MICROSPORIDIA

The microsporidia are obligate intracellular parasites that have been recognized in a variety of animals, particularly vertebrates. Typical sizes of the spores range from 1.5 to 2.0um in humans. The infectious stage, the spore, contains a coiled polar tubule, which is an extrusion mechanism for injecting the infective spore contents into host cells. Demonstration of the coiled polar tubule within spores is diagnostic for microsporidial infections. Currently, there are eight genera of microsporidia that can infect humans. the more common are Encephalitozoon spp., Septata intestinalis and Enterocytozoon bieneusi; the less common are Brachiola spp, Microsporidium spp., Nosema spp., Pleistophora spp., and Trachipleistophora spp., and Vittaforma spp.. Essentially every body site can be infected with one or more of these eight genera; some organisms will tend to disseminate to other parts of the body from the primary site of intection (often the GI tract).

Human infections occur through ingestion, inhalation, and probably