Diagnosis of toxoplasmosis by electron microscopic fine-structural analysis

The analysis of fine structures by electron microscopic examination of ultrathin tissue sections permitted a diagnosis of toxoplasmosis in a fatal human case that would have gone undiagnosed by conventional methods. Examination of histologically prepared sections revealed organisms that were morphologically nondiagnostic. Fine-structural analysis showed the organisms to be 3 x 2 micrometer in size, to contain few micronemes, to contain as many as nine rhoptries, to possess an apical conoid, and to multiply by endodyogeny. The features corresponded to those observed in fine-structural analyses of Toxoplasma gondii grown in animals by Scholtyseck and Mehlhorn. Fine-structural analysis can be a valuable adjunct in the diagnosis of toxoplasmosis.