Definition

Artifacts: other things, living or artificial, present in
the stool that are not parasites and could mislead the
laboratory worker.

Note: “Artifacts not to be mistaken for cysts”.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Blastocystis
• Round or oval,
sometimes with angular
irregular edges, contain
one large vacuole taking
up almost the whole
cell, the compressed
cytoplasm forms a
granular ring round it.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Blastocystis
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Yeast
• Oval, often with buds, often
contain eccentric cluster of
3-6 small granules.
• Some related forms of yeast
are rectangular, with a very
clear oval cytoplasm inside:
arthrospores.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Yeast
Yeast
Giardia lamblia cyst
Yeast in an iodine-stained concentrated wet mount of stool. Yeast in
wet mount may be confused for Giardia.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Leukocytes
• Round or slightly elongated,
with an irregular outline.
• Contain refractile cytoplasm,
clear and granular with tiny
vacuoles.
• Nucleus indistinct,
sometimes with a starshaped false karyosome.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Pus
• Pus can be seen by the
naked eye as opaque,
greyish streaks( not
transparent like mucus).
• Under the microscope it
appears as a mass of more
or less degenerate
leukocytes
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Bacteria
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Coccidia
• These are protozoa that may be parasite of men without
causing any significant pathogenic effects, or may be found in
transit in stool following the consumption of infected foods.
• They appear in stool in a form resembling cyst called oocysts
or sporocysts.
• An elongated oval, sometimes tapered at one pole.
• There three types:
a. 4 sporozoites (small banana shaped rods), each containing
a small round nucleus, sometimes a few large granules
massed at one pole.
b. One large round granular cell.
c. Refractile granules completely fill the interior.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Coccidia (cont.)
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Coccidia (cont.)
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Air bubbles
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Oil droplet
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Fungal spores
Entamoeba histolytica/dispar
Fungal spore in a wet mount of stool. Such spores cyst
may be confused for the
Fungal spore
cysts of Entamoeba spp.
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Plant fiber
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Strongyloides stercoralis larvae
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Misdiagnosis can lead to improper treatment
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Hair fiber
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Plant cell
May confused with helminthes eggs
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Planet cell
• Plant material in an iodine-stained concentrated wet mount of stool.
This material can be confused for a hookworm egg
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Charcot-Leyden crystals
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Epithelial cells
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Macrophages
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RBCs
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Digested meat fibers
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Pollen grains
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Pollen grains
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Soap
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Starch granules
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Crystals
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Non- parasitic structure found in stool
 Non parasitic objects may be misidentified as parasites. The
differentiation of the most common pseudoparasites is as follow:
1. Protozoan cyst: may be confused with air bubbles, fat globules or
yeasts.
– Iodine should be added to the wet preparation so that the internal
structure of the cyst is stained and identifiable.
2. Amoebic trophozoites: must be differentiated from non- pathogenic
protozoan trophozoites and macrophages.
– Trophozoites of Entamoeba histolytica/dispar must be motile and
hematophagus.
– Macrophages found in cases of intestinal amoebiasis are distinguishable
from amoebic trophozoites by possessing a larger nucleus and, although
they can haematophagus, they are only motile for a very short time.
Their pseudopodia are small, blunt and granular.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Cont.
3. Ova, their general shape, except for Entrobius, is perfectly
symmetrical, distinguishing them from various objects
found in stools.
4. Trichuris and Taenia ova may be confused with pollen
grains.
5. Ascaris ova may be confused with vegetable cells, the
latter having smooth, thick walls but irregular shape.
6. Strongyloides or hookworm larvae can be confused with
hair or vegetable fibers. The latter are usually tapered at
one end and the other being blunt and with no internal
structure.
– Free living nematode larvae may be found in concentrates if
contaminated water is used
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Cont.
7. Fasciola ova resemble vegetable cells.
8. Insect and may be found in stools as spurious infection.
Mite eggs may be confused with hookworm eggs.
9. Dipylidium caninum eggs sacs can look similar to
vegetable cells.
10. Other structure found in stool are crystals, CharcotLeyden are the breakdown products of eosinophil cells
and may be present in stools or sputum.
11. Starch granules are sometimes seen in stool. When
undigested, they appear as concentric rings and stain blue
with iodine, when partially digested, they stain red.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Entamoeba histolytica/ dispar
• E. histolytica inhabit large intestine and cause amoebic
dysentery.
• There is two diagnostic stages for E. histolytica/ dispar:
1. Cyst (infective stage).
2. Trophozoite (motile form, motility by pseudopodia).
• Diagnosis:
1. Stool examination to see cyst stage, or trophozoite
stage if the sample is fresh.
Raed Z. Ahmed, Medical Parasitology Lab.,2012
Life cycle
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Entamoeba histolytica/ dispar Cyst
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Entamoeba histolytica/ dispar Trophozoite
Raed Z. Ahmed, Medical Parasitology Lab.,2012