Giardiasis

The structure of trophozoite and cyst are shown in Figure 27.2. Trophozoites have two nuclei and each nucleus contains a prominent karyosome, giving the parasite its characteristic face-like appearance. In addition it has four pairs offlagella, an axostyle (a microtubule-containing organelle to which the flagella attach), a ventral disk and two median bodies, organelles whose function is not known. Cysts, which are slightly smaller than trophozoites, have a carbohydrate-rich cell wall which likely protects them from the environment and two to four nuclei. Giardia is an aero tolerant anaerobe that metabolizes glucose and scavenges cholesterol, phospholipids, purines, pyrimidines and amino acids. Giardia does not contain classical mitochondria but does make ATP in double-membraned organelles called mitosomes, which may represent degenerate mitochondria. The lack of Medical Parasitology, edited by Abhay R. Satoskar, Gary 1. Simon, Peter J. Hotez and Moriya Tsuji.