Giardia lamblia is a protozoan parasite which causes giardiasis.
it belongs to the phylum mastigophora and infect mainly the small intestine.
it exist in two forms; trophozoite form and the cyst form.
The trophozoite is pear shaped with 2 nuclei and it has 4 pairs of flagella.
it has a sucking disk which helps it to adhere to the epithelial lining of the intestine.