Acknowledgements n n n n Addisa Ababa University
Acknowledgements n n n n Addisa Ababa University Jimma University Hawassa University Haramaya University of Gondar American Society for Clinical Pathology Center for Disease Control and Prevention-Ethiopia
1. INTRODUCTION TO MEDICAL PROTOZOOLOGY 3
Learning objectives Upon completion of this unit , you should be able to: ¨ Describe the general characteristics of Protozoans ¨ Describe the basic structure of protozoa ¨ Describe the basic properties of protozoa ¨ Describe the classification of parasitic protozoa 4
OUTLINE Ø General Introduction to protozoa Ø Definition Ø Diversity and importance of protozoa Ø General morphology protozoa Ø Basic structure of protozoa Ø Basic properties of protozoa 5
Out… Ø Protozoan life cycle stages Ø Protozoan taxonomy Ø General characteristics of the five main groups of protozoa 6
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General introduction to protozoa Definition =single-celled eukaryotic organisms =kingdom Protista =Vary in size (1 -150 um ) 8
Int… =Unknown until the invention of the microscope in 1675 =First recognized by antony van leewenhoek in 1676 = He described it as little animal or animacula 9
Diversity and importance of protozoa Diversity = protozoa are extremely diverse organisms and found in a variety of niches 10
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Div… = 200, 000 named species = Most species are free-living in = Freshwater = marine environments = decaying organic matter and soil = Few are adapted to a parasitic life but all plant and animal species have at least one protozoan parasite 12
Div… =~10, 000 are parasites in a wide range of hosts =Vertebrate = invertebrate = Plants = ~20 human pathogens =Adapted to life in a wide range of sites within the host 13
Ecological Niches in the Human Body: ¨ Skin: ¨ Eye: Leishmania Acanthamoeba ¨ Mouth: ¨ Gut: Amoebae and flagellates (usually non-pathogenic) Giardia, Entamoeba (and invasion to liver), Cryptosporidium, Isospora, Balantidium ¨ G. U. tract: Trichomonas ¨ Bloodstream: 14 Plasmodium, Trypanosoma
Div… ¨ Spleen: ¨ Liver: Leishmania, Entamoeba ¨ Muscle: ¨ CNS: 15 Leishmania Trypanosoma cruzi Trypanosoma, Naegleria, Toxoplasma, Plasmodium
Importance of protozoa n Medical importance ¨ Cause of more sickness and death than any other disease- causing organisms ¨ significant ü brain (African sleeping sickness), eyes (acanthamoeba keratitis), heart (toxoplasmosis) ¨ reduced ¨ Loss 16 damage to specific organs working capacity of productivity
Imp… n Veterinary importance ¨ Death ¨ Potential losses n coccidiosis costs £ 8 million/yr. . Prophylactics n Animal trypanosomiasis ¨ 17 Zoonoses
General morphology of protozoa n Protozoa exhibit a wide variety of morphologies 18
morp… n Size: range from 1 to 150 um ¨ • The smaller members, 1 -10 um • include most of the intracellular parasites (e. g. plasmodia, Leishmania … ¨ The biggest in size belongs to ciliate e. g. Balantidium coli n Shape: ü No single shape that represent all ü Ranges from amorphous shapeless amoeba to relatively rigid forms 19
Basic structure of protozoa 1. Cell membrane 2. Cytoplasm ectoplasm endoplasm 3. Nucleus: two kinds of nuclei: vesicular; compact 20
Stru … 1. Cell membrane: chemically similar to all eukaryotic cells n Thin & flexible layer called plasmalemma (sarcodina) n Also called pellicle or ectoderm or outer membrane n More rigid wall , usually supported by microtubules (subpellicular microtubules) 21 n Results in more constant and uniform shape than that of amorphous amoeba n Characteristics some flagellates and most ciliates
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Stru… 2. Cytoplasm : divided in two areas n Ectoplasm=outer transparent layer ¨ Locomotion, ¨ protection ¨ Sensation, respiration ¨ Excretion, Ingestion of food & etc n Endoplasm= inner granular layer ¨ More fluid than ectoplasm, contains nuclei , mitochondria, vacuoles & etc ¨ metabolism 23
Stru… 3. Nucleus n n well defined nuclei bounded by nuclear envelop Most easily identifiable structure in protozoan cell ¨ Single/multiple ¨ Important ¨ Similar for reproduction in size or not Eg G. lambilia, cilliate( micronuclei & macronuclei ) 24
Stru… n Two morphologically distinct nuclei: ¨ Vesicular n with a clearly defined internal space resulting from irregular distribution of chromatin n 25 Nucloplasm contains one or more Karyosome ¨ nucleoli-like body Most protozoa of humans exhibit the vesicular type
Stru… ¨ Compact appears to be a solid mass n densely packed chromatin n Larger than vesicular nucleus n Are found in ciliates n n Other structures like § Mitochondria : sites for aerobic metabolism § Lysosmes : degradation ingested materials § Ribosome : sites for protein synthesis 26
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Prop… A. Locomotion : Structures that mediate 28
Prop… B. Reproduction -General Protozoan Reproduction Binary Fission Asexual Reproduction Mutiple Fission Endodyogeny Sexual Reproduction Conjugation Singamy 29
Prop… 1. Asexual reproduction ¨ Fission n A. Binary fission n Each parent gives rise to two progeny n 30 Division follows a sequence: ¨ organelles then nucleus then cytoplasm Seen in amoeba , flagellates , ciliates
Prop… B. Multiple fission/ Schizogony/ Merogony ¨ Rapid organelle and nuclear divisions occur at the cell periphery ¨ Cytoplasmic segmentation to form separate organisms called merozoites ¨ The Parent or multinucleated cell is called the schizont or segmenter and the daughter cells are merozoites ¨ Seen 31 in apicomplexan
Prop… C. ENDOPOLYOGENY n Daughter cells form in the center of the mother cell (internal budding) rather than at the periphery n 32 Endodyogeny is a form of endopolyogeny where two daughters are formed
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Prop… Sexual Reproduction A. Conjugation ¨ Specialized sexual reproduction (mostly in ciliates) 2. ¨ Involves 34 nuclear exchange and union after cells join
35 Sexual Recombination in Paramecium
Prop… B. Syngamy üunion of the entire cell (gametes fuse), seen in apicomplexan 36
Prop… C. Feeding n Most parasitic protozoa are heterotrophic Ø ingest particulates (phagotrophy) Ø Phagocytosis Ø Ø Engulfment of solid material Ø predation on bacteria or other protozoa Pinocytosis Ø 37 Invagination of membrane surrounding liquids
Prop… Ø Peristome or cytostomal feeding Ø Food is ingested at a definite site, using a specialized feeding structure Ø Diffusion =absorb solutes (osmotrophy) through cell membrane n Food may be retained in special intracellular reserves, or vacuoles n Some protozoan are photosynthetic (autotrophy) or combination 38
Prop… D. Excretion n Undigested particles and wastes are extruded at the cell surface by mechanisms that are the reverse of those used in ingestion ¨ diffusion (primary mechanism) ¨ contractile 39 vacuole (osmo-regulation)
Prop… E. Respiration n Both aerobic (Malaria) and anaerobic respiration (dysenteric amoeba) n Most parasitic protozoa are facultative anaerobes n 40 They can live in reduced oxygen environments
Prop… Protozoa life cycle stages/terms 1. Vegetative form: trophozoites, zoitos ¨ stage of active feeding and reproduction ¨ commonly n 2. the pathogenic protozoan form Excystation : For the completion of life cycle , cysts ingested by the definitive host has to change to vegetative form Resístant form: cyst ¨ Stage ¨ Most 42 of inactivity resistant stage = hard to kill (no medication )
Prop… Encystation n Many protozoa form cysts – round cytoplasmic mass surrounded by a rigid or semi-rigid cyst wall secreted by organism n Function: 1. Protect against unfavorable external environmental conditions 2. Are the infective or transmissible form of parasite 43
Prop… Conditions for encystment: n Deficiency of host nutrient essential to the parasites n Desiccation n increase in osmotic pressure n Accumulation of waste product in the medium n Crowding n 44 Low p. H , Temperature change
Prop… 3. Oocyst: ¨ results from fusion of gametes in the Sporozoa ¨ Infective n n 45 stage in most cases: passed in host feces in case of intestinal protozoans or in gut of the mosquito vector in the case of Plasmodium
Prop… 4. Sporozoite: n Formed within oocyt via asexual fission & infects new host cells of ¨ intestinal epithelial cells in intestinal protozoans or ¨ hepatocytes 46 in case of Plasmodium
Prop… 5. Merozoite: n Resulted from schizogeny of sporozoites n May infect n intestinal epithelial cells in intestinal coccidian or n Red blood cells in the case of Plasmodium. … 47
Prop… 6. Gametocyte: n result of merozoite cell fission n Fusion of these results in formation of oocyst n Other life cycle stages ¨ Amastigote, Promastigote, Epimastigote , Trypomastigote & Metacyclic Trypomastigote 48
Example of Protozoa life cycle 49
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The life cycle of Plasmodium species 51
Protozoan Taxonomy • Confused, controversial and constantly changing • No universal agreement = many systems & frequent changes § Several bases of classification, • light microscope = Originally based on motility • electron microscope =Ultrastructural criteria used since 1960’s 4 -6 phyla? In the kingdom protista • Molecular technique: DNA sequences 52
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General Characteristics of five main groups Of protozoa 1. Amoebas (Subphylum Sarcodina) = Move by extending blunt, lobe like projections pseudopodia (false feet) = 54 Amoebas engulf food with pseudopods & phagocytize it
Char… 55
Char… • Several genera: • Entamoeba, • Iodamoeba, • Endolimax, • Naegleria (CNS), • Acanthamoeba (CNS) 56
Char… 2. The Flagellates (Mastigophora) = Move by means of rotation of a whip-like organell called a Flagellum (plural: flagella) = The flagella can also be used for gathering and sorting food = Some species have organelles for the purpose of food ingestion (gullet or cytostome), and for excretion (cytopyge) 57
Char… = several genera § Giardia § Chilomastix § Dientamoeba § Trypanosoma § Leishmania § Trichomonas 58
Char… Giardia intestinalis Cyst 59 Trophozoite
Char… Trichomonas T. vaginalis 60 T. intestinalis
Char… Trypanosoma 61
Char… Leishmania Amastigote 62 Promastigote
Char… C. Apicomplexans (Phylum Apicomplexa) Ø Have specialized organelles at tip (apex) of cells that penetrate host tissues Ø Locomotion of mature form by body flexion or gliding 63
Char… Ø Obligate intracellular parasites Ø usually 2 or more hosts Ø Their life cycles have asexual and sexual phases Ø several forms (sporozoites , trophozoites , merozoites , gametocytes , oocyst & cyst 64
Char… Toxoplasma gondii (Toxoplasmosis) Bradyzoite Sporulated oocyst Oocyst Merozoite Gamete 65 Sporocyst
Char… n Includes ¨ 1. Intestinal coccidian n Cryptosporidium n Isospora n Cyclospora ¨ 2. Blood and tissue coccidian n Plasmodium n Toxoplasma n Babesia n Sarcocystis 66
Char… D. ü Ciliates (Phylum Ciliophora) Move and obtain food using cilia üDistinct cytostome (mouth) Structure üDimorphic nuclei, typically larger macronuclei and smaller micronuclei üOnly known human pathogen is Balantidium coli 67
Char… E. Microsporans (Phylum Microsporidia) u Obligate intracellular spore forming parasites u Discovered in 1984 to cause chronic diarrhea and conjunctivitis, mainly in AIDS patients u at least 14 microsporidian species identified as human pathogens: Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon hellem …. 68
1. 7. Protozoans associated with HIV/AIDS n Cryptosporidium parvum, I. belli and Cyclospora cayatenensis : causing enteritis n Microsporidia species : causing a diarrhea with wasting, eye disease, and disseminated disease n Pneumocystis carnii: causing life threatening pneumonia n Blastocystis hominis : cause severe enteritis 69
Pro … ¨ T. gondii: causing cerebral toxoplasmosis ¨ Leishmania species – emerging as a major pathogens in HIV infected persons 70
Summary Protozoa n n n unicellular eukaryote organisms kingdom Protista extremely diverse and found in a variety of niches Have complex internal structure several modes of reproduction Cause of more sickness and death, than any other diseasecausing organisms n No universal agreement on classification there are many systems & frequent changes
Review questions 1. Explain the characteristics of Protozoans ? 2. List and discuss about the structure of protozoa ? 3. Explain the properties of protozoa? 4. Discuss about the classification of parasitic protozoa? 73
References 1. Awole M. , Cheneke W. Medical Parasitology for Medical laboratory Technology students. Upgraded lecture Notes Series. 2006. 2. Cheesbrough M. District laboratory practice in tropical countries United Kingdom, Cambridge university press, 2000, part I 3. Jaffeey and Leach. Atlas of Medical Helminthology and Protozoology 2 nd edition 4. Murray P. R. , Rosenthal K. S. , Kobayashi G. S. , Pfaller M. A. , Medical Microbiology, 4 th edition. Mosby, 2002
5. WWW. CDC. gov 6. Guerrant R. L. , Walker D. H. , Weller P. F. Tropical infectious Diseases Elsevir Inc. 2 nd, 2006 7. Gillespie S, Pearson R. D. Principles and practice of Clinical Parasitology. John Wiley and Sons Ltd, 2001
The next unit focus on Sarcodina ( Amoeba)
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