Some ultrastructural data on Microsporidium ceylonensis, a cause of corneal microsporidiosis.

Sections of corneal tissue infected with Microsporidium ceylonensis were restained or processed for electron microscopy. Confirmation was obtained that the parasite develops in macrophages and that spores are uninucleate. New information is provided that sporoblasts and spores develop synchronously within a membrane in the host cell, spores have an anisofilar polar tube of 6-10 wide coils and 2-3 narrow coils and details are given of the spore wall and internal organisation. The parasite was compared on the one hand with Encephalitozoon, which exhibits asynchronous intravacuolar development of merogonic and sporogonic stages and has spores with isofilar polar tubes and on the other hand with species reported from mammals, of which the sporogonic stages develop synchronously within sporophorous vesicles and the spores have anisofilar polar tubes. Even so, a generic emplacement could not be established. Attention is drawn to the similarities between M. ceylonensis and Nosema sp. described from the cornea of a woman in Botswana.