Microsporidiosis is an opportunistic intestinal infection that causes diarrhea and wasting in immunocompromised individuals (HIV, for example). It results from different species of microsporidia, a group of microbial (unicellular) fungi. Microsporidiosis is an opportunistic intestinal infection that causes diarrhea and wasting in immunocompromised individuals (HIV, for example). It results from different species of microsporidia, a group of microbial (unicellular) fungi. In HIV infected individuals, microsporidiosis generally occurs when CD4+ T cell counts fall below 150. Although it is classified as a protozoal disease in ICD-10, their phylogenetic placement has been resolved to be within the Fungi, and some sources classify microsporidiosis as a mycosis, however, they are highly divergent and rapidly evolving. At least 15 microsporidian species have been recognized as human pathogens, spread across nine genera: The primary causes are Enterocytozoon bieneusi and Encephalitozoon intestinalis. (Coded to image at right). Fumagillin has been used in the treatment. Another agent used is albendazole.