Evidence for the occurrence of Trypanosoma brucei rhodesiense sleeping sickness outside the traditional focus in south-eastern Uganda

The occurrence of Trypanosoma brucei rhodesiense west of the River Nile, in Masindi district in the mid-western part of Uganda, is confirmed. Masindi borders the traditional belt of T. b. gambiense infection in the north-west , Gulu in the north and the Democratic Republic of Congo in the west. Of th e 702 persons tested for sleeping sickness in Masindi, 113 (16%) were posit ive by the card agglutination test for trypanosomiasis (CATT). Trypanosomes were observed in samples of cerebrospinal fluid (CSF) from two (0.3%) of t he subjects: a 7-year-old girl, who had been ill for 2 weeks and yet was in good general condition, with three white blood cells (WBC)/mu l CSF; and a 47-year-old woman who had been ill for 8 months, looked sickly, had seven WBC/mu l CSF, but was still able to dig in her gardens. Rats and mice inocu lated with blood from the two parasitologically confirmed cases became para sitaemic on day 3 post-inoculation, indicating that the parasites were T. b . rhodesiense. Isoenzyme analysis revealed that the parasites isolated from one of these confirmed cases belonged to a zymodeme (449) which has not be en previously observed among isolates from south-eastern or north-western U ganda. Although the isolate shared PGM2 and ICD3 patterns with T. b. gambie nse and T. b. rhodesiense, respectively, it did not have the SOD3:5 pattern characteristic of T. b. gambiense. The spread of T. b. rhodesiense beyond its traditional focus and the development of al eas where this subspecies a nd T. b. gambiense are co-endemic will complicate the control of sleeping s ickness in Uganda; although the CATT is very useful for the mass screening of populations for T. b. gambiense area, it is not applicable in the detect ion of T. b. rhodesiense.