COMPARATIVE PATHOLOGY OF MICROSPORIDIOSIS

The obligate intracellular protozoan parasites belonging to the phylum Microspora are ubiquitous. They parasitize insects and ail five class es of vertebrates. Only one genus infects mammals and birds but at lea st four genera affect humans. Two genera have been isolated from human specimens and both infect experimental animals. Some genera (eg, Ente rocytozoon and Pleistophora) seem to be limited to a very few tissues but others (Encephalitozoon and the Encephalitozoon-like genus Septata ) can infect multiple organs. Lesions range from classic mitrogranulom as to foci of infected cells unaccompanied by any inflammatory respons e. The most commonly occurring microsporidia infection of man (Enteroc ytozoon bieneusi) is characterized by infection of enterocytes of the villus tips of the small intestine, accompanied by villus blunting, cr ypt hyperplasia, sloughing of infected villus tip cells, and increased numbers of intraepithelial lymphocytes.