This protozan was initially named Cercomonas intestinalis by Lambl in 1859 and renamed Giardia lamblia by Stiles in 1915, in honor of Professor A. Giard of Paris and Dr. F. Lambl of Prague. However, many consider the name, Giardia intestinalis , to be the correct name for this protozoan. The International Commission on Zoological Nomenclature is reviewing this issue.
Cysts are resistant forms and are responsible for transmission of giardiasis.
The cysts are hardy, can survive several months in cold water. Trophozoites multiply by longitudinal binary fission remaining in the lumen of the proximal small bowel where they can be free or attached to the mucosa by a ventral sucking disk . Encystation occurs as the parasites transit toward the colon. The cyst is the stage found most commonly in non-diarrheal feces . While animals are infected with Giardia , their importance as a reservoir is unclear.