NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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watercourses, and while these are drying in the sun, oil may be poured
on them with great advantage.
On account of the fact that special precautions are necessary when kerosene oil
is used as a larvicide on the watercourses, this method can only be
carried out under careful supervision.
II.—Methods employed for pools and other collections of
stagnant water.
(a) Pools formed in connection with irrigation.
These comprise firstly, large, more or less permanent pools formed from
time to time by the overflow of a watercourse or the breaking down of its banks.
Such pools were, as far as possible, prevented from being formed by paying
constant attention to the watercourses, building up their banks wherever there
was danger of overflow, and digging them out in order to keep the water level
below the height of the bank. When any such pools had formed they were
temporarily covered with a layer of oil and afterwards filled in with earth.
Secondly, a number of small pools are formed in the gardens by reason of the
fact that all the water given to an area in one day does not always sink in or
dry up before the next day's supply of water reaches it. Any small pool
formed in this way is replenished daily so that a pool lasting ten or twelve days
is formed. In the weekly examinations of the gardens section, pools of this
nature containing anopheles larvæ were frequently found. As the owners of the
gardens might object to kerosene oil being used on land where plants and
flowers were growing, the water of these pools was either drained away, or
emptied out and thrown over the land. Thirdly, numerous pools are left in the
beds of the watercourses after the supply of water is cut off. As a rule, these
pools contained many larvæ. By connecting one pool with another throughout
the length of a watercourse, it was often possible to dry the whole of these pools
quickly ; where this could not be done, oil was poured on the separate pools.
After the water-supply is cut off a pool also remains in the bottom of each jalahar .
These pools were dried by emptying out the water with tins and buckets.
( b) Rain-formed pools.
These are very numerous during the months of June and July. First there
are the large shallow ponds of water formed almost throughout the lines on the
level plain after every shower of rain. In the Royal Artillery lines the chief
ponds of this nature, are formed on the parade, ground, on the football ground,
and near the Royal Artillery bazaar. As a rule, these superficial pools dry up in
two or three days, but if before the end of that time more rain falls, they remain
sufficiently long for larvæ to develop in them. By digging small channels
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in various directions it was comparatively easy to drain these away into the
irrigation watercourses, and this was done every time rain fell.
More dangerous breeding grounds are formed by the surface drains which
exist throughout the lines. From the fact that these drains have little or no fall,
rain accumulates in them for many days, and after a week or so they swarm
with anopheles larvæ. Owing to the large amount of water they contain they are
difficult to deal with. Some were dried out with buckets, and on others oil was
poured. During 1902 the rainfall was a very small one, but in years of heavy
rain a great deal of labour would be required to keep these drains free from
larvæ.
(c)Permanent " tanks " and pools.
One large " tank" near the Royal Artillery bazaar was filled in by the can-
tonment authorities. Over 250 smaller tanks and pools have been filled in by
contract labour.
(d)Numerous other breeding places have been dealt with as they have
been discovered. The small drains carrying off water from the
baths, standpipes, etc., in which larvæ were frequently found, have
been swept out regularly, tins and buckets kept full of water in the
lines in case of fire have been emptied weekly, as have also the horse
troughs and cisterns. The only breeding places which have not
been dealt with in any way are the swimming baths. Numerous ano-
pheles larvæ were found in the two large swimming baths in August
and September. As they take three days to empty and a fortnight
to refill, it was difficult to suggest any effective method of preventing
them from acting as breeding places.
The following details of the work are taken from my diary during the year.
The operations were commenced under favourable circumstances, for at the
end of March no adult anopheles mosquitoes could be found by careful search
in the houses, and as the irrigation water-supply had been cut off for some time,
there were comparatively few breeding places to be dealt with.
The first object was to get all the irrigation watercourses thoroughly
cleaned out and their edges made smooth and free from grass and weed.
Twenty coolies under a headman of the canal department were engaged, and
work on the watercourses was started on the 2nd of April. The fresh supply
of water entered the canals on the 9th April, and a very few anopheles larvæ were
found in them on the 13th and 14th. Some of the watercourses were almost
hidden from view by thick pampas grass and branches of trees which grew on
their banks, and as it was very necessary that this thick growth of vegetation
should be cleared away as quickly as possible, so that the watercourses might be
converted into clean channels exposed to the sun and air, it was found desirable
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to employ a larger staff of temporary men to carry out this first work. From the
21 st of April to the end of the month, therefore, between forty and fifty coolies
were employed daily on the irrigation watercourses. By the end of April all the
watercourses in the area of the operations had been thoroughly cleaned out
all the grass growing on their banks had been cut down, and their edges had
been made as smooth as possible. On the 20th of April the water-supply
of the canals was again shut off. As a result of this many pools were left in.
the watercourses and in the jalahars. A few anopheles larvæ and numerous
culex larvæ were found in all these pools. Most of them were dried out by
the men with tins and buckets, but as an experiment a few of the pools were
covered with a layer of kerosene oil. This killed all the larvæ present in
about twenty minutes, but three days afterwards (on the 24th) young anopheles
and culex larvæ were again found in these pools. On the evening of the 24th
of April heavy rain fell for some hours. This caused many pools to form
throughout the area and gave an indication of what pools would be most
dangerous during the rainy season. A map showing the more permanent pools
was now made, and additional men employed to commence filling them in with
earth. In the meantime the water of the superficial pools was drained away by
digging small channels leading into the irrigation watercourses, and, until the
more permanent pools could be filled in, they were dried by baling out the water
with buckets, and throwing it on the open plain where it would dry quickly in the
sun. After all the watercourses had been dealt with for the first time in the
manner described, two men were permanently applied to each branch. Their
duties were
—
(1) To keep the edges free from grass and weed.
(2) To keep the sides smooth and regular by scraping away the earth at
some places and filling in any small bays and irregularities at others.
(3) To constantly remove all leaves, sticks, straw, and other floating débris.
For this purpose the men were provided with shallow round baskets
and by walking in the water and scooping the basket along the edge
underneath the surface, all the floating débris was collected and
thrown out on the bank. This was a very important part of their
work, for dead leaves were constantly falling into the water from
the trees above, and under their shelter larvæ were constantly found.
If left alone the leaves collected in a thick mass at each bridge,
impeding the flow of water and forming an excellent breeding ground
for larvæ.
Two men could in this way go over their own branch three times daily..
They were constantly supervised and directed in their work by myself, my hos-
pital assistant, and by an overseer of the canal department.
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The irrigation water-supply started again on May 6th and was not shut off
for more than two or three days at a time throughout the summer.
In spite of the constant cleaning operations a few anopheles larvæ, and a
considerable number of culex larvæ were found in the watercourses on May 12th
By covering the shallow baskets with muslin the men were able to catch and
destroy a good number of these larvæ at the same time as they collected the
leaves.
On May 15th the bricking of the watercourse running through the centre
of the lines was commenced, and for this purpose the water was shut off from
this branch and the others which obtained their supply from it.
On the 14th of May slight rain fell, and the pools formed were treated in
the same manner as on the previous occasion. The filling in of permanent
pools with earth and the cleaning of the watercourses was continued steadily,
but in spite of this, a certain number of anopheles larvæ were found in all the
watercourses from May 15th onwards. Along the smooth edges they were not,
as a rule, to be found, but in many of the watercourses roots of trees projected
into the channel, and in their shelter larvae were generally present. All the
larger roots were therefore cut off with hatchets to the level of the bank and
so got rid of.
From May 30th to June 3rd inclusive I made careful observations throughout
the area of operations and throughout another part of the cantonment to ascertain
whether any success in the reduction of the number of larvae and adult mosqui
-toes had been attained. The results showed that although in the area of opera
-tions a few larvæ could be found in all the watercourses by careful search, the
number present was far less than in the uncleaned watercourses in other parts
of the cantonment. In the watercourses of the British Infantry bazaar for
example an enormous number of larvæ were found, and even without dipping
with a tin they could be seen among the grass and weed at the edges. It was
evident that up to the end of May the breeding of larvæ in the watercourses of
the area of operations had been prevented to a very considerable extent. Cor
-responding success was attained with regard to the number of adult insects to
be found in the houses. On June 3rd after careful search for over an hour I
could not find a single adult anopheles mosquito in the Royal Artillery bazaar.
On the same day I caught ten adult A. culicifacies in the British Infantry
bazaar in about half an hour without much difficulty.
During June, however, the number of larvæ in the watercourses of the area
of operations increased considerably in spite of the same methods being con
-tinued. I have already mentioned that by reason of some of the watercourses
having no outlet, the water in them is stagnant except for about three hours a
day while the Persian wheels are working. However clean they are kept, they
E
form for this reason exceedingly favourable breeding grounds for anopheles mos-
quitoes. Finding that cleaning operations were not completely successful in pre-
venting larvæ from appearing in large numbers in these watercourses, I tried the
plan from June 15th of making a " band " at the beginning of each branch, empty-
ing out all the water in the branch, allowing it to dry in the sun, and again letting
in fresh water [method (c) page 20]. By this means all the larvæ present in the
branch at the time were killed. During the month of June I found that larvæ
required ten to twelve days to develop from the very young stage into adults,
and to kill all larvæ it was therefore necessary to dry each branch about once
every ten days. I carried out this plan for six weeks, but on account of the
expense of drying out the branches, which was done partly by working the
Persian wheels and partly by baling out the water with tins and buckets, and the
fact that such operations interfered to some extent with irrigation, I ceased
it about the middle of July and returned to the method of keeping the edges of the
watercourses clean and removing all floating leaves and débris.
From the beginning of June the operations carried on, and the results of ex-
aminations for larvæ and adults, may be more conveniently described under the
headings of the various sections into which the area of operations was arbitrarily
divided.
I.—The Watercourses.
In the area of operations there are ten watercourses. As the methods
employed and the results obtained were practically the same in all, it will be
sufficient to give the details concerning one watercourse only, noting that similar
operations were carried out on different dates in all the other watercourses and
almost similar results obtained.
The following account refers to the first watercourse through the gar-
dens :—
On the 7th of June a fair number of nearly full-grown anopheles larvæ
were found in this branch. A band was made at its commencement, and it was
dried out and cleaned on the 8th. Fresh water was let in on the 9th, but on the
12th very young anopheles larvæ were again present. The number and size of
the larvæ found, gradually increased, and on the 19th this watercourse con-
tained a good many nearly full-grown larvæ. The water was therefore again
shut off on the 20th and the watercourse was dried and the mud it contained
dug out. As irrigation was not required from this branch at the time, fresh
water was not let in until the 26th of June. Three days later a few very young
larvæ were again found. Cleaning of the sides and removal of leaves was
carried on daily, but on the 8th July many young anopheles larvæ and a few full-
grown ones were found throughout its length. On the 9th of July the water was
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again shut off and the branch dried, but before the drying was completed the
branch was refilled by rain on the 10th, so it was again dried and fresh
water let in on the 13th. New broods of larvæ were not found again until the
17th. On the 22nd there was very little water in this branch and numerous full-
grown and young anopheles larvæ were found in it. As the supply of water was
so small that none could reach the Persian wheel, oil was poured on the branch,
which killed all the larvæ. Sufficient water for irrigation did not reach this
branch again until the beginning of August, and on the 9th of August young
larvæ were found. Full-grown larvæ were not found until the 22nd, when this
branch had again become so shallow as to form only a series of pools. These
pools were dried out. With the return of the irrigation water-supply cleaning
operations were carried on daily, but in spite of this very many full-grown larvæ
and innumerable young ones were again found on the 31st of August. With proper
precautions to prevent any oil reaching the Persian wheel [see method (d) page 20],
I therefore covered the whole branch with a layer of kerosene oil. On the next day
no larvæ at all were found. The good effect of the oil lasted about a week; on
the 7th of September young anopheles larvæ were again found and on the 15th
numerous full-grown larvæ. With the same precautions as before, oil was again
poured on the first half of the branch on the 17th of September, and on the 18th
no larvæ were found, except a few at the very end where the oil had not reached.
On the 24th of September a few very young larvæ were again found (the effect
of the oil having passed off) and on the 28th when the branch was so shallow
as to form only a chain of pools, full-grown larvæ were present. These pools
were dried out. At the beginning of October the irrigation water-supply was
cut off and this branch was dry throughout its length on the 3rd of October.
The supply re-commenced on the 9th of October and young larvæ were found
on the 14th. On the 22nd it contained many full-grown larvæ and some pupæ,
but on this date the irrigation-supply was again cut off, so that on the 23rd this
branch contained only a few pools which were easily dried out. On the 24th of
October fresh pools were formed by rain, but on the 27th no larvæ were found
in these pools and they were dry on the 28th. The irrigation-supply was
resumed on the 5th of November, but it only ran for three days, and on the 11 th
with the exception of some pools under the bridges, this branch was dry
throughout. A few young anopheles larvæ were found in these pools. They
were dried out, and together with all the other watercourses this one remained
dry until the irrigation water-supply was again given on the 29th of November.
This branch had now been dry for fully twenty days, and as at this time no adult
anopheles mosquitoes could be found in the houses, it afforded a good opportunity of
testing whether any adults were really present, though none could be detected by
careful search, or not. If adult anopheles mosquitoes were present in the houses
,
E 2
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it is reasonable to suppose that they would again lay their eggs in the branch as
they had done throughout the year. No young larvæ were, however, found
in this or in any of the other branches from the time of arrival of fresh water on
November 29th up to the end of the winter. On December 5th the irrigation
supply was again cut off and a chain of pools left in the branch. These were
allowed to dry in the sun, and afforded exceedingly favourable breeding places, but
no eggs or larvæ appeared in them or in the pools of any of the other branches.
A few details may now be given regarding the watercourse which was
rendered permanently smooth and free from weed and grass, by lining it with
bricks plastered with cement. The total length of the bricked portion is 4,985
feet. Before being bricked, it formed an exceedingly dirty weed-grown ditch
containing almost stagnant water, running through the centre of the lines and
within a few yards of the front of the barracks, the military prison, and the hospital.
In addition to its being a favourable breeding ground of anopheles mosquitoes, it
formed the depositing-ground for most of the old tins, bottles, and rubbish of all
descriptions from the lines and barracks. As a result of the bricking it has been
converted into a clean-flowing channel about five feet wide and four feet deep,
running with moderate velocity and in an efficient manner. A sliding door has
been placed at its commencement by means of which the flow may be regulated
and the channel flushed out. The bricking was commenced on May 15th and
completed at the end of July.
Although from a sanitary point of view the bricking of this watercourse has
been of great benefit, the result from the point of view of destruction of anopheles
breeding grounds has not fully realized our expectations. We had hoped that after
bricking this channel the flow of water in it would be sufficiently swift to entirely
prevent its acting as a breeding place. This, however, is not the case, and, if
left entirely alone, it still remains as a breeding ground of anopheles mosquitoes,
though not nearly to the same extent as formerly.
This is due partly to the fact that the flow of water is still only very
moderate, and partly to the numerous leaves which, falling into the water from
the trees above, collect at the bridges and form a suitable shelter for larvæ.
During part of August I did no cleaning operations whatever on this water-
course with the object of testing the efficacy of the work of bricking. Although
no larvæ could, as a rule, be found along the clean plastered sides of the channel,
they were numerous at the bridges and under the leaves. After this I constantly
employed two men with baskets to take out all the leaves and to keep the sides
of the channel clean and free from mud. As a result of this the number of
larvæ to be found was very much diminished, and it may fairly be said that,
while the water is actually running, one or two men constantly employed in this
way could keep this bricked watercourse almost completely free of anopheles
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drains in this section were found also to afford excellent breeding places for ano-
pheles mosquitoes, and during this month it required great care to keep them free
from larvæ. Another class of breeding place found during this month were the
drains and pools formed by the waste water of the wells. This waste water of
wells is difficult to deal with, for it cannot be drained away on account of the level-
ness of the ground. In this section it was dealt with by collecting it in a deep
pool, which was kept constantly covered with a layer of oil. During July, in spite
of constant attention being paid to all breeding places, the number of adult mos-
quitoes (A. culicifacies and A. Rossi) found in the houses, increased considerably,
and towards the end of the month specimens of both species could be caught
fairly easily at any time.
During August the chief breeding places in this section were the roadside
surface drains, the deep pools of the roadsides, the drains carrying off water from
the wells and from the bazaars, a few irrigation pools in a garden in front of the
bazaar, and the gumlahs of water kept outside each house. During part of the
month the road in front of the bazaar was being relaid. In road-making it is the
practice of the contractors to use the surface drain, which runs at the side of the
road they are laying, as a reservior of water. One end of the drain is closed by a
barrier of bricks and earth, and the drain is then filled with water for use in their
work. A collection of water fifty yards or more in length is thus made, which
quickly becomes swarming with anopheles larvæ. Within the limits of the can-
tonment the practice of filling these drains with water was stopped with some
difficulty, as the workmen refused to continue laying the roads unless it was.
allowed. Outside the cantonment limit it was still carried on, and the constant
emptying out of the water in these drains every few days required much labour.
In the absence of urgent work of this kind my men were employed filling in the
roadside pools with earth. In the meantime all pools were kept covered with a
layer of oil.
In this month it was found necessary to repeat the oiling of pools at least
every three days as the larvæ developed so rapidly, and under the great heat the
oil quickly evaporated.
During the month of August a very large number of A. Rossi were present in
the houses of the bazaar. The number of adult A. culicifacies had also increased
somewhat, though they were not by any means as plentiful as A. Rossi, nor were
they so common as in other bazaars of the cantonment where no operations had
been carried on.
During September and October the same class of breeding places had to
be dealt with. Most of the pools had by this time been filled in with earth, and,
as the rains had almost ceased, the work was less. Constant inspection, however,
was necessary to keep larvæ from appearing in every collection of water in and
round the bazaar. Tins and other receptacles of water had to be constantly