Abstract:
Human Afiican trypanosomosis (sleeping sickness) is a protozoan disease caused by
trypanosome parasites transmitted by tsetse flies (vectors) through bites. It is found mostly in
Afiica where about 60 million people are at risk. Studies using clones in the laboratory show
variations in pathogenicity and drug sensitivity compared to their respective natural isolates for
various trypanosome species. This suggests that within isolates there exist sub-populations due to
change overtime. The objective of this study was to characterize T13/panosoma brucei
rhodesiense isolated fi'on1 patients in two different sleeping sickness foci, (Busoga and Busia)
and evaluate the change in drug sensitivity and pathogenicity with time of isolation. For this
study, various T rypanosoma bmcei rhodesiense clones and their respective isolates were tested
for pathogenicity and sensitivity to drugs (Suramin and Mel B) in Swiss white mice. The clinical,
pathological and sensitivity parameters were determined and the quantitative data were
statistically analyzed using standard methods. Results showed that when compared with the
specific isolates, clones had lower mean pre-patent periods and lower mean post infection
survival periods. Busia KETRI 3800 and Busoga KETRI 3380 clones extracted from isolates
collected in 2000 and 1976 respectively appeared most pathogenic with the lowest mean survival
periods of 20 and Zldays respectively. Furthermore, when compared with the controls, PCV
changes for all the clones were significantly different (p<0.05) but this was not the case for the
isolates. Clinical signs were more pronotmced in mice infected with clones than those infected
with the isolates. Mice infected with isolates fiom Busia and Busoga had no significant
differences (p>0.05) in their PCV and bodyweights. However, mice infected with isolates
collected earlier (in 1987 and 1971 respectively) recorded lower PCV and survived for a shorter
period. On the other hand, Busoga isolates (EATRO 2285 and EATRO 1886) appeared chronic
with the highest survival periods, of 44 and 47 days respectively. Some infected non treated mice
although weak, with low PCV and very high parasitaemia were live by the time the experiment
was terminated. This study concluded that the clones were more pathogenic than their isolates.
Drug sensitivity results for various isolates and their respective clones were comparable at all
dosages except for EATRO 1886 isolate which was found to be resistant to 2.5mg/kg of
Suramin. Age of the isolate played an important role in the pathological variations observed
between isolates of the same area.
