Isospora belli infection: observation of unicellular cysts in mesenteric lymphoid tissues of a Brazilian patient with AIDS and animal inoculation.

We describe the finding of unizoic cysts of Isospora belli in lymphoid tissues of a Brazilian patient with AIDS, and discuss the possibilities of their drug resistance, they being the cause of relapses, and of being an indication for the existence of intermediary or paratenic animal hosts.