Giardia intestinalis was described 1859 by Wilhelm Lambl as Cercomonas intestinalis. Since then, the organism has undergone multiple name changes and several names are in curent use including Giardia lamblia, Giardia duodenalis and Giardia intestinalis. Some prefer Giardia intestinalis (Kulda and Nohynkova 1995. Giardia in humans and other animals, pp. 225-422 - in particular pp. 270-271 - in: Kreier, J.P.: Parasitic Protozoa volume 10, Academic Press). Other authors have argued that if there is a single species of Giardia in humans and other mammals, than duodenalis should have priority over intestinalis (Monis, Caccio et Thompson 2009). And Adam states after a review of the nomenclatural history that there does not appear adequate reason to abandon the term G. lamblia, which has been widely accepted in the medical and scientific literature (Adam RD 2001. Biology of Giardia lamblia).