Electron microscopic changes in Enterocytozoon bieneusi following treatment with albendazole

To identify and describe electron microscopic changes occurring in Enterocytozoon bieneusi in patients treated with albendazole.

Eighteen HIV seropositive patients with E bieneusi infection of the small intestine were treated with albendazole 400 mg twice a day for one month. Duodenal biopsy specimens obtained before and at the end of treatment were examined electron microscopically by a pathologist who was unaware of the clinical response. A semiquantitative assessment of the parasite load and description of the parasite morphology was made.

A complete resolution of diarrhoea occurred in nine patients and a further three had a greater than 50% reduction in baseline stool frequency or volume. Three of the non-responders were also infected with cryptosporidium. There was a reduction in parasite load in those responding to treatment and an increase in abnormal forms in both responders and non-responders.

The clinical response to albendazole treatment seen in some patients with small intestine microsporidiosis may be due to damage to the developmental stages, causing a partial inhibition of parasite reproduction.