A TRACHIPLEISTOPHORA-LIKE MICROSPORIDIUM OF MAN - ITS DIMORPHIC NATURE AND RELATIONSHIP TO THELOHANIA-APODEMI

The structure of the human microsporidium found by Yachnis and colleag ues in two AIDS patients (Am. J. Clin. Pathol. 106. 535-43, 1996) ther eafter referred to as HMY) was investigated by light and transmission electron microscopy and compared with Thelohania apodemi Doby, Jeannes et Raoult, 1963, a microsporidian of small rodents. The fine structur e of the HMY was found to be similar to that of Trachipleistophora hom inis Hollister, Canning, Weidner, Field, Kench et Marriott, 1996. Char acteristic is the presence of a thick layer of electron dense material on the outer face of the meront plasmalemma, which is maintained duri ng the whole life cycle and which later persists as an el(:ctron dense coat on the sporophorous vesicle (SPOV). However, HMY is distinguishe d from T. hominis during sporogony, as two types of SPOV and spores ar e formed in HMY. One type of SPOV contains thick-walled spores (usuall y 8 or more in number) with anisofilar polar filaments of 7 + 2 patter n, while the other type contains only two thin-walled spores with a sm aller number (3-5) of isofilar polar filament coils. The HMY differs f rom T. apodemi which also forms SPOV with 8 spores inside, but the spo res of which are larger in size and have 9 + 2 polar filament pattern.