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Strongyloides stercoralis rhabditiform larvae detected by stool ovum and parasite microscopy. |
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Parasitology
Routine ova and parasite examination: Stools are double-concentrated, stained with special stains, and examined microscopically for ova and parasites. Other samples (sputum, eye scrapings, liver aspirates, etc.) can also be examined or in some cases cultured (such as for Acanthamoeba) for parasites if the laboratory is notified in advance. Two stools collected on two separate days are recommended.
Giardia antigen detection by enzyme immunoassay: Stool submitted in preservative is tested weekly for Giardia antigen by EIA. Giardia is the most common parasitic cause of diarrhea in the U.S. This test is at least twice as sensitive as conventional ova and parasite examinations for Giardia detection and should be ordered first if Giardia is in the differential.
Cryptosporidium direct fluorescent antibody stain: Cryptosporidium causes travelers’ diarrhea and can cause protracted diarrhea in immunocompromised patients. Cryptosporidium Oocysts can be visualized with this stain, which is more sensitive than conventional examination methods.
Worm and tick identification: Worms and ticks submitted in a container with a moist cotton ball are identified based on visual macroscopic and microscopic characteristics. In addition, ticks are sent to a public health laboratory for more specialized studies.
Microsporidium and Isospora special stains: These unusual parasitic agents of diarrhea, almost exclusively in immunocompromised patients, are detected using a modified acid fast/trichrome stain combination.
