Microsporidiosis
Microsporidiosis is an opportunistic disease typically affecting immunocompromised patients. Microsporidia have now been re-classified as fungi and consist of several species. Enterocytozoon bieneusi and Encephalitozoon intestinalis are most commonly found in the small intestine, whereas Encephalitozoon cuniculi may be systemic in location.
Encephalitozoon hellem may present as cause of ocular lesions or keratitis. Although rare, Trachipleistophora hominis may be detected in muscle biopsies by PCR and microscopy, and Vittaforma corneae in ocular samples (including corneal scrapes) for investigation of keratitis.
Diagnosis of Microsporidiosis by microscopy
Microscopy is rarely used in the diagnosis of microsporidiosis due to molecular techniques showing significantly improved sensitivity and the ability to identify the infecting species. Microscopy may be attempted on individual high value, small volume samples such as corneal scrapes, where the entire sample may be analysed for a small number of spores, although PCR is preferable.
- Sample type: please consult the Department of Clinical Parasitology for advice if considering such an investigation.
Diagnosis of Microsporidiosis by PCR
- Sample type: Unfixed stool, tissue and urine samples.
Stool samples for the molecular test must NOT be in any fixative as this may cause false negatives.
Please note: requests for microsporidiosis should be clearly marked.
The molecular test for microsporidial species offers several advantages over standard microscopy. The assay is significantly more sensitive (greater than one hundred fold improvement in the limit of detection) than light microscopy. In addition, the assay is semiquantitative and can therefore reveal detailed information on the response of a patient’s parasitic load to subsequent
drug therapy.
Finally, the assay can differentiate between morphologically identical microsporidia, a feat only possible previously with electron microscopy.
Please note this test has not been validated on tissues and urines but will still be performed upon request.
Diagnosis of Microsporidiosis by serology
Serology is NOT available for these parasites.