Download (direct link):
PRINCIPLES AND PRACTICE OF CLINICAL PARASITOLOGY
with 10 wide and three narrow coils of polar tube. The fibrillar matrix with tubules in the sporophorous vesicles (Figure 8.3K) is denser than the matrix of T. hominis (Figure 8.3J). Pleistophora sp. of Grau et al. (1996) is probably also a Trachipleistophora sp. Few details can be discerned from the original publication but one unpublished micrograph provided by D. S. Ellis shows an anisofilar polar tube (Figure 8.4M).
In Trachipleistophora anthropophthera (Figures 8.5G,H,K,L on Plate IV; 8.3B,M,N,O), merogony is as in T. hominis. Sporogony: dimorphic, one sporogonic sequence resembling T. hominis, forming eight or more large spores. A second sequence produces only two spores in small sporophorous vesicles (Figure 8.3M). Spores: (a) 3.7 x 2.0 pm (fixed) with six to eight wide and one to three narrow diameter polar tube coils (Figure 8.3N); (b) 2.2-2.5 x 1.8-2.0 pm (fixed) with four or five isofilar coils (Figure 8.3O). (For details, see Yachnis et al., 1996; Berg et al., 1996; Vavra et al., 1998a,b.)
In Microsporidium ceylonensis (Figure 8.3P), merogony and sporogony are unknown except for synchronous development of several sporoblasts in a vacuole. Spores: 3.5 x 1.5 pm (fixed) in groups of eight or more in vacuoles in macrophages. Polar tube anisofilar, with six to ten wide coils and two to three narrow coils (Figure 8.3P). In the case history given by Ashton and Wirasinha (1973), genus is indeterminate, so the species was placed in the collective genus Microsporidium and named by Canning and Lom (1986); ultrastruc-tural data are given by Canning et al. (1998).
In Microsporidium africanum, merogony and sporogony are unknown. Spores: 4.5-5.0 x 2.5-
3.0 pm (fixed) in groups in macrophages. The single published electron micrograph shows at least eight wide coils and three narrow coils of the polar tube (Pinnolis et al., 1981).
Spores of all species in this anisofilar group, measured fresh (T. hominis) or fixed (T. anthro-pophthera, M. ceylonensis, M. africanum) are generally larger (^4.0 pm long) than those of other microsporidia infecting man. The only species in man with larger spores (5.0 x 3.0 pm) is Nosema ocularum (see below). It also appears to have an anisofilar polar tube and, on the published evidence, there is no certainty that the nuclear complement is diplokaryotic. It may also be one of the anisofilar group.
Pleistophora sp. (Figures 8.1B, 8.3L). Merogony and sporogony: multinucleate plasmodia surrounded by a thick surface coat with branched extensions forming links between adjacent parasites. The surface coat becomes a sporophorous vesicle, within which groups of 12 or more sporoblasts are formed from the plasmodium. Spores: 3.2-3.4 x 2.8 pm (fixed), with 11 coils of the polar tube. The published micrograph suggests that the polar tube may be anisofilar. However, the multinucleate plasmodia resemble the genus Pleistophora rather than Trachipleistophora. (For details, see Ledford et al., 1985; Cali and Owen, 1988.)
The Diplokaryotic Group
All stages diplokaryotic, lying in direct contact with host cell cytoplasm, no sporophorous vesicles.
Fig. 8.4 (opposite) (A-F) Vittaforma corneae: characteristic ribosome-studded encircling cisternae of endoplasmic reticulum (er), indicated by arrows. (A) Meront with two diplokarya (n). Bar=1.0 pm. (B) Sporonts with electron dense surface coat (arrowheads). Bar=0.5 pm. (C) Elongate sporont, progenitor of about eight sporoblasts. Bar=1.0 pm. (D) Early sporont showing membrane-filled invagination of sporont surface membrane and the encircling er cisterna. Bar=1.0 pm. (E) Almost complete division of sporont with new cross walls in vicinity of membrane-filled invaginations (arrowheads). Bar=0.5 pm. (A-E) from Silveira and Canning (1995), by permission of the Journal of Eukaryotic Microbiology. (F) Region of spore showing *polaroplast, close apposition (arrow) of the two nuclei (n) and polar tube coils (arrowheads). Bar=0.5 pm. From Shadduck et al. (1990), by permission of the University of Chicago Press. (G-I) Brachiola vesicularum: characteristic vesiculotubular structures are indicated by arrows. All stages have an electron-dense surface coat. (G) Diplokaryotic proliferative stage. Bar=1.0 pm. (H) Region of spore showing only the anterior (wide) polar tube coils. Spore is free of tubules but an adjacent meront (m) has a polar group of tubules (arrowhead). Other bundles of tubules (arrows) lie in lysed host cell cytoplasm. Bar=1.0 pm. (I) Elongate proliferative stage bearing cytoplasmic extensions (arrowheads) with attached tubules and a cap of tubules at one end (arrow). Bar=1.0 pm. From Cali et al. (1998), by permission of the Journal of Eukaryotic Microbiology. (J-L) Brachiola connori. (J) Spore showing diplokaryon (n). Bar=1 pm. (K) Vesiculotubular structures free and attached to cytoplasmic extensions of proliferative stage (p). Bar=1.0 pm. (L) Part of spore showing seven wide coils and five narrow coils. Bar=0.25 pm. Original micrographs of Dr J. A. Shadduck. (M) Pleistophora sp. of Grau et al. (1996). Region of spore showing anisofilar polar tube. Bar=1.0 pm. Original micrograph of Dr D. S. Ellis