Introduction to Protazoa

Question 1

Is Protozoa multicellular or unicellular? What else is important about them?

Answer 1

Unicellular
- single celled, distinct nucleus, microscopic, with greater complexity than other unicellular forms ( bacteria)
- Each protozoa possess specialized organelles
and function as independent organism

Question 2

Are most Protozoa pathogenic?

Answer 2

Most are free living and are not pathogenic but some co-
exist with animal hosts (parasitic protozoa)

Question 3

What is the life cycle of Protozoa?

Answer 3

Life cycle – direct (e.g Eimeria) or indirect (e.g Sarcocystics, Trypanosoma)

Question 4

What kind of reproduction is seen in Protozoa?

Answer 4

Asexual (e.g Giardia) or alteration of sexual and asexual lifecycle (e.g Toxoplasm

Question 5

Do Protozoa gravitate to a specific host?

Answer 5

Varied host specificity – High (e.g Sacocystics, Eimeria) or low (e.g Cryptosporidium)

Question 6

What is the pathogenicity caused by protozoa?

Answer 6

Pathogenicity is caused either by destruction of host cells, toxins or by changes in host immune
system

Question 7

What is an important consideration for protozoa?

Answer 7

Important to consider zoonotic potential

Question 8

What is important to remember when trying to control, diagnose, and treat protozoal infections?

Answer 8

• Control requires knowledge of complete lifecycle
• Diagnosis – Morphology, Serological and molecular
• Treatment may not kill all stages

Question 9

What are the four groups of Protozoa of veterinary importance? What are they grouped by?

Answer 9

Flagellates
Amoebas
Ciliates
Apicomplexans

They are grouped based on their locomotion

Question 10

What is some important characteristics of Flagellates?

Answer 10

• Locomotion by flagella
• Mucosoflagellates (Direct life cycle, ex: giardia)
• Haemoflagellates (Arthropod transmitted, ex: trypansoma)

Question 11

What is some important characteristics of Ameobas?

Answer 11

Locomotion by pseudopodia

• Direct life cycles
• Ex: Naegleria fowleri, E. Histolytica

Question 12

What is some important characteristics of Cillates?

Answer 12

Locomotion by cillia

• Direct life cycles
• Eg. balantidium coli

Question 13

What is some important characteristics of Apicomplexans?

Answer 13

Locomotion by gliding

Coccidia:

• Direct life cycle (Ex: elmeria, crypto)
• Indirect life cycle (Ex: Toxoplasma)

Haemosporida

• Arthropod transmitted (Ex: Babesia)

Question 14

What is the morphological characteristics of muscoflagellates?

Answer 14

• Pear shaped
• Most have direct life cycle
• e.g Giardia, Tritrichomonas spp. – direct lifecycle
• Histomonas – Indirect lifecycle ( transmitted by another
  parasite)
  Two stage: Cyst and Trophozite ( only stage in Trypansoma)

Question 15

In Muscoflagellates, what are the key differences between Trophozoites and cysts?

Answer 15

Trophozoite
• Active motile form

• Vegetative form – divides by binary
fission

• Doesnot survive well in the
environment

• Only stage in Trypanosoma

Cyst
• Non-motile

• Environmentally resistant stage

• Can survive for months in wet and
cool conditions

Question 16

In muscoflagellates, what is a more simple breakdown of trophozoite vs. cyst stages?

Answer 16

Trophozoite stage is the feeding stage of the protozoan. Cyst stage is the dormant, resistant infectious stage of the protozoan

Question 17

How are hemoflagellates transmitted?

Answer 17

Arthropod transmitted

Question 18

Where are hemoflagellates found?

Answer 18

Lie in blood/ tissues of animals/ humans

Question 19

What are the 3 different forms of hemoflagellates and what makes them differ from one another?

Answer 19

• Amastigote – Mammalian intracellular form
  No flagella or undulating membrane
• Promastigote – Arthropod gut form
  Long flagella, spindle shaped body
• Trypomastigote- Mammalian blood form
  Long flagella, spindle shaped body

Question 20

What are apicomplexans? What are some key characteristics?

Answer 20

• Obligate intracellular pathogens
• Designed to get inside cells – Apical complex (organelle for invasion)
• Complex lifecycle – Direct (D) or indirect (I)
• Life cycle alternates between sexual and asexual reproduction

Question 21

What are 3 types of apicomplexans?

Answer 21

1. ) Intestinal (coccidia)
2. )Systemic
3. ) Blood

Question 22

What kind of life cycle do intestinal apicomplexans have and what are some examples?

Answer 22

Direct Lifecycle (Examples: Cryptosporidium, Eimeria, Cystoisospora)

Question 23

What kind of life cycle do Systemic apicomplexans have and what are some examples?

Answer 23

Indirect lifecycles ( Toxoplasma, Neospora, Sarcocystis)

Question 24

What kind of life cycle do blood apicomplexans have and what are some examples?

Answer 24

Indirect- Arthropod transmitted

(Ex: Babesia, Cytauxzoon)

Question 25

What are the steps to the lifecycle of intestinal coccidia?

Answer 25

1.) Dog is infected (sporulated oocysts of isospora enter the gut) 2.) The shell of the oocyst Sexual reproduction breaks down and (GAMETOGONY) – releases parasitic production of male and sporozoites, which female gametes and penetrate intestinal fusion, resulting in epithelial cells fertilized zygote 3. ) Asexual Reproduction (Merogony) 4. ) Sexual reproduction breaks down and (GAMETOGONY) – releases parasitic production of male and sporozoites, which female gametes and penetrate intestinal fusion. 5. ) Zygote is created 6. )Zytoge developes into an oocyst that exits the canine host in feces\\ (6) the oocysts sporulate (SPOROGONY) in the environment in a few days and becomes infectious to new dogs.

Question 26

What is the lifecycle of systemic coccidia (toxoplasma)?

Answer 26

Asexual (merogony) and sexual (gametogony) phase in definitive hosts - Only asexual (division, multiplication) in Intermediate hosts - Only for toxoplasma, transmission can occur between intermediate hosts! - For other systemic coccidia (Sarcocystis, neospora) - transmission to definitive hosts occurs by ingesting the cysts in the tissue of the IH, and - transmission to IH occurs via ingestion of sporulated oocyst!

Question 27

What is the lifecycle of blood apicomplexa?

Answer 27

Ex: Babesia Canis 1. ) Tick has blood meal from infected animal, and sporozoites remain in the salivary glands of ticks. 2. ) Sexual reproduction of protazoa occurs within the tick, and tick takes bloodmeal from new host. 3. ) New host is innoculated via bite. 4. ) Asexual reproduction occurs within the hosts erythrocytes. Cycle repeats.

Question 28

What is a rare way blood ampicomplexans can be transmitted, other than through an arthropod vector?

Answer 28

Iatrogenic transmission is also possible through blood transfusion or blood- contaminated fomites.

Question 29

How can you diagnosis a protozoal infection? What does each test detect?

Answer 29

1. ) Fecal testing- microscopy (fecal float/ smear for intestinal protozoa) - can detect f cysts, torphozoites, oocysts in feces (quick diagnosis in clinical cases) 2. ) Blood testing- Direct smear, stained smear (Blood protozoa are specific on the types of blood cells they infect!) 3. ) Serological/ Molecular methods - Examination of blood/ serum for Antibody against parasites (serology) - Examination of feces for parasite/ antigen ( active infection) - Extracting DNA of the parasite and sequencing- High accuracy.