NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
31
flight to take them to their food. Whilst then a house on a \ill\
or a line on an exposed area of ground, may cause anopheles to find'
their way considerable distances, it does not follow that they will,
without obvious reasons, be always found at such a distance from the
breeding place.
It also Cannot be assumed that an anopheles covers the whole
distance in a single flight or in a single night. A ship lying off a har-
bour seems at first sight an excellent test of the power of flight of
mosquitoes, bitt it is in reality no test of the distance that anopheles
will penetrate an area free from breeding places On land, "the ques-
tion of flight and penetration are very important. Very often breed-
ing places exist a few hundred feet from where adult anopheles are to 1
be found in dwellings ; but ; does not always follow that these are the
main sources whence they come. Experience has shown us that the
abolition of such breeding places often does not at all influence the
prevalence of the adults. An illustration of this was seen by us at a
garden called Mean Glas in the Duars. In this garden the Manager
had greatly interested himself in a systematic attempt at petrolage
of the breeding places around his btingalow and certain of his coolie
lines. From May onwards systematic petrolage was carried out
round the bungalow to a distance of quarter-mile radius. In August
one of us examined the treated area, but after a careful search found
only a few very young and half-grown larvæ, though just beyond the
limits of the area were drains with numerous full-grown anopheles
larvæ and nymphs.
Nevertheless in the bungalow adult M. listoni and N. theobaldi
were abundant and could be seen at night and in the very early morn-
ing endeavouring to enter through the screens of wire gauze, with-
which the bungalow was in the process- of being protected.
After our visit Mr. Wallich extended his operations to a half-
mile radius and when we visited him during the first week in Nov-
ember the absence of larvæ in the treated areas was very striking,
Nevertheless adult anopheles were still to be caught in the bunga-
low.
32
The experiment also suggested that different species behave
differently in respect of the distances they travel. Most of the drains
at Mean Glas just beyond the area of operations contained larvæ of
M. listoni and N. theoba-ldi ; but one stagnant drain contained con-
siderable numbers of the larvæ of M. barbirostris and A. aitkeni.
Only very few specimens, however, of the adults of these two
latter species were caught, two of the one and three of the other being
seen in the course of ten days.
In many instances we found anopheles mosquitoes in dwellings'
although it was impossible to find any breeding places except at a
great distance ; whether in any particular instance this is the result
of flight or of a condition to which we shall now refer is often very
difficult to determine.
RESIDUAL ANOPHELES.
Apart from an allowance for flight and penetration there is
another condition which requires mention. When extensive breeding
places dry up adult anopheles are very frequently found, often
in considerable numbers, for weeks or even months afterwards.
The condition in which adults are present in the absence of
breeding places we shall call one of residual anopheles. This is a
very common condition, and is important, since not to recognise it
may lead to considerable error in estimating the nature, means and
extent of prophylactic measures required.
Where a number of breeding 'places have dried up it is easy to
explain residual anopheles ; but residual anopheles may be found
where the only explanation of their prdsènce seems to be that under
certain conditions very suitable for the adults these make use of the
most temporary means of breeding to maintain their numbers.
A very paradoxical condition, which wo can only explain on this
hypothesis, was found by us in certain gardens in the Dina-Torsa
district situated on peculiar, porous, alluvial slopes, uninterrupted for
very long distances by permanent streams or ravines. In this area
the ground is so porous that the heaviest rain only servos to create
very temporary freshets which cease to flow and are more or less
completely absorbed within a few hours. Many streams indeed,
33
which during the heavy rain sweep through the upper portion of the
district, never reach the lower part, the water being completely ab-
sorbed. In the gardens referred to the water supply is a difficult
problem, water having to be brought several miles in pipe lines from
the hills or obtained from deep wells sunk to a depth of from sixty to
ninety feet. At Gundarpara, one of these gardens, we found ano-
pheles in small numbers in the bungalow, but wo failed to find any
source of these insects ; at most of the other gardens in the same area
similar conditions existed. At Hantapara we caught M. listoni,
N. theobaldi and P. rossi ; yet the only breeding places to be found
were a few small pools of waste water from taps, in which a very few
larvæ of P. rossi were found. During the height of the rains we found,
however, at a considerable distance a swampy freshet and at one end
of the very extensive lines a few pools of dirty water suitable for the
breeding of P. rossi. It may be suggested that in these cases anopheles
have been breeding in the hollows of large-leaved plants ; but in the
Duars we have been unable to find larvæ in such situations and the
species found were the stream breeding M. listoni and puddle-breeding
P. rossi. At Binaguri, Lankapara, and Bandapani the same extra-
ordinary conditions occurred. It is of course possible that import-
ation may be partly responsible for these seemingly extraordinary
results ; but the condition of residual anopheles, whatever be the
explanation of its occurrence in its different places, is an important
feature of the epidemiology of malaria in the Duars. It prevails
throughout the greater portion of the Duars when, as a result of
drought—a circumstance of constant occurrence during many months
of the year—breeding places have become very greatly reduced
in numbers ; and it serves to keep supplied with anopheles aggre-
gations of human beings, however favourably they may be situated.
RESIDUAL MALARIA.
In the Duars some of the gardens are on comparatively high,
land, some on land that can be described as almost waterless ; others
on ground intersected in every direction with streams, and abound-
ing in springs and swampy places. The conditions as regards
facilities for the breeding of anopheles therefore vary very greatly
1 SC
E
34
But in regard to malaria the drier gardens show but a slightly lower
rate of malarial infection and perhaps a lesser tendency for Europeans
to contract the disease than those intersected by innumerable streams
arid swamps. For all practical purposes the native malaria and es-
pecially the endemic index is the same throughout the whole district
whatever the physical conditions may be. Again for some seven
months of the year there is a steady reduction in breeding places which
"by January have in many places almost or entirely disappeared,
and a great reduction in the number of adult anopheles. Yet at no
time of the year is there any marked reduction of the endemic index.
Tor example, the northern end of a particular line was during the
dry weather at least a mile from the nearest water. Yet the endemic
index after this condition had existed for some months was still 67
per cent. The prevalence of malaria at a time when anopheles are
greatly reduced and their breeding places abolished reaches its
acme on those gardens to which we have already referred as situated
on the peculiar tract of sloping porous land in the Dina-Torsa district.
These gardens to judge from their apparent unsuitability for ano-
pheles, should have been almost free from malaria ; as a mutter
of fact they are not so. At one of them, on the contrary, we found in
April, May and August as remarkable an intensity of malaria as at any
place we have visited. Not only were the endemic index and the
spleen rate extremely high, but we saw an amount of sickness and
misery the result of Malaria nothing, short of astonishing in the cir-
cumstances. Clearly some very definite condition was involved
enabling malaria thus to maintain itself under circumstances so
apparently unsuitable for its spread. We believe this condition to
be the fact that in certain conditions the amount of human infec-
tion may remain undiminished owing to the suitability of the host
to the continuance of infection for long periods, and thus a mini-
mum number of anopheles serve to keep up a maximum amount of
infection.
Wo have referred to this condition in the introduction as "resi-
dual malaria " and in conditions tending to make communities suitable
for such a state we seem to have at work some of the most potent factors
in the causation of hyper-endemicity.
3$
If x anopheles be sufficient to cause 100 per cent, of infection;
then x anopheles, it is obvious, cannot further increase the mischief
but we have no data as to the figure x in different conditions. Our
own experience seems to point to its being in the Duars at any
rate very small, so small that the probable success of human efforts
to reduce anopheles to below this figure does not seem very great in
this district.
This aspect of affairs has not apparently been recognised in.
numerous instances where the malaria of a community has been
judged as necessarily directly proportionate to the number of ano-
pheles present, and where it has been supposed that a partial reduc-
tion of anopheles was in itself bound to influence malaria to an appreci.
able extent in any given community.
The general nature of the causes. bringing about residual malaria-
we have already indicated in the introduction, and since these causes
seem in the Duars at once most concerned and most controllable
they are those upon which we shall have to lay most stress.
E2
36
IV.—IMMIGRATION.
The coolie population on the tea gardens of the Duars, which
roughly-speaking numbers 150,000 persons, is almost entirely immi-
grant in character ; not only so, but it has all been recruited during the
past thirty years. The districts from which it has been mainly drawn
are—
(a) The various districts of Chota Nagpur and the Santal
Pargannas.
(b) Nepal and the Darjeeling Hills.
The races concerned are chiefly the so-called Chota Nagpuris,
Kols, Santals, and Nepalese.
In the absence of the registration the number of persona enter-
ing the Duars every year can only be very roughly computed.
Even the numbers recorded on the different garden books represent
only actual labourers. In our experience at least twenty-five per
cent. has to be allowed in the case of Chota Nagpuri and Santali
labour for young children and dependants. The number of immi-
grant adult labourers alone, not including children and depen-
dants entering the tea-gardens from Bengal, appears to be not
less than 7,000 to 8,000 per annum, and we have been informed that
during the year 1907-08 the total number recruited by all gardens
in the Duars probably reached a total of 20,000.
Regarding the yearly immigration into the Duars from the
Darjeeling hills and Nepal, we have absolutely no data and any esti-
mation is rendered very difficult by the fact that, in addition to the
large numbers of Paharia coolies, who yearly enter the Duars with
the intention of remaining one or more seasons, numberless gangs
of labourers come down every year from the hills in order to find
employment during the cold weather months, returning again to
the hills on the approach of the rainy season. But approximately
there would seem to be about half as many semi-permanently settled
Nepalese and Paharias as people from the plains and, allowing for
dependants and children, total yearly immigration of these classes
37
must number annually some 4,000 to 5,000 persons exclusive of the
cold weather labourers.
The total yearly immigration to the tea gardens from the hills and
plains together cannot, we believe, be less than 12,000 persons ; and in
some years it is probably very greatly in excess of this number. Thus
in 1907-08, in coolie lines examined by us with a view to ascertaining
the proportion of new coolies, we found these to form between ten to
fifty per cent of the whole and an ave age of twenty-five per cent.
of the whole seemed to be very general throughout the district. This
would give the extraordinarily high figure of an annual influx of
over 30,000 persons—men, women and children—which is, we believe,
nearer the truth than our minimum calculation.
These figure assume great significance when we remember that the
Duars is by no means a very large tract. And, when we compare the
annual influx into Assam, it is at once apparent that immigration into
the tea gardens of the Duars, which totals some 80,000 acres under tea,
is at present relatively greatly in excess of that into the tea districts of
Assam which has an area under tea four times as great.
It is necessary to follow out in some detail the actual conditions
associated with this annual influx of strangers.
CONDITION OF NEW ARRIVALS As REGARDS MALARIA.
Examination of coolies entering the Duars shows that the great
majority are free from malaria. This point is well illustrated in the
following examples :—
Among 60 adults 14 children and 5 infants who had come up
from part of Chota Nagpur not one had an enlarged spleen,,
nor did the examination of their blood show parasites.
The blood of the babies and children also was normal and:
offered a remarkable contrast to that of children of a
similar ago resident some time in the Duars.
Among three hundred coolies recruited in a single year from
the Santal pargannas and Singhbhum, examination of the
38
young children between the ages of 2 and 9 years yielded
the following results —
(1) Children, old 'esidents
(2) Children resident in the
Dua\ill\s 3 months.
(3) Children resident only
2 months.
(4) Chi dren resident only
one month.
(5) Children day of arrival
{ 18 with enlarged spleen
}
3 with no enlargement
2 with enlarged spleen.
1 without enlarged spleen
7 with enlarged spleen
8 without enlarged spleen
5 with enlagrod spleen
0 without enla- ged spleen
0 with enlarged spleen
11 without enlarged spleen
per cent.
86
67
47
33
0
In a small line of hota Nagpuri coalies, 25 children were
examined and 16 were found to have enlarged spleens, while
9 showed no enlargement. Enquiry showed that every
one of the latter were recent; arrival's from their count'y.
Out of another large batch of new children, 29 in num-
ber, who had come with their parents from Ch ibassa less
than a month previously, only 2 had splenic enlargement.
Among 46 others, resident about 3 months; 22 showed en-
larged spleen, while 24 now children, resident 5 or 6 months,
every one showed splenic enlargement.
Of 9 coolies from Chota Nagpur up a few days, 2 showed slight
enlarged spleen. Of 29 coolies from Kuru (Ranchi) only 2
showed enlargement of the spleen . But among 15 coolies-
from the same district up one to two months 8 showed
splenic enlargement; and among S69 adult natives examin-
ed in the Duars without reference to their length of resi-
dence, 257 showed splenic enlargement.
These figures indicate that to the vast majority of immigrants en-
tering the Duars the conditions there present as regards malaria are-
quite new and totally different to what they have been accustomed to
in their own homes.
Occasionally, however, a batch of coolies may show the presence of
a good deal of malaria, having evidently come from some locality or
community where malaria was very prevalent. For example : —
Among 12 coolies from Lahardugga, workers in ironstone excava-
tions in the hills, 11 showed enlargement of the spleen when,
seen on the day of their arrival in the Duars.
Plate II.
B. Recruiting districts shewing projection
of component colonies of the above
portion of a line.
To illustrate the formation of "colonies" from various districts and the composite nature of "lines"
39
MIXTURE OF DIFFERENT RACES AND PEOPLE fROM VARIOUS
LOCALITIES.
Under the Dual's 'sardari system, a sardar or his deputy, year after
year, visits the recruiting district and returns with a number of new
coolies. These coolie's are in the majority of cases recruited from some
group of villages with which the recruiter is familiar and has some
personal connection. On their arrival on the garden, 'the new coolies
settle down in close proximity to coolies that have been brought up in
Former years by the same sardar, for the reasons that—
(a) They belong to the same sardar and work in his gang.
(b) They get houses given to them in his particular line.
(c) They usually find themselves among people from their own
locality.
It thus comes about that garden lines, which to casual inspection
seem to be mere collections of huts, are in reality composed of separate
colonies, each one recruited from some particular group of villages or
localities.
Some idea of the wide range from which the component colonies of
a line are drawn and the resulting mixture of peoples will be gathered
from the accompanying plan of a small portion of a line, and the projec-
tion on the map of the recruiting districts of the source of the various
colonies composing it.
Most of the recruiting localities, if We may judge by the coolies
coming from them to the Duars, are comparatively healthy; others
are more or less malarious, and some even apparently intensely so
Thus in the Duars malaria carriers from malarious districts and
susceptible people from healthy areas are mingled ; and, in the
presence of anopheles, we have ready the constituents for an explosion
of epidemic malaria.
The actual conditions as they now exist are, however, even more
favourable to malaria as will be seen in the next section.
40
MIXTURE OF NEW AND OLD COOLIES,
It is evident that each year every colony in every line throughout
the Duars is liable to receive its annual addition of new arrivals. Hence
new-comers are at once distributed throughout the whole community.
An example of this is shown in the accompanying plan of a line taken
at the end of the recruiting season.
In the year or two following their arrival these new-comers are in
the position of being susceptibles received into a hot bed of infection.
They at once become infected, and in proportion to their susceptibility
become disseminators of infection. They thus tend to raise still higher.
the intensity of malaria in the lines. This process repeated year by
year tends to maintain a permanent condition of exalted epidemic mala-
ria.
In addition to the mixture produced in the Ways we have described
there is also a great tendency, for reasons which We need not here
specify, for large numbers of the population to move about from garden
to garden.
Under conditions where the mingling of infected persons and sus-
eeptibles was less complete we might expect that the health of each com-
munity would depend upon its relatively healthy or unhealthy situation,
and its history and constitution but in the Duars the conditions suit-
able for the spread of infection approximate everywhere so much to
the optimum that, provided there are any anopheles at all, a state of
maximum infection seems everywhere to result.
If under these conditions we wish to reduce disease, it is obvious
that we have to think about trying to protect or render the com-
munity unsuitable to malaria, especially the new-comers. For, given
a moderate degree of infection, the older and more or less immune
coolies will manage to retain their health ; it is the new coolies
those within the first few years of their arrival, who form as it
were the most inflammable fuel, and not only suffer themselves, but
raise the amount of prevailing infection for old and new alike.
Plate III.
To illustrate Non-Immune Immigration.
Reg. No. 3553 E. 11.—H.—400.
Portion of a coolie line at the end of the recruiting season shewing
the settlement of new coolies among the older residents.
41
Yet in the next few chapters we shall see that it is just this por-
tion of the population which bears the brunt of the conditions we are
about to describe.
EFFECT UPON THE RECRUITING DISTRICTS.
Coolies from the Duars in a certain proportion of oases return for
a time or permanently to their own country. Practically every such
coolie is in greater or less degree an infected person. Where any group
of fairly healthy villages is exposed to the constant influx of infected
persons they run the danger of becoming foci of epidemic malaria.
1 SC
42
V—DUARS' LABOUR SYSTEM.
The first tea gardens established in India were those in Assam and
Cachar. These were at first worked by local labour ; but as far back
as 1859 local labour was found to be insufficient, and the rapid exten-
sion of the industry in these districts led to the recruitment of labour
from other parts of India. This recruitment carried on under no legal
or sanitary restrictions led to many abuses, and the morality on the
journey to and at the gardens became too great to be overlooked. In
1861 a committee was appointed by Government to enquire into the
system under which the emigration of coolies to Assam, including the
Surma and Brahmaputra valleys, was conducted. As a result of this
enquiry and subsequent events, various Acts have been passed at
different times regulating the recruitment of coolies and insisting
upon sanitary and other provisions in regard to their treatment on
the journey and while living on the gardens.
For a long time the only important centre of the industry outside
Assam was in the Darjeeling hills, and in this case the influx of local
labour from Nepal and Sikkim afforded an ample supply of workers.
But the opening of the gardens in the Darjeeling terai and later the ex-
tension of the industry to the Duars, a tract ceded to the British after
the Bhutan war, led to the demand for immigrant labour on an in-
creasing scale for these districts also; especially has the Duars with its
great extent of virgin soil offered a new and rich field for the exploita-
tion of tea and the consequent importation of labour.
But in the Duars the regulations applying to Assam have never
been enforced, and the recruitment of labour has gone on under what
is known as the " voluntary" or " sardari" system, which, since it
entails no legal binding of the coolie; is generally considered as not
necessitating measures for his protection. Whilst then the Duars
has advanced to a foremost place among the tea districts, it has
become above and beyond this an example of the working of the
special system of labour peculiar to itself; for we shall see the
" voluntary " system in the Duars differs in one important respect
at least from the so-called " sardari " system known in Assam.