Skip directly to search Skip directly to A to Z list Skip directly to site content
CDC Home
For questions about DPDx, contact us

DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit


[Giardia duodenalis (syn. G. lamblia, G. intestinalis)]

Laboratory Diagnosis

G. duodenalis cysts and C. parvum oocysts - IFA

Cysts of G. duodenalis (lower right) and Cryptosporidium (upper left) labeled with commercially available immunofluorescent antibodies.

Giardiasis is diagnosed by the identification of cysts or trophozoites in the feces, using direct mounts as well as concentration procedures. Cysts are typically seen in wet mount preparations, while trophozoites are seen in permanent mounts (i.e. trichrome). Repeated samplings may be necessary. In addition, samples of duodenal fluid (e.g., Enterotest) or duodenal biopsy may demonstrate trophozoites. Alternate methods for detection include antigen detection tests by enzyme immunoassays, and detection of parasites by immunofluorescence. Both methods are available in commercial kits.

Direct Immunofluorescence Assay (DFA)

A direct immunofluorescence assay (DFA) is available for diagnosing Giardia duodenalis 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. This test includes antibodies for Cryptosporidium and both diseases can be tested for simultaneously.

Back to Top

For questions about DPDx, contact us
  • Page last reviewed November 29, 2013
  • Page last updated November 29, 2013
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
  • Notice: Linking to a non-federal site does not constitute an endorsement by HHS, CDC or any of its employees of the sponsors or the information and products presented on the site. The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Road Atlanta, GA 30329-4027, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO