391 
H. L. Duke 
first to appreciate, many of tlie old fly-shores on Bugalla Island have been 
practically cleared of tsetse by the removal of suitable shelter all along the 
lake edge by the hungry antelopes. Branches are cropped off to within 
four or five feet of the ground, and all undergrowth is grazed off shoit. This 
denudation is also occurring on Damba, but has as yet had little effect on the 
density of the fly. 
(19) It remains to be seen whether, as time goes on, the brucei- like 
organism will become increasingly common. At present the main differences 
between the Damba-antelope trypanosome and the other lake-shoie strains 
are the disease which it produces in monkeys, and its greater virulence to 
other laboratory animals. Posterior-nuclear forms are also more commonly 
met with than in the mainland and island fly-strains. Damba Island will not 
be interfered with during the progress of the repopulation scheme, as I have 
especially requested that it be left undisturbed, in order to test this point. 
In the absence of leopards, crocodiles and pythons are the only enemies of 
the situtunga on this island, and the animals will presumably continue to 
multiply until either disease or failure of food checks their increase. Migration 
to the neighbouring island of Kome has occurred and will continue. It is 
possible that the animals will multiply to such an extent that direct trans¬ 
mission of their trypanosomes will become possible and will actually occur, 
with consequent increase in virulence for this now tolerant host, and the 
production of an epizootic of trypanosomiasis. 
(20) The 'practical importance of this discussion lies in the answer to the 
question as to whether or not , simultaneously with the acquisition of these minor 
changes , these strains may have lost their capability of survival in man. It is 
possible that, in regions where man plays a big role in the fly s food supply, 
his removal and the substitution of another mammal the situtunga in his 
place may, in the course of years, lead to changes in the constitution of the 
trypanosome. It is easily conceivable that those species of tiypanosom.es 
which possess the power of utilising man as a host may lose this pov ei if 
maintained for sufficiently long periods under natural conditions exclush el\ 
in ruminants. 
(21) We have at present, under Mr Fiske’s scheme for repopulation of 
the islands on sanitary principles, a considerable number of natives exposed 
to fly bite. In the course of the preliminary clearing, which is an impoitant 
part of the scheme, frequent exposure is unavoidable. Furthermore, in the 
past few years a number of canoemen have been extensively exposed to fh 
in areas where the gambiense- like organism occurs in buck and fly. b>o fai no 
cases of trypanosomiasis have occurred, but the experiment for such it is 
is still too recent to be conclusive. 
(22) It may be contended that these wild-fly and antelope trypanosomes 
are not and never have been T. gambiense, but belong to some species proper 
to antelope and as yet unnamed. This contention is irrefutable by diiect 
experiment, but the great bulk of the evidence indicates that w e ai e dealing 
Parasitology xm 
