Human microsporidial infections

Abstract

Microsporidia are obligate intracellular spore-forming protozoal parasites belonging to the phylum Microspora. Their host range is extensive, including most invertebrates and all classes of vertebrates. More than 100 microsporidial genera and almost 1,000 species have now been identified. Five genera (Enterocytozoon spp., Encephalitozoon spp., Septata spp., Pleistophora sp., and Nosema spp.) and unclassified microsporidia (referred to by the collective term Microsporidium) have been associated with human disease, which appears to manifest primarily in immunocompromised persons. The clinical manifestations of microsporidiosis are diverse and include intestinal, pulmonary, ocular, muscular, and renal disease. Among persons not infected with human immunodeficiency virus, ten cases of microsporidiosis have been documented. In human immunodeficiency virus-infected patients, on the other hand, over 400 cases of microsporidiosis have been identified, the majority attributed to Enterocytozoon bieneusi, an important cause of chronic diarrhea and wasting. Diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves. Initial detection of microsporidia by light microscopic examination of tissue sections and of more readily obtainable specimens such as stool, duodenal aspirates, urine, sputum, nasal discharge, bronchoalveolar lavage fluid, and conjunctival smears is now becoming routine practice. Definitive species identification is made by using the specific fluorescein-tagged antibody (immunofluorescence) technique or electron microscopy. Treatment options are limited, but symptomatic improvement of Enterocytozoon bieneusi infection may be achieved with the anthelmintic-antiprotozoal drug albendazole. Preliminary observations suggest that Septata intestinalis and Encephalitozoon infections may be cured with albendazole. Progress is being made with respect to in vitro propagation of microsporidia, which is crucial for developing antimicrosporidial drugs. Furthermore, molecular techniques are being developed for diagnostic purposes, taxonomic classification, and analysis of phylogenetic relationships of microsporidia.

Prevalence of antibodies to Encephalitozoon cuniculi in European hares (Lepus europaeus)

“…Humans may be infected by the ingestion of food and water contaminated with spores of this parasite, [1] but it is possible that there are other ways of infection. In humans, E. cuniculi may affect the nervous and respiratory system, digestive tract, kidneys, and also the endocrine and lymphatic systems [20,21] with diarrhoea, pneumonitis, urinary tract infection and systemic diseases described among immunodeficient patients [21,22]. The infection in a healthy population is mostly without clinical signs.…”

Disseminated Microsporidiosis Caused by Encephalitozoon cuniculi III (Dog Type) in an Italian AIDS Patient: a Retrospective Study

“…Although E. cuniculi infection has been described in humans since 1959, the initial reports concentrated on histological and ultrastructural studies, which cannot distinguish E. cuniculi from E. hellem (19). However, more recent reports of E. cuniculi infection in both HIV-positive and -negative patients with renal, respiratory, ocular, oral, and maxillary sinus involvement have been based on more precise molecular methods (14, 20 -22).…”

“…Previously, reports of hepatitis caused by Encephalitozoon, described in a few patients with granulomatous and suppurative or necrotic portal and parenchymal microsporidial lesions (19,27), have been based purely on morphological studies, and hence the species involved has been questionable. However, the hepatic lesions caused by E. cuniculi infection in our patient were confirmed by precise molecular methods.…”

“…Particular attention has been given by some authors to brain involvement during disseminated microsporidiosis because of its significance in animals (2,29). The first detection in humans of Encephalitozoon spores was in the cerebrospinal fluid of patients with neurological symptoms (19). Weber et al (8) have more recently reported another case of disseminated E. cuniculi Genotype I infection, in which the presence of protozoa in the cerebrospinal fluid was associated with diffuse cerebral lesions revealed by magnetic resonance imaging and computed tomography.…”

Microsporidios en humanos

“…y se detectó IgM e IgG contra Encephalitozoon cuniculi (5). Con el advenimiento de la epidemia de SIDA, a partir de 1985 se han descrito varias patologías en las que se encuentran los microsporidios como agentes etiológicos (6-1 1).…”