422 
Tsetse Flies and Trypanosomiasis 
population and fly continued, sleeping sickness has been practically, if not 
completely, wiped out from those parts of Uganda adjoining Victoria Nyanza. 
Thus both the exponents and the critics were in part justified by the out¬ 
come, and in part confused by it, for both had based their arguments on the 
belief that complete severance of contact was necessary in the case of human, 
as in that of bovine trypanosomiasis, and this is proved to be unnecessary. 
VII. COMPARISON BETWEEN BOVINE AND HUMAN TRYPANOSOMIASIS 
IN UGANDA. 
The following comparison may now be drawn between bovine trypano¬ 
somiasis as transmitted by G. morsitans, and human trypanosomiasis, as 
transmitted by G. palpalis in Uganda. 
(a) Points of similarity disclosed by technical research: 
Both diseases are caused by trypanosomes which are parasitic on game 
and tsetse flies. In both cases the parasite undergoes an “endogenous'' repro¬ 
ductive cycle in the vertebrate host and an “exogenous” reproductive cycle 
in the insect. In both cases the parasite is transmitted by the insect in the 
act of feeding. 
( b ) Points of dissimilarity disclosed by the outcome of the measures for 
the suppression of sleeping sickness: 
Cattle cannot be herded in territory infested to a measurable degree by 
straggling flies of G. morsitans without grave danger of infection and death, 
but densely gathered populations have existed for years (as at the lake ports) 
in territory infested by G. palpalis to an easily measurable degree, and no 
cases of sleeping sickness are known to have resulted. Cattle cannot wander 
or stray for even an hour or two into territory thickly infested by G. morsitans 
without grave danger, but many poachers and trespassers wander and stray 
into territory densely infested with G. palpalis and no cases of sleeping sickness 
are known with certainty to have resulted. 
If a herd of cattle is driven into or through a region infested by G. morsitans , 
some animals are almost sure to become infected and die, even though ex¬ 
posure to fly lasts for no more than an hour or two; but large parties of natives 
have been sent on expeditions into territory infested by G. palpalis, and have 
resided there continuously for many months, and it is not certain that any 
cases of sleeping sickness have resulted. 
It is plain from this comparison that the parallel between “fly sickness” of 
cattle and “sleeping sickness” of man is by no means so exact as would 
naturally be expected, in view of the points of similarity disclosed by the 
technical research in the laboratory. In consequence it does not appear 
necessary, for practical purposes, to resort to such extreme measures for the 
control of the human disease as are necessarily used for controlling the cattle 
disease. 
