Microsporidia typing
Microsporidia are obligatory intracellular protozoa parasiting many animal hosts. Their implication in human pathology is recently known, especially in the etiology of chronical diarrheas, keratitis or systemic infections in AIDS patients. Microsporidia are composed of about twenty genus and about one hundred species. Only 6 genus have been found in Human: Enterocytozoon, Encephalitozoon, Nosema, Pleistophora and Trachipleistophora, Vitaforma, Brachiola.
Some rare self-resolving cases of microsporidiosis were reported among immunocompetent patients or HIV-negative immunodepressed patients, particularly in cases of grafts (kidney, heart, lung). But most of the observations concern AIDS patients in advanced stage (< 50 CD4) and are caused mainly by Enterocytozoon and Encephalitozoon microsporidia.
Enterocytozoon bieneusi is the only known specie of Enterocytozoon. This parasite of small intestine enterocytes would be responsible for 15 to 30 % of chronical diarrheas associated to bad-absorption syndrom in these patients. That can involve progressive slimming, dehydration and denutrition. E. cuniculi, E. hellem, E. intestinalis belong to Encephalitozoon genus. The affinity of these parasites for macrophages explains their dissemination in the organism with various clinical symptoms (hepatitis, peritonitis, kerato conjunctivitis, sinusitis, pneumopathy). Only E. intestinalis develops in the enterocytes of the small intestine and in macrophages, it is responsible for chronic diarrhea and disseminated infection (kidney, sine, bronchi…).
The spore is the form of resistance and dissemination. It is spread mainly through spores contamination of water or food and sometimes through breeding.
Currently, there is no successfull teatment for all microsporidian species infecting Human. Only E. intestinalis is sensitive to a treatment based on albendazole. Fumagilline is also very effective to treat infections caused by E. hellem or E. intestinalis and would be also effective against gastro-intestinal infections with E. bieneusi. However, its prescription remains delicate because of its strong toxicity.