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[Giardia intestinalis (syn. Giardia lamblia)]

A direct immunofluorescence assay (DFA) is another method for diagnosing Giardia intestinalis infections.  Antibodies tagged with fluorescent markers are added to stool and incubated.  Visualization under a fluorescent microscope shows the Giardia cysts as green, glowing ovoid objects.

Cysts of G. intestinalis (lower right) and oocysts of C. parvum (upper left) labeled with commercially available immunofluorescent antibodies.