NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
20
SLEEPING SICKNESS.
To return to the subject of Sleeping Sickness the question was—
Does some reptile, bird or mammal living on the lake shore act as
a reservoir of the virus of Sleeping Sickness ?
An answer to the question was sought in various ways :
(a) The blood of various creatures could be searched in the hope
of finding Trypanosoma Gambiense.
(b) The blood of such creatures could be injected at once after
death into susceptible animals.
(c) Blood containing Trypanosoma Gambiense could be
injected into various animals and the fate of the try-
panosomes studied.
(d) Animals considered likely to be "reservoirs" might be
artificially infected with Sleeping Sickness and an
attempt made to transmit the disease from them to
healthy animals either by inoculation of blood or
better still by using laboratory bred tsetse fly to carry
the infection from the sick to the healthy animals.
All these methods were used.
For the first year or so of the time in Uganda all manner of
creatures, lizards, snakes, amphibians, birds, and mammals were
killed and their blood subjected to careful scrutiny.
The result was that a regular museum of blood parasites was
obtained, but neither the Trypanosoma Gambiense or any very near
ally was found. A number of blood films were sent to England and
were entrusted to the care of E. A. Minchin, M.A., Professor of
Protozoology in the University of London, who kindly described
them.
His paper (No. 6) which is beautifully illustrated from his own
and Lady Brace's drawings may be studied by those interested in
blood parasites, but as it has no direct bearing on the subject of
this paper nothing further need be said about it.
A paper (No. 1, vide Summary, page 37) entitled " Trypano-
soma Ingens " contains an interesting observation on the subject
of " reservoirs." This huge (amphibian like) trypanosome was
found in the blood of cattle and also in bush buck, a species of
wild antelopes, which frequented the same feeding ground as the
cattle.
SLEEPING SICKNESS.
21
It is quite possible that one of these animals was acting as a
reservoir to the other, but as neither seemed to suffer from the
effect of the trypanosome, the subject in this particular instance
is of academic interest rather than of practical importance.
The second method of injecting the blood of a newly killed
animal into a susceptible animal was also carried out in a number of
instances, but without success. In most cases it was the blood of
lake shore birds that was used, but that of hippopotamus, crocodile
and antelope was also injected. It was not surprising that this
method failed because where reservoirs exist they generally only form
a very small proportion of the class of animals they represent. Then
the blood has to be injected at once into the test animal, which in this
case meant that monkeys had to be carried about on all shooting
expeditions. This involved the fallacy that by taking a susceptible
animal into a fly belt known to be infective it is liable to contract
the disease naturally.
The animals to which most attention was paid were those found
most frequently on or near the lake shore. As a representative of
the birds the common fowl had to be used, as it was not found pos-
sible to experiment with the divers, cormorants and other species
actually found on the lake shore.
Next the domestic cattle were examined.
Lastly the wild antelope which infest the shores were subjected
to special attention.
A number of attempts to transmit Sleeping Sickness by means
of laboratory bred tsetse flies from infected or potentially infected
fowls to clean monkeys were made—but with negative results.
The conclusion was that the domestic fowl cannot act as a reser-
voir of the virus of Sleeping Sickness, but we pointed out that this
negative result does not necessarily apply to the birds found
naturally in the fly area.
Native cattle were then examined. The importance of the
animals being a reservoir is obvious, for they go down to the water's
edge daily to drink and generally live amongst the people in or about
the kraals. They might act readily as a go-between if proved to be
susceptible to infection with Trypanosoma Gatnbiense.
The experiments detailed in Paper No. 8 (vide Summary, page
37) prove that cattle are susceptible to Trypanosoma Gambiense,
22
SLEEPING
SICKNESS.
The facts brought out may conveniently be presented in the
form of question and answer :—
Question 1.—Are cattle capable of being infected with
Sleeping Sickness by the subcutaneous injection of
blood containing Trypanosoma Gambiense ?
Answer.—Yes, they may be infected in this way. The try-
panosome appears in small quantities in the blood, and
the blood when injected into susceptible animals, such
as monkeys, gives rise to a fatal form of the disease
in them.
Question 2.—Can cattle be infected with Sleeping Sickness
by the bites of artificially infected Glossina Palpalis ?
Here the tsetse flies were first fed on infected monkeys and after
the necessary interval on an ox day by day.
Answer.—Two experiments were performed to show that· cattle
could be infected in this way and that their blood was
infective to monkeys.
Question 3.—Can cattle be infected with Sleeping Sickness by
the bites of naturally infected flies caught on the lake
shore ?
Answer.—Three experiments proved this possible and again
the blood of the cattle was proved to be infective to
monkeys and to a goat when it was injected into them.
Question 4.—Is it possible to infect tsetse flies by feeding them
on cattle suffering from Sleeping Sickness and after-
wards to transmit the disease by means of these flies to
healthy animals ?
This experiment approximated still more to natural conditions
of infection and nothing but laboratory bred and therefore
" clean " flies were used.
Five experiments were done, three were negative and two were
positive.
The experiments are so important that one will be given in detail
to show how it was done.
Experiment 1602.—Fifty laboratory bred flies were fed for four
successive days on an ox whose blood contained Trypanosoma
Garabicnse.
SLEEPING SICKNESS.
23
After a period of starvation they were applied to a monkey and
a goat on alternate days.
The monkey died (accidentally) before it could have become
infected, but the goat developed Sleeping Sickness 20 days after
the flies had had their first infected feed.
The remainder of the flies, 32 in all, were dissected and five were
found to contain flagellates. The alimentary contents of one of
these flies were injected into a monkey and after an incubation
period of 13 days Trypanosoma Gambiense appeared in its blood.
Answer.—Laboratory bred flies can be infected by feeding them
on cattle infected with Sleeping Sickness and after-
wards the disease can be transmitted to healthy animals
by means of these flies.
Question 5.—Do cattle when living in the fly areas actually
carry the virus of Sleeping Sickness ?
This is the last link in the chain of evidence and again it was
positive.
One out of 17 cattle which were presumed to have been exposed
to the bites of Glossina Palpalis was found to contain Trypanosoma
Gambiense in its blood.
Answer.—Yes, cattle in their natural state and apparently in
good health may harbour the virus of Sleeping Sickness.
As a final conclusion to this very important paper it was stated
that it is possible that cattle and antelope living in the fly area may
act as " reservoirs " of the virus of Sleeping Sickness and so keep
up the infectivity of the tsetse fly.
The next Paper (No. 18, vide Summary, page 37) shows how the
problem was applied to the antelope.
There are many antelope living on the lake shore besides bufia-
los, hippopotami and other game, and now that the human popu-
lation has been compulsorily removed the wild animals are greatly
increasing in number so much so that the two mile zone is becoming
a huge game reserve. The experiments with antelope were carried
out on partially tamed animals of various species caught when
young.
A freshly recovered strain of human trypanosome was used
and only laboratory bred flies were used.
24
SLEEPING SICKNESS.
The steps of the scheme were very similar to those described in
the last paper and the following questions were set for solution :—
I. Can antelope be infected with Sleeping Sickness by the
bites of laboratory bred and laboratory infected Glos-
sina Palpalis ?
Eleven experiments were done and all were positive, the answer
is therefore in the affirmative.
II. If antelope can be infected with the virus of Sleeping Sick-
ness, can they transmit the infection to clean laboratory
bred Glossina Palpalis when these tsetse flies are allowed
to feed on them ?
Further if these Glossina Palpalis become infected, can they
transmit the virus to susceptible animals ?
To answer the question 24 experiments were done, and of these
17 were positive (70·84 per cent.) The shortest time before the
flies became infective was 24 days and the longest 49 days. It is
interesting to note that tsetse flies were more readily infected from
antelope and in a larger number than any other kind of animal
used by the Commission.
The observers add :—
" The most significant of the above observations is the one in
which it is shown that 55 days after the last feed of infected Glossina
Palpalis on bush buck (Experiment 2328) the blood of this buck
was capable of infecting clean laboratory bred flies though Try-
panosoma Gambiense had never been seen in its blood.
III. If Glossina Palpalis can be infected with the virus of
Sleeping Sickness by feeding on the blood of Trypano-
soma Gambiense infected antelope, what percentage of
flies are found to be infected ?
In the sixteen positive experiments 1,102 flies were dissected,
and of these 119 (54 65 ) were found to be swarming with
developmental forms of Trypanosoma Ganibiense, that is about
10 per cent.
IV. How does Sleeping Sickness affect the health of the ante-
lope ?
They do not seem to suffer any inconvenience from the pre-
sence of the trypanosoine.
SLEEPING SICKNESS.
25
The final question was—Are antelope living in the fly area
naturally infected with Sleeping Sickness ?
A large antelope drive had been arranged to try and prove the
point, but the Commission left before it was carried out.
The conclusions which terminate this important paper are given
as below :—
1. Water buck, bush buck and reed buck can readily be
infected with a human strain of the trypanosome of
Sleeping Sickness by the bites of infected Glossina
Palpalis.
2. One exposure to the bites of infected flies is sufficient to
infect an antelope with the virus of Sleeping Sickness.
3. Though the blood of an antelope may be proved to be in-
fected with Trypanosoniti Gambiensa, careful and con-
tinued examinations over prolonged periods may fail to
reveal the presence of the parasite in the blood.
4. The incubation of the disease in the antelope is probably
seven days.
5. Antelope of the water buck, bush buck and reed buck
species, when infected with the virus of Sleeping
Sickness, can transfer the infection to clean labora-
tory bred Gkssina Palpalis.
6. This transmission of the infection to clean laboratory bred
flies may occur at least 81 days after the last feed of the
infected flies on a buck.
7. Glossina Palpalis when infected with the virus of Sleeping
Sickness obtained from the blood of infected antelope,
are capable of transmitting the virus to susceptible
animals.
8. An appreciable percentage of Glossina Palpalis will become
infected with the virus of Sleeping Sickness should these
flies feed on antelope suffering from this disease.
9. It follows from the above conclusion that antelope living
on the fly areas are " potential " reservoirs of the virus of
Sleeping Sickness.
10. No antelope up to the present has been found naturally
infected with Trypanosonw, Gambisnse.
26
SLEEPING
SICKNESS.
Although the last link in the chain of evidence is missing, few
people who read the above evidence or, better still, the original
paper, will have much doubt as to the evil potentialities of the ante-
lope as a reservoir of Sleeping Sickness.
TREATMENT,
It is outside the scope of this paper to say anything on the re-
sult of treatment especially as with one exception the Commission
did not touch on the subject.
Suffice it to say that though many drugs have the power
of driving trypanosomes out of the blood stream for the time being,
none can be credited with effecting a permanent cure except per-
haps in the very early stage. The course of the disease in man may
be very prolonged and persons apparently cured have succumbed
to the disease even eight or ten years after infection. Sleeping
Sickness is still a disease with a mortality not far off an hundred per
cent.* One series of experiments was done by the Commission to
ascertain whether treatment of Sleeping Sickness patients with the
usual trypanocidal drugs rendered them non-infective to tsetse
flies, and as the question involved is one of great practical importance
the experiment will be now outlined.
In this case the Trypanosoma Gambiense was obtained directly
from man instead of from animals infected in the laboratory. Firstly,
an attempt was made to transmit the disease mechanically by the
method of interrupted feeding from infected men to monkeys.
Those who read the previous remarks on the subject of mechani-
cal transmission will not be surprised to find that all the fifteen
experiments were negative. Secondly, an attempt was made to
transmit the disease from Sleeping Sickness patient to monkey
after the parasite had completed its development in the fly.
Six experiments were carried out on patients in whose glands
trypanosomes had been found at some time or another but who still
appeared to be in good health.
All had received trypanocidal treatment. None of the tsetse
flies became infected, that is to say, all the experiments were
negative.
* These remarks apply particularly to the disease as is met with in Uganda
and surrounding countries. It acems that the West African type is not so
dreadfully fatal.
SLEEPING SICKNESS.
27
In the next series patients were used who were in a more
advanced stage and in whom the disease might reasonably have
been diagnosed on clinical grounds alone.
Twenty-five patients were the subject of the observation and
of these six were tintreated and the remainder had had trypanocidal
drugs.
All the treated and four of the untreated proved non-infective,
that is, only two patients and those both untreated, proved to be
infective to the flies which in their turn passed on the infection to
clean monkeys. Finally, some experiments were done on patients
on an advanced stage of Sleeping Sickness. Ten experiments were
done and one was positive. This patient had been under treatment
for a month and had been given during that time two grammes
of soamin and 0·08 gramme of Perchloride of Mercury.
Seventy-four flies from this positive experiment were dis-
sected and four flies were found to contain flagellates on the 28th,
39th, 40th and 46th day, respectively, after their first infected feed.
We may therefore conclude that—
Firstly, Glossina Palpalis fed on natives suffering from Sleeping
Sickness and untreated by drugs may become infected
and be capable of transferring the disease to healthy
animals.
Secondly, that Glossina Palpalis fed on natives suffering from
Sleeping Sickness and treated by arsenic and other drugs
may also become infected and capable of transmitting
the disease to healthy animals.
THE PREVENTION OF SLEEPING SICKNESS.
This may be attempted by attacking any one of the three
factors on which the disease depends—
(a) The human factor.
(6) The tsetse fly.
(c) The reservoir of infection.
In the past the pandemic of Sleeping Sickness in Africa has been
caused by the opening up of trade routes and by human intercourse,
and it is by legislation applied to human beings that the principal
efforts are being made to check its progress.
28
SLEEPING SICKNESS.
The infected areas are pretty accurately known and to a less
extent the areas of potential epidemicity, the latter, in our present
state of knowledge, being taken to coincide with the distribution of
Glossina Palpalis or at any rate of tsetse flies in general. The
enlargement of the cervical lymphatic glands is taken as a working
diagnostic sign of the disease in the earlier stage and all persons
possessing this sign are forbidden to enter non-infected areas.
This is an excellent prophylactic method as far as it can be
carried out, but the loopholes are numerous.
Clearing the epidemic areas of human inhabitants is effective
up to a point, but it means handing over the position to the enemy,
and the present condition of the lake shore as our experiments show
is probably worse than the first.
It also has the economical disadvantage of giving back some of
the most fertile parts of the country to the jungle.
The prophylactic administration of drugs to the native has not
been tried on a large scale, but from our experiments just referred
to it would probably be ineffectual.
Man does not appear to be capable of responding to the virus of
Sleeping Sickness by producing any marked active immunity, so
that channel of prevention does not seem hopeful.
It is probable that the West African natives may have in gener-
ations acquired some immunity, but there is no way yet known in
which this can be hastened.
Is it possible to stamp out Sleeping Sickness by exterminating
the tsetse fly ?
Without answering that question one may ask another. Has
anyone succeeded in stamping out plague by exterminating the rat
or the flea ? It is true that the tsetse fly may be got rid of in small
areas by laying the country bare of trees and all jungle, but this as
a general measure applicable to wide areas of infection is quite
impracticable and may be dismissed as such.
The third method of prophylaxis is that directed towards the
destruction of the " Reservoir·." If the antelope and other wild
game in the fly zone are carrying and disseminating the virus of
Sleeping Sickness, it is evident that they will have to be extermin-
ated.
SLEEPING SICKNESS.
29
It seems unfortunately true that the presence of game in any
number is incompatible with the march of civilization, and this
applies as much to stock raising in general as it does to Sleeping Sick-
ness in man.
The new Commission, which has just gone to Nyassaland to in-
vestigate the question of Sleeping Sickness there, will make this
question of animal reservoirs their special study.
CAN SLEEPING SICKNESS GET A FOOTHOLD IN INDIA ?
This extremely important question is one to which it is not
possible to give a decided answer : the probabilities are against it,
but it would be unwise to neglect precautionary measures. In
another part of the paper it was stated that Sleeping Sickness had
not been known to spread in the proved absence of tsetse flies, and
authorities like Koch and Bruce have given decided opinions
against the possibility of the disease spreading by the agency of
any other insect. Mr. H. Maxwell Lefroy, Entomologist to the
Government of India, states in the " Preliminary Account of the
biting flies of India," p. 41 :—
". . . . There is no record yet of Glossina, the tsetse fly of
Africa, nor is there at present any reason to believe that it occurs
in India ; in fact the work of the last two years goes to confirm the
belief that this genus will not be found in India."
If this is true and if it is also true that the tsetse fly is a sine quâ
non in the distribution of the disease then India is safe. Consider-
able support is given to this belief by the results of a natural experi-
ment done on a large scale in the early part of the last century.
In the days of the slave trade between the West Coast of Africa and
the West Indies and the Southern States of North America negroes
stricken with Sleeping Sickness were imported into the New World.
The disease however did not spread, for although one may assume
the presence of many parasitic insects the tsetse fly did not exist
there. At the same time against this optimistic outlook one must
remember that tsetse flies can live in other parts of the world besides
Africa. They have been found in Arabia and some pupæ which we
sent home from Uganda to the Zoological Gardens, London,
hatched out as healthy insects.
30
SLEEPING SICKNESS.
There are many Indians living in Uganda and doubtless in other
endemic centres of infection and most of these return sooner or later
to settle in their native land.
It is highly probable that from time to time the disease will be
in this way imported into India from East Africa or the Soudan to
the ports on the west side of India.
IMPORTATION BY SEA.
The Government of India are fully alive to this possibility and
Regulations to prevent the importation of Sleeping Sickness into
India were made as far back as 1903. In 1908 fuller precautionary
measures were instituted and these are at present in force pend-
ing new rules relating to Sleeping Sickness which are to be pro-
mulgated as the revised uniform rules under the Indian Ports
Act, 1908, for all infective and contagious diseases. The rules now
in force are briefly as follows.
If a case or suspected case of Sleeping Sickness or a death from
the disease has occurred on board any vessel coming from a port
beyond India, the master of the vessel shall report the same to the
Boarding Port Officer. The Health Officer shall be immediately
informed and he shall proceed on board and carry out the neces-
sary examination. If any person is suspected to be suffering from
Sleeping Sickness he shall be removed to a hospital and "shall be
isolated in such a manner as will prevent, as far as possible, the
communication of the disease to persons by the agency of biting
flies and shall continue to be so detained and isolated until a
Medical Officer authorised by the local Government on this
behalf certifies that he is not suffering from Sleeping Sickness, or
that having suffered from the disease he has been cured." In the
revised Regulations referred to which are under consideration the
rules are as follows :—·
33. In the case of a vessel having on board a person suffering,
or suspected to be suffering, from Sleeping Sickness, the person or
persons shall not be permitted to land without the specific written
permission of the Health Officer, who may, pending the receipt of
written instructions from the local Government, permit the landing