Introduction to Medical Protozoa

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Introduction to Medical Protozoa

• Department of parasitology
• Shenyi He

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General Concepts

• Eukaryotic Organisms
• Generally unicellular
• Found in every conceivable damp habitat
• Approximately 60,000 living species
• Largest visible to the naked eye
• Smallest only seen with the EM
• have all necessary life activities.

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• Protozoa are one-celled animals found
  worldwide in most habitats. Most species are free
  living, but all higher animals are infected with
  one or more species of protozoa. Infections range
  from asymptomatic to life threatening, depending
  on the species and strain of the parasite and the
  resistance of the host.

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Structure

• Protozoa are microscopic unicellular
  eukaryotes that have a relatively complex
  internal structure and carry out complex
  metabolic activities. Some protozoa have
  structures for propulsion or other types of
  movement.

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Classification

• On the basis of light and electron
  microscopic morphology, the protozoa are
  currently classified into seven phyla. Most
  species causing human disease are members of the
  phyla Sacromastigophora and Apicomplexa.

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Classification
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Reproduction

• Binary fission, the most common form of
  reproduction, is asexual multiple asexual
  division occurs in some forms. Both sexual and
  asexual reproduction occur in the Apicomplexa.

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Nutrition

• All parasitic protozoa require preformed organic
  substances that is, nutrition is holozoic as in
  higher animals.

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Life Cycle Stages

• The stages of parasitic protozoa that actively
  feed and multiply are frequently called
  trophozoites in some protozoa, other terms are
  used for these stages. Cysts are stages with a
  protective membrane or thickened wall. Protozoan
  cysts that must survive outside the host usually
  have more resistant walls than cysts that form in
  tissues.

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Basic structure

• 1. Cell membrane
• 2. Cytoplasm
• organelles pseudopodium(-dia-
• amoeba) flagellum(-lla-flagellate)
• cilium(cilia-ciliate)
• 3. Nucleus two kinds of nuclei
• vesicular
• compact

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Characteristics of Pathogenesis 

• 1. proliferation
• 2. Diffusion (disperse )
• 3. Opportunistic parasitosis

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Ecological Niches in the Human Body

• 1. Skin Leishmania
• 2. Eye Acanthamoeba
• 3. Mouth Amoebae and flagellates
• (usually non-pathogenic)
• 4.Gut Giardia, Entamoeba (and invasion to
• liver), Cryptosporidium,
• Isospora, Balantidium
• 5. G.U. tract Trichomonas

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Ecological Niches in the Human Body

• 6. Bloodstream Plasmodium,
• Trypanosoma
• 7. Spleen Leishmania
• 8. Liver Leishmania, Entamoeba
• 9. Muscle Trypanosoma cruzi
• 10. CNS Trypanosoma, Naegleria,
• Toxoplasma, Plasmodium