ITS CONTROL AND SUPPRESSION
PLAGUE PREVENTION.--At present the most promising and the most
rationally based phase of plague control is that of prevention. The
reason for this is plainly apparent. If the facts in the case are as
stated and if the conclusions of the Plague Commissioners and students
of epidemiology the world over are correct, to eradicate plague we need
only to control its carriers.
To exterminate the rat (and perhaps the marmot and ground squirrel), to
prevent the transportation of rats or of infected rat fleas in ships,
trains, clothing, merchandise and upon the bodies of men and animals
from the numerous foci or plague centres of the world to non-infected
localities, is a beautiful plan indeed.
Restricted to single communities, even where the intelligence,
patriotism, effort and wealth of the whole people are enlisted, the
undertaking is formidable, with obstacles to its execution, and
discouragement must often be expected. Extended in its application to
the whole plague-infected world it becomes an undertaking seemingly
impossible of accomplishment.
Yet we are encouraged to face the situation by a glance at what has
been accomplished. The United States, perhaps, presents the highest
examples of achievement in the cases of San Francisco and Manila. The
work in San Francisco is too recent and has been too well published to
require detailed review here. A successful campaign against rats in
1907 practically terminated an epidemic of considerable proportions
well within a year. Behind this movement, however, were the powerful
machinery of the Federal Government, money in generous amount and a
considerably aroused public, resentful of the mismanagement of the 1903
epidemic, whereby, through pure fear of financial loss to commercial
interests and by a disgraceful suppression of the truth, California was
made, permanently perhaps, one of the world's plague centres.
It has been estimated that the rat population of the world is equal to
the human population, and this estimate does not appear to be
unreasonable when one considers as indices the destruction of the
rodents in cities by the hundreds of thousands, upon single farms by
the thousand, and the wonderful procreative powers of the rat.
ECONOMIC IMPORTANCE OF RAT DESTRUCTION.--It is certain that the
economic importance of rat destruction upon grounds other than those
purely sanitary must be impressed upon the public wherever a rat
campaign is to be carried on.
The absolute inutility of the rat, its enormous destructiveness to
crops, to merchandise in warehouses and in transit, to poultry, eggs,
fruits and vegetables, to buildings and furniture, and its incendiary
habits causing annual fire losses of considerable magnitude, must be
emphasized in season and out of season. Such items as the value of the
grain consumed by a single rat per year, as estimated by the experts of
the Agricultural Department, are convincing arguments in the case. At a
daily consumption of two ounces, the ration for a full-grown rat, this
grain value varies from sixty cents per year, for wheat, to two dollars
per year, for oatmeal, for each rat subsisted. Similar data in great
variety, relating to direct and indirect losses, are available for the
purpose of making impressive the economic need for rat destruction.
Accumulated experience from various countries and cities shows plainly
that there is no single method of rat destruction to be depended upon
to the exclusion of all others and it also shows that without
governmental direction and supervision, backed by ample authority and
the ability and willingness to expend considerable money, neither
single nor combined methods will be successful. Moreover in the
countries where special effort is most needed there is often distrust
on the part of the natives, religious prejudice against the destruction
of animal life and frequently open opposition to the authorities in
their efforts to destroy rats. The same superstitions and religious
beliefs which prevent the killing of venomous snakes in India, at the
annual cost of thousands of human lives, operate against most measures
of rat destruction proposed by the Government.
EXTERMINATION METHODS.--The plans and weapons of warfare against rats
include the use of poisons; traps; starvation; rat-proof construction
of buildings, wharves, bakeries, stables, granaries, etc.; the
introduction of diseases among the rat population by bacterial viruses
and the conservation of the natural enemies of the rat, such as the
cat, the dog, the ferret, the mongoose, and certain wild animals and
birds of the woods and fields.
Among the most widely used and most effective poisons is arsenous acid
boiled with rice, or mixed with cheese or cornmeal in the form of a
paste, or placed upon sweets and fruits.
Crude phosphorus is chiefly used in similar pastes. When mixed with
glucose its inflammable properties are said to be lost. Its
inflammability is, of course, a serious obstacle to its general use.
Strychnine, owing to its bitter taste, is of little value in poisoning
rats, and when used is best combined with glucose and one per cent. of
cyanide of potassium. Soaked wheat, bread or similar food is then
treated with this mixture and placed where rats may eat it. It is said
to be eaten readily by ground squirrels with fatal effect. It is,
however, expensive and apt to be taken by domestic fowls. Most rat
poisons have the disadvantage of being dangerous to human life and must
be used with caution wherever children and ignorant native persons are
about.
TRAPPING.--Trapping has been found to be a very effective means of rat
destruction in cities. (See later pages for relative efficiency of
traps.) Rat traps are of several varieties and are constructed upon
various principles. It is sometimes desirable to catch the rats alive
and uninjured, and for this purpose barrel traps, wire cage traps and
similar devices are placed in the rat highways. These highways are
readily discovered in the cities. Considerable care must be taken to
overcome the natural caution of the rat, and this includes judgment in
the use of attractive bait, the concealing and smoking of traps after
handling and perhaps the use of some scent, such as the oil of anise,
of which rats seem to be fond. As a general rule bait should differ
from the food naturally supplied by the locality. For example, about
granaries and stables fresh animal food should be used for bait, while
about slaughter houses, meat-markets, fish-markets and similar places,
where animal offal is abundant, the rat should be tempted with
vegetable bait.
Where the circumstances will permit, and this is apt to be so for
ground-squirrel destruction, the burrows may be filled with some
asphyxiating or poisonous gas. In this manner whole families of
rodents, and their fleas as well, are destroyed.
The system is not often applicable in houses, but aboard ships it is
found most effective, the holds of ships being flooded with sulphur
dioxide, developed by burning sulphur in a special furnace provided
with a pumping and piping system for delivering the gas at distant
parts of the ship. In empty ships' holds and elsewhere the simple
burning of sulphur in open vessels effects the same results, provided
sufficient sulphur and a sufficient number of vessels be used and
further provided that the generation and confining of gas be
sufficiently prolonged. In San Francisco harbor, where for more than a
year nine vessels were disinfected per day, this method was adopted as
more effective, speedy and economical than any other system. It has the
disadvantage, in the case of laden ships, of affording some danger of
fire.
Carbon bisulphide has been extensively used in California in the
burrows of ground squirrels. Its fumes, being heavier than air,
penetrate the burrows and promptly poison or asphyxiate all living
animals and fleas. Absorbent material of some kind is saturated with
the liquid and placed in the entrance of the burrow, which is then
quickly sealed to confine the gas.
It will be seen that, in common with other methods of rat destruction,
fumigation has a limited application and a number of serious
objections. It is particularly useful aboard ships.
The method should never be employed by unskilled persons or those
unacquainted with the dangers to human life from noxious or
asphyxiating gases.
STARVING RATS.--The subjects of the starvation of rats and rat-proof
construction may be considered together.
Just as the pig in the Philippine Islands and elsewhere in the Orient
must give place as a scavenger of human excreta to modern and decent
methods of waste disposal, so must the rat, a garbage scavenger the
world over, give place to systematic garbage collection and removal,
with temporary storage of garbage in covered metal cans (rat proof).
Incidentally it may be mentioned that the effect of such measures upon
the prevalence of flies and the transmission of disease by these
insects will be very great and very beneficial to the public health.
Food must be kept from rats and rats must be kept from the food.
Perhaps the greatest resorts of rats are the places where cattle are
fed, where grain is stored and where animals are killed. Slaughter
houses, markets, grocery stores, restaurants, bakeries, wharves and
warehouses must be regulated by ordinances duly enforced. Much can be
done with screens of heavy iron wire with a mesh of less than one inch.
When concrete and metal have displaced wood and plaster as construction
materials; when plank sidewalks and refuse piles are no more and when
the catch basins of sewers have been made rat-proof the subsistence
problem for the rat will be greatly increased in difficulty, and
starvation should then begin to lessen the rat population, at least in
the cities.
RAT-PROOFING.--Municipal authorities should take up the matter of
rat-proof construction for new buildings and the rat-proofing of old
ones by approved alterations. In Manila, Hong Kong and elsewhere these
methods are receiving attention and encouraging reports are recorded,
more particularly with regard to the disappearance of plague in
districts so treated than in the disappearance of rats. This is most
important, for if the rat and his fleas are excluded from houses and
therefore from intimate association with man (an apparently feasible
matter through the rat-proof construction of buildings), protection
against human plague is in great measure accomplished.
[Illustration: RAT PROOF STRUCTURE WITH SOLID CEMENT BASE, SOLID
CONCRETE POSTS, AND UNBOARDED CEILING]
In Manila the disappearance and continued absence of human plague in
previously infected localities goes hand in hand with the introduction
of systematic rat-proofing in sections where cases of human plague
occur.
These measures were first instituted in 1906 and plague disappeared
from Manila in the same year and did not reappear until 1912.
From 1900 to 1905, $15,000 was paid in rat bounties and $325,000 was
paid for salaries, wages and expenses in rat catching, with little
appreciable effect upon the number of rats and without causing the
plague to entirely disappear. It must be admitted, however, that
practical control of the disease was attained during this period.
Rat-proofing of dwelling houses is less expensive than perpetual
wholesale rat destruction and is a perfectly effective measure against
human plague. In the suppression of the San Francisco epidemic in 1907
rat-proofing was also extensively resorted to.
The expense of rat-proofing has been generally considered as
prohibitive, but if the work be confined at first to the vicinity of
infected centres and if it be carried on subsequent to rat-destruction
in corresponding areas the expense need not always be prohibitive--at
least in American governed cities. The Manila plan of plotting the city
into "plague-infected" areas corresponding with the capture of
plague-diseased rats and systematically working within geographic
boundaries in which rat plague exists or is likely to spread, as
determined by rat captures and examinations of the rats for signs of
plague, has proved to be a good plan.
To prevent the transportation of rats in ships, trains and merchandise
is an undertaking of difficulty as well as of importance. In the case
of vessels it involves an understanding of the manner by which rats
gain ingress to the ship and the ways of preventing them from entering.
Few facts are better known, perhaps, than the fact that all ships
harbor rats, but, except to the initiated, the extent to which some
ships are infested is by no means understood. I have made voyages upon
steamships, which upon alternate trips carried forage for animals in
the holds, when the conditions were, to say the least, uncomfortable.
To have one's state-room taken possession of by rats, his clothing
carried away, or to awake with a rat in his berth are unpleasant, but
not uncommon, experiences. I personally know of a woman, prostrated
with sea-sickness, who was obliged to remain in her berth and see four
large rats disport themselves about her room, and in another case, on
the same ship, a rat jumped from the washstand into the berth of a
sleeping woman, running across her exposed face and arm.
In travelling upon small dirty steamers in the Orient I have often
slept on deck, quite as much to avoid the rats and vermin in the
state-rooms as for better ventilation. In a certain ship in which I
travelled some of the ship's officers amused themselves by shooting
rats with an air-rifle in the lower decks, quietly hiding themselves in
dimly-lighted places and shooting the rats as they crossed the lighter
spaces.
In many ships the rat population far exceeds the human population. In
San Francisco 310 rats were destroyed by a single fumigation on a
vessel of only 260 tons burden. In Bombay 1300 rats were destroyed at
one time upon a single ship and in London 1700 were secured at one
fumigation.
The ease with which rats adapt themselves to new environment is shown
by the fact that they live, when permitted to do so, in cold storage
and refrigerating rooms where they grow heavy coats of fur for
protection against the cold.
They gain ingress to ships in three principal ways: (1) By coming
overside upon gang-planks, wharf stringers, etc. (2) By passing along
the lines by which the ship is made fast to the dock, through hawse
holes, the rat being an expert rope walker. (3) By coming aboard in the
cargo.
By the latter method rats are often brought aboard by whole families,
their fleas included. Many styles of packages such as barrels, bales,
crated goods, grain in sacks and matting in rolls present the rat with
abundant opportunity to take passage and it is probably thus, as
stowaways, that rats go to sea in the largest number. Plainly, then,
the placing of rat-funnels upon all lines from ship to wharf, the use
of special fenders, the raising of gang-planks and even anchorage in
the stream will not prevent rats from getting aboard ships unless cargo
disinfection be practised before loading the vessel. The ship itself
should be fumigated every three months if possible.
Rats are doubtless carried in considerable numbers upon railway cars,
both freight and passenger.
While riding in a street car in Manila in 1908 I saw a rat run along
the window ledge, to the mingled fright and amusement of the
passengers.
The same principles which apply in the case of ships apply to cars and
trains as well. Grain cars in particular should receive especial
attention.
RAT DESTRUCTION BY THE SPREAD OF RAT DISEASES.--The proposal to destroy
rats by wholesale, by spreading epizoötic diseases among them, through
feeding them bacterial virus, has received much attention in the last
ten years. In 1900 Danysz isolated a bacillus from field mice suffering
an epidemic disease communicable to rats, and great hopes were
entertained that by means of this method decided reductions in the rat
population would result. Indeed the results in Cape Town, South Africa,
in 1901, and in Odessa, Russia, in 1902, seemed to justify the hope to
some extent and certain observers still believe the method to be
effective. Experience with the Danysz and other organisms has shown,
however, that introduced epidemic diseases do not destroy rats in
sufficient number to do much good and that nearly all the viruses
experimented with are more or less unreliable.
Most of the organisms are apparently related to the colon, typhoid or
hog-cholera groups. The mouse-typhoid bacillus (_B. typhi murium_) was
originally isolated by Loeffler in 1899. The paratyphoid bacillus and
Gärtner's _B. enteritidis_ correspond closely with the Danysz organism
and can scarcely be separated culturally. In rodents they produce
enteritis, sometimes hemorrhagic in character, and they are by no means
to be regarded as harmless for man, as originally supposed. In Japan,
in particular, serious and fatal cases of diarrhœal disease have
followed the accidental eating by man of food treated by these
bacterial poisons.
On account of the natural resistance of rats to diseases of bacterial
causation (plague being the most notable exception to this rule), and
the clinical fact that no sufficient death rate among rodents is
produced by feeding them upon bacterial viruses, as well as on account
of the dangers to man just mentioned, this method of rat destruction is
not in favor at present.
Poisoning rats and ground squirrels by chemical poisons seems to be a
preferable method, at least equally effective and without most of the
disadvantages of uncertainty and danger which attach to the bacterial
viruses.
RAT DESTRUCTION BY DOMESTIC ANIMALS.--Concerning the utility of such
domestic animals as are natural enemies of the rat, in the warfare
against the offending rodents, there is considerable difference of
opinion, based upon varying experiences. I leave out of consideration
all but the cat and dog.
It will be found that wherever cats and dogs are well housed (indoors)
and well fed they are apt to be fat, lazy and inefficient. House cats
of this class will catch mice but will often leave rats alone, but
half-wild cats, obliged to forage for their own subsistence, are often
excellent rat-catchers. Small, active dogs, particularly of the terrier
breeds, will often keep houses practically free from rats and upon
farms they are especially valuable, particularly if the construction of
buildings is such as to permit them to get beneath the floors. The
employment of these animals will necessarily be confined to individuals
for the freeing of individual premises from rats.
A fact to be borne in mind is one already cited, viz.: that cats and
dogs sometimes harbor the same fleas as the rat. Infected rat-fleas
often leave dead rats for other animals and, all things considered,
there are many other objections to the intimate house dog and house cat
which find comfortable resting places impartially upon the beds of
adults or the cribs of babies and children.
Furthermore, my personal observations have been such as to cause
me to place small reliance in the value of the ordinary dogs and
cats found about habitations wherein the construction is favorable
to rat-harboring.
SUMMARY OF PREVENTION FOR THE COMMUNITY.--Before passing to the
consideration of other matters I would sum up the measures of
preventive treatment for the community. There must be (1) Active
warfare against rats and other plague-affected rodents and their fleas;
(2) Modified quarantine--detention or disinfection applied to persons,
goods and animals; (3) Disinfection of cargoes shipped from infected
ports; (4) Isolation of the sick and proper disposal of the dead; (5)
International notification between governments of the occurrence of
plague within their respective territories; (6) Lastly,--but we might
say first in importance,--the early recognition of the presence of
plague and the _rapid diagnosis_ in individual cases, both of which are
dependent upon laboratory workers.
All of these measures must be fostered, directed and aided in every
possible way by competent authority (national if possible), whose
officers must be men of great moral courage and of unselfish purpose.
Behind all of this must be generous financial support.
I can best emphasize the importance of the observance of the principles
I have laid down by introducing personal experiences in the conduct of
the antiplague campaign in Manila during 1912, 1913 and 1914.
I therefore present here the following account of the epidemic, the
campaign of suppression and the various lessons learned.
It should not be difficult for the reader to make applications of the
principles already set forth and to confirm by the reported facts the
assertion that methods based upon these principles are effective.
If repetitions of any of the foregoing principles occur it is hoped
that, when taken in connection with concrete applications cited, they
will not appear as redundant.
THE MANILA EPIDEMIC OF 1912 TO 1914.--The chronologic facts concerning
the development and extension of plague in Manila in 1912, 1913 and
1914 are as follows:
The disease made its reappearance in Manila, after an absence of six
years for the human disease and five years for rodent plague, two
verified human cases having been recorded in June, 1912.
Preceding the appearance of the first Manila cases there occurred upon
incoming ships a number of cases of plague during the Spring of 1912,
detected at quarantine. Although there is no conclusive evidence which
connects these imported cases, originating in Hong Kong, China, with
the epidemic which broke out in Manila a few months later, the fact of
their occurrence and recognition is interesting enough for us to
consider before taking up the study of the Manila epidemic. Concerning
these imported cases Dr. Victor G. Heiser, then Director of Health for
the Philippines, wrote as follows in the _Philippine Journal of
Science_, in February, 1914.
UNUSUAL CHARACTER OF PLAGUE AT QUARANTINE.--It is perhaps
worthy of note that, prior to the appearance of plague in
Manila a number of cases of the disease were found on incoming
steamers. For instance, on April 6, 1912, a death was reported
on the steamship _Zafiro_, which had arrived the day previous
from Hongkong and had been in the harbor for twenty-four hours
at the time of the death. At the medical inspection of the
vessel, which was made the day previous, no illness was
detected. An investigation showed that the victim had been on
deck on the night of April 5, 1912, in apparently good health.
The next morning, at 6 o'clock, he was found dead in his
bunk. The necropsy and subsequent biological findings
reported by Dr. R. P. Strong of the Bureau of Science showed
that death was due to pneumonic plague.
On April 7, 1912, the steamer _Loongsang_ arrived in Manila
from Hongkong, and the captain reported that a death had
occurred the day previous in a Chinese member of the crew.
Upon investigation of this case, the captain stated that the
man was apparently in good health, but that while hauling on
a rope he fell over in an apparent faint and was placed in a
chair and in the course of a few hours expired. The necropsy
and animal inoculations showed that he had died of plague and
probably of the pneumonic variety.
Beginning April 7, 1912, the temperature of all members of
the crew and of the passengers that arrived in vessels from
foreign ports was taken with a view to detecting any possible
cases of plague.
On the arrival of the steamship _Taisang_ from Amoy at the
Mariveles Quarantine Station at about 6.30 A.M. on April 30,
1912, the entire personnel was carefully examined and found
free from sickness of a suspicious nature and from elevations
of temperature. Seventy-three persons were detained to serve
a quarantine detention of seven days. On the evening of April
30, a Chinese passenger, aged fifty-one years, was found to
have a temperature of 39° C. with a pulse of 100. He was
placed in the hospital, but protested vehemently that he was
not sick. He was carefully watched from the first; there was
a slight cough; physical examination of the chest revealed a
few râles; smears made of the sputum and stained for plague
bacilli were negative. On the fifth day, the fever still
persisted, but the patient stated that he did not feel ill
and demanded to be released from the hospital. On this day,
the expectoration was blood-stained, but no suspicious
organisms could be found in the smears nor could any physical
signs of pneumonia be detected. Furthermore, there were no
palpable glands. On the morning of the seventh day, the
temperature and pulse dropped and the general condition was
distinctly worse. The patient now admitted that he felt ill.
Several hours later, he flinched when pressure was made in
the right axilla. Lymphatic enlargement was now made out, and
by the evening of the seventh day the bubo in the axilla had
increased markedly in size, the swelling approximating 3 by 7
centimetres. Glands now became palpable in other portions of
the body, particularly in the cervical region, and a few
hours later there were inguinal and femoral buboes. The
patient became rapidly worse, and died at 7 o'clock on the
morning of the eighth day of his illness. At the necropsy,
the glands of the right axilla and those of the right side of
the neck were found enlarged; the other lymphatic glands were
also enlarged, but to a lesser degree. There was
consolidation of the lower lobe of the right lung, and the
spleen was about twice its normal size. In brief, the
necropsy findings of a typical case of septicæmic plague were
present. Smears from the spleen and the right axillary gland
showed immense numbers of bipolar-staining organisms.
Cultures made from fresh pieces of tissues and later
inoculated into animals gave positive results for plague.
BEGINNING OF THE MANILA EPIDEMIC.--Proceeding with the Manila epidemic
inaugurated with the two cases referred to as recorded in June, 1912,
we find that the total number of cases recorded from the time of the
outbreak in 1912 until the last case in 1914 was 90. (This includes
none of the imported cases from China which developed en route to
Manila from Chinese ports.)
Of these 90 human cases, 76 were fatal and autopsies were performed in
all instances. Fourteen persons recovered. The number of cases of
animal plague up to July, 1914, was 53. This refers only to
laboratory-proven cases of rat plague. As a matter of fact, hundreds of
dead rats, almost certainly plague rats, were found in the course of
rat-proofing operations.
Although the period covered by this epidemic approximates two years, it
must not be supposed that the progress and extension of the epidemic
was an uninterrupted or unobstructed one.
On the contrary, such extension as occurred was made in spite of the
most active suppressive effort, and it is believed that this effort
brought about a creditable result, as indicated by the accompanying
record.
When one considers the favorable conditions for the natural spread of
plague, both in Manila and throughout the Philippine Islands, and
realizes the interposed difficulties and obstructions, natural and
unnatural, geographic, human and domestic, which confront us at every
turn of the path to correction, removal and reformation, our success in
checking the spread of plague appears as a real achievement, especially
when contrasted with the results of effort during the same period in a
British city of similar size but a few days' sail from Manila, where
the cases were numbered by thousands and where the infection still
persists.
FIRST MANILA CASES.--The first case of plague (June 12, 1912) occurred
in a resident of Tondo, 920 Calle Antonio Rivera, and in the light of
subsequent developments it may perhaps be grouped with the October
cases traced to the Manila Railway Company's freight station and yard,
as 920 Calle Antonio Rivera is but a stone's throw from the Manila
Railway property. The connection, however, is not clear, and, on the
other hand, it is not wholly inconceivable that the rat epidemic and
human plague cases at the railway station in October may have been
secondary to this June case. Such speculation is fruitless, however, so
far as establishing facts is concerned.
The second case of human plague occurred 13 days later, June 25, in a
resident of a district somewhat removed from the first case, but in
the same general section of the city.
Then came a lull of more than a month, until August 4, during which
time no case of plague occurred; or at least none was reported.
August brought forth five cases on the fourth, eighth, fifteenth, and
twenty-first days of the month, in residents of the Quiapo and Binondo
districts.
These cases were unrelated to the preceding ones so far as could be
ascertained.
Another lull of a month, until September 24, now occurred without a
reported case of human plague. During this time, however, the first
cases of rat plague were discovered, one on August 30 and two on
September 6, all of them in the Quiapo district.
From this time (September 24) on, however, human cases occurred at
intervals of a few days until Christmas Day, 1912, the longest
plague-free period being one week; the number of cases by calendar
months being distributed as follows: September, 3 cases; October, 22
cases; November, 12 cases; and December, 6 cases.
GEOGRAPHIC GROUPING.--Not until October 21 was there any apparent
geographic grouping of cases indicating a well localized infected
centre. Upon this date there began the outbreak of plague among the
employees of the Manila Railway Company, laborers at the freight
station and yard of the company. This freight station and yard is
located between Calle Azcarraga, Calle Dagupan and Calle Antonio
Rivera. The outbreak totalled 17 human cases, all fatal, and extended
into November. Indeed, the last case traced to this focus occurred on
December 7, 1912.
During the present epidemic of plague in Manila this focus was the only
one to which a larger number of cases than five could be traced, and in
all the other instances where multiple cases were traced to an infected
centre, the foci were all single buildings.
The locations giving rise to multiple infections and the number of
cases of plague developing at each address, with months of incidence,
are as follows: Calle San Fernando (804-814), November, 1912, 4 cases;
Calle Teodoro Alonzo (518), November and December, 1912, 2 cases; Calle
Cabildo (Intramuros), November and December, 1912, 2 cases; Calle
Comercio (1028), February, 1913, 2 cases; Calle Sande (1364), April,
1913, 5 cases; Calle Juan Luna (1226), May, 1913, 2 cases.
Returning to the Manila Railway outbreak, it is necessary to state
that a well-defined epidemic among rats preceded this outbreak,
resulting in the death of a large number of rodents (undoubtedly from
rat plague). This epidemic was not reported by the railroad company
until the outbreak of human plague had begun. It was then too late to
identify plague in the dead and mummified rats found under floors,
platforms and elsewhere, but the fact that large numbers of rats had
recently died here was established by the unanimous testimony of the
employees at the freight station and the finding of rat cadavers.
As stated, the human outbreak here occurred upon October 21, and
fifteen cases developed within 3 days.
This indicates an extensive desertion of fleas from plague rat cadavers
and an attack upon human beings, after a fasting period, on the part of
the fleas, of several days. The human outbreak at the station and the
death of a large number of rats at the same place, just previous,
correspond to a nicety and establish to a moral certainty the
connection necessary to explain the epidemic.
After the railway epidemic of human plague, cases continued to occur
through November and December, without apparent relation to each other,
except in the following instances, which have already been mentioned:
Four cases under one roof on Calle San Fernando (November 12, 13, 16
and 22); 2 cases in one house on Calle Teodoro Alonzo (November 26 and
December 2); and 2 cases in the same house on Calle Cabildo
(Intramuros), November 23 and December 11.
These multiple cases will be referred to elsewhere.
The other cases during October, November and December were apparently
sporadic and unrelated, either to the other human cases or to the few
scattering cases of rat plague discovered from time to time. Without
doubt, however, all were actually related to preceding cases of rat
plague, _i.e._, to undiscovered rat cadavers, dead from plague and
deserted by infected fleas.
In the following plague houses (see list of cases) dead rats were
actually found, although the advanced degree of desiccation and
mummification defeated the biologic determination of the cause of
death: 518 Calle Teodoro Alonzo; 973 Calle Azcarraga; 282 Estero de
Binondo.
In other plague houses the recent finding of dead rats was alleged by
the occupants, but rather too indefinitely to record positively.
A study of the maps and lists showing the localities in which cases of
rat plague had been found up to this time (December 26, 1912), in
connection with the location of plague houses, was much less suggestive
than a similar study of the lists and maps covering the cases of 1913.
However, the existence of concurrent rat plague and human plague, in
corresponding sections of Manila, had been well established already by
bacteriologic studies of captured rats, made at the Bureau of Science.
Of nearly equal weight was the observation concerning the two
epidemics, rat and human, at the Railway Station, which I have already
described.
The year 1912 closed, then, with a recorded total of 50 human cases and
7 verified cases of rat plague.
January, 1913, saw but a single case of human plague. This occurred on
January 24, just a month from the last previous case, that of Christmas
Day. During this month no case of rat plague was reported.
In February, 3 human cases occurred and in March, 4 cases were
recorded.
Early in March, 1913, cases of rat plague began to occur in the Tondo
district in a section lying between Manila Bay and the Estero de la
Reina and extending northward from Calle Moriones. This was a new
district for rat plague and as the cases increased in number we were
able to foresee and predict the appearance of human plague in the same
district, which in point of congestion of population, poverty of its
residents and in the matter of dilapidation of its light material
houses and shacks, is about the worst locality in Manila.
From March 22 to September 20, 1913, all the cases of human plague, 11
in number, occurred in the midst of this district. During the same
period 25 cases of rat plague were reported from the same section, and
a glance at a map of this part of Tondo instantly shows the
relationship existing here between rat plague and human plague.
This relationship is additionally emphasized by referring to the
memoranda concerning certain overcrowded houses, in the midst of the
rat plague district, where multiple human cases occurred. (See
memoranda in re 1226 Calle Juan Luna and 1364 Calle Sande.)
[Illustration: CLEANING AND RAT PROOFING IN BASEMENT OF 1226 CALLE JUAN
LUNA IN WHICH TWO CASES OF PLAGUE OCCURRED. RAT CADAVERS FOUND UNDER
BROKEN FLOORS (MANILA PLAGUE CAMPAIGN)]
The human cases in April were 5 in number, all originating in the same
house, and the May cases numbered 4, two of which occurred in the same
house.
It may be explained, in passing, that two cases of human plague,
discovered in Malolos, 25 miles from Manila, on March 23 and March 26,
respectively, were definitely traced to the same house in Manila,
number 12 Calle Aguila, Tondo, both patients having lived in the
basement of this house until within 48 hours of the development of the
disease. These persons were unrelated and were two of a large number of
people who lived in a tenement at this address. Both patients were
detected, while still alive, in Malolos, where they were living in
different and widely separated houses. One of the patients died in
Malolos but the other one was brought to Manila by train and died at
San Lazaro Hospital. Fortunately no infection was transferred to
Malolos by these two persons. In this connection it is interesting to
note that no other cases have been reported from outside of Manila,
except the small outbreak in Iloilo in the southern islands, where the
antiplague work was successfully directed by Dr. Carroll Fox.
Concerning this outbreak, Dr. Heiser, then Director of Health for the
Philippines, writes as follows (_Philippine Journal of Science_,
February, 1914):
PLAGUE IN ILOILO.--In Iloilo, a case suspicious of plague was
reported on July 5, 1912, and this diagnosis was subsequently
confirmed by the laboratory. It occurred in the person of a
Chinaman who was reported to have come from Bais, Oriental
Negros, but later investigation showed that he had been a
resident of Iloilo at least since February, 1912. The next
case was reported August 18, and the last case, September 17,
1912. There was a total of 9 cases. All of the cases were
confined to two houses. During July, August, September, and
October, 1146 rats were caught in the vicinity of the houses
in which the human cases had occurred, along the water front,
and in the places which were regarded as suspicious, but in
not a single instance was an infected rat found.
DIRECTED TO TAKE CHARGE OF PLAGUE SUPPRESSIVE MEASURES.--Upon my
arrival in Manila from the United States, on October 23, 1912, I
received orders from the Director of Health to take charge of all
plague suppressive measures in Manila and I remained in charge of this
work continuously until July 11, 1914.
PLAGUE FIGHTING ORGANIZATION.--The plague fighting organization was
composed of three American Sanitary Inspectors and from ten to fifteen
native Assistant Sanitary Inspectors of the Bureau of Health, rat
catchers and laborers of the Bureau and laborers of the City of Manila
supplied by the Department of Sanitation and Transportation. The
combined force varied in numerical strength from 100 to 150 men and was
usually divided into three parties, distributed in various parts of the
city according to the local indications and needs from time to time.
After the invasion of Tondo by rat plague we made special effort to
rat-proof the light material houses of that section, in the course of
our cleaning operations, by the closure of the open ends of bamboo
timbers with cement and with tin cans, in the manner shown in
photographs herewith. In addition to this, special attention was given
to the repair of broken cement work, and hundreds of Bureau of Health
orders, verbal and written, were issued to owners, at my request, in
the rat plague districts.
The number of houses in which bamboo timbers were closed by cement or
tin exceeded a thousand.
In addition to these means, the very important matter of depopulating
the insanitary basements of the light material houses in squares where
plague has occurred was given attention, with the result that hundreds
of families were moved from these insanitary and dangerous ground-floor
rooms to quarters well above ground and measurably removed from the
rats, which roam over the ground from house to house, foraging for food
under kitchens and in ground-floor storerooms, tiendas and eating
places. The fish packing factories afford them abundant food and a
number of cases of plague have occurred adjacent to these fish-drying
establishments.
RAT-PROOFING AND RAT DESTRUCTION.--While it is frankly admitted that
rats may not be completely exterminated by poisoning and trapping, the
statement, so frequently repeated of late, that destructive measures
really increase their number, is unwarranted and unsustained by facts,
at least in Manila. It seems to be the common practice for disbelievers
in trapping and poisoning to array the methods of rat-proofing and rat
destruction as alternative policies, whereas everyone practically
familiar with the work in such cities as Manila--or even in the United
States--knows that there is often no choice permitted. Rat-proofing is
highly desirable, permanent in its results, and in every respect the
"method of election." On the other hand, it is entirely inapplicable at
certain times and in certain localities where poverty, lack of interest
of property owners, and ofttimes lack of interest and of money on the
part of municipalities, absolutely preclude its immediate application.
It is therefore unfortunate that the statement, that rat poisoning and
trapping are ineffective, either in controlling plague or in reducing
the numbers of rats, is circulated. It may be shown easily, by the
daily records, that within a few weeks after extensive rat poisoning
and trapping (with the breaking up of nests) is pursued in a given
locality, the rat catch drops in the most decided manner.
Individual premises may be practically cleared of rats by continued
intelligent rat catching and poisoning, and while the normal rat
birth-rate may keep pace with the normal rat death-rate it will not
keep pace with the normal death-rate plus the poisoning and trapping
death-rate in any given locality, provided that the poisoning and
trapping, with the destruction of nests, be intelligently and
continuously carried out.
Rat-proofing and rat destruction, then, should not be contrasted as
alternative procedures or policies. Both are valuable and each has a
proper place. In communities non-infected with plague and unexposed to
infection it will probably be found that rat-proofing, carried out in
connection with the repairs of old buildings and the erection of new
ones, will meet the requirements. On the other hand, in cities exposed
to plague infection or already infected, rat destruction is bound to be
necessary for years to come.
In emergency, the removal of people from intimate relationship with
rats (so far as is possible), as practised recently in Tondo district,
Manila, will often have to take the place of rat-proofing; and rat
destruction and expulsion will be found, in the last analysis, to be
the methods upon which success or failure in fighting plague during
epidemic time will depend.
In this connection I quote correspondence which passed between the
Director of Health and myself in 1913.
Upon March 22, 1913, I directed the following letter to the
Director of Health:
SIR: I have the honor to state that Estaban Masibac, aged
twenty-two, laborer, who died at 140 Perla of bubonic plague,
slept upon the ground floor of this house upon a bamboo bed.
All these basement dwellers in this district now infected
with rat plague are in considerable danger.
The roving rats which wander over these ground surfaces from
house to house come into pretty close contact with these
basement dwellers, and it would appear that they visit the
upper stories of the houses rather infrequently, unless food
is stored there. Upon the ground they forage upon the food
dropped there by the residents of the houses.
I would like to have authority to order the vacation of these
basement rooms which are almost invariably unfit for human
habitations.
I look upon this measure as an important one at this
threatening time and believe it should be enforced in every
square or block where plague rats have recently been found.
If this authority is granted it will be used judiciously.
Very respectfully,
[Signed] T. W. JACKSON,
_Medical Inspector in Charge of Plague Suppression_.
Upon March 24 I received the following letter of authorization:
SIR: Confirming my verbal instructions of yesterday I have to
request that, in accordance with the recommendation contained
in your letter of March 22, that on account of the danger of
the spread of plague in the district in which plague has
appeared extensively, the basement dwellers in blocks, or
squares, in which plague has been found, should be ordered to
vacate.
Very respectfully,
[Signed] VICTOR G. HEISER,
_Director of Health_.
Upon November 26, 1912, five dead rats were reported from the U. S.
Army Commissary Warehouses on the Pasig River near the Malecon. They
were found dead by workmen there and were thrown into the river by the
finders and thus, unfortunately, examination for plague was prevented.
Upon November 27, a cat, known to have caught and eaten rats recently
at the same place, was reported to be sick. I took the cat to the
Bureau of Science where she was observed until she died, three days
later.
At autopsy, typical bubonic plague (cervical) was disclosed, and
several guinea-pigs inoculated from the spleen and bubo died from the
same disease. A guinea-pig, inoculated from a swab introduced into the
cat's rectum, also died from plague (see report of Dr. Schöbl).
Four kittens, recently born of this plague cat, were observed for two
weeks but showed no sign of the disease.
Subsequently about 80 rats were caught at these warehouses and in the
vicinity, but none of them showed post-mortem signs of plague. The
Medical Department, U. S. Army, then took up the matter of rat catching
on all military reservations in Manila and in all buildings thereon,
but no more cases of animal plague were discovered.
FLEAS AND THEIR HABITS.--In "Observations Upon the Bionomics of Fleas
Bearing Upon the Epidemiology of Plague in Eastern Java," by N. H.
Swellengrebel, Ph.D., published by the government at Batavia, Dutch
India, in 1913, some interesting facts, developed by study and
experimentation, are presented. Some of these facts have a bearing on
the plague problem in the Philippines, for it should be borne in mind
that certain climatic similarities and racial similarities pertain
commonly to the Javanese and Filipinos and their respective countries.
While we are not prepared at present to make general application of the
Javanese findings to the Philippine Islands, for lack of parallel or
confirmatory studies in the Philippines, we may state some of the
conclusions of the Java workers with propriety, and we may also point
out similarities in the construction of certain Filipino and Javanese
habitations in their relation to rat harboring.
Swellengrebel, in Java, noted the number of fleas per rat, dealing with
_Xenopsylla cheopis_ (the commonest rat flea in Java) almost
exclusively. This flea, it will be remembered, is also the common rat
flea of India, the Philippines, Australia, Italy, Brazil and tropical
countries generally, being variously known as _Lœmopsylla cheopis_,
_Pulex pallidus_, _P. brasiliensis_, _P. philippinensis_, and (in
Italy) _P. murinus_.
It would not be unreasonable, therefore, to expect to find at least
some of his observations applicable to the Philippine Islands.
Swellengrebel failed to find _Ctenocephalus canis_ (dog flea), _C.
felis_ (cat flea) and _Ceratophyllus fasciatas_ (the common rat flea of
the United States and Europe) upon Javanese rats. In attempting to
determine the normal flea census he found that field rats, and field
rats caught indoors, as well, generally carry fewer fleas than house
rats and that the number of fleas per house rat varies in different
districts from .02 per rat to 2.3 or 4 per rat and that this variation
is not invariably constant with the presence or absence of rat plague.
Concerning the question whether or not a high flea census may indicate
rat plague, Swellengrebel offers the reasonable opinion that there is
little doubt that plague in rats increases the number of fleas per rat
above normal and that, consequently, a sudden or marked increase in
the number of fleas per rat, without a known normal cause, indicates
increased rat mortality and probably rat plague.
As to the influence of temperature and humidity on the hatching of
larvæ, he concludes from experimentation that the duration of
development of the egg varies under various hygrometric conditions, the
general rule being, "the lower the humidity the longer the development
period."
As to the influences of temperature and humidity upon the transition of
larva to imago he finds that if humidity diminishes, a smaller number
of larvæ reach the adult stage; and also that a saturated humidity (in
artificial cultures), causing condensation of water in the substratum,
is very fatal to larvæ. He offers the thought that this, perhaps,
explains why only small numbers of fleas are found on field rats which
live in holes in rice fields which are necessarily damp, especially in
the rainy season.
His experiments to determine the duration of life of fasting fleas were
made with laboratory-bred fleas which had never fed on blood and with
fleas which had already sucked blood.
The duration of life was variable, but of those fleas already fed with
blood three-quarters (¾) perished within 10 days and the remainder
lived from ten to twenty days, only one-tenth, however, surviving for
13 days, if moist conditions were maintained. High temperature was
determined to be an unfavorable condition.
If from these findings one should attempt to predicate or predict the
extension of plague in house rats--based on flea prevalence--and this
with relation to climatic conditions, we should be led to the
conclusion that the rainy season, with its greater humidity, would be
quite the most favorable time of year for rat plague extension in
Manila and, upon the contrary, that the hot dry season through its
unfavorable influence upon flea breeding would be the least favorable
season for rat plague in Manila.
The hot months of 1913 did not bear out this reasoning, however, for
during these months rat plague was at its height.
That increased prevalence of human plague has not gone hand in hand
with increased prevalence of rat plague in Manila, may be explained, I
feel sure, by the activity of our efforts to destroy rats and to remove
the people from close relationship with them.
Another factor of possible explanation of the greatest prevalence of
human plague in Manila during the late rainy season of 1912 (October),
is the fact that rats are certainly driven above ground into houses and
therefore into closer relationship with man by heavy rainfall and the
consequent flooding of their subterranean homes.
It appears, therefore, that the seasonal explanation of greater plague
prevalence, rat or human, is susceptible of several interpretations and
I feel sure that in countries like the Philippines seasonal variations
in heat do not suffice to rid the rats of fleas during any months of
the year. If, then, conditions of rainfall serve to drive the rats
above ground and indoors during certain months, it would be reasonable
to expect more human plague from closer relationship of rat and
man,--provided that no special measures were carried out.
Such, however, is not invariably the rule, if statistical studies are
to be taken as evidence, and so we are reminded that generalizations
for countries of different climates and seasons are not wholly
reliable.
Rat breeding, as well as flea breeding, is influenced by climate, but
as the reproductive activity of the rat is most retarded by cold
weather--an unknown condition in the Philippines--and as the climate
of Manila is fairly equable so far as heat and cold are concerned, the
only factor which needs to be considered is that of rainfall. As
already mentioned, rainfall doubtless serves to drive rats above ground
and so, to a certain extent, away from their nests in burrows and
underground.
Their well-known adaptability to changing conditions, however, permits
them to house themselves comfortably above ground when driven out of
these burrows and holes.
JAVAN OBSERVATIONS.--The following conclusions were reached by Dr.
J. J. van Loghem in a report upon "Some Epidemiological Facts
Concerning the Plague in Java" (published by Civil Medical Service in
Netherlands India-Batavia, 1912):
1. In plague-infected villages, as distinguished from
plague-free villages, there exists a considerable mortality
among house rats.
2. Rats in plague houses and plague quarters have repeatedly
died from plague. Fresh plague rats appear more often in the
houses adjoining plague houses than in the houses themselves.
3. The house rat exists even in the immediate vicinity of
man.
4. The ordinary parasite of the house rat is _Xenopsylla
cheopis_, which experimentally is known to choose man as a
host when starving.
5. Fresh plague rats have repeatedly been found to harbor a
great number of fleas.
6. Virulent plague bacilli have been demonstrated in the
stomachs of such fleas.
Concerning the prevention of plague by improving the native dwellings,
the same observer says: "Obviously an increase in the distance between
man and rat becomes an important factor as a means of preventing the
disease."
CONDITIONS OF MANILA HABITATIONS FAVORABLE TO RATS AND PLAGUE.--As
shown by our own experiences in Manila, this end, the separation of
rats and men, is not obtainable by destruction of rats by poison, traps
and rat catchers. Rats dying of plague in their nests furnish the
greatest danger to man. The plague problem, therefore, where rats are
already infected, from the stand-point of direct prophylaxis, is the
problem of dwellings. It was from this stand-point that we attacked the
problem in the Tondo (Manila) campaign in 1913.
MANILA VERIFICATION OF JAVAN OBSERVATIONS.--Having in mind the
experiences of the plague investigators in Java during the recent
epidemics there (1911-1912), we sought, from the time the Manila
outbreak occurred, to verify some of the findings of the Java
investigators, at least with special reference to the nesting of rats
in close proximity to human beings and the consequent exposure of these
persons to the infected fleas which desert the rats dying from plague
in these nests.
Not until rat plague invaded the special district of Tondo, in Manila,
in March, 1913, did the opportunity present itself. Theretofore the
Manila cases had generally appeared in houses of the so-called "hard
material districts," where house construction is entirely unlike that
with which the Java workers dealt. With the invasion of Tondo, however,
the Java and Manila conditions became similar. I quote the descriptions
of Javanese house construction from the report of Dr. J. J. Van Loghem,
"Some epidemiological facts concerning the plague in Java," Batavia,
1912.
THE JAVAN VILLAGE HOUSE.--In substance, he says that the Java village
house, as a general type, is a one-storied structure with its roof
sloping to the front and back, _i.e._, with its ridge parallel with the
front and back aspects of the building. It is not elevated above the
ground by supports or palisades and has no separate floor, the earth
serving as the floor.
The outer frame is of strong bamboo poles and the inner frame is also
constructed of bamboo. These bamboo timbers are perforated at various
points to permit of framing with other pieces of bamboo and for the
entrance of pegs, etc.
The roofs of these houses are often made of tiles, but at times the
familiar thatched roof is seen. In both cases the supports or rafters
are bamboo poles. The principal piece of furniture is the "bale bale,"
or bedstead, usually made of bamboo, except in the houses of the
well-to-do. Small storerooms are often located in the houses, and
stables are sometimes built against them. In many cases the family
provisions are kept in the house and the cattle are housed here as
well.
MANILA LIGHT MATERIAL HOUSES.--If, now, we turn our attention to the
average Tondo (Manila) light material house it will be apparent that
the description given for the Java village house fairly describes the
Tondo house, except that the Philippine house is commonly elevated 2
metres or more above the ground upon bamboo supports (see photographs).
The basement is usually enclosed in a manner similar to the principal
room of the Java house and the basement room may fairly be compared,
structurally and in the matter of its floor, with the one-story Java
house. In the Manila house, however, the floor of the upper room takes
the place of the roof of the Java house and like it is supported by
bamboo timbers.
Here, then, in our enclosed basement story, we have a practical replica
of the one-storied Java house.
Here, also, the principal piece of furniture is often a bamboo bed,
practically identical with the Java "bale bale," if we may judge from
photographs.
In the Java houses the favorite nesting places for rats were found to
be the interiors of horizontal bamboo pieces of the roof, house frame
and bedstead.
The rat usually gains entrance by gnawing through the natural
partitions between the bamboo sections near the outer end of the pole.
Our Manila photographs show both the natural open ends of such timbers
and the rat-gnawed perforations in the partitions.
In Java, rats also nest in the thatched roofs, as they occasionally do
in the Philippines.
NEST MATERIALS.--The materials utilized for nests by rats in Manila
and Java seem to be identical also. Straw, dry leaves and pieces of
cotton are mentioned in the Java reports. The same materials and
additional ones will be found mentioned in our reports upon nests.
[Illustration: BAMBOO HOUSE SUPPORTS NOT SEALED WITH CEMENT. NOTE HOLES
GNAWED IN BAMBOO ENDS. RATS FREQUENTLY MAKE NESTS IN THESE HOLLOW
BAMBOO RAFTERS.]
The presence of food was also noted in the bamboo nests in Java and we
often find articles of food in our Manila nests.
Dr. Korn, P. H. Service, and the writer (T. W. J.) investigated a good
many of these bamboo house-timbers and we not only found such evidences
of rats as food, rat fæces and nest materials, but in one case a rat
was actually driven out of a bamboo nest by introducing a long thin
strip of wood. The evidence of similar conditions then is complete.
We also duplicated the experiences of the Java workers in finding dead
rats inside of the bamboo house timbers in close proximity to patients
sick (or dead) with plague (see memoranda in the case of Esteban
Masabik, of 140 Calle Perla, March 22, 1913).
Very extensive rat destruction and cleaning operations, covering a
large portion of the city of Manila and including all sections where
cases of rat plague or human plague developed, were undertaken and
this work was carried on without interruption for about two (2) years.
City laborers to the number of 60 to 150 were used and the work was
supervised by Sanitary Inspectors Brantigan and Searcy, of the Bureau
of Health. During a part of the time a flying column of 50 men, under
Sanitary Inspector Hunniecutt, was detached from the main party and
employed at placing rat poison.
The total amount of accumulated dirt removed from houses and yards
approximated 5250 tons (for 17 months ending November 1, 1913).
Without doubt this general cleaning campaign and the removal of this
enormous accumulation of dirt and rubbish was of great value as an
antiplague measure.
The rat catch will always be found to depend upon several factors,
viz.: the number of persons employed; the number of traps and portions
of poison placed; the location of the operations and the length of time
a given locality is trapped, poisoned and cleaned. The variety of baits
and poisons will also affect the results.
In addition to these factors certain others are found to operate in
reducing the rat catch, as, for example, weather conditions and the
occurrence of Sundays, holidays and the days just preceding and
following holidays.
Upon rainy days and the days just mentioned the rat catch almost
invariably falls off.
From statistics collected by me in connection with this work, Dr. V. G.
Heiser, then Director of Health for the Philippine Islands, published
the following memorandum in 1914. As it is a correct transcript of my
records I introduce it here in its entirety.
COMPARATIVE STATISTICS IN RAT-CATCHING METHODS.[3]--With a
view to ascertaining which type of rat trap was most effective
and also the average number of rats that are caught by a given
number of poisoned baits that are set out, statistics were
kept during the antirat campaign in Manila. The ratio
maintained in catching rats with two types of traps is
indicated in the following table, a perusal of which will show
that for the three months ended June 30, 1913, there were
120,565 spring or snap traps set and that for every 100 of
this type of trap set there were caught 6.9 rats. During the
same period there were 47,075 wire cage traps set; the total
number of rats caught was 339; which gives 0.72 rat caught for
each hundred traps set. For the quarter ended September 30,
130,627 spring or snap traps were set and 9,753 rats were
caught, which gives 7.47 for each 100 traps set. During this
period 40,621 wire cage traps were set and 395 rats were
caught, which gives 0.97 rat caught for each 100 wire cage
traps set.
[3] Reprint from the Public Health Reports, Vol. 29, No. 6, February
6, 1914.
===================+==========================+=========================
| Quarter ended June 30 | Quarter ended Sept. 30
+---------+---------+------+---------+---------+-----
Kind of trap | | Number | | | Number |
or poison | Number | of rats | Per | Number | of rats | Per
| set |caught or|cent. | set |caught or|cent.
| |poisoned | | |poisoned |
-------------------+---------+---------+------+---------+---------+-----
Spring or snare | | | | | |
traps | 120,565 | 8,377 | 6.9 | 130,627 | 7,753 | 7.47
Wire cage traps | 47,075 | 339 | .72 | 40,621 | 395 | .97
Poison bacon, rice,| | | | | |
or coconuts | 166,237 | 1,216 | .731| 177,309 | 216 | .12
-------------------+---------+---------+------+-----+---+---------+-----
| Quarter ended--
+---------+---------
| June 30 | Sept. 30
----------------------------------------------------+---------+---------
Number of rats: | |
Caught by dogs | 160 | 5
Killed with clubs and other weapons | 2,889 | 3,818
Found dead from other causes | 316 | 297
----------------------------------------------------+---------+---------
No accurate record was kept of the number of each kind of rat
bait set. Only the total of all was recorded. Bacon or coconut
with strychnine and rice with arsenic were used. For instance,
for the quarter ended June 30, 1913, there were 166,237 poison
baits set in new territory and the rats found poisoned average
for each 100 baits 0.72. During the next quarter there were
177,309 baits set in territory that had been worked over, and
only 216 rats, or 0.12 rat per 100 baits, were killed. From
the foregoing it appears that the rat poison ranks lowest in
efficiency but perhaps highest in economy. In view of the
fact that the original cost of the cage trap is many times
more than that of the spring trap, and the cost of maintenance
is very high, it will be apparent that the spring trap is by
far the more economical as well as more effective of the two.
Generally speaking, however, the number of rat catchers engaged and the
location of their operations has the largest influence upon the total
catch of rats. For the fiscal year July 1, 1912, to June 30, 1913,
inclusive, the total catch was 55,101 rats (Manila only); to December
1, 1913, 79,676.
The most natural explanation of the general correspondence between the
highest rat catch and the highest incidence of human plague would be
upon grounds of greater activity in rat catching effort at times of
greatest plague prevalence, but from the inauguration of general
systematic rat catching there was no cessation of effort, even during
the abatement of plague, and in consequence this explanation does not
apply strictly.
It is true, however, that whenever plague occurred in districts
theretofore free from the disease, rat catching was pushed vigorously
in the surrounding localities.
Making due allowance for all the factors mentioned I am impressed with
the probability, amounting almost to certainty, that the catch of more
than 79,676 rats definitely affected and checked the spread of plague
in Manila in 1913; and I am of the opinion that systematic and
wholesale rat catching, carried out in the most economical manner
possible, should be persisted in indefinitely, at least until plague
disappears, wherever the disease occurs.
Efforts to prevent the spread of plague to the provinces of Luzon, by
way of the railways, were successful and the present measures employed,
freight inspection, the fumigation of packages suspected or likely to
contain rats, and the similar treatment of freight cars showing signs
of rats, should be continued. In a few cases these measures have driven
rats out of both packages and cars and the animals have been killed by
the sanitarians on duty at the station.
The matter of water transportation was entirely within the control of
the authorities in charge of inter-island quarantine affairs.
Rat catching in Manila was systematically performed and all rats
captured were turned over to the Bureau of Science for examination for
plague.
[Illustration: MATERIALS MUST BE MOVED ABOUT IN THE SEARCH FOR RATS
(MANILA PLAGUE CAMPAIGN)]
When plague foci were discovered the localities were trapped and
poisoned both circumferentially and centrally, with a view to
preventing the diffusion of infected rats throughout the city.
RAT-PROOFING.--The theoretic desirability and superiority of "out
building" the rat, over all other methods of rat suppression, is
admitted. The apparent impracticability of actually rat-proofing Manila
at the present time and our inability to starve the animals out,
justify the other and less permanent measure, viz.: rat catching.
However, I heartily favor and urge the most complete and thorough-going
rat-proofing of buildings actually infected with human or animal
plague, in all cases. The building ordinances of Manila already provide
for rat-proof construction in all new buildings erected.
With a view to cutting off the food supply of the rat, more than 1100
orders upon householders, to provide covered garbage cans, were served
in the district of Tondo alone.
The open ends of bamboo timbers in more than 2300 houses were closed,
either by cement or tin cans, during 1913.
THEATRE DISINFECTION.--All the cinematographs and theatres in the city
were disinfected upon repeated occasions by spraying with petroleum
and cresols, with a view to destroying fleas and preventing plague
infection.
Attempts at deception and concealment of plague patients, upon the part
of members of their families, were numerous, but with the close
scrutiny of death certificates and dead bodies exercised at all health
stations it is believed that all cases were recognized.
One case of extremely careless diagnosis occurred. A death certificate
was furnished by a local native doctor who certified the cause of death
to be "uterine hemorrhage." Suspicion arising, an autopsy was ordered
and a pronounced case of bubonic plague was disclosed postmortem. No
evidence of uterine hemorrhage, except slight menstrual signs, was
found.
The destruction of infected fleas in plague houses is of course the
primary object of the disinfection by spraying, which is thoroughly
carried out in every house where a case of human plague or rat plague
appears. The method is a simple one and consists in spraying a mixture
of cresols (2 per cent.) and kerosene (98 per cent.) over all surfaces
of the house, floors, walls, underlying ground, furniture and the
spaces above ceilings, etc., using the mixture liberally and securing a
general surface distribution. There is no doubt of the toxicity of this
mixture to all fleas and bed-bugs which it reaches, and it is
undoubtedly an effective measure in rendering an infected house safe.
All of the instances of multiple house infections, where the cases
recurred after disinfection, in Manila, have been in houses where, for
one reason or another, the recommended structural rat-proofing has been
postponed or where it has not been done. Thus, on Calle San Fernando
the sequence of the four cases (their progress by days and in
consecutive houses) is explained by the travel of rats through
efficient rat runs present in the walls and ceilings, rather than by
the passage of fleas through partition walls, from uncommunicating
house to house.
[Illustration: A RAT INFESTED PLAGUE INTERIOR]
So also at Calle Cabildo, where the superstructure of the house was a
veritable sieve, there was a series of communicating double walls.
At the house on Calle T. Alonso a similar condition existed, but here
the two cases which occurred may have been synchronously infected, or
nearly so, previous to disinfection of the premises.
At Calle Comercio, where six days elapsed between two cases, the rooms
and building were piled full of merchandise, defeating immediate
disinfection, that is, efficient disinfection, until all the
merchandise was moved and the rooms were emptied.
At 1364 Calle Sande, Tondo, where 5 cases originated, the infections
were undoubtedly almost synchronous and no infection occurred after
disinfection of the house, while at 1226 Calle Juan Luna, Tondo, the
two cases were plainly infected at about the same time and this
previous to disinfecting the premises.
GUINEA-PIGS AS INDICATORS OF INFECTED HOUSES.--The following experiment
shows strikingly the necessity for disinfecting houses where human or
animal plague cases have occurred.
Upon December 17, 1912, Dr. O. Schöbl, of the Bureau of Science, and
myself, placed two healthy guinea-pigs, free from fleas, in a wire trap
cage in the house at No. 4 Calle Barraca, a few hours before the house
was disinfected, a patient with plague from this house having died
within the preceding twelve hours. The cage containing the guinea-pigs
was placed exactly where the patient had slept upon the floor, as
indicated by the other tenants of the house. Disinfection was delayed
for a few hours and the guinea-pigs were left in the house for one
day. Upon December 21 one of the guinea-pigs died from typical bubonic
plague--anatomically and bacteriologically positive--other inoculated
experimental animals also developing the disease.
Other guinea-pigs placed in plague houses on Calle Cabildo and Calle
San Fernando, after disinfection of the premises, failed to acquire
plague.
NATURAL ENEMIES OF THE FLEA.--It was observed during the studies in
Java that certain natural enemies of fleas exist and operate against
their laboratory cultivation and their natural reproduction.
Ants of several varieties, large and small red ants and small black
ones, were found to be very antagonistic to fleas, both in the larval
and adult states, destroying them actively.
Fleas in the laboratory were found to be affected with mites, with a
resultant high mortality among the insects. The same parasites were not
found upon wild fleas. On account of the prevalence of mites upon the
laboratory fleas certain experiments concerning the transmission of
plague were vitiated.
The activity of ants in attacking and disposing of rat cadavers found
in our antiplague work in Manila was frequently brought to my
attention. We invariably included an attack upon ants in treatment of
houses known to harbor, or suspected of harboring, plague rats. The
combination of kerosene and cresols, elsewhere referred to, was found
to be perfectly satisfactory in the destruction of ants; assuming, of
course, that the necessary procedure of exposing the ants, by the
moving of merchandise, boards or other protecting materials, was
performed, so that contact, by spraying the insecticide mixture, was
secured.
ACTIVITY OF FLEAS.--It was also observed during the Java studies that
the rat flea, while rather lazy, may and does cover distances of five
metres and that he sometimes covers eighteen centimetres at a single
leap.
In addition to this, of course, there must be considered the
possibility of his falling considerable distances.
ZOÖLOGIC CLASSIFICATION OF RATS.--The matter of accurately,
systematically and scientifically cataloguing and classifying rats is
one of great difficulty and is not to be undertaken by anyone but a
trained naturalist. However, some of the notes we have at our disposal,
gathered from many sources, may be set before the reader. It is
extremely difficult to find exact correspondence of statement in the
various classifications offered by writers upon plague and rats.
Dr. Lantz gives the following brief classification in his section of
the publication, "The Rat and Its Relation to Public Health."
Order: _Rodentia._
Family: _Muridæ._
Genus: _Mus._
Species are many, but only three or four are cosmopolitan.
Cosmopolitan species: _Mus rattus_--black, brown, and roof
(_Alexandrine_) rat; _Mus decumanus_--gray, barn, wharf,
sewer, and Norway rat.
_Mus rattus_ has many varieties known throughout the world and these
are named according to color and habitat.
In addition to the names given in Lantz's classification, we constantly
see reference to the black house rat, the brownish-gray rat (_Mus
Alexandrinus_), the ordinary ship rat, the field rat, etc.; terms
descriptive of habitat and appearance being very loosely applied.
Little account is taken, by many, of the well-known variations in the
coloration of rats due to climate and season and of the well recognized
aptitude of the rat for living in-door or out-door according to
circumstances of food supply, weather, etc. The "sawah" rat of Dutch
India, implicated in the prevalence of plague there, was formerly
considered a variety of _Mus decumanus_, but is now described as a
field variety of _Mus rattus_. So too, varieties of _Mus decumanus_ are
frequently named according to alleged geographic origin, habitat, color
and habits, viz.: sewer rat, brown rat, Norway rat and migratory rat.
The inevitable confusion bound to arise from such loose classification
is obvious.
Another genus, _Gunomys_ (_Nesokia_), implicated in plague, is
represented in India by two species and by at least one (an
undetermined one) in Java, some confusion existing in the matter as
yet. Members of this genus are described as large, rough-coated rats
which live both as house rats and field rats. In India the Plague
Commission reported specimens of this genus as particularly susceptible
to plague.
In the Philippine Islands no specimens of _Gunomys_ have been observed,
but _M. rattus_ and _M. decumanus_ are both present and numerous and
both are subject to plague, as shown by the presence of the disease in
specimens examined.
In view of the unreliability of the points of difference in rats
usually given as identifying data, such as the number and location of
the mammæ, the variations in color and the peculiarities of the
footpads, the Javan observers depend upon the conformation of the
skulls for the determination of genera, the skull of _M. rattus_ being
oval and arched, that of _M. decumanus_ more closely approaching the
square and rectangular conformation, and that of _Gunomys_ being
broader, higher and longer than either.
In _M. rattus_ the prominent borders which separate the parietal from
the frontal surfaces of the skull are oval; in _M. decumanus_ they are
parallel or slightly divergent; in _Gunomys_ they are lyre-shaped.
[Illustration: _M. rattus_]
[Illustration: _M. decumanus_]
[Illustration: _Gunomys_]
To determine these differences the heads of the rats are cut off, the
tissues desiccated by antiformin, or by boiling and stripping.
From experiences in Porto Rico, Creel, of the U. S. Public Health
Service, concludes that _M. norvegicus_ (_decumanus_), while
essentially a burrowing animal and not addicted to climbing or
swimming, is nevertheless quite capable of doing either. He was found
to burrow in the hardest earth to a depth of two and one-half feet and
to pass through all kinds of wood, soft brick and lime mortar, probably
by gnawing.
The black rat and Alexandrine rat (_M. rattus_) in Porto Rico,
according to the same observer, do not burrow at all, but can climb and
jump in expert manner, and are the species found in the rural
districts, remote from houses. He found that all varieties of rats may
swim, from ships to the shore, distances of from one-fourth to one-half
mile, but that they lack the sense of direction and probably do not
land from ships naturally in this manner (_Public Health Reports_, No.
9, February 28, 1913).
The female _decumanus_ is a prolific breeder and brings forth larger
litters than the _Mus rattus_ female.
_Mus decumanus_ is generally conceded to be larger and more ferocious
than _Mus rattus_. For this reason he drives the smaller rats to the
upper floors, the _decumanus_ species generally living near the ground.
He is a burrower and is rarely found in the upper stories of
buildings. _Decumanus_ is known as a wharf rat, but is rarely trapped
on ships on the Pacific Coast, according to the observations of Surgeon
Simpson of the U. S. Public Health Service (_Public Health Reports_,
April 11, 1913). According to the same observer, _Mus rattus_ is the
commonest ship-borne rat. He also states that the black rat and the
roof rat (_Alexandrinus_), both varieties of _M. rattus_, differ
chiefly in color. They live in upper floors, between ceilings, in walls
and roofs and are remarkable climbers as well as being expert
rope-walkers and wire-walkers. On account of their natural wariness and
caution it is not always easy to induce them to enter or approach
traps.
The photographs introduced were taken under my direction in Manila in
1912, 1913 and 1914. Some of them show the character of the house
construction in Tondo District, Manila, where plague flourished in
1913. Others illustrate methods of rat-proofing bamboo timbers in
houses of light material. These end openings were either closed by
introducing cement or by placing tight-fitting tin cans over the ends
of the bamboo rafters.
There are many interesting memoranda, gathered and made in connection
with our antiplague work in Manila, especially concerning the location
and construction of rat nests found by our laborers; the materials used
and the fabrication of the nests. Memoranda giving details of rat
catching and rat-proofing are also presented and notes showing the
location of dead rats found in relation to dead human bodies of plague
victims.
Notes concerning cases of multiple house infection are also presented
as being of possible interest.
The Javan studies in 1911 and 1912 establish the fact that it is
possible to form a fair judgment as to the length of time a rat has
been dead, up to ten or twelve days, from the condition and appearance
of the rat cadaver, both as to decomposition and drying. A series of 50
rats was studied. It is to be understood that the conditions under
which these observations were made were tropical conditions. They would
be fairly comparable with summer conditions in America, but should not
be followed too closely at other seasons of the year. In my own
experience I have observed that ants are likely to attack the cadaver
early and to obscure the deductions by their destruction of the body.
[Illustration: PROGRESSIVE POST-MORTEM CHANGES IN RAT CADAVERS. THE
NUMBERS INDICATE THE NUMBER OF DAYS AFTER DEATH]
Days after death Appearance
First to third day Distention of the abdomen, increasing.
Second to third day Loosening of hair by gentle pulling.
Third to fourth day Loosening of the epidermis by gentle
pulling.
Third to fifth day Perforation of abdominal wall with
collapse and disappearance of distention.
This perforation may result from bursting
of abdominal wall, or through anus, vulva
or thorax.
Fourth to sixth day Moist shrinking of the body. Swarming of
maggots. Spontaneous shedding of tufts of
hair.
Fifth to eighth day Drying of body.
Eighth to twelfth day Complete dryness and rigidity.
Photograph (after _Publications of the Civil Medical Service in
Netherlands, India_) shows the progressive postmortem changes in rat
cadavers, the numbers indicating the number of days after death.
A COLLECTION OF NOTES CONCERNING RAT RUNS, RAT NESTS, THEIR LOCATION
AND OTHER DATA.--Attention is invited to the following collection of
notes concerning rat runs, rat nests and their locations and other data
collected by the various working parties under the direction of
Sanitary Inspectors Brantigan, Renner and Kennard, of Manila.
Special attention has been given to the finding and destroying of rat
nests, and in this connection please note that during the month of May,
1913, one party of workmen (20 men) under Inspector Brantigan, killed
by hand 511 rats out of a total of 1319. This means that many nests
were broken up and that much breeding was interfered with. In June,
1913, two parties (40 men) killed 772 rats by hand out of a total of
3019.
This work occurred in Tondo District in connection with extensive
cleaning and moving operations.
At 1279 C. Sandejas[4] 7 rats were found in a nest at the foot of a
cluster of bamboo trees, between the trunks. Nest was made of leaves.
[4] C. is abbreviation for Calle, the Spanish term for street.
At 728 C. Velasquez, Tondo, 12 rats were driven from a burrow
underneath a thick cement floor by formaldehyde gas delivered in the
burrow through a rubber hose. This burrow was in sand and the rats came
out about ten minutes after the flow of gas began. All were killed or
captured and two or three died from the effects of the gas.
On October 27, 1912, two of the rat terriers belonging to the Bureau
of Health caught 192 rats in one storeroom at the Manila Railway
Station, in 38 minutes. At various times they have killed from 10 to 25
rats at a single location, in connection with the cleaning and moving
work done by the laborers. The dogs caught about 600 rats in all.
On March 11, 1913, 27 rats were caught by laborers at 202 Calle Concha.
They were nesting in straw covers which had been removed from bottles.
On March 11, 1913, 13 rats were found beneath a pile of loose tiles at
203 C. Sardinas. The nest was made of fibres from coconut shells and
straw.
On March 13, 1913, 12 rats were found among stones scattered in a
shallow pile on the ground at C. Conservador (interior). Nest was made
of rice chaff and small pieces of cloth.
On March 15, 1913, 9 rats were caught at 1353 C. Anloague on the ground
floor beneath a pile of boards. Nest was made of coconut fibre and
shavings.
On March 16, 1913, 24 rats were caught at 934 (interior) Velasquez
beneath a wood pile. Nest was made of coconut-shell fibre and pieces of
cloth.
On March 17, 1913, 14 rats were caught under a pile of hay and straw
at 173 Velasquez. Nest was made from straw, chaff and hay.
The following articles of food were found in the above-mentioned nests:
chicken bones, rice, coconut, fish and bread.
MEISIC DISTRICT
At 822 Sacristia 6 dead rats found in holes.
At 540 T. Alonso a family of 8 rats was smoked out and all were killed.
At 514 same street 6 rats were smoked out and killed.
At 538, interior, same street, 4 rats were smoked out and killed.
At 546 same street 4 rats were smoked out and killed.
At 715 San Bernardo dead rat found in a hole. Nest made of banana
leaves and rags.
At 627, interior, Zacateros, 9 rats were smoked out and killed.
At 669 Benavides 6 rats were smoked out of four runs and were caught.
At 631 Zacateros 2 rats were smoked out and killed.
At 417, interior, Misericordia, 4 rats were secured in two holes under
a tile floor. Many rats were caught at this number (interior) in traps.
At 221 Espelita 7 rats were found in a nest made of palm leaves and
excelsior; location of run way and nest beneath tile floor.
At 124 Tetuan, in a nest of straw and lint, 5 rats were caught by hand,
alive.
At 415 T. Alonso one live rat and 3 dead ones were dug out from beneath
a tile floor.
SAMPOLOC DISTRICT
At 1001 Bilibid Viejo there were 5 rat runs, in a Chinese store. Eight
rats were secured in a nest under the cement floor. Nest made of straw
and paper.
At 928 San Sebastian there were 8 rat runs. In one of them there were
caught 8 rats. The nest was made of straw.
At the same address, later, 3 rats were caught in another run and 8
young rats, with eyes still unopened, were found in a nest of straw. A
supply of bread was on hand in this nest.
At 629 Tanduay 20 rats and nests of straw and paper were found.
At the same address upon another day another rat run was found and one
large rat and 16 small ones were taken from a nest made of rags, straw,
and fibres.
PACO DISTRICT
At 1115 San Andres in a Chinese tienda (food store), a long rat run and
a nest of rags, straw, and paper, and 30 small rats were found.
One nest in a bamboo tree 30 feet above ground was found. Rats had been
observed going up the tree and one was caught at the foot of the tree
in a trap.
SAMPOLOC DISTRICT
At 629 Tanduay 14 young rats and a nest of straw, paper and rags were
found in a stable.
Same address, later, one rat run and nest of straw and rags with one
large rat and 16 small ones were found.
TONDO DISTRICT
March 27, 1913, one rat was caught alive inside of a bamboo timber in
house at 51, interior, Pesqueria.
At 631 Azcarraga 4 young rats were found in a nest of paper, leaves,
and hay. Chicken bones, crab shells, and rice were present in the nest.
A young python was caught in a lumber yard in the Santa Cruz District
in June, 1913. In his stomach was found a half-grown rat. Another snake
was caught in a rat trap at the same address about the same time.
PLAN FOR HOUSEHOLD RAT DESTRUCTION.--The following plan for household
rat destruction was proposed by me to the Director of Health. It is
considered worthy of trial if rat plague appears in new districts.
Proposal for periodic household rat poisoning in Manila.
Proposed that, upon a certain day of each week, rat poison be
issued free to all applicants (householders) in Manila who
agree to place same about their premises, permitting the
poison to remain in place for 48 hours.
Instructions and poison placards to be issued with the
poison. Issues to be made from Station Health Offices and
records of issue to be kept.
Collections of dead rats to be made at the end of 24 hours
and 48 hours by Bureau of Health employees. Poison portions
to be collected and turned in at the Station Health Offices
at the end of 48 hours, that is, at the time of the last rat
collection. Rats to be tagged and examined for plague in the
usual manner.
Due newspaper notice of the plan and of the gratuitous issue
of poison to be given to the people and their coöperation
requested.
Plan to be tested for at least two months.
MULTIPLE HOUSE INFECTION
Memorandum concerning 1364 Calle Sande:
Within 72 hours (April 25-27) five fatal cases of plague, all in
Filipinos, occurred in Manila. The five deceased persons lived at 334
C. P. Rada (Meisic), 1419, interior, C. Dagupan, 1364 C. Sande (Tondo),
642 C. Ylala (Meisic), and 1492, interior, C. Dagupan (Tondo).
The following relationships were established by inquiry and
investigation and the circumstances point strongly to a common source
of infection and to a single geographic focus of plague infection in
connection with all of the cases, viz.: at 1364 C. Sande (Tondo).
José Raymundo, boy, aged fifteen, lived at 334 C. P. Rada and
worked daily until taken sick on Tuesday, April 22, at 1364
Sande, in the shop of Simplicio Enriques, a silversmith, who
lived part of the time at the same address.
José Raymundo died of bubonic plague at San Lazaro Hospital
on Friday, April 25, 1913.
Norberta Mendoza, woman, aged fifty-six, lived at 1418,
interior, C. Dagupan. She was the mother-in-law of Simplicio
Enriques, the silversmith at 1364 Sande, and visited her
son-in-law there frequently and within a few days of her last
illness. She was taken sick April 22 and died at 1419,
interior, C. Dagupan, on the morning of April 26. At autopsy
at San Lazaro morgue, the same day, bubonic plague was found
to be present and the cause of her death.
Trinidad Galves, a young woman, aged sixteen, lived at 1364
Sande and was taken sick there on April 25. She was removed
to San Lazaro Hospital and died there April 26, extensive
plague lesions being found at autopsy.
Pablo Banzon, man, aged twenty-six, living at 646 C. Ylaya,
was taken sick on Friday, April 25. He was removed to San
Lazaro Hospital Saturday afternoon and died there Sunday
evening, April 27. He was shown to have plague by
bacteriologic examination made at the Bureau of Science. He
worked at 1364 Sande as a silversmith, with José Raymundo and
was employed by Simplicio Enriques.