NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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By emulsifying kerosene oil, therefore, its effectiveness is almost doubled, the
difference being due to the much more perfect film produced. The cost of the
soap and the small amount of labour necessary (the oil readily emulsifying) may
be neglected, and a saving in the amount of oil used is effected. In experiments in
which pure oil and half the quantity of emulsion were used on canals the pure oil
was found to be somewhat more effective, so that in actual practice the difference
was not so marked, and on the whole it was found most convenient to use ordi
- n a r y o i l . U n d e r c e r t a i n c i r c u m s t a n c e s , h o w e v e r , t h e e m u l s i o n m i g h t b e u s e d
with benefit, especially where very large amounts of oil are used, or where it is
desired to prevent the oil being taken for other purposes than those intended.
Although, after each oiling, larvæ in a canal were found to have completely
disappeared, yet within two or three days young larvæ were always found to be
present. As the season advanced, larvæ in the canals, and especially in certain
portions of these, became more and more abundant in spite of the oiling. It
appeared at this time that adult culicifacies were increasing in the area in spite
of the operations.
Several times during the season the water of the canals was shut off for a
variable number of days. On these occasions the water remaining in the canal
was at first baled out, but the process was not persevered with, since the water
was readmitted before the mud became dry, and experiments had shown that
larvæ could remain alive a considerable time even upon mud that was nearly
dry (see notes on the biology of mosquitoes in Mian Mir, Part IV). At the time
when the water was cut off and consequently lying very low in the canal, it was
usual t o f i nd l ar væ i n much gr eat er number s. The expl anat i on at f i r st seemed
difficult, but appeared to be that with the fall of the water larvæ were washed out
from numerous Persian wheels and other cul-de-sacs, and, passing beneath the
syphon bridges, entered the canals in the area. Whenever, therefore, the water
was shut off, the residual waters were oiled. From October the water in the
canals was shut off for ten days or more at a time. When such an opportunity
occurred, the whole of the canals in the area were baled out, and became quite
dry. Unfortunately at this time larvæ were diminishing in numbers and the fever
season was nearing its end.
II.—Miscellaneous breeding-places.
In the next section it will be seen that by drainage and filling up, all pits
and sheets of water were removed from an area of about a square mile immedi-
ately around the barracks, bazaar, and bungalows. In spite of this, however, a
good many small breeding-places were still left which required to be searched
for and destroyed. Larvæ were found in small cement tanks in connection with
wells and with garden irrigation, also in waste water from large wells and other
No. 850, Secy to the Sany. Comr., India.—Mar. 04.—1,145.
MAP OF AREA OF OPERATIONS
Litho., S. I. O., Calcutta.
Showing the irrigation canals and other breeding places of Anopheles. Pools and channels marked
in blue were permanently done away with. Pools marked in red indicate the chief breeding
places of A. Rossii. The explanation of the map is given in the text.
To face page 11 of the Second Report of the Antimalarial Operations at Mian Mir.
sources, as well as in kerosene tins, earthenware vessels, etc., left full of water.
Breeding-places of this nature were carefully sought for and destroyed, the whole
area being examined at least once a week.
Although those just mentioned are the breeding-places which would, in an
ordinary way, have been dealt with in operations confined to the immediate neigh-
bourhood of the barracks, I am of opinion that they were of little comparative
importance. As sources of anopheles, such breeding-places in Mian Mir were
infinitely small compared with the canals and with innumerable pits which sur-
rounded the area on all sides (see map). In this connection I may remark that
our experience in Mian Mir has led us to look upon measures confined to the
pits and puddles in the immediate neighbourhood of buildings as quite futile.
III.—Rain-formed pools.
Before the rains the irrigation canals form the only important breeding-
places of anopheles. The whole area and surrounding district may be searched
without a trace being found of a breeding-place that is not in connection with the
irrigation system. In the rains the conditions are entirely different, and collec-
tions of water are to be found in every part of the area.
The rains are of very short duration, and the average total fall during the
year is under 20 inches. They consisted in the present year of six downfalls,
the first of which fell on the 14th July and the last on the 8th September.
Each downpour lasted for about two days, but the latest rain of the season fell
continuously for four days and left lasting effects in the shape of pools and
sheets of water. The intervals between the downpours were 5, 6, 8, 15 and
15 days, respectively. The long intervals between the downpours was very
favourable and allowed of baling out and other operations being carried
on. Had rain fallen at shorter intervals, it would have been very difficult to
effectively destroy breeding-places over such a large area. It was found that
the heavy rain filled many of the pits to overflowing, and washed the larvæ out
over the land. Such larvæ were then found in shallow puddles among grass
and it was frequently very difficult to destroy them. Unless, then, all breeding-
places were destroyed prior to a shower of rain, complete destruction of larvæ
could not be carried out.
Nature of the rain-formed pools.— It has been already noted that the coun-
try about Mian Mir is extremely flat, and that the soil being impervious, water
tends to collect in shallow sheets wherever the land is rather low. A good many
of such sheets, some of considerable size, existed around the Royal Artillery
bazaar, and required a good deal of attention until, as will be seen later, they were
permanently done away with by drainage. As a result also of the want of slope
c2
in the land, both brick and earth drains are liable to remain full of water, and in
some of the latter larvæ of A. culicifacies were found.
Perhaps the most noticeable and important feature of Mian Mir in the
rains is the presence of numbers of "rain-filled pits." In the building of every
native hut, the making of walls, rifle butts, and other structures, it is the practice
to dig earth from the ground somewhere in the neighbourhood. The result is the
formation of a large number of pits varying from a few feet in diameter to 50 yards
or more, and from one to ten feet in depth. In the more central area these pits
were, as a rule, small and not very numerous, but near the cantonment limits they
occur in hundreds and under natural conditions swarm with the larvæ of
A. Rossii.
A. Superficial drainage. — In spite of the difficulty of ensuring a sufficient
fall for drainage, it was found possible with some care and thought to drain the
surface waters from almost the whole area. Within an area of about a square
mile immediately around the bazaar and the barracks, over 50 sheets of water
were permanently drained by earth-cut channels, and required no further attention
throughout the rest of the season. Most of these required only a broad shallow
channel to be cut in the line of greatest fall. In some cases, by making rather
large drains, whole systems of pools could be drained into them and ultim-
ately into the canals. The most important of the drainage operations were
carried out to the south of the bazaar, where an extensive series of large sheets
of water was drained into the canals. In this case treatment by drainage
appeared at first sight impossible, and had this been so the large marshy pools
would have defied almost any treatment, since long grass and other vegetation
grew luxuriantly, and made "oiling" a very uncertain and expensive measure.
Eventually two long drains, each nearly a quarter of a mile long, and a number of
collateral drains effectually removed the whole of the water. In many cases, when
a drain had been dug through a pool, the ground, instead of remaining muddy
and full of puddles due to the trampling of oxen and men, became hard and
dry within a few hours of the cessation of rain.
On the whole, surface drainage was found, even in Mian Mir, the most effec-
tive and satisfactory of all the operations. Very little labour was required to
carry it out, and, once established, the whole area became automatically dry
within 24 hours of the heaviest rain.
B. Filling with earth. —Although surface drainage was so efficient in the
case of rain-formed surface pools, it could not be used for the rain-filled pits
already mentioned. In this case several methods of preventing the breeding of
anopheles were employed. Naturally the best way of dealing with these was to fill
them up again with earth or rubbish. It has already been noted that 250
such pits were filled during the period that the operations were under the
13
direction of Captain James. There remained, however, within the area under-
taken at least an equal number more, and as the filling of these was a work of
great magnitude, only those pits in the more central area were filled during
the present operations. In endeavouring to fill a large number of pits in so flat
a country as Mian Mir, difficulty arises as to the source from whence the earth
with which to fill them can be obtained. Most of the pits in the present instance
were filled by earth taken from old rifle butts and a disused brick kiln. In
filling pools it was found advisable to fill them to a higher level than the sur-
rounding ground, since subsidence takes place after a time and a new pool
reforms on the site of the old. In some cases pits were purposely only partially
filled, since rain does not at first collect in these owing to the porous nature of
the freshly laid down earth. Such pits are, however, liable at any time to
become breeding-places and require to be constantly watched.
In some cases very large pits were only partially filled, in order that the
operation of " baling-out" might be more readily performed.
C. Baling-out—1n the account of the rains it will be seen that, especially
between the later downpours, intervals of as much as a fortnight occurred.
Under these conditions the process of baling out the water from pits was found a
very satisfactory one. Directly after a downpour of rain attention was concen-
trated upon the more central area, and all water lying in the brick and earth drains
was removed by men with empty paraffin tins. At first these operations took
at least five days to complete, but after the draining of the superficial sheets and
the filling of the pits, a much less time, at most two days, was required. By the
the time that operations in the central area were finished a partial sinking of the
water in the pits of the outlying area had occurred, and the delay of a few days
was thus advantageous, since it lessened the amount of water to be removed. In
numerous observations as to the time of development of A. Rossii in deep and
shallow pools it was found that pupæ were never formed before the twelfth day
after the formation of a pool. Twelve clear days were thus given in which bal-
ing-out operations could be carried on, provided, that is, no second shower of rain
fell in the meantime. The time of the next rain was of course never known, so
that baling operations were carried on as actively as possible, and the whole area
was gone over in about eight days. If at any time rain threatened before all the
pits were baled out, those remaining were at once oiled, since, as noted before, a
fall of rain on pits already full of larvæ was to be avoided.
The pits, some idea of the number of which may be gathered from the map,
were of various depths and extent. As a rule, they held, a few days after rain,
from 100 to 400 gallons of water. There were, however, certain large excavations
which became filled with water (Group B) and contained some thousands of
gallons. At the commencement of the operations these were oiled, since to empty
them occupied several days. Later, however, when operations had been simpli-
fied by many small devices, it was found possible for twelve coolies to empty them
in a single day. In baling out water, devices for hastening the process may be
very advantageously employed. The large pits just mentioned, which contained
water over 10 feet in depth, were first partially filled by tearing down the earth
at their sides. The result of this was to enlarge their area, but to greatly dimin-
ish their depth. A channel with a deep hole at the end was then dug in order to
bring the water to the edge of the pit, where it was baled out with ease by relays
of two men at a time. In some cases a double channel had to be formed in order
to lift the water to the desired height. In others two channels were made to
enable relays of four men to operate. By making a few small " bands" water was
prevented from flowing back into the pit. Once the coolies employed in baling
out realised the great saving of labour to be obtained by such devices, they
showed much ingenuity in applying them.
The operation of baling out appeared to be particularly adapted to opera-
tions at the end of the rains. In the present instance within ten days of the
cessation of the last rain the whole of the pits in the area were rendered free
from water and thus eliminated as breeding-places. The only groups shown in
the map not so treated were the Group P. and some few others to be noted in
the next paragraph, which required different treatment.
D. " Oiling."—In the early part of the season most of the pits in the out-
lying area were not generally baled out, since the rain fell at too frequent inter-
vals to make this a practicable measure. In order to prevent breeding in these
they were therefore " oiled " by pouring just sufficient kerosene from a watering
pot to destroy the larvæ. A very good test of the efficacy of the oiling was the
appearance of immense numbers of dead water beetles and other insects on the
surface of the water. Unfortunately the great importance of some of these out-
lying pits, most of them at a distance of half a mile, was not at first recognised,
so that it was only from the end of August, when larvæ were found swarming
in them, that actual measures were adopted. (See occurrence of adult A. Rossii
in area, Part IV.)
Oiling, both in the case of pits and canals, was always certain in its results
where no vegetation existed. The cost, if used indiscriminately for all breeding-
places, was considerable, and in order to employ it to the most advantage, it was,
if possible, used when pits were reduced in size by drying, but before pupæ
were found. The Group M. (see map) on the 4th of September, eleven days after
rain, consisted of 50 water-containing pits and required only about 6 gallons of oil.
On the 11th of September, soon after rain, the same group consisted of nearly
100 pools, some of large size, and 15 gallons of oil had to be used. Had all the
pools in the area been oiled weekly, about 200 gallons, costing Rs. 50, would be
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required per month. This is less than the cost of wages to coolies for baling
these out, so that, except at the end of the rains, oiling would appear to be the
most suitable means to adopt against pools of the above nature when these cannot
be permanently obliterated by filling them with earth. There were in the area
two large wells used by washermen, the waste water from which was allowed to
sink into the ground. After a time the ground became so saturated that the
whole area in the neighbourhood of the wells was boggy and full of innumerable
puddles. Such collections are shown on the map at V and IV. At IV it was
found possible to conduct the waste water into a large drain and so to dispose of
the pools. At V, however, it was impossible to drain the area, and since larvæ of
anopheles and culex swarmed in the puddles in spite of the foulness of the water,
oiling had to be resorted to. The water was, however, almost hidden in the
grass, and oiling was found quite ineffective unless very large quantities of oil
were used. In order that the oiling might be effective, it was in this case neces-
sary to have most of the grass scraped away by coolies.
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PART III.
RESULTS.
IN order to test the efficacy of the operations it is well to discuss
separately :—
I.—The effect upon breeding-places and upon the number of larvæ.
By the permanent removal of some breeding-places and the constant
destruction, by oiling and other means, of all others, the whole area of four square
miles had, to all appearances, been rendered free from breeding-places of ano-
pheles. It is, of course, impossible to say with absolute certainty that no breed-
ing-places were overlooked. The greatest care was, however, taken to examine
at short intervals every part of the area, and as the operations had been in pro-
gress for some time, most of the land was very accurately known, and large
numbers of places where breeding-pools might occur were noted. The only
point to be regretted was that some groups of pools in the outer circle were not
attacked sooner. All these pools were at such a distance (over half a mile) that
at the time their importance was not realised. It is believed, however, that
no breeding-places escaped attention in the more central area from July on-
wards, and very few in the outer area from the end of August.
In the operations the destruction of larvæ was enormous. A single oiling of
a canal in the later months must have destroyed millions, since it was not unusual
to remove fifty or more specimens in a single dip of the dipping can. In the pits
also, where larvæ were often so abundant as to give the appearance of a scum,
the repeated oiling and baling out must have accounted for vast numbers.
It appears almost certain that a very small proportion of larvæ in the area were
allowed to hatch out after the end of August, when periodical oiling of the whole
canal system and destruction of the outer circle of breeding-places was com-
menced. It would certainly appear likely that after such destruction larvæ
would recur in lessening numbers. It was surprising, therefore, to find that
within a few days of every oiling, whether of a canal or a pit, an undiminished
and even increased swarm of young larvæ were present. The presence of the
larvæ undoubtedly depended upon that of adults in the area, for there was much
evidence to show that the eggs were laid in situ and were not to any extent
carried down stream from outside the area. This was shown in the case of a
small length of canal forming a cul de sac, and especially noticeable as contain-
ing large numbers of larvae after each oiling. A " band" was made across the
entrance from the main canal and the whole oiled. In spite of no fresh water
being admitted, lame were in a few days present in large numbers. The
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number of larvæ in the area, in spite of repeated wholesale destruction, showed
no tendency to diminish.
II.—The effect upon the number of adults.
It has been already noted that two species, A. culicifacies and A. Rossii,
were the common anopheles in Mian Mir, and that the habits of each were
markedly different. In the period devoted to research a very fair idea of the
prevalence of these in the different bazaars was arrived at. It was, however,
impossible to give any accurate measure of their numbers, since so much
depended upon the facilities for seeing them. Of anopheles in general, it may be
said that they are difficult of detection and require concentrated attention on the
part of the searcher, if they are not to be overlooked. A. Rossii, however, is a
mosquito fairly easy of detection, and it is possible to employ comparative terms,
for their numbers, such as " swarming," " abundant," "scanty," " found with
difficulty," or " not found at all." In the case of A. culicifacies it is harder to
arrive at any definite idea as to their numbers. This species is extremely careful
to secrete itself, and if there are no suitable collecting places, it may very easily
be considered absent when in reality it is abundant. Should, however, a
low-roofed, rather dark shed be available, adults are usually caught readily.
With regard to this species then we can only say that "it was caught readily by
looking in suitable places," or that " a few specimens only were to be caught,"
or that " they were not found."
In the saddle rooms adjoining the stables of the Royal Artillery, adult
anopheles were particularly easy of detection, since they were found resting on the
inner surface of the hanging saddles. On the 19th July 1903 search in these
rooms did not reveal a single adult. On the 8th September 1903 A. Rossii were
abundant. On the 27th September 1903 A. Rossii were swarming, A. culicifacies
were fairly abundant, and specimens of A. fuliginosus and A. pulcherrimus were
not uncommon. In the bazaars in the area exactly the same conditions occurred.
On the 17th July 1903 no adults were seen after a long search in the Royal
Artillery bazaar. On the 5th September 1903 A. Rossii was abundant and
A. culicifacies was readily caught. Occasional specimens of A. fuliginosus
and A. pulcherrimus were also found.
Whether A. culicifacies was diminished in September in the bazaars and
saddle rooms it is very difficult to say for the reasons noted above. With regard
to A. Rossii, however, it is quite certain that no perceptible diminution whatever
had occurred.
The outcome of our experiment in regard to the effect of anti-culicidal
measures against anopheles is therefore at direct variance with the results
of such operations as have been hitherto recorded. It is hut fair, however, to
D