Environmental kinetoplastid-like 18S rRNA sequences and phylogenetic relationships among Trypanosomatidae: paraphyly of the genus Trypanosoma.

Using kinetoplastid-like sequences from deep-sea environmental samples as an outgroup, we applied phylogenetic analysis to 18S rRNA sequences of the families Trypanosomatidae and Bodonidae (Eugelenozoa: Kinetoplastida). The monophyly of the genus Trypanosoma was not supported by a number of different methods. Rather, the results indicate that the American and African trypanosomes constitute distinct clades, therefore, implying that the major human disease agents T. cruzi (cause of Chagas' disease) and T. brucei (cause of African sleeping sickness) are not as closely related to each other as they were previously thought to be. Likewise, the results did not support monophyly of the genera Leishmania, Leptomonas, Bodo and Cryptobia.