Unravelling the phylogenetic relationships of African trypanosomes of suids

African trypanosomes of the subgenera Nannomonas and Pycnomonas have been r ecorded from both wild and domestic suids. However, complete descriptions o f some of these trypanosomes with regard to host range, pathogenicity, tran smission and distribution are still lacking. Neither the recently described Trypanosoma (Nannomonas) godfrei nor Trypanosoma (Nannomonas) congolense T savo have been isolated from mammalian hosts, while Trypanosoma (Pycnomonas ) suis remains the rarest of the Salivarian trypanosomes. The only isolate presumed to be of the latter species is maintained at the Ken! a Trypanosom iasis Research Institute, Nairobi. The present here the results of characte rization of this isolate by. morphology, tsetse transmission, the use of sp ecies-specific DNA probes and DNA sequence analysis. Morphology in stained blood smears revealed a small trypanosome with a free flagellum. Experiment al transmission through Glossina,morsitans morsitans showed a developmental cycle typical of subgenus Nannomonas. A positive identification was obtain ed with species-specific PCR primers for T. congolense Tsavo; moreover, the sequence of the SSU rRNA gene was almost identical to that of T. congolens e Tsavo on database. In phylogenetic anal)sis of the SSI! rRNA genes of Sal ivarian trypanosomes, T. congolense Tsavo grouped with T. simiae rather tha n T. congolense, suggesting that the name T. simiae Tsavo is more appropria te.