How is giardiasis diagnosed?

Updated: Oct 01, 2018
  • Author: Hisham Nazer, MBBCh, FRCP, DTM&H; Chief Editor: Burt Cagir, MD, FACS  more...
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The traditional basis of diagnosis is identification of Giardia intestinalis trophozoites or cysts in the stool of infected patients via a stool ova and parasite (O&P) examination. Stool antigen enzyme-linked immunosorbent assays also are available. (See Workup.) Standard treatment for giardiasis consists of antibiotic therapy. Metronidazole is the most commonly prescribed antibiotic for this condition; however, tinidazole is also approved in the United States and is considered a first-line agent outside the United States. (See Treatment.)

A G intestinalis cyst is seen in the image below.

A Giardia intestinalis cyst. A Giardia intestinalis cyst.

See Common Intestinal Parasites and 5 Cases of Food Poisoning: Can You Identify the Pathogen?, Critical Images slideshows, to help make an accurate diagnosis.

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