Diagnosis of intestinal microsporidiosis in patients with AIDS and others with unexplained diarrhea, especially after overseas travel
See Parasitic Investigation of Stool Specimens Algorithm in Special Instructions for other diagnostic tests that may be of value in evaluating patients with diarrhea.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Microsporidia are obligate protozoan parasites which have been documented to infect invertebrates and vertebrates. They are very small organisms (1-2 microns, about the size of bacteria) and are classified in a phylum, microspora, characterized by the structure of their spores which contain polar tubules which are extruded to inject infective material into host cells.
The microsporidia known to infect humans include Enterocytozoon bieneusi (intestinal microsporidiosis), Encephalitozoon hellem (eye infections), and Enterocytozoon (Septata) intestinalis (intestinal and disseminated infections, especially to the biliary tree).
Human infections have been reported most frequently in patients with AIDS, but also can occur sporadically in immunocompetent patients. The primary clinical findings are chronic diarrhea, weight loss, and malabsorption.
Enterocytozoon bieneusi is found in the duodenal mucosa and infection is accompanied by a wide spectrum of histopathologic changes ranging from normal architecture to almost complete effacement of the villi and virtual obliteration of the lamina propria by inflammatory cells.
The anti-helmintic drug, albendazole has been found effective in some infections due to Enterocytozoon bieneusi and Encephalitozoon (Septata) intestinalis.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
If positive, reported as microsporidia
Presence of microsporidia in stool may or may not be associated with symptoms in infected persons and may or may not be the cause of any symptoms since patients with AIDS may be infected with more than 1 intestinal pathogen at the same time.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
These organisms are very difficult to identify among the multitude of organisms and artifactual debris present in the stool.
The sensitivity and specificity of the stain have not been determined.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Weber R, Bryan RT, Schwartz DA, Owen RL: Human microsporidial infections. Clin Microbiol Rev 1994;7:426-461
2. Goodgame RW: Understanding intestinal spore-forming protozoa: cryptosporidia, microsporidia, isospora, and cyclospora. Ann Intern Med 1996;124:429-441
3. Wanke CA, DeGirolami P, Federman M: Enterocytozoon bieneusi infection and diarrheal disease in patients who were not infected with human immunodefeciency virus: case report and review. Clin Infect Dis 1996;23:816-818