Introduction to protozoa (2).ppt for all medicals

protozoa

1. Introduction to Protozoa
Proto – First; Zoa – Animals
Protozoa
Single – Celled eukaryotic organisms
Kingdom Protista
Vary in size (3 – 2000mm)
•First recognized by Antony Van Leewenhoek in 1676 as
little animal “animacula”

2. Diversity
•Extremely diverse and found in a variety of niches
•Human body niches (skin, eye, mouth, gut, genitourinary tract, blood
stream, spleen, liver, muscle, CNS)
•>200,000 species
1.Most species are free-living in Freshwater, Decaying organic
matter , Soil ( 190, 000)
2.Few are adapted to a parasitic life (all plant and animal species
have at least one protozoan parasite) (10,000)
•Some are beneficial to mankind by:
Being part of the food chain
Serving as experimental subjects.

3. Importance of protozoa
Medical Importance:
1.More sickness and death
2.Reduced working capacity
3.Loss of productivity
Veterinary Importance
1.Loss of productivity (milk and meat)
2.Death
3.Reduced reproductive potential
4.Costy

4. General morphology
Diverse morphology
Size: smallest intracellular leishmania and toxoplasma (1-
10m) to largest ciliate
Shape: from amorphous amoeba to relatively rigid forms
(cysts) – no single shape

5. Structure
Protozoa have structures which perform the functions of:
Locomotion
Metabolism
Reproduction
Basic structures:
1.Cell membrane
2.Cytoplasm
3.Nucleus

6. Structure
Cell Membrane (plasmalemma)
Also called pellicle (in ciliates) or ectoderm or outer membrane
Microtubules line outer membrane (sub-pellicular microtubules)
Cytoplasm:
Outer transparent ectoplasm (for locomotion, protection, sensation,
excretion and ingestion of food)
Inner granular endoplasm (for nutrition and reproduction)

7. Structure

8. Single/multiple
Contains karyosome & chromatin granules
Nucleoli-like body is Karyosome which contains DNA in
apicomplexans (but parasitic amoebas lack DNA)
Two types:
Vesicular (has a clearly defined internal space and Scattered
chromatin) – most human protozoa have this type
Compact (solid mass with densely packed chromatin)
Structure: Nucleus

9. Axostyle: a central supporting structure embedded along the
longitudinal axis on the cytoplasm (some flagellates) and protrudes at
the posterior end.
Axoneme: an inner, central delicate filament extending from the
region of the kinetoplast to the cell membrane. It provides skeletal
structure and carries a whip – like appendage (cilia or flagella). It
represents the cytoplasmic part of the flagellum.
Cytostome or cell mouth for ingesting fluids (flagella pocket)
Contractile vacuoles: presumably for osmo-regulation (often seen in
sarcodinas and ciliates)
Structure: other structures

10. •Undulating membrane: a membranous structure which connects the
flagellum to the body of the parasite. It is thrown into folds as the
parasite moves, giving it an undulating (rolling) appearance.
•Apical complex: specialized organelles at tip (apex) of cells that
penetrate host tissues.
Costa: a rod-like cytoplasmic thickening (ribs) seen at the base of
the undulating membrane in some flagellates
•Flagellum: an elongated hair-like organelle used for locomotion.
Structure: other structures

11. Structure
Apicomplexa
Sarcodina
Mastigophora

12. Basic Properties of Protozoa

13. 1.Movement
Structures that mediate locomotion:
Pseudopodia
Cilia
Flagella
Gliding

14. Fission Sequence: division sequence of organelles then nucleus then cytoplasm
2.Reproduction

15. Asexual ReproductionAsexual Reproduction
Sexual ReproductionSexual Reproduction
Binary FissionBinary Fission
Multiple Fission Multiple Fission
(Schizogony) (Schizogony)
EndodiogenyEndodiogeny
ConjugationConjugation
SyngamySyngamy
2.Reproduction

16. 3.Feeding mechanisms
Most parasitic protozoa are heterotrophic procuring nutrients (mostly
bacteria)
1.Phagocytosis
•Engulfment of solid material
•Predation on bacteria or other protozoa
2.Pinocytosis
•Invagination of membrane surrounding liquids
3.Peristome or cytostomal feeding
•Food is ingested at a definite site, using a specialized feeding
structure
4.Diffusion
• Absorb solutes (osmotrophy) through cell membrane
•Food may be retained in special intracellular reserves, or
vacuoles.
Some protozoan are photosynthetic (autotrophy) or combination

17. Protozoa life cycle stages
Most protozoa exist as Vegetative/Resístant form:
1.Vegetative form: trophozoite
Stage of active feeding and reproduction
Commonly the pathogenic protozoan form.
Formed by asexual fission or by gamete fusion in the Sporozoans.
2.Resístant form: cyst/oocyst
Stage of inactivity
Most resistant stage = hard to kill.
Multiplication occurs within cysts of some protozoa

18. Protozoa life…

22. PROTOZOAPROTOZOA

23. Ameba:
•Entamoeba histolytica
•Entamoeba dispar
•Entamoeba coli
•Entamoeba
hartmanni
•Endolimax nana
•Iodamoeba bütschlii
INTESTINAL PROTOZOA
Apicomplexa:
•Cryptosporidium
hominis
•Cryptosporidium parvum
•Cyclospora cayetanensis
•Isospora belli
Flagellates:
•Giardia lamblia
•Dientamoeba fragilis
•Chilomastix mesnili
•Trichomonas hominis
•Enteromonas hominis
•Retortamonas intestinalis
Other:
•Blastocystis hominis
•Balantidium coli

24. Fecal-Oral Transmission
Factors
•Poor personal hygiene
•Food handlers
•Institutions
•Children in day care
centers
•Developing countries
•Highly endemic
•Poor sanitation
•Travelers diarrhea
•Water-borne epidemics
•Male homosexuality
•Oral-anal contact
•Zoonosis
•Entamoeba = no
•Cryptosporidium = yes
•Giardia = controversial

25. •Improve personal hygiene
•Especially institutions
•Treat asymptomatic
carriers
•Eg, family members
•Health education
•Hand-washing
•Sanitation
•Food handling
Control/Prevention
•Protect water supply
•Treat water if
questionable
•Boiling
•Iodine
•Not chlorin