Detection of T.b. rhodesiense trypanosomes in humans and domestic animals in south east Uganda by amplification of serum resistance-associated gene.

The human serum resistance-associated (SRA) gene was identified in 28 (80%) of the 35 T.b. rhodesiense trypanosomes from parasitologically confirmed sleeping sickness cases, using the primers designed by Radwanska and in 27 (77.1%) of the same 35 T.b. rhodesiense trypanosomes using the primers designed by Gibson. However, about 20% of the 35 T.b. rhodesiense trypanosomes could not be detected by SRA-polymerase chain reaction (PCR) even when an aliquot of the first PCR was used in the second PCR, indicating that the gene may be absent in those trypanosomes or the trypanosomes could be having another variant of SRA not detectable by these primers since three variants of SRA genes have so far been identified or the amount of trypanosomal DNA extracted from infected blood was too low to be detected. The trypanosome isolates that are SRA gene negative may indicate the presence of some T.b. rhodesiense trypanosomes with modified or lack SRA genes or simple loss of the SRA gene from the expression site in which it resides during antigenic variation. Analysis of trypanosomes derived from domestic animals showed that 79 (90.8%) of the 87 trypanosomes isolated from cattle were positive by Trypanosoma brucei (TBR)-PCR, indicating that they were Trypanozoon while 8 (9.2%) of the trypanosome isolates which were negative by TBR-PCR could be T. vivax, T. congolense, or T. theileri. When subjected to SRA-PCR, 10 (11.5%) of the 87 trypanosomes isolates derived from cattle were positive, indicating that there could be T.b. rhodesiense circulating in cattle, which is similar to the percentage of T.b. rhodesiense previously obtained in cattle in Serere, Soroti district.