PARASITOLOGY LAB
,Protozoa is a unicellular parasites.
These are most commonly found in the lower gastrointestinal tract.
Most of species can form non-feeding, non-motile cysts,thisstage of life cycle could
be infective stage in humans.
This is also considered as the transfer stage of most species. Transmission of
amoeba is generally by ingestion of cysts in fecallycontaminated food and water.
Nuclei of each species are quite different for the different genus of amoeba. For this
reason, identification of stained nuclear structure aids in diagnosis.
In cystic stage, the number of nucleus varies as well, which is also crucial for correct
identification. Other diagnostic features present in the cystic stages includes size,
shape of cyst and other inclusion bodies.
The trophic stage (vegetative stage), diagnostic features includes size, cytoplasmic
inclusions and type of motility exhibited. The trophozoite is the motile and feeding
stage of amoebas.
•Trophozoites can be destroyed by iodine
•A specialized structure known as pseudopodia enables the organism to move.
•This structure arises from the cytoplasm and is characteristic structure for
amoebas.
•Entamoeba histolytica is the medically important species in this group and is
the cause of amoebic dysentery in humans. This organism can occur in other
primates, dogs, cats, and rats.
•All other organisms (amoeba) are considered as non-pathogenic.
• If the organism is genus Entamoeba (true amoeba) –peripheral chromatin
(visible nuclear membrane in both trophozoite and cyst) and chromatoidal in
cyst only.
• If the organism is genus Endolimax or Iodamoeba(other amoeba) –neither
, peripheral chromatin or non chromatoidalbody are present.
Pathogenic Amoeba: Entamoeba histolytica
Non-Pathogenic Amoeba: Entamoeba dispar, Entamoeba moshkovskii, Entamoeba
hartmanni
Features of Entamoeba histolytica
Trophozoites
• It measures 12–60 μm(average 15–20 μm) in diameter
•Cytoplasm of trophozoite is divided into a clear ectoplasm and a granular
endoplasm
•Granular endoplasm looks as ground glass appearance and contains red blood
cells (RBCs), white blood cells (WBCs) and food vacuoles containing tissue debris
and bacteria. RBCs are found only in the stage of invasion
•Pseudopodia: Ectoplasm has long fingerlike projections called as pseudopodia
(organ of locomotion); which exhibits active, unidirectional rapid progressive and
purposeful movement
Trophozoites
•Nucleus is single, spherical, 4–6 μmsize, contains central dot like compact
karyosome surrounded by a clear halo.
•Nuclear membrane is thin and delicate and is lined by a layer of fine chromatin
granules. The number of chromosomes varies between 30 and 50
•The space between the karyosomeand the nuclear membrane is traversed by
spoke like radial arrangement of achromatic fibrils (cart wheel appearance)
•Amoebic trophozoites are anaerobic parasites. They lack mitochondria,
endoplasmic reticulum and Golgi apparatus.
,Protozoa is a unicellular parasites.
These are most commonly found in the lower gastrointestinal tract.
Most of species can form non-feeding, non-motile cysts,thisstage of life cycle could
be infective stage in humans.
This is also considered as the transfer stage of most species. Transmission of
amoeba is generally by ingestion of cysts in fecallycontaminated food and water.
Nuclei of each species are quite different for the different genus of amoeba. For this
reason, identification of stained nuclear structure aids in diagnosis.
In cystic stage, the number of nucleus varies as well, which is also crucial for correct
identification. Other diagnostic features present in the cystic stages includes size,
shape of cyst and other inclusion bodies.
The trophic stage (vegetative stage), diagnostic features includes size, cytoplasmic
inclusions and type of motility exhibited. The trophozoite is the motile and feeding
stage of amoebas.
•Trophozoites can be destroyed by iodine
•A specialized structure known as pseudopodia enables the organism to move.
•This structure arises from the cytoplasm and is characteristic structure for
amoebas.
•Entamoeba histolytica is the medically important species in this group and is
the cause of amoebic dysentery in humans. This organism can occur in other
primates, dogs, cats, and rats.
•All other organisms (amoeba) are considered as non-pathogenic.
• If the organism is genus Entamoeba (true amoeba) –peripheral chromatin
(visible nuclear membrane in both trophozoite and cyst) and chromatoidal in
cyst only.
• If the organism is genus Endolimax or Iodamoeba(other amoeba) –neither
, peripheral chromatin or non chromatoidalbody are present.
Pathogenic Amoeba: Entamoeba histolytica
Non-Pathogenic Amoeba: Entamoeba dispar, Entamoeba moshkovskii, Entamoeba
hartmanni
Features of Entamoeba histolytica
Trophozoites
• It measures 12–60 μm(average 15–20 μm) in diameter
•Cytoplasm of trophozoite is divided into a clear ectoplasm and a granular
endoplasm
•Granular endoplasm looks as ground glass appearance and contains red blood
cells (RBCs), white blood cells (WBCs) and food vacuoles containing tissue debris
and bacteria. RBCs are found only in the stage of invasion
•Pseudopodia: Ectoplasm has long fingerlike projections called as pseudopodia
(organ of locomotion); which exhibits active, unidirectional rapid progressive and
purposeful movement
Trophozoites
•Nucleus is single, spherical, 4–6 μmsize, contains central dot like compact
karyosome surrounded by a clear halo.
•Nuclear membrane is thin and delicate and is lined by a layer of fine chromatin
granules. The number of chromosomes varies between 30 and 50
•The space between the karyosomeand the nuclear membrane is traversed by
spoke like radial arrangement of achromatic fibrils (cart wheel appearance)
•Amoebic trophozoites are anaerobic parasites. They lack mitochondria,
endoplasmic reticulum and Golgi apparatus.
