Chapter 2

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 beprohibitive—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 wasobliged 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 paratyphoidbacillus and Gärtner'sB. enteritidiscorrespond 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 againstthe 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 therapid diagnosisin 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 mustbe 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 diseaseand 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 thePhilippine 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 steamshipZafiro, 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 hisbunk. 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 steamerLoongsangarrived 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 steamshipTaisangfrom Amoy at the Mariveles Quarantine Station at about 6.30A.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. Onthis 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.

On April 7, 1912, the steamerLoongsangarrived 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 steamshipTaisangfrom Amoy at the Mariveles Quarantine Station at about 6.30A.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. Onthis 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 recordedfrom 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, naturaland 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 somewhatremoved 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 ofcases 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 ofdeath: 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.)

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 thesmall 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 importantmatter 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 oftenno 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, shouldnot 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 districtnow 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 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 districtnow 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.

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 Manilaand 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 withXenopsylla 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 asLœmopsylla 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 findCtenocephalus canis(dog flea),C. felis(cat flea) andCeratophyllus 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 markedincrease 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 thegreatest 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—anunknown 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):

In plague-infected villages, as distinguished from plague-free villages, there exists a considerable mortality among house rats.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.The house rat exists even in the immediate vicinity of man.The ordinary parasite of the house rat isXenopsyllacheopis, which experimentally is known to choose man as a host when starving.Fresh plague rats have repeatedly been found to harbor a great number of fleas.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 thetime 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 fairlybe 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 fornests 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.

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