PARASITOLOGY

• Human parasitology is the study of those organismis which parasitize humans
• Human parasitology, an important part of parasitology, study the medical parasites including their morphology, life cycle, the relationship with host and environment
• Parasitic infection /or parasitic diseases are still one of the important problems in public health in our country
• Parasite


  An organism which has become adapted to living on or in some other organism, the host, which is usually larger than itself
• Parasitism


  A relationship between two species where member of one species (smaller, called parasite) derived food and shelter from member of another species (larger, called host)
• Types of Parasites


  • Obligatory
  • Facultative
  • Endoparasite
  • Ectoparasite
  • Permanent
  • Temporary
  • Microparasite
  • Macroparasite
  • Extracellular
  • Intracellular
  • Proliferous
  • Accidental
• Types of Hosts


  • Definitive
  • Intermediate
  • Reservoir
  • Vector (Biological & Mechanical)
  • Carrier
  • Accidental
• Host Selection


  • Monoxenous (single host)
  • Oligoxenous (small range of hosts)
  • Polyxenous (many suitable hosts)
• Types of Parasitic Life Cycle

  • Simple or Direct
  • Complex or Indirect
• Stages Involved in Parasitic Life Cycle

  • Infective
  • Diagnostic
• Sources of Infection


  • Soil
  • Water
  • Food
  • Direct Contact
• Taxonomic classification of human parasites follows the hierarchy of biological classification: Kingdom, Phylum, Class, Order, Family, Genus, Species
• Categories According to Residency

  • Intraintestinal
  • Extraintestinal
  • Intestinal
  • Intestinal-Tissue
  • Lymphatic-Tissue (Vector-dependent)
  • Liver
  • Lung
  • Blood
  • Intestinal
  • Liver/Lung
• Protozoans


  • Consist of a single "cell-like unit" which is morphologically and functionally complete and can perform all functions of life
  • Made up of a mass of protoplasm differentiated into cytoplasm and nucleoplasm
  • Reproduce sexually & asexually
• Amoebas


  • Unicellular membrane bound organisms that have the ability to change their shape
  • Found in water bodies such as ponds, lakes and slow-moving rivers
  • Equipped with "Pseudopods"
  • Multiply asexually
  • Facultative parasites
  • Have two morphological forms: Cyst and Trophozoite
• Entamoeba histolytica Life Cycle

  1. Mature cysts ingested (Infective Stage)

  2. Excystation (Trophozoites)

  3. Multiplication

  4. Noninvasive Colonization

  5. Intestinal Disease

  6. Extraintestinal Disease

  7. Cysts and trophozoites passed in feces (Diagnostic Stage)
• Entamoeba histolytica Trophozoite


  • Motility: Progressive, finger-like pseudopodia
  • Number of nuclei: 1
  • Cytoplasmic inclusions: Ingested RBC
• Entamoeba histolytica Cyst


  • Shape: Spherical to round
  • Number of nuclei: 1-4
  • Cytoplasmic inclusions: Chromatid bars, rounded ends and diffuse glycogen mass
• Naegleria fowleri


  • Has three morphological forms in its life cycle: Trophozoite, Cyst, Flagellate
  • Considered the only amoeba that infects humans
• Acanthamoeba species


  • Trophozoite has sluggish, spine-like pseudopods
  • Cyst has a characteristic double cell wall (inner smooth, outer ragged)
• Ciliates


  • Single-celled organisms that possess cilia, short hairlike organelles used for locomotion and food gathering
• Cytoplasmic inclusions: Bacteria and other cells

  • Amoeboid
  • Trophozoite
  • Cyst
  • Flagellated form
• Naegleria fowleri


  Considered as the only amoeba that has three morphological forms in its life cycle that infects human
• Acanthamoeba species: Trophozoite


  • Motility: Sluggish, spine-like pseudopods
  • Number of nuclei: 1
  • Cytoplasmic inclusions: Leukocytes and few lymphocytes
• Acanthamoeba species: Cyst


  • Shape: Roundish with ragged edges
  • Number of nuclei: 1
  • Cytoplasmic inclusions: Bacteria or fungi
  • Has a characteristic of double cell wall: Inner-smooth, Outer-ragged
• Naegleria fowleri and Acanthamoeba species are typically found in warm bodies of water, they are pathogenic and produce variety of severe diseases particularly in the brain and cornea
• The Ciliates


  • Have thick round bundles of cilia called cirri which act like legs and enable the organism to actually walk over a surface
  • Possess two kinds of nuclei, macro and micronucleus
  • Divide by fission (asexual), conjugation (sexual)
  • Also found in fresh water environment
  • Has two (2) morphological forms: Cyst, Trophozoite
• Balantidium coli


  The most important specie of the phylum ciliophora, it is the largest protozoan parasite of humans that usually present in pigs feces
• Balantidium coli: Trophozoite


  • Motility: Spiral
  • Number of nuclei: 2 (Macro and micro)
  • Cytoplasmic inclusions: Starch grains, cell fragments, bacteria and erythrocytes
  • Distinction: Presence of cytostome (Mouth)
• Balantidium coli: Cyst


  • Shape: Spherical or oval
  • Number of nuclei: 2 (Macro-kidney shape, Micro-small spherical)
  • Distinction: Double protective cyst wall
• The Flagellates


  • They are equipped with whip-like appendages called "flagella" mainly for locomotion and feeding
  • Reproduce by binary fission
  • Can be colorless or green
  • Facultative parasite
  • Some specie have known without cyst stage on their life cycle
  • Highly motile
  • Has two (2) morphological forms: Cyst, Trophozoite
• Giardia intestinalis/lamblia: Trophozoite


  • Motility: Falling leaf
  • Shape: Pear, teardrop
  • No. of nuclei: 2
  • No. of flagella: 4 pairs
  • Distinction: Bilaterally symmetrical
• Giardia intestinalis/lamblia: Cyst


  • Shape: Ovoid
  • Number of nuclei: (2) Immature, (4) Mature
  • Distinction: Smooth cell wall, interior flagellar structures
• Trichomonas vaginalis: Trophozoite


  • Motility: Rapid, jerky
  • Shape: Ovoid, round
  • No. of nuclei: 1
  • No. of flagella: 3-5
  • Distinction: Undulating membrane extending half of body length, granules along axostyle
  • NO CYST STAGE
• Chilomastix mesnili: Trophozoite


  • Motility: Stiff, rotary, directional
  • No. of Nuclei: One
  • No. of Flagella: Four
  • Distinctive Feature: Prominent cytostome extending 1/3 to 1/2 body length, spiral groove
• Chilomastix mesnili: Cyst


  • Size Range: 5-10 μm
  • Shape: Lemon
  • No. of Nuclei: One
  • Distinctive Feature: Clear hyaline knob, well defined cytostome located on one side of nucleus
• Dientamoeba fragilis: Trophozoite


  • Motility: Progressive, broad hyaline pseudopodia
  • No. of Nuclei: Two
  • Distinctive Feature: Each nucleus consisting of massed clumps of 4-8 chromatin granules
• Entamoeba histolytica: Trophozoite


  • Motility: Nervous, jerky
  • No. of Nuclei: One
  • No. of Flagella: Three to five
  • Distinctive Feature: Axostyle extends beyond posterior end, full body undulating membrane
• Entamoeba tenax: Trophozoite


  • Motility: Nervous, jerky
  • No. of Nuclei: One
  • No. of Flagella: Five total
  • Distinctive Feature: Undulating membrane extending 2/3 of body length, thick axostyle
• Retortamonas intestinalis: Trophozoite


  • Motility: Jerky
  • No. of Nuclei: One
  • No. of Flagella: Two
  • Distinctive Feature: One flagellum directed anteriorly and one extending posteriorly