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microsporidiosis
Etiology:
1) Enterocytozoon bieneusi
2) Encephalitozoon cuniculi
3) Enterocytozoon hellum
4) Septata intestinalis
Epidemiology:
1) Microsporidia infest a large variety of animals, including humans, but reservoir hosts have not been identified
2) serious pathogens in immunocompromised hosts
3) may account for 30% of unexplained diarrhea in AIDS patients
Pathology:
1) organisms multiply intracellularly (merogony)
2) spores are formed (sporogony) that rupture the host cell (duodenal enterocyte) & infect adjacent cells or are passed in the feces
3) spore contains a coiled polar tubule which is extruded to penetrate the membrane of the recipient cell
4) the sporoplasm is injected through the tubule into the cytoplasm of the host cell, where it multiplies
Clinical manifestations:
1) chronic diarrhea (mean duration 8.5 months)
2) weight loss
3) dissemination (some species)
4) malabsorption
5) hepatic, ocular, CNS, muscle manifestation (other species)
Laboratory:
1) modified trichrome staining of stools for spores
a) 1.5-3 um elliptical spores stain red against a faint green background
b) some spores have band across midsection
2) fluorochrome stains of feces
a) Uvitex 2B
b) calcofluor white
c) may be more sensitive than modified trichrome staining
3) small size of spores makes detection difficult
4) small bowel biopsy
a) trichrome, Brunn & Brenn, or Giemsa stain
b) electron microscopy for species identification
5) fecal fat may be positive
6) abnormal D-xylose absorption test
7) serum albumin is generally normal
Management:
1) no definitive therapy
2) albendazole 400 mg QD for 1 month for intestinal disease
3) fumagillin may be effective for keratoconjunctivitis
Related
microsporidia
General
protozoan infection
References
- Medical Knowledge Self Assessment Program (MKSAP) 11, American
College of Physicians, Philadelphia 1998
- Grimm L
What's Eating You: 12 Common Intestinal Parasites.
Medscape. November 25, 2019
https://reference.medscape.com/slideshow/intestinal-parasites-6010996