[Isoenzymatic strains of Trypanosoma cruzi: recent or ancient, homogeneous or heterogeneous origin?].

Genetic variability studied among 13 Trypanosoma cruzi laboratory reference stocks confirms the existence of three principal isozymic categories. As the main part of enzymic variability is now recognized, it seems possible to attribute any stock to the taxon T. cruzi with safety. Genetic parameters allow to infer two main hypotheses relative to the evolutionary origin of these categories: ancient origin (either by mitotic evolution or by speciation), or recent origin (by clone sampling among a sexual ancestral population). The possibility of a heterogeneous origin of the strains is discussed.