Giardia lamblia

Last edited 02/2020 and last reviewed 06/2021

Giardia duodenalis, also known as Giardia intestinalis and Giardia lamblia or Lamblia intestinalis is a flagellate protozoal parasite which exists in two forms, a trophozoite and cyst.

It infests man, and a number of other mammalian species.

The motile, binucleate trophozoite is found in the duodenum and upper jejunum and it is only rarely found in the stool. It attaches to, but does not invade, the small bowel. The form usually found in the stool is the cyst which survives in fresh water and would resist domestic chlorination were it not removed from municipal water supplies by filtration.