver fever), Trichomonas vaginalis (STI)

Where can you find organisms in phylum Metamonada?

Intestines, urogenital tract

List examples of parasitic protozoa in phylum Euglenozoa.

Leishmania spp., Trypanosoma spp. (sleeping sickness)

Where can you find organisms in phylum Euglenozoa?

Blood, intracellular (macrophages)

List examples of parasitic protozoa in phylum Ciliophora.

Balantidium spp.

Where can you find organisms in phylum Ciliophora?

Large intestine

List examples of parasitic protozoa in phylum Apicomplexa.

Plasmodium spp. (malaria), Toxoplasma gondii, Cryptosporidium spp., Babesia spp., Coccidian

Where can you find organisms in phylum Ciliophora?

Blood cells, intracellular tissue

List examples of parasitic protozoa in phylum Amoebozoa.

Entamoeba spp.

Where can you find organisms in phylum Amoebozoa?

Colon, liver (invasive)

Define endocytosis.

When membrane surrounds substance and brings it into the cell, pinches off forming membrane-bounded vesicle

Define exocytosis.

Elimination of waste or undigested material

Define phagocytosis.

A form of endocytosis where a cell engulfs large particles using its plasma membrane

Define pinocytosis.

A form of endocytosis where a cell engulfs fluids using its plasma membrane

Define cyst.

Infectious stage; dormant and environmentally resistant

Define trophozoite.

Active, feeding, reproductive stage

Define encystment.

The biological process where an organism reverts back into a cyst.

Define excystment.

The biological process where an organism escapes from its protective cyst wall to return to its active vegetative form

What is the function of the apical complex in Apicomplexa?

A set of specialized organelles that enables penetration of host cells during the infectious stage; secretes enzymes to facilitate parasite entering the host cell

What organelle is used for locomotion in Metamonada and Euglenozoans?

Flagella

What organelle is used for locomotion in Ciliophora?

Cilia

What organelle is used for locomotion in Amoebozoans?

Psuedopodia

How do flagellated parasites typically move and where are they usually found?

They use whip-like flagellum to propel through liquid environments, found in blood, CSF, or lymph.

List common morphology associated with flagellated protozoans.

• Present filamentous projections of cytoplasm

• MTs in complex arrangement

• Undulating membrane

• Present in trophozoites

• Bring contents in via endocytosis

Define recurrent flagellum.

Loops from the flagellum pocket back along the body

Define pseudopodia.

Cellular protrusions, extensions of the cytoplasm

Most protozoan reproduce _.

Asexually

Describe sexual reproduction in parasitic protozoans.

• Rare; only occurs in definitive hosts

• Conjugation: in ciliates, cells fuse, exchange genetic   material, separate, then each divide via mitosis (in some apicomplexans)

Describe asexual reproduction in parasitic protozoans.

Occurs in intermediate hosts (if applicable)

List pros of sexual reproduction

Genetic diversity

List cons of sexual reproduction.

• Requires mates

• May lose advantageous alleles in offspring

Define Mueller’s ratchet.

The irreversible accumulation of harmful mutation in asexual lineages due to a lack of genetic recombination.

List pros of asexual reproduction.

• Faster

• Lots of progeny in short time

• No need for mates

List cons of asexual reproduction.

• less genetic diversity

• Muller’s ratchet

How does location of a parasite within a host affect pathology?

Even few parasites in a critical site can cause serious symptoms due to weaker immune surveillance.

What factors influence the pathology of parasites within the host?

1. Density

2. Location

3. Metabolic requirements

4. Immune evasion strategies

5. Drug resistance

How does a parasite’s high metabolic requirement affect disease pathology?

It will increase the severity of the disease.

How does a higher density of parasite in sensitive location affect disease pathology?

It will increase the severity of the disease.

List ways a parasite can avoid the host immune system.

• Immune or divert host immune responses

• Avoid or inhibit of intracellular responses

• Inhabit parts of the body without immune responses

How do parasites use antigenic variations to evade the host immune system?

By changing their surface proteins, making existing antibodies ineffective.