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| − | {{toplink
| + | #REDIRECT[[:Category:Protozoa]] |
| − | |backcolour =
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| − | |linkpage =Infectious agents and parasites
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| − | |linktext =INFECTIOUS AGENTS AND PARASITES
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| − | |pagetype=Bugs
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| − | |sublink1=Parasites
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| − | |subtext1=PARASITES
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| − | }}
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| − | ==Introduction==
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| − | [[Image:Balanditium.jpg|thumb|right|150px|Balantidium coli - trofozoite and cyst - Wikimedia Commons]] | |
| − | [[Image:Flagella.jpg|thumb|right|150px|Flagella of ''E.coli'' - Nicolle Rager Fuller, National Science Foundation]]
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| − | All protozoa are unicellular eukaryotic organisms which store their genetic information in chromosomes in a nuclear envelope. Protozoa are classified depending on their structure and life cycle. This reflects the similarities of the diseases which they cause.
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| − | Protozoa usually range from 10μm-50μm but can grow up to 1mm. Thus, they are usually observed and classified using a microscope.
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| − | Protozoa multiply sexually, asexually and can also use a combination of both, for example, the coccidia class. Replication can be by binary or multiple fission. Different protozoa use different forms of motility, including flagella, cilia, pseudopodia and gliding.
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| − | ==Structure and function==
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| − | *Motile
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| − | *Organelles and otehr cellular structures enable the protozoa to lead an '''independent exsistence'''
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| − | *Cilia
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| − | **Fine, short hairs covering the protozoal surface
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| − | **Hairs beat in unison to enable the protozoa to move
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| − | **Wafts food towards the cytostome (mouth opening)
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| − | **E.g. ''Balantidium''
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| − | *Flagellum
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| − | **Contractile fibre
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| − | **Contracts in a whip like motion to propel protozoa
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| − | **Attached to body of protozoa by an '''undulating membrane'''
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| − | **E.g. ''Trypanosoma''
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| − | *Pseudopodia
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| − | **Extensions of the cellular cytoplasm
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| − | **Cytoplasm flows into the pseudopodia allowing movement of the protozoa
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| − | **Also acts in a phagocytic manner surrounding food particles and enclosing it in a vacuole
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| − | **E.g. ''Entamoeba''
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| − | *Gliding
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| − | **No obvious means of locomotion
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| − | **E.g. ''Eimeria''
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| − | ==Nutrition and digestion==
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| − | [[Image:Pinocytosis.jpg|thumb|right|150px|Pinocytosis - Mariana Ruiz Villarreal]]
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| − | *Pinocytosis
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| − | **Droplets of fluid taken into the cell
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| − | **Generates small vesicles
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| − | **Usually used for extracellular fluid ingestion
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| − | **Requires ATP
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| − | *Phagocytosis
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| − | **Larger particles of matter taken into the cell
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| − | **Usually solid particles ingested
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| − | *Cell membrane envelops the fluid or food taking it into the cell
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| − | *Lysosomes fuse with the fluid/food initiating digestion
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| − | *Diffusion through the cell membrane allows excretion of metabolic products
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| − | ==Life Cycle==
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| − | *Most protzoal reproduction is asexual using binary fission, schizogony and sporogony
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| − | *Some protozoa also use sexual reproduction called gametogony
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| − | *In some species, sexual and asexual reproduction occurs in the same host, whilst in others asexual reproduction occurs in the vertebrate host and sexual reproduction in the arthropod vector
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| − | *Homogenous
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| − | **Parasite uses a single host species during its life cycle (direct)
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| − | **E.g. ''Eimeria''
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| − | *Heteroxenous
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| − | **Parasite uses more than one host during its life cycle (indirect)
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| − | **E.g. ''Trypanosomes''
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| − | *Facultatively heteroxenous
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| − | **Parasite '''may''' use more than one host during its life cycle but this is not essential
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| − | **E.g. ''Toxoplasma gondii''
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| − | ===Example of a Protozoal Life Cycle===
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| − | [[Image:Coccidia.jpg|thumb|right|150px|Coccidia - Joel Mills]]
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| − | ''The following refers specifically to the life cycle of Coccidia spp.''
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| − | *The '''oocyst''' is the resistant stage in the environment
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| − | *The infective '''sporozoite''' is released from the oocyst
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| − | *Inside the host, the sporozoites invade the intestinal epithelial tissue
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| − | **Sporozoites feed and grow
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| − | | |
| − | *As the sporozoites grow the nucleus divides forming a '''schizont'''
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| − | *The schizont contains numerous elongated '''merozoites'''
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| − | *The formation of merozoites is the first asexual reproductive stage called '''schizogony'''
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| − | *The schozont ruptures releasing the merozoites which also invade the epithelial cells
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| − | *Another generation of schizonts form which is the beginning of the sexual phase of reproduction called '''gametogeny'''
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| − | *The merozoites form male '''microgamonts''' or female '''macrogamonts'''
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| − | **Collectively known as gamonts or gametocytes
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| − | *The microgamonts released from the microgametocyte penetrate and fertilise the macrogamete (which is contained within the macrogametocyte)
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| − | *Gametogeny forms the '''zygote'''
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| − | **Surrounded by a cyst wall
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| − | **Forms the '''oocyst'''
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| − | *The oocyst is passed in the faeces as unsporulated
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| − | *The oocyst becomes sporulated in the second asexual reproductive phase called '''sporogeny'''
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| − | *Once the oocyst is sporulated it is infective
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| − | ==Protozoa of Veterinary Importance==
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| − | [[Coccidia]]
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| − | *''Eimeria''
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| − | *''Isospora''
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| − | [[Tissue cyst-forming coccidia]]
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| − | *''Toxoplasma''
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| − | *''Neospora''
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| − | *''Sarcocystis''
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| − | [[Piroplasmida]]
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| − | [[Cryptosporidium|Cryptosporidium and Cyclospora]]
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| − | [[Babesia]]
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| − | [[Tropical Protozoa]]
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| − | *''Theileria'' spp.
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| − | *''Trypanosoma'' spp.
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| − | *''Leishmania'' spp.
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| − | [[Giardia]]
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| − | [[Other Important Protozoa]]
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| − | *''Tritrichomonas foetus''
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| − | *''Histomonas meleagridis''
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| − | *''Balantidium''
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| − | *''Entamoeba''
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| − | *''Microsporidia''
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