Parasitism is a _______ relationship, where the ______ is injured by the activities of the parasite
Define definitive host
Host where the reproductive stage exists
What two groups can parasites be divided into?
Unicellular or Protoza
Multicellular or Metazoa
What are the 5 most common protoza?
What are the 6 most common Metazoa?
What types of specimens may be examined for parasites?
Fluid aspirates, urine, sputum, CSF, genital swab, corneal scrapings, stool sample
Why must stool sample be collected before administration of barium?
May delay detection for a week or longer
What else can delay parasite identification?
Mineral oil, bismuth, tetracycline
What is the usual recommendation for stool sample collection?
3 specimens collected within 10 days or less
What is required for the testing of live protozoans?
Fresh, non-preserved specimens
Observation within 30 minutes of passage for liquid stool
Observation within 1 hour for semiformed/soft stool
Is the observation timeline usually met?
Protozoa, ova, cysts, tend to ______ on standing
What are the two collection systems?
Two vial system using PVA
One vial system using SAF
Describe vial one in the PVA preservation method
Preserve cysts, and helminth (worm) ova
Does not preserve protozoan trophozoites
Describe vial two in the PVA preservation method
Polyvinyl alcohol (PVA)
Preserves trophozoites and cysts, but not helminth ova
What is the disadvantage of the PVA system?
Contains mercuric chloride
When is the PVA system considered a good preservative?
When stain preparations are being used, especially trichrome
What cannot be performed from the PVA and why
Kills all of the bacteria in sample
Describe the one SAF preservation method
Sodium Acetate Formalin (SAF)
Preserves trophozoites, cysts, and ova
Which stain gives the best results with SAF?
What may be needed to make the material adhere to the slide?
Why can a stool culture not be performed from the SAF?
Kills all of the bacteria
Parasite organisms can exit in what stages?
Cysts, trophozoites, ova, and worms
Most protozoa have a _____ and _____ stage
Which parasite does not follow the exit stages
Metazoa are ________ parasites with both _____ and ______ stages
Multicellular, ova, worm
Resting stage of protozoan parasite
Actively motile, feeding
Reproductive stage of protozoan parasite
Eggs of parasitic worms (Metazoa)
Adult form of Metazoa
Why are wet preps occasionally performed?
To detect live protozoan trophozoites
How is a wet prep prepared
Fresh and liquid sample mixed with saline and placed on slide
In a wet prep, how are trophozoites recognized?
What does the addition of Lugol's or D'Antoni iodine stain? Why is this performed?
Cysts, makes identification of some (Giardia) possible
When are permanent stains neccesarry?
Identification of protozoan trophozoites and cysts
What are the two common stains for protozoan trophozoites and cysts?
What are the results of the trichrome stain?
Parasite nuclear material, rbcs, chromatin bars: Purple/red
What are the results of the Iron hematoxylin stain?
Parasite cytoplasm: blue-grey
Parasite nuclear materia: dark blue-black
Slide background: light blue-grey
What does the addition of an acid fast component allow in permanent stains?
Pink staining of Cryptosporidium
What is the concentration procedure used for?
Concentration of ova and protozoan cysts
Removal of fecal debris
Preservation of parasitic structures
What is the sedimentation technique used in conjunction with?
What are the 3 layers following concentration?
Sediment, ova, and cysts