NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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PART V.—RELATION OF INSANITARY CONDITIONS TO
THE SPREAD OF PLAGUE.
A.—Influence of insanitary conditions considered without refer-
ence to rat plague upon the spread of the epidemic.
B.—Influence of insanitary conditions upon the spread of rat
plague and upon the transference of infection from rats to man—
(1) The conditions which favour the spread of rat plague over a
city, or through a village.
(2) The conditions which favour the spread of rat plague into
and throughout inhabited buildings.
C.—Incidence of plague on different classes of the community.
When we consider in what manner insanitary conditions might
influence a plague epidemic, it is evident that, accepting as true
the conclusion that the epidemic is wholly dependent upon the
rat epizootic, the problem divides itself into two parts, namely,
(1) the influence of insanitary conditions considered without refer-
ence to rat plague upon the spread of the epidemic, and (2) the
influence of insanitary conditions upon the spread of rat plague and
upon the transference of infection from rats to man. These two
problems have to be kept entirely separate.
A.—INFLUENCE OP INSANITARY CONDITIONS CONSIDERED WITHOUT
REFERENCE TO RAT PLAGUE UPON THE SPREAD OF THE EPI-
DEMIC.
When we consider the manner in which insanitary conditions,
such as defective ventilation, bad lighting, etc., may affect a plague
epidemic, it is evident, in the light of what has gone before, that
we have to consider only the possible effect of such conditions
in lowering the resistance to infection of persons who are exposed
to them. It cannot be denied that insanitary conditions may exert
such an influence. On the other hand, there can be no doubt that
plague is a disease which most frequently attacks men and women
in full vigour of the prime of life. Leaving, however, a priori
reasoning behind, the Commission examined, as far as was possible,
the question during the epidemic of 1906 in Bombay. They used
chiefly the statistical method and the results were as follow :—
(1) Personal experience of native houses in Bombay leads \ill\
the belief that the ventilation of these houses is not on the whole
70
defective. Moreover, from experience of the ventilation of houses
in which plague cases occurred and from statistical data based on
observations of the state of ventilation of a large number of plague
houses, the Commission were led to form the conclusion that no
relation exists between the incidence of plague in these houses and
their ventilation.
(2) Similar evidence relating to the conditions as regards
lighting, which are found to obtain in plague houses, led also to
the conclusion that no relation exists between such conditions and
the incidence of plague in these houses.
(3) It is certain that in many of the sections of Bombay dense
overcrowding of the population exists. The evidence obtained
bearing upon the relation of this overcrowding to the incidence of
plague was of two kinds—
First, statistical data relating to three criteria of overcrowding
were compiled, namely—
(a) the number of inhabitants per acre ;
(6) the number of inhabited buildings per acre ;
(c) the average number of inhabitants per occupied build-
ing.
These data were compared graphically with the incidence of
plague per mille of the population for each section.
Secondly, an analysis was made of data relating to the amount
of space available for each occupant in over 4,000 houses in which
plague cases occurred.
Consideration of the whole of the evidence led the Com-
mission to the conclusion that, although the incidence of plague
was highest in the most crowded tenements, it was apparently
unaffected, so far as the City of Bombay is concerned, by the
density of population in the different sections of the City, the
smallest areas regarding which figures could be obtained.
(4) It cannot be denied that the system of the disposal of night
soil and sullage water, that is to say, the system of open drains
or gullies between the buildings, which prevails in the native
city of Bombay, is a highly insanitary one. Nevertheless, if
the rat epizootics are excluded, the Commission were unable to
discover any definite relation connecting this state of affairs
with the spread of epidemic plague. In confirmation of this view
71
the case of the outlying villages in the island, which possess no
such system and which nevertheless are liable to severe
epidemic outbreaks, may be cited. Again, in Bombay itself
severe attacks may occur in buildings provided with an excellent
water carriage system.
In short, the Commission felt justified in coming to the
conclusion that the insanitary conditions which exist in Bombay
have no influence which acts directly on the spread of epidemic
plague.
In support of this conclusion attention can be drawn to a severe
epidemic which occurred in a number of new chawls recently built
by the Improvement Trust, buildings which in respect of their
sanitary arrangements could not be improved upon. Reference
will be made to this outbreak later on. It is, of course, also true
that during the epidemic many buildings in the City in a highly
insanitary state escaped infection altogether.
B.—INFLUENCE OF INSANITARY CONDITIONS UPON THE SPREAD
OF RAT PLAGUE AND UPON THE TRANSFERENCE OF INFEC-
TION FROM RATS TO MAN.
It will be convenient to consider this part of our subject under
two heads, namely, (1) the conditions which favour the spread
of rat plague through a city such as Bombay and through a
village, e.g., in the Punjab ; and (2) the conditions which favour the
spread of rat plague into and throughout inhabited buildings.
1. The conditions which favour the spread of rat plague through a
city e.g., Bombay, or through a village, e.g., in the Punjab.
In Bombay we have seen that the spread of epidemic plague
through the City is directly due to plague in Mus decumanus. It
follows, therefore, that the conditions which favour this species of
rat will be the conditions which favour the spread of the epidemic
through the city. We have already drawn attention to the habits
of M. decumanus, so that all that is now necessary is to mention
briefly those conditions obtaining in an oriental city like Bombay
which are favourable to its existence.
In the first place, the structure of the buildings is for the most
part of the flimsiest description. The foundations are not by any
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means rat proof and as a rule there are no solid masonry plinths.
The buildings in consequence are easily infested by Mus decu-
manus.
In the second place, separating the buildings from one
another, there is a system of gullies, which are simply open
drains. These gullies communicate freely, on the one hand,
with the ground floors of the buildings and, on the other hand,
with the sewers and storm-water drains. The latter come
into complete function only in the rainy season and, therefore,
during the greater part of the year are practically dry, and
must then offer excellent shelter for rats with habits like M. decu-
manus.
In the third place, scattered throughout the City there are
innumerable stables and store houses or godowns of all descriptions,
situated either in detached buildings or more often on the
ground floors of inhabited buildings. These afford excellent
shelter for rats.
Finally, the food supply for rats is abundant. The stables
and godowns themselves contain a good food supply, and into
the gullies, court-yards and lanes the inhabitants throw all the
remains of their food, the sweepings of the rooms and other garbage.
It is, moreover, a common custom to tether goats, sheep and
cattle in the court-yards, lanes and entrances to the houses. A
special corps of municipal servants, the sweepers, is entertained
to keep the streets and gullies clean, but even with their best
endeavours this is an almost impossible task.
To sum up then, the flimsy structure of the houses and the lack
of solid plinths, the system of gullies and drains in general, the
stables and godowns so common throughout the city in close con-
nection with the human habitations, the abundant food supply,
all play their parts in attracting and fostering M. decumanus.
These conditions, therefore, have an indirect influence on the diffu-
sion of plague throughout the city.
As regards the Punjab villages we have already seen that the
case is simplified on account of the absence of M. decumanus. We
have seen also that the chief factors which favour M. rattus are, the
configuration of the villages, the close aggregation of the houses,
the mud walls and floors easily permeable by rats and the abun-
73
dant food supply present in the court-yards and the houses them-
selves. These are the conditions, therefore, which favour the
diffusion of plague throughout the villages.
2. The conditions which favour the spread of rat plague into and
throughout inhabited buildings.
We have already come to the conclusion that the rattus epizootic
in Bombay is directly attributable to the decumanus epizootic.
Now M. rattus is, as we have seen, essentially a house rat and to
plague in this species the whole or by far the greater part of the
house infection is due. It follows, therefore, that those conditions
which favour the coming together and meeting of M. decumanus
and M. rattus will be the conditions which are responsible for the
spread of plague into buildings, while those conditions which favour
the existence of M. rattus in the buildings will be responsible for
the diffusion of the disease throughout the buildings.
As regards the first point, namely, the conditions which favour
the coming together and meeting of the two species, we have
already pointed out that M. rattus and M. decumanus in Bombay
are closely associated with each other in gullies, on the lower floors
of houses and in godowns, which localities appear to be their common
meeting ground. It is evident, therefore, that the gully system
of drainage, the unsubstantial character of the foundations and
plinths of buildings, which render the latter easy of access by
rats, the presence of godowns, stables, etc., on the ground floors of
buildings, are the conditions which are mainly responsible for
the spread of plague into the buildings.
In the case of the Punjab villages the same conditions, which
we have seen favour the diffusion of the epizootic through the
village, namely, the close aggregation of the houses, their mud
walls and floors, etc., favour its entrance into the houses. .
Passing on to the second question, namely, the diffusion of the
epizootic throughout the buildings, we find present in all Indian
houses conditions which are eminently favourable for the exis-
tence of Mus rattus.
The structure of the houses does much to favour this species.
The flimsy walls and floors, the mud walls of the Punjab village
house, the country-tiled roof, the general condition of disrepair,
all offer attraction and afford good shelter to Mus rattus. But
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as important, if not more so, are the conditions which depend
upon the habits and customs of the people themselves.
In the first place, the natives of India are universally
indifferent to the presence of rats in their houses and in some
instances go so far as to protect them from molestation.
In the second place, the people are in the habit of filling their
houses with all kinds of useless articles and accumulations of
rubbish. Small lofts are improvised with planks or bamboos,
and in these lofts are stored all kinds of odds and ends, such as,
earthenware and brass jars, pieces of matting, firewood, old clothes,
etc. In the interior of the houses, therefore, there are
splendid shelters and breeding places for the house rat.
In the third place, the food supply is abundant. The supplies
of raw material, grain, seeds, ghee, etc., are stored in wooden chests,
earthenware pots, etc. (in the case of the Punjab houses there are
special grain receptacles), all of which are easily accessible to rats.
The food is cooked and eaten in the room off plantain leaves or
brass platters placed on the floor, neither tables nor chairs being
used.
As an illustration of the influence of the habits of the people
and the conditions resulting therefrom on the spread of plague
inside buildings, we may with advantage instance the case of the
Improvement Trust chawls, to which passing reference has already
been made. These chawls, 16 in number, were built recently
by the Bombay City Improvement Trust and, in fact, some of them
had only just been occupied before the plague epidemic of 1906
began. The walls are solidly built of brick and are supported
on high, solid, masonry plinths. The floors are of concrete or
patent stone and the roofs of flat Mangalore tiles. The verandahs
and corridors are also paved with concrete and are wide and airy,
the lighting and ventilation of the whole building leaving nothing
to be desired. There are no gullies, and excellent water closets
are provided. In short, the buildings in themselves offer no
shelter to rats. In spite of this M. rattus is common in the houses.
It is further certain that the rat infestation of the buildings is
entirely due to the habits of the people in the matter of the dis-
posal of their household belongings and food stores as described
above. In the plague season of 1906 these chawls were so badly
infected, that the people had to evacuate and live in huts made of
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bamboos and matting built on an adjoining piece of vacant ground.
They have a population of about 4,000 and no fewer than 57
cases of plague occurred amongst the inhabitants. It may be add-
ed that at the time of the epidemic in the chawls there was a
considerable mortality amongst the rats, several of which on
examination were proved to be plague infected.
C.—INCIDENCE OF PLAGUE ON DIFFERENT CLASSES OF THE
COMMUNITY.
It has been the general experience in India of all plague
workers that the incidence of the disease is not so great amongst
the well-to-do classes as amongst the poorer population.
Europeans are practically exempt. The Commission's experience
bears this out, and certain statistical data which they
collected are in harmony with it. The explanation is not
far to seek. The description of the houses and habits of the
people which we have given above apply only to the poorer
classes. As the people rise in the social scale, their houses
are of better structure and, more important still, their mode of
living becomes more like that of Europeans. The compounds
of the houses are kept clean and the household rubbish which
accumulates is relegated to a godown. There is, therefore,
little or no shelter or attraction for rats. Further, the people
themselves, like Europeans, show much aversion to live in
association with rats. It can, therefore, be readily under-
stood that the houses of the well-to-do Indians in a city such
as Bombay, as well as the houses of the Europeans, do not harbour
anything like the number of rats which are to be found in the
houses of the poor population. It would appear, in consequence,
that the explanation of the fact that the incidence of plague is
much greater on the poor population than on the well-to-do Indian
and European is ultimately to be found in the different conditions
in which they live and in their different habits.
77
PART VI.—THE RECURRENCE OF PLAGUE IN HOUSES
IN SUCCESSIVE EPIDEMICS.
It has often been alleged that infection may persist in a house
or in a locality apart from rats and that plague tends to recur in
certain houses in successive epidemics. It has generally been
assumed that the plague bacillus is able to live for long periods
in soil, and that infection may lie latent there until the next
plague season, when it breaks out afresh in a virulent form.
Associated with this assumption is the idea that the conditions in
certain houses are especially favourable for the persistence
of infection, so that the inhabitants of these houses are attacked
by plague year after year.
The evidence obtained by the Commission is quite against
this view.
In the first place, all experiments show that the plague bacillus
very soon dies in soil; it seems to have no existence in nature
outside an animal body.
In the second place, a number of houses in Bombay which were
plague infected during the epidemic of 1906 were experimentally
investigated at regular intervals during the period of one year, but
no evidence of the persistence of infection in any of them was ob-
tained nor did plague occur in them during the subsequent season.
In the third place, the question was investigated by the stat-
istical method, both in the Punjab villages and in Bombay City.
The results obtained in the former are worth detailing.
An attempt was made to determine whether houses in Dhund
and Kasel which were infected in one epidemic were especially
liable to be again infected in any subsequent epidemic. All parti-
culars of the incidence of plague in houses during previous epidemics
were ascertained and lists of the houses in which plague cases had
occurred were prepared for each epidemic. Table 1 shows the total
number of occupied houses and the number of houses infected in
each epidemic, for both Dhund and Kasel. Table 2 shows the
actual number of houses which were infected in one epidemic only,
in any two, in any three and in all four epidemics ; while Table 3
gives the figures, which have been calculated from the data in
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Table 1, showing the probable number of houses which would have
been infected in 1, 2, 3 and 4 epidemics, on the assumption that the
houses were equally liable to infection throughout all four epi-
demics.
The close correspondence between the actual and calculated
figures suggests that the assumption on which the latter figures
were worked out is a legitimate assumption or, in other words, that
plague showed no tendency to recur in houses during successive epi-
demics.
Similar results were obtained in Bombay, so the epidemiological
evidence supports the experimental in showing that infection does
not persist in a house apart from rats and that there is no such
thing as a " plague house," in which the disease is liable to recur
in successive epidemics.
TABLE I
Showing the total number of occupied houses and the number of
houses infected in each epidemic in Dhund and Kasel.
Village.
Dhund .
Kasel
Total No. of
occupied
houses.
418
806
NO. OF HOUSES INFECTED.
In first
epidemic.
101
308
In second
epidemic.
198
252
In third
epidemic.
40
230
In fourth
epidemic.
26
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TABLE II
Showing the actual number of houses in Dhund and Kasel, which were
infected in 1, 2, 3 and 4 epidemics.
NO. OP HOUSES INFECTED.
Village.
Dhund
Kasel
In onepide-
mic only.
208
383
In any two
epidemics.
65
169
In any three
epidemics.
9
43
In all four
epidemics.
0
2
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TABLE III
Showing the probable number of houses which would have been
infected in 1, 2, 3 and 4 epidemics, if all houses were equally
liable to infection throughout; all epidemics calculated from
Table I.
Village.
Dhund
....
Kasel
....
No. OF HOUSES INFECTED .
In one epi-
demic only.
201
393
In any two
epidemics.
73
162
In any three
epidemics.
8
40
In all four
epidemics.
0 3
2
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PART VII.—THE IMPORTATION OF INFECTION FROM
AN INFECTED TO AN UNINFECTED LOCALITY.
A.—Conveyance of infection by rats.
B.—Conveyance of infection by infected rat fleas.
Having excluded all probable modes of spread of infection
of plague other than the rat and the rat-flea, we are led to the
conclusion that the importation of the disease into an uninfected
locality must be attributable solely to the conveyance of the
infection in the rat or in the rat-flea.
A.—CONVEYANCE OF INFECTION BY EATS,
As regards this method of importation from place to place
we have already dealt with the subject of migration of rats in
general and have seen that all the evidence pointed to there being
no such thing as a general migration of rats even as a result of a
severe mortality amongst them. While this is so, it cannot be
denied that a plague-infected rat may be conveyed into an unin-
fected locality in merchandise, e.g. in hay, bales of cotton, grain,
etc. The Commission, however, obtained no direct evidence
on this point.
B.—CONVEYANCE OF INFECTION BY RAT-FLEAS.
Consideration of what has gone before will suffice to con-
vince the reader, that transportation of the plague bacillus in the
body of the rat-flea is not only conceivable, but under certain
circumstances a very likely contingency. Thus, it is conceivable
that infected rat-fleas might be imported from an infected to an
uninfected locality by one or other of the following means :—
(1) On the host, namely, rats, carried in merchandise, etc.
(2) In merchandise, grain, etc., the host not being transferred
with the fleas.
(3) On the person or clothing of a man, who has been in
a plague-infected house, the man himself being either
plague stricken or healthy.
(4) In bundles of clothing, bedding, etc., removed from a
plague-infected house.
19 S. C.
82
As there is no direct evidence bearing on the first two pos-
sibilities, nothing further need be said about them.
As regards the importation of infected rat-fleas by the direct
agency of man, on his person, amongst his clothing, etc., or by
bedding and such like articles coming from a plague-infected house,
the following observations have a direct bearing—
(a) We have seen that rat-fleas will under certain circum-
stances come on to a man and in some instances will be attracted by
him, but not feed on him for some time.
(b) We have seen that rat-fleas fed on man may remain
alive for two or three weeks ; also, that infected rat-fleas if fed may
remain infective for 15 days. In this connection it is important to
remember that experiments have demonstrated that an animal,
e.g., a guinea-pig, may pick up fleas in a plague house and still not
contract plague, while a second animal to which the fleas are trans-
ferred may develop the disease.
(c) Rat-fleas if starved may remain alive for several days.
(d) During the visits of the Commission to plague houses in
Bombay the members and their assistants often carried away
fleas on their persons and clothing, some of which proved to be rat-
fleas.
(e) Experiments were made with bundles of bedding, cloth-
ing, etc., got from houses in Bombay in which plague cases had
occurred. Rat-fleas were taken on guinea-pigs brought in close
contact with these articles ; one of the guinea-pigs died of plague
with a bubo in the neck, and a rat-flea which was dissected had
abundant plague bacilli in its stomach contents.
In this connection it is to be remembered that a plague-infected
house may contain a very large number of infected rat-fleas.
(f) Histories of the probable importation of plague into an unin-
fected village in the Punjab by human agency are common.
Thus, in a district in the Punjab in which this question
was carefully investigated in 80 per cent. of the infected villages
there was a clear history of probable importation by men coming
from infected localities.
(g) Some observations made by the Commission in the outly-
ing villages of Bombay are worthy of reference in this connection—
(1) In the case of Sion Koliwada village, enquiries showed that
the origin, of the rat epizootic was probably due to the