Unravelling the phylogenetic relationships of African trypanosomes of suids

African trypanosomes of the subgenera <e1>Nannomonas</e1> and <e1>Pycnomonas</e1> have been recorded from both wild and domestic suids. However, complete descriptions of some of these trypanosomes with regard to host range, pathogenicity, transmission and distribution are still lacking. Neither the recently described <e1>Trypanosoma (Nannomonas) godfreyi</e1> nor <e1>Trypanosoma (Nannomonas) congolense</e1> Tsavo have been isolated from mammalian hosts, while <e1>Trypanosoma (Pycnomonas) suis</e1> remains the rarest of the Salivarian trypanosomes. The only isolate presumed to be of the latter species is maintained at the Kenya Trypanosomiasis Research Institute, Nairobi. We present here the results of characterization of this isolate by morphology, tsetse transmission, the use of species-specific DNA probes and DNA sequence analysis. Morphology in stained blood smears revealed a small trypanosome with a free flagellum. Experimental transmission through <e1>Glossina morsitans morsitans</e1> showed a developmental cycle typical of subgenus <e1>Nannomonas</e1>. A positive identification was obtained with species-specific PCR primers for <e1>T. congolense</e1> Tsavo; moreover, the sequence of the SSU rRNA gene was almost identical to that of <e1>T. congolense</e1> Tsavo on database. In phylogenetic analysis of the SSU rRNA genes of Salivarian trypanosomes, <e1>T. congolense</e1> Tsavo grouped with <e1>T. simiae</e1> rather than <e1>T. congolense</e1>, suggesting that the name <e1>T. simiae</e1> Tsavo is more appropriate.