Treatment

Albendazole is a benzimidazole derivative with broad-spectrum antihelminthic and antifungal activity. Albendazole interferes with tubulin polymerization and binds to the colchicine-binding site of beta tubulin leading to inhinition of spore germination. Clinical studies have demonstrated that albendazole is effective in clearing E. intestinalis from the gastrointestinal tract of AIDS patients, but albendazole is less effective against E. bieneusi (MacDonald et al., 2004).

Fumagillin, an antibiotic and antiangiogenic compound produced by Aspergillus fumigatus, was more broadly effective against Encephalitozoon spp. and Enterocytozoon bieneusi, but was toxic when administered systemically (Molina et al., 2002).

Beauvais et al. (1994) evaluated the effectiveness of atovaquone (antiprotozoal drug has been used to treat mild to moderate Pneumocystis carinii infection, as well as ocular and cerebral toxoplasmosis in AIDS patients intolerant to more standard therapies)in vitro against E. cuniculi grown in cultures with MDCK cells. A tovaquone was ineffective in either altering parasite morphology or eliminating or slowing the growth or proliferation of the microsporidia.

Coyle et al. (1996) performed in vitro drug inhibition studies using the human microsporidial pathogen Encephalitozoon cuniculi grown in RK-13 cells found that the polyamines analogue norspermine (BE-3-3-3) completely inhibited microsporidial growth.

Antiretroviral therapies that inhibit HIV-infec­tion and thereby partially reconstitute the immune status have reduced the occurrence of opportunistic infections including microsporidiosis (Wiwanitkit, 2006).

Recent study indicated that the aspartyl protease inhibitors used in the highly-active antiretroviral therapy cocktail also inhibited the growth of E. intestinalis in tissue culture (Menotti et al., 2005).

Azithromycin was used in treatment of microsporidial infections but the results were unsatisfactory, as azithromycin was not seen as an effective form of therapy. In vitro evaluation of azithromycin against the microsporidian E. cuniculi, a human pathogen closely related to E. intestinalis showed no efficacy in the eradication of the parasite (Beauvais et al., 1994).

Patients with E. bieneusi infection are chronically dehydrated and may be depleted of both macronutrients and micronutrients. Electrolyte and mineral deficits, particulary K⁺, Ca²⁺, and Mg²⁺, may be severe. A recent study demonstrated stabilization of weight and body cell mass in patients receiving an oral semi-elemental diet (Melchior et al., 1996).

Current studies are focusing on compounds that tar­get microsporidian polyamines (e.g. polyamine ana­logues), methionine aminopeptidase type 2 (e.g. fu­magillin-related compounds and analogues), chitin (e.g. nikkomycins), and topoisomerases (e.g. fluoro­quinolones). However, since E. bieneusi cannot be grown in long-term tissue culture, these studies have been based on cultivatable species of microsporidia as Encephalitozoon spp. (Zhang et al., 2005 and Didier et al., 2006).