Goat Anti-G. lamblia Polyclonal antibody for ICC, IF, IHC-Fr. Giardiasisis a diarrhoeal illness caused by a single celled microscopic protozoan parasite ,Giardia lamblia, also known as Giardia intestinalis. Giardia lamblia exists in two forms, an active form called a trophozoite, and an inactive form called a cyst.