Taxonomy of the Sleeping Sickness Trypanosomes

Arguments are presented for making Trypanosoma (Trypanozoon) gambiense and T. (T.) rhodesiense synonymous with T. (T.) and for classifying them according to their undoubted differences in epidemiology, clinical pattern, and morphology at a subtaxonomic level as strains or demes. Similar arguments cannot, at present, be applied to other members of subgenus Trypanozoon (i.e., T. (T.) evansi, T. (T.) equinum, and T. (T.) equiperdum). The term clonal pleomorphism is used to describe the diversity of form which occurs in species of subgenus Trypanozoon in order to avoid confusion with genetic polymorphism which is also found in T. (T.) brucei. In discussing the brucei group trypanosomes: Trypanosoma brucei, T. gambiense, and T. rhodesiense, which he later placed in the subgenus Trypanozoon, Hoare (1943) pointed out that their differences were not sufficiently marked to warrant classification as separate species. In his subsequent revision of their classification (Hoare, 1966) he suggested that they should be considered as subspecies of Trypanosoma (Trypanozoon) brucei, the oldest of the three species, by using the quadrinomials: Trypanosoma (Trypanozoon) (type species choice by elimination Hoare, 1964) for the pleomorphic trypanosome of animals other than