Answer to Case 726

 Answer to the Parasite Case of the Week 726: Microsporidia spores; genus and species not determined

These small spores stain deep red with the chromotrope 2R method and its modifications. They are oval shaped and often have a darker-staining equatorial band in the middle of the spore. Spores of Enterocytozoon bieneusi are very small (0.8 to 1.4 micrometers long), whereas other species such as Encephalitozoon spp., Vittaforma cornea, and Anncaliia algerae are a little larger. Some (e.g., Anncaliia) are up to 4 micrometers long and may be mistaken for small years such as Histoplasma capsulatum (especially because they are focally GMS positive!)

As Dr. Couturier pointed out, microsporidia are not parasites, but fungi (his words: "Not a parasite LOL Get those buggers off this page and send them to the Mycology lab. 😉) . They are obligate intracellular, unicellular, spore-forming eukaryotic organisms comprising more than 220 genera and 1,700 species.  Microsporidia itself is NOT a genus and should not be italicized.