Human Microsporidial Infections

Microsporidia are eukaryotic, spore forming obligate intracellular parasites, first recognised over 100 years ago. Microsporidia are becoming increasingly recognised as infectious pathogens causing intestinal and extra-intestinal diseases in both immuno-competent and immuno-suppressed patients. They are characterised by the production of resistant spores that vary in size depending on the species; and poses a unique organelle, the polar tubule (polar filament), which is coiled inside the spore as demonstrated by its ultra structure. Other unusual characteristics are the lack of mitochondria and the prokaryotic-like ribosomes, which indicate the primitive nature of the group. Presently there are seven genera, Enterocytozoon, Encephalitozoon, Nosema, Pleistophora, Trachi pleistophora, Brachiola, vittaforma species which have been reported from human hosts as agents of systemic, ocular, intestinal and muscular infections, are described and the diagnosis, treatment, and source of infections discussed.