INTESTINAL AND LUMINAL PROTOZOA

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INTESTINAL AND LUMINAL PROTOZOA  
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• A parasite is an organism that obtains food and
  shelter from another organism and derives all
  benefits from this association. The parasite is
  termed obligate when it can live only in a host
  it is classified as facultative when it can live
  both in a host as well as in free form. Parasites
  that live inside the body are termed
  endoparasites whereas those that exist on the
  body surface are called ecto-parasites. Parasites
  that cause harm to the host are pathogenic
  parasites while those that benefit from the host
  without causing it any harm are known as
  commensals.

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• The organism that harbors the parasite and
  suffers a loss caused by the parasite is a host.
  The host in which the parasite lives its adult
  and sexual stage is the definitive host whereas
  the host in which a parasite lives as the larval
  and asexual stage is the intermediate host. Other
  hosts that harbor the parasite and thus ensure
  continuity of the parasite's life cycle and act
  as additional sources of human infection are
  known as reservoir hosts. An organism (usually an
  insect) that is responsible for transmitting the
  parasitic infection is known as the vector.

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Taxonomic classification of protozoa
Sub kingdom Phylum Sub-phylum Genus- examples Species- examples

Protozoa Sarcomastig-ophora further divided into Sarcodina-- - move by pseudopodia Entamoeba E. histolytica

Mastigophora move by flagella Giardia G. lamblia

Apicomplexa no organelle of locomotion Plasmodium P. falciparum, P. vivax, P. malariae, P. ovale

Ciliophora move by cillia Balantidium B. coli

Microspora Spore-forming Enterocyto-zoa E. bienusi

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• V. PROTOZOA
• Unicellular, chemoheterotrophic, eukaryotic
  organisms of kingdom Protista (3-2000 mm).
• Protozoan means first animal.
• 20,000 species, only a few are pathogens.
• Most are free-living organisms that inhabit water
  and soil. Some live in association with other
  organisms as parasites or symbionts.
• Reproduce asexually by fission, budding, or
  schizogony.
• Some exhibit sexual reproduction (e.g.
  Paramecium).
• Trophozoite Vegetative stage which feeds upon
  bacteria and particulate nutrients.
• Cyst Some protozoa produce a protective capsule
  under adverse conditions (toxins, scarce water,
  food, or oxygen).

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• V. PROTOZOA (Continued)
• Nutrition
• Most are heterotrophic aerobes. Intestinal
  protozoa can grow anaerobically.
• Some ingest whole algae, yeast, bacteria, or
  smaller protozoans. Others live on dead and
  decaying matter. Parasitic protozoa break down
  and absorb nutrients from their hosts.
• Some transport food across the membrane.
• Others have a protective covering (pellicle) and
  required specialized structures to take in food.
• Ciliates take in food through a cytostome.
• Digestion takes place in vacuoles.
• Waste may be eliminated through plasma membrane
  or an anal pore.

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Protozoan classification

• Four major groups of protozoa are recognised and
  often given the status of phylum . Note,
  however, that in the animal kingdom proper
  (Metazoa ), phyla are distinguished on their
  different body plans and that no comparable body
  plans are found in Protozoa.

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Protozoan classification

• The groups are
• flagellates (or Mastigophora)
• amoebae (or Sarcodina)
• sporozoans (or Sporozoa, Apicomplexa) and
• ciliates (or Ciliophora).

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• Kingdom Animalia
• Subkingdom Protozoa
• Phylum Sarcomastigophora
• Phylum Apicomplexa
• Phylum Ciliophora
• Phylum Microspora
• Subkingdom Metazoa
• Phylum Nematoda
• Phylum Platyhelminthes

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Protozoa as Human Parasites Taxonomy Kingdom
Protista
Genera Subphylum Phylum
Trypanosoma, Leishmania, Giardia, Trichomonas Mastigophora (mastigo whip flagellates) Sarcomastigophora
Entamoeba, Naegleria, Acanthamoeba Sarcodina (amoebae)
Plasmodium, Toxoplasma, Cryptosporidium, Isospora Apicomplexa
Balantidium Ciliophora
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• INTESTINE
• Entamoeba histolytica
• Giardia
• Isospora
• Cryptosporidium
• Cyclospora
• Strongyloides
• Ascaris
• Trichuris
• hookworm
• pinworm
• tapeworms
• intestinal flukes

• SYSTEMIC
• Toxoplasma
• malaria
• filaria
• Toxocara
• hydatid cysts
• cysticercosis
• Schistosoma
• liver flukes
• lung flukes
• Protozoa
• Nematodes
• Cestodes
• Trematodes

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Protozoa

• .eukaryote..has genetic material encased in a
  nuclear membrane (unlike bacteria and viruses)
• ..classified traditionally by morphology (eg.
  organelles of locomotion), life cycle and
  mechanisms of reproduction etc.

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• Mastigophora movement with flagella - e.g.
  Trichomonas, Giardia
• Sarcodina pseudopodia, e.g. Entamoeba
  histolytica
• Apicomplexa apical complex, no locomotor
  apparatus
• sexual reproduction, e.g. cryptosporidium,
  malaria, toxoplasma
• Ciliophora movement with cilia, e.g. Balantidium.

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INTESTINAL PROTOZOA

• Pathogenic
• Entamoeba histolytica
• Balantidium coli
• Giardia lamblia
• Dientamoeba fragilis
• Cryptosporidium parvum
• Enterocytozoon bieneusi
• Septata intestinalis
• Cyclospora cayetanensis
• Isospora belli

• Commensal
• Entamoeba hartmani
• Entamoeba dispar
• Entamoeba coli
• Endolimax nana
• Iodamoeba bütschlii
• Chilomastix mesnili
• Trichomonas hominis
• Blastocystis hominis

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• Sarcodina (pathogenic)
• Entamoeba histolytica             
• Entamoeba dispar 
• Iodomoeba butschliiDientamoeba
  fragilisEndolimax nana  Entamoeba
  coliEntamoeba hartmani

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Entamoeba histolytica(amoebiasis)

• Phylum Sarcomastigophora.
• Subphylum - Sarcodina pseudopodia,
• Life Cycle                         

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Biology

• Two morphological stages occur
• Trophozoite - metabolically active invasive
  stage, moves with pseudopodia, ingests RBC, lives
  in  colon and is found in fresh diarrheal stool
• divides by binary fission.
• Trophozoite 10-60 µm
• cogwheel distribution of nuclear chromatin
• Hematophagous
• unidirectional movement with pseudopodia

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• Cyst - "vegetative" inactive form resistant to
  unfavourable environmental conditions outside
  human host
• 4 nuclei
• This is the infective form resistant to stomach
  acid if swallowed
• survives up to 30 days
• excyst to trophozoite on passing through stomach
• cyst 10-20 µm
• chromotoidal body        

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Adaptations

• Cyst a dormant form characterized by a hardened
  external covering in which metabolic activity has
  ceased.
• Form in response to nutrient deficiency, drought,
  and decreased oxygen concentration, or pH or
  temperature changes.
• Emerge when conditions improve

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Contractile vacuole

• An organelle that expels fluid from the cell.
• Freshwater organisms are usually hypertonic
  relative to their environment so water
  continually diffuses into them.
• To maintain homeostasis, it must use contractile
  vacuole to rid cell of excess water.

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Pathogenesis

• Digests (liquifies) human host cells (colon wall,
  neutrophils, liver cells)
• Disease states- asymptomatic carrier--
  symptomatic infection- amoebic dysentery -
  mucoid bloody    - amoebic - liver or lung
  abscess

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Diagnosis

• - stool examination - for trophozoites and
  cysts- amoebic serology- abscess aspirate -
  Entamoeba dispar  a non-pathogen is
  indistinguishable by microscopy and is a much
  more common intestinal protozoan than Entamoeba
  histolytica. Antigen capture and PCR tests can
  distinguish E. dispar from E. histolytica in
  heavier infections.            

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• TreatmentInvasive states (Dysentery, Liver
  abscess) metronidazole
• Carrier states diiodoquine, diloxanide furoate,
  or paromomycin

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Other Sarcodina
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Phagosytosis
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