The record-union., 1896-11-05
AN AFRICAN PEST.
The nystery of the Tsetse.Fiy Un-
raVeled by q Scientist.


The mystery which has hung so long
ov er the cause Of that peculiar African
epizootic known as Fly disease" dis
ease of certain domestic animals, which
our great traveller Livingstone was
among the first to describe accurately
and make familiar to the English read
er, seems, says the British Medical
Journal" at last to be in a fair way
Of being cleared up. It has all along
been believed, both by the natives and
by the majority Of travellers, that the
tsetse fly (Glossina morsitans, West
wood was. if not the cause, at all
events the principal medium fer the
distributionn Of the disease it seemed
to be associated with. This fly Is a
dipterous insect, slightly larger than
the common domestic fly It Is pro-
vided with powerful maxillary appara-
tus by which 1t Is enabled to penetrate
the skin and suck the blood Of the low
ar animals, and even traversins the
clothes of man himself
AS the tsetse Is a voracious blood
sucker. passing in search OF food from
one animal to another, 1t is we'll
adapted as q medium for the convey
ancs and transmission OF the germs Of
blood diseases. It has an extensive
distribution. being found here and there
over almost the whole Of Central
Africa; 1t abounds to the north Of the
Transvaal, and on the right bank of
the Zambesi, and 1t Is also common on
the low country lying between the
Ougogo and the eastern shore of the
continent. It shuns villages and cuI-
tivated places. preferr1ng the borders
Of swamps and woody places, and, Gu
rtous enough, La some way or other,
Its distribution Is bound up with and
depends on the presence of large game.
The goat, the buffalo, the antelope, the
zebra, and man are not seriously af-
fected; but the dog, the OK, the sheep,
the ass, and the horse, when bitten by
1t under what are now we'll known con-
diticns. are doomed to almost certain
death. Travellers tell us how large
herds OF oxen have perished, one ami
NAL after another, and how, In this
way, 1t IS a serious obstacle to the set
tlement and civilization Of the Dark
Continent.
Hitherto the nature Of the poison, as
sunaed to be introduced into its victim
by the tsetse-fly was unknown. Liv-
ingstone suggested that it might be de-
rived from the secretion of certain
glands which are rather a conspicuous
feature in the anatomy of the insect.
Others conjectured that it might be a
germ Of some description. Others again
have denied that the fly was in any way
the cause Of the disease. It would now
appear that the natives were right and
that to certain extent Livingstone,
too, was right, in 80 far as he recog-
nized the casual relationship of the fly
to the disease, though wrong as to the
nature OF the virus. Surgeon-General
David Bruce has shown that the true
cause Of the tsetse-fly disease Is not
any secretion Of property Of the fly IT.
self, but that the fly Is merely the pas
sive agent for conveying a living virus
from infected to uninfected animals.
The virus is found to be q micro-or-
ganism, a protozoon. resembling that
which produces a similar disease, the
surra in India. The connection Of the
fly disease with the presence Of large
game is explained by the fact that the
larva of the fly develops In the dung of
the buffalo The fact that the micro
organism distributed by the fly is 50
deadly to some animals and so compar-
atively harmless to others has not been
explained, but it Is a quality possessed
also by other germs, which appear to
thrive in the blood Of one creature while
that Of another Is fatal to them.
In closing the editors Of the journal"
make the following remarks: Surgeon
Captain Bruce's discovery will draw at
tention once more to the part played
by insects, particularly blood suckers,
as factors in pathology. The role of the
mosquito is beginning to be recognized;
that Of the tsetse is now established,
and possibly ere long other blood suck
ers will be found to possess similar
properties, either as active agents In the
biological cycle Of disease germs. as in
the case of the mosquito, or as media
for their conveyance from one human
teing or from one animal to another, as
in the case OF the tsetse fly. Disease
with peculiarly localized geographical
Observation-Disclosures apparently
not directly dependent on climate, but
on some strictly local and limited cir
cumstances-may be conveyed in the
same way as this tsetse-fly disease, and
owe their peculiar geographical distri-
buttons to something Of the same sort" I"