Enterocytozoon

Lavergne, Ravisse and Modigliani, 1985. The type species is E. bieneusi Desportes, Le Charpentier, Galian, Bernard, Cochard-Priollet, Lavergne, Ravisse and Modigliani, 1985, primarily in enterocytes of the small intestine of humans, Homo sapiens (Primates, Hominidae), especially AIDS patients. Also in gall bladder, bile duct and nasal epithelia and in lungs. The ultrastructure has been described in detail by Cali and Owen (1990). Monomorphic, monokaryotic throughout life cycle. Meiosis unknown. Transmission presumed to be per os but has not been investigated. All stages are in direct contact with host cell cytoplasm, lying in enterocytes between the host cell nucleus and brush border. Merogony: rounded or irregular cells with several elongate nuclei. Expanded regions of nuclear envelope or of cytoplasmic parts of the endoplasmic reticulum form electron lucent clefts with dense borders. Division is presumed to be by fission into smaller meronts. Sporogony: sporonts do not immediately secrete the electron dense coat. They are identified by the presence of electron dense discs, which arise at the borders of the electron lucent clefts. The discs accumulate in stacks and eventually fuse to form the polar tubes. In the multinucleate sporonts, each nucleus becomes associated with a set of organelles, characteristic of the spore: these are the anchoring disc, polar tube with manubrial and coiled regions, and the polaroplast. Invagination of the plasma membrane, which is concurrently thickened by addition of the surface coat, separates the uninucleate sporoblasts each with a complete set of spore organelles. Sporogony is thus polysporoblastic with precocious spore organelle formation. Spore maturation involves only the secretion of a thin endospore layer beneath the surface coat (exospore). Spores, 1.5 x 0.9 µm, are ellipsoid and uninucleate with lamellar polaroplast and about six coils of the polar tube in two ranks. Intestinal infections are often associated with chronic diarrhoea in AIDS patients.