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Medical Parasitology Lab. Artifacts. 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”. Blastocystis.
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Medical Parasitology Lab. Artifacts
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”.
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.
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.
Yeast Giardia lamblia cyst Yeast Yeast in an iodine-stained concentrated wet mount of stool. Yeast in wet mount may be confused for Giardia lamblia cyst.
Leukocytes • Round or slightly elongated, with an irregular outline. • Contain refractile cytoplasm, clear and granular with tiny vacuoles. • Nucleus indistinct, sometimes with a star- shaped false karyosome.
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
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: • 4 sporozoites (small banana shaped rods), each containing a small round nucleus, sometimes a few large granules massed at one pole. • One large round granular cell. • Refractile granules completely fill the interior.
Fungal spores Fungal spore Entamoeba histolytica/dispar cyst Fungal spore in a wet mount of stool. Such spores may be confused for the cysts of Entamoebaspp.
Plant cell May confused with helminthes eggs
Plant cell • Plant material in an iodine-stained concentrated wet mount of stool. • This material can be confused for a hookworm egg
RBCs Raed Z. Ahmed, Medical Parasitology Lab.,2012
Non- parasitic structure found in stool • Non parasitic objects may be misidentified as parasites. The differentiation of the most common pseudoparasites is as follow: • 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. • 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.
Cont. • Ova, their general shape, except for Entrobius, is perfectly symmetrical, distinguishing them from various objects found in stools. • Trichuris and Taenia ova may be confused with pollen grains. • Ascaris ova may be confused with vegetable cells, the latter having smooth, thick walls but irregular shape. • 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
Cont. • Fasciola ova resemble vegetable cells. • Insect and may be found in stools as spurious infection. Mite eggs may be confused with hookworm eggs. • Dipylidium caninum eggs sacs can look similar to vegetable cells. • Other structure found in stool are crystals, Charcot- Leyden are the breakdown products of eosinophil cells and may be present in stools or sputum. • 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.
Intestinal Protozoa Entamoeba histolytica/ dispar
Entamoeba histolytica/ dispar • E. histolytica inhabit large intestine and cause amoebic dysentery. • There is two diagnostic stages for E. histolytica/ dispar: • Cystis regular round measuring measure 10 – 20u in diameter with 4 nuclei, and it’s the infective stage. • Trophozoite is the motile form, measure 15-20u in diameter with large nucleus. (motility by pseudopodia). • Diagnosis: • Stool examination to see cyst stage, or trophozoite stage if the sample is fresh.
