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.[1]
In
HIV infected individuals, microsporidiosis generally occurs when
CD4+
T cell counts fall below 150.
Microsporidia have emerged with significant mortality risk in
immunocompromised individuals. These are small, single-celled, obligately
intracellular parasites linked to water sources as well as wild, and domestic animals.[2] They were once considered
protozoans or
protists, but are now known to be
fungi,[3] or a sister group to fungi.[4] The most common causes of microsporidiosis is Enterocytozoon bieneusi and Encephalitozoon intestinalis.
Cause
At least 15 microsporidian species have been recognized[5] as human
pathogens, spread across nine genera:
During sporogony, a thick wall is formed around the spore, which provides resistance to adverse environmental conditions. When the spores increase in number and completely fill the host cell cytoplasm, the cell membrane is disrupted and releases the spores to the surroundings.
These free mature spores can infect new cells thus continuing the cycle.
Diagnosis
The best option for diagnosis is using PCR.[citation needed]
Diagnosis with Microsporidia can be done through
gram-
positive,
acid-fast spores in stool and biopsy material with morphologic demonstration of the organism. Initial detection through light microscopic examination of tissue sections, stools, duodenal aspirates, nasal discharges,
bronchoalveolar lavage fluids, and conjunctival smears.[7] Definitive diagnosis can also be achieved through fluorescein-tagged antibody
immunofluorescence or electron microscopy,[7] and species identification can be done through
PCR.[8]
Classification
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,[9] however, they are highly divergent and rapidly evolving.[10][11][12]
Because of its severe mortality risk in immunocompromised individuals, two main agents are used:
Albendazole, which inhibits
tubulin, and
Fumagillin, which inhibits methionine aminopeptidase type two.[15]