Acute human African Trypanosomiasis (HAT) caused by Trypanosoma brucei rhodesiense (Tbrh) continues to spread north towards chronic T. b. gambiense (Tbg) areas of NW Uganda; this would complicate definitive diagnosis and treatment. We carried out surveys to identify trypanosomes in humans, domestic animals and tsetse flies.
PCR for the Internal Transcribed Spacer (ITS1) of rDNA, Serum Resistance Associated (SRA) gene specific for Tbrh and the Tbg Surface GlycoProtein (TgSGP) was performed on purified DNA. Active screening of humans detected only 4 cases; 2 from Dokolo/Lira were Tbrh, while the 2 from Amuru district about 100 km northwest were Tbg. Over 140 passively detected cases at Lwala hospital serving the mid-north region were PCR identified as Tbrh. Of 11915 domestic animals tested, 1096 (9.2%) were parasite positive. ITS1-PCR detected mixed infections in animals, mainly T. congolense/T. brucei. The proportion in infected cattle with T. congolense ranged 2-57.1%, being highest in Aleptong district. Trypanozoons (a complex including the human infective subspecies) were the most prevalent in Amuru (65.3%) and Kole (63.4%) district; coincidentally, Kole had the first case of HAT identified in December 2010. Interestingly, Oyam that is within 50 km of Tbg active foci (Amuru) had the highest proportion of animals with SRA+ infections (30.5%), indicating that Tbrh in animals is moving well in advance of the human disease and further incriminating cattle reservoirs in HAT spread. Surprisingly few tsetse flies were positive, none with SRA- or TgSGP- positive trypanosomes.
Overall, our findings suggest that the two forms of HAT are still confined to distinct foci less than 100 km apart, with Tbrh moving further north towards Tbg foci. The interface districts have 7.7-30.5% of the cattle carrying Tbr; this with the high tsetse challenge justifies urgent aggressive control efforts.
- 02 Feb 2015
- Prof. Enock Matovu and Dr. Anne Kazibwe