NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
79
present in fewer numbers, however, this was the species in which alone infection
was found as the following table shows.—
s p e c i e s o f a n o p h e l e s
Number dissecte
d
Percentage of infection with sporozoites
in the glands.
A: culicifacies
•
•
•
6 9
87
A. Rossii .
240
Nil
At this place, therefore, it was also certain that whereas A. Culicifacies was
carrying malaria, A. Rossii was not.
The above facts afford a strong argument in favour of the view that whereas
A. Fluviatilis and the species allied to it are very good carriers of malaria,
A. Rossii is under natural conditions a very inefficient carrier, if indeed under
such conditions it is able to exercise any influence whatever on the prevalence
of malaria.
Feeding Experiments.—From some negative feeding experiments which we
made at Calcutta with A. Rossii, added to the fact that working with this species
in Calcutta Major Ross had previously been unable to cultivate human malaria
in it, it seemed probable that even under experimental conditions A. Rossii did
not carry malaria, but at Nagpur where we had an opportunity of feeding
anopheles on some very suitable cases of malaria we were able to show that
under experimental conditions both zygotes in the stomach and sporozoites in
the salivary glands are readily developed in this species as in all the other
species of anopheles (seven in number, viz.:—A. Fluviatilis, A. Culicifacies,
A. Turkhudi, A. Stephensii, A. Theobaldi, A. Barbirostris, A. Fuliginosus)
with which we experimented.
We have therefore the two facts that whereas A. Rossii is capable of carry-
ing malaria under experimental conditions, it certainly was not doing so under
natural conditions at any of the places we examined.
The explanation of these two apparently contradictory facts may possibly
lie in a closer study of the habits of this species in nature—possibly in nature it
habitually feeds not on the blood of man but on that of the cows, horses and
other animals which are kept in every Indian village. The explanation certainly
does not lie in the species of parasite which is present in the children, for in the
Duars we were dealing almost entirely with Quartan parasites, in Ennur with
Quartans and simple Tertians, and in Mian Mir chiefly with malignant Tertian
parasites. Under experimental conditions we were able to show that the three
species of parasite developed equally well in this mosquito.
Regarding the connection of other species of anopheles than those above
referred to with malaria in India, the majority do not, I think, occur in sufficient
8o
numbers in houses to have very much effect on the amount of malaria..
A. Barbirostris and A. Sinensis are certainly " wild " species very rarely found in.
houses. We have however shown that under experimental conditions the para-
sites of human malaria are capable of developing in A. Barbirostris. A. Pul-
cherrimus is a rare species which cannot, I think, exercise any influence .on the.
amount of malaria. A. Fuliginosus is very common in houses and stables in
some districts. Under experimental conditions, we have shown that the para-
site of human malaria can develop in this species, and though we have never
found it infected in nature, it is possible that it may occasionally have some
influence. A. Maculata, A. Stephensii, A Theobaldi, A. jamesii, and A. Tur-
.khudi are all moderately frequent in some districts and may occasionally be
responsible for some of the malaria, though we have never found any of these
species infected in nature.
The group of anopheles which is certainly more important than any other
from the point of view of malaria in India is the group of small brown anopheles
comprising A. Fluviatilis, A. Culicifaciesa n d t h e i r a l l i e s . T h e m e m b e r s o f t h i s
group are the only ones that we have found infected in nature in India, and from
this fact and the fact that in places of high endemicity one or other of the members
of this group are always found to be present, while in places where there is
little or no malaria the members of this group are absent, it is almost certain that
this is by far the most important group of anopheles in India, and that in
nature its members are better malaria carriers than any other anopheles.
II. The effect of the importation of non-immunised strangers into an immune
district, and the effect of social status on endemicity.
Koch has shown that the importation of a number of non-immunised
individuals into an immune district may bring about an increase in the fever rate,
and that after a time the fever rate again declines as the new-corners become
immune. This might partly account for the high endemicity of the Duars where
coolies are imported for the tea plantations ; but the parents of the children
examined by us in this district had for the most part lived many years on the
plantations and all the children had been born there, so that but little, if any, influ-
ence can be assigned to this cause. Moreover, no immigration occurs in many
of the other areas of high endemicity which we examined, as, for example,
at Mainaiguri in Bengal (endemic index, 25 per cent.) or at Ennur in Madras
(endemic index, 54 per cent.).
As regards the influence of social status, children of low social status
frequently showed a high rate of malarial infection, but on the other hand there are
many instances (e.g., Calcutta, and Vizagapatam village, endemic index, o per
cent.), where people of very low social status showed little or no malaria, so that but
little importance attaches to this factor.
•
81
III. The effect of Seasonal Variation.
In many parts of India the seasonal variation in the amount of malaria is
very marked. In the south of India, where the temperature is fairly uniform all
the year round and abundant anopheles are always present, this seasonal variation
is not so marked as in the north where the climatic conditions vary extremely.
Good examples of the effect of this cause may be taken from Mian Mir in the
Punjab.
The malaria-carrying species of anopheles in Mian Mir breeds almost
entirely in the irrigation watercourses, and the prevalence of this species
(A. Culcifacies) throughout the year is influenced partly by the times at which the
water in these watercourses is shut off and let in. The seasonal prevalence of this
mosquito in Mian Mir is roughly as follows :—A few larvæ of A. Culcifacies
may possibly be found if the water in the watercourses is turned on in March.
No adults, however, will be found in the houses at this time. The water is usually
shut off during the latter part of March and the beginning of April, and no adults
or larvæ will be found at this time. During the latter half of April a few Culici-
facies larvæ will be found in the watercourses, and from the beginning of May,
when the water is usually turned on permanently, the number of larvæ in the
watercourses gradually increases steadily month by month.
By careful search in the houses of the bazaars a few adult Culicifacies may
be caught as early as May 15th, but until the beginning of June they are very
rare. Throughout the month of June the number of adults increases gradually,
but it is not until about the first week in July that they are sufficiently numerous
to be caught with ease. In the beginning of this month, too, other species, and
especially A. Rossii, which has previously been entirely absent, begin to appear in
large numbers. The appearance of A. Rossii is dependent on the formation of
pools by rain, whereas the prevalence of A. Culicifacies is, to a great extent,
independent of the rainfall. From July until the end of October the numbers of
larvæ and adults increase very rapidly, and during August and September
especially very large numbers of adults can be caught with ease in any of the
bazaars, in the harness rooms and in the barracks of the men. All the irrigation
watercourses are at this time swarming with larvæ (chiefly A. Culicifacies), and
in the numerous rain-formed pools abundant larvæ of A. Rossii are present.
During November the numbers of adults and larvæ gradually decrease,
but a fair number of adults can still be caught in the bazaars as late as the 20th
— 2 5 t h o f N o v e m b e r .
By the beginning of December extremely few larvæ will be found in the
watercourses, and the adults will have completely disappeared from the houses
by December 10th. They will not be seen again until the end of April or
beginning of May.
The above brief account refers to the years 1901 and 1902. A more
82
detailed account of the seasonal prevalence of the mosquitoes and of malaria will
be given in a later report.* The following are examples of the seasonal variation
in the malaria at Mian Mir :—
TABLE III.—THE EFFECT OF SEASONAL VARIATION ON THE AMOUNT
OF MALARIA.
Name of place.
Date
Endemic index,
per cent.
Spleen rate,
per cent.
Mian Mir Infantry Bazaar .
.. October 5th, 1901.
52
80
Ditto
.
.
. November 25th, 1901.
2 0
38
Mian Mir Artillery Bazaar .
. October 8th, 1901.
35
75
Ditto
.
.
. December 3rd, 1901.
2 9
34
Mian Mir Syce lines .
.
October 30th, 1901.
56
48
Ditto
.
.
. December 22nd, 1901.
15
30
Mian Mir Cavalry Lines
.
. November
1901.
24
36
Ditto
.
.
. December 10th, 1901.
6
13
IV.—The effect of altitude.
We have found that under 4,000 feet altitude has no effect on the amount of
malaria. If in a hill district at a lower height than this the slopes are very steep,
so that there is no place where water can lodge and form breeding places ,there
will be little or no malaria, but if, on the other hand, there are extensive plateaus
among the hills and good breeding places, there will in all probability be a good
deal of malaria, unless the hills are more than 4,000 feet high.
The following table summarises our observations in connection with this
subject :-
TABLE IV.—MALARIA IN HILL DISTRICTS.
District,
Name of Place,
Height.
Endemic
index,
per cent.
Spleen rate,
per cent.
Anopheles present and
breeding places.
DUARS .
.
Rangamutty
.
800 ft.
43
83
A. Fluviatilis.
A. Maculata.
A. Rossii.
' Streams, etc.
Naigaisurie
.
1,200 ft.
55
82
Ditto.
Sam Sing .
.
3,000 ft.
28
7
A. Maculata.
Rice-Fields.
•
DARJEELING .
Seypudura .
.
2,000 ft.
0
12
A. Maculata, scanty.
Springs.
Lower Singell •.
Garden, Kurseong
4,000 ft.
0
5
A. Rossii, A. Maculata,
A. Fuliginosus.
Upper Singell.
Garden, Kurseong
4,400 ft.
0
0
A Maculata, A. Linde-
sayii.
Tonetta
6,000 ft.
0
A. Lindesayii.
JEYPUR HILLS
.
Sunki
2,000 ft.
5 0
55
A. Culicifacies,
Streams.
Patungi
.
2,800 ft.
70
5 0
A. f eyporiensis,
Marsh.
Koraput
.
.
2,000 ft.
20
70
A. f eyporiensis,
Marsh.
* A Report on the Anti•Malarial Operations at Mian Mir, 1902, by Captain S. P. James, I.M.S.
O
83
V. There are doubtless other factors which influence malarial endemicity
than those given above. The low endemicity of such places as Calcutta,
Madras, and Salur is difficult to explain. The particular species of anopheles
present may have some influence (as in Calcutta), although at Salur abundant
A. Culicifacies,a g o o d m a l a r i a c a r r i e r , w e r e f o u n d a n d y e t t h e e n d e m i c i t y w a s
nil. This species is also present in small numbers in Madras. In some cases
special local conditions doubtless affect the amount of malaria to a great extent.
When all factors are considered, some regions, too, appear in themselves to
be more or less malarious than others and some importance doubtless attaches
to the "Regional Factor" (the expression used in this connection by Drs. Ste-
phens and Chr i st opher s) ; t hus, i n t he pl ai ns of Bengal we have a r egi on of l ow
endemicity, in the Duars and in the Jeypur hills regions of intense malarial
endemicity, where Blackwater Fever is found, in the Punjab (Mian Mir) a region
of high malarial endemicity, and in the Central Provinces a region of not
very intense malarial endemicity with marked local variations.
M 2
85
IV.—THE RELATION BETWEEN ENLARGED SPLEENS AND MALARIAL
INFECTION IN INDIA.
The prevalence of enlargement of the spleen is very great in India , and in
almost every hospital a number of cases suffering from chronic enlarge-
ment of the spleen will be found.
In Africa, on the contrary, we are told that enlargement of the spleen among
adult natives is very rare or almost entirely unknown.
As malaria is practically the only tropical. disease which causes chronic
enlargement of the spleen, one would naturally expect that the more malarious a
country is, the greater would be the number of cases of enlarged spleen that we
should find among the general population, and it comes therefore rather as a
surprise to hear that enlarged spleen is rare among the inhabitants of Africa.
When we enquire closely into the subject, however, the facts are not, I think,
difficult of explanation.
But before going into the question of enlarged spleens in India, I must
refer briefly to two points regarding malaria in India which have a bearing on this
subject.
I. I have already indicated the fact that in all the parts of Africa which
have been examined, there appears to be but one type of malarial region, viz.,
that in which a high percentage of malarial infection is found in the children, this
infection decreases rapidly with advancing age, and the adults are relatively quite
immune to malarial infection.
In India, however, we may say that there are three types of malarial
regions :—
(1) Regions of intense malarial prevalence exactly comparable to the
malarial regions of Africa. The Duars, such places as Mian Mir,
and the Jeypur hill districts, are examples of these regions. In
these parts a very high rate of infection is found in the young
children, this decreases with advancing age, and the adults are
more or less immune.
(2) Regions of less intense malarial prevalence such as Jalpaiguri and
other places in the plains of Bengal, and places in the Central
Provinces. In these parts the liability to become infected with
malaria is not so great. In the very young children no infection is,
as a rule, found, in the children from five to ten years of age
a moderate percentage of infection may be found, and the rate of
infection increases instead of decreasing up to almost adult age.
Presumably the rate begins to decrease after 20 or 25 years of age,
but very slight immunity is established in the adult.
(3) Regions of little or no malaria, such as the cities of Calcutta and
Madras, and some of the places in the Central Provinces, and
other parts of India. The liability to infection in these places is
very slight. Even in children up to ten years of age very few
cases may be found. With increasing age periods the percentage
infected will be greater and the highest amount of malaria will be
found in the adults. No immunity occurs in such places as these.
II. The length of time which infection, as shown by the presence of parasites.
in the peripheral circulation, lasts, when no reinfections occur.
Some light is thrown on this point by the results of the monthly examina-
tions of children in Mian Mir.
TABLE TO SHOW THE GRADUAL DISAPPEARANCE OF PARASITES FROM
THE PERIPHERAL CIRCULATION, IN THE ABSENCE OF REINFECTIONS.
Mian Mir.
Endemic index,
October
1901, per cent.
Endemic index,
November
1901, per cent.
Endemic index,
December
1901, per cent.
Endemic index,
April
1902, per cent.
Endemic index,
June
1902, per cent.
Artillery Bazaar
...
35
*
29
20
5
Infantry Bazaar
...
5 0
22
*
8·3
Hospital Followers ...
6 0
*
*
*
Nil
No new infections occurred from about the middle of November, and from
that time until the end of June there had been a steady disappearance of para
-sites from the peripheral circulation. The asexual parasite sdisappear first,
crescents and other gamete forms are the last to go; they probably last long
enough to start the new series of infected mosquitoes of the following year.
We may say then that in the majority of cases of untreated malaria the
parasites will, in the absence of reinfection, disappear from the peripheral circula-
tion in seven or eight months.
Turning now to the question of enlarged spleens, we know that practically
in every case of malaria the spleen becomes more or less enlarged, although the
enlargement is not always sufficient to enable it to be detected by palpation. It
is impossible, I think, to agree with Drs. Stephens and Christophers † that a high
endemic index may exist without any appreciable spleen rate (Africa).. One can
easily understand that with a high endemic index there may exist no appreciable
spleen rate in the adults and F. Plehn ‡ evidently referred to adults only when he.
* Not examined.
† Reports to the Malaria Committee of the Royal Society, 6th Series, page 23.
‡ "Die Kamerun-Kūste," page 97.
87
said " In the great majority of cases, it (the spleen) is not larger than in the
cases of typhoid I have observed in Germany, often indeed smaller," but it is
difficult to understand how a very high parasite rate could have existed in the
children without a correspondingly high (or even higher) spleen rate. The
sequence of events in India is, first, infection with parasites; secondly, enlarge-
ment of the spleen; thirdly, disappearance of the parasites; and fourthly, gradua
reduction in size of the spleen. In all probability the same sequence occurs in
Africa. As soon as the parasites disappear the spleen begins to reduce in size,
but this always takes longer than does the disappearance of parasites, and for this
reason it is quite possible to have a high spleen rate in children, without a corre-
sponding parasite infection, but not, I think, the reverse. The reduction in the
spleen rate with a reduction in the parasite rate is shown in the following table:—
Mian Mir.
October
1901,
per cent.
November
1901,
per cent.
December
1901,
per cent.
April 1902,
per cent.
June 1902,
per cent.
Artillery Bazaar .
Endemic index
.
35
...
29
20
5
Spleen rate .
.
75
*
34
31
33
Infantry Bazaar .
Endemic index
.
50
22
*
*
8.3
Spleen rate .
.
82
38
. . .
...
26
The sudden decrease in the spleen rate in November and December repre-
sents the acute cases of enlargement which quickly disappear with the disappear-
ance of parasites; the percentage of enlarged spleens which remain throughout
the year, in spite of the absence of parasites, represents the chronic cases in
which the spleen has become so enlarged as the result of former infections that
it has not time to regain its normal size, before the new infections of the next
season begin. In these cases we should not expect to find parasites, because
we know that, without reinfection, the parasites disappear from the peripheral
circulation in seven or eight months. When the series of new infections begins
in the following year, some of these cases of chronically enlarged spleens may
again become infected, and then parasites will be again found, the spleen will
enlarge somewhat more, and after seven or eight months the parasites will
disappear but the spleen remain enlarged.
From such cases as these we may pass on to the numerous cases of
chronic enlargement of the spleen which are seen in Indian hospitals. At
Calcutta we examined 80 of such cases. The prominent symptoms were
the greatly enlarged spleen and marked anæmia. In some, there was irregular,
more or less continued fever, between 99° and 101°, which went on for many
weeks or months. In none of these cases did we find parasites or any indication
* Not examined.
* Not examined.
88
whatever of a comparatively recent malarial infection. Nor indeed would one
expect to find parasites in such cases, for few, if any, of them had been for
some time in places where they would be very liable to contract a new infection,
and I have already mentioned that parasites are not likely to be found in the
peripheral circulation, unless a new infection has been received within seven or
eight months of the examination of the case. The enlarged spleens are but the
after-effect of former malaria which may have disappeared several years before.
No parasites were found on puncture of the spleen or post-mortem in the organs
of several cases which died.
The mere presence of an enlarged spleen has no influence in preventing the
appearance of parasites in the peripheral circulation. If in any of these chronic
cases a new infection with parasites occurs, the temperature chart at once assumes
the ordinary malarial character of the particular species of parasite, and parasites
are found in the peripheral circulation. This occurred in one of the Calcutta
cases. A man who had an enormously enlarged spleen, and in whom no parasites
had been found on repeated occasions, suddenly developed typical Quartan fever
and Quartan parasites in abundance were found, which went through their cycle
just as though there was no enlargement of the spleen at all.
It is doubtless on account of the large number of these chronically enlarged
spleen cases in adults, which are treated in the hospitals of Calcutta and Madras,
that these places have acquired the reputation of being very malarious, although,
as a matter of fact, they are very slightly so. For the same reason, if one
regarded the percentage of adults with enlarged spleens as a true test of the
prevalance of malaria and the danger of infection in a district, many of the
places in the plains of Bengal, which are in reality no more malarious than
Calcutta or Madras, would be considered very much so, whereas such places as
the Duars, Mian Mir, etc., which are really very malarious, to say nothing of the
West Coast of Africa, would be regarded as being almost free from malaria.
In both Calcutta and Madras no enlarged spleens were found among the
young children, but the cases in the hospitals show that it is a common disease
among the adults. It is interesting, therefore, to enquire into the reason of this.
I believe the reason is that in slightly malarious places a much larger number
of cases of fever and enlarged spleen will be found among the adults than
among the children; in fact the less liability to infection there is in a place the
greater will be the proportion of infected adults to infected children.
I have already pointed out that there are at least three types of malarial
regions in India.
The Duars or Mian Mir or Ennur may be taken as types of the first region
(region of intense malaria).
In these regions there is very great liability to infection, so much so that
even the young babies of a few months' old are frequently infected with