Part 1
TREASURY DEPARTMENT
Public Health and Marine-Hospital Service of the United States
THE RAT AND ITS RELATION TO THE PUBLIC HEALTH
BY VARIOUS AUTHORS
PREPARED BY DIRECTION OF THE SURGEON-GENERAL
[Illustration: [Logo]]
WASHINGTON GOVERNMENT PRINTING OFFICE 1910
TABLE OF CONTENTS.
Page.
_Introduction_ (Walter Wyman) 9
_Natural History of the Rat_ (David E. Lantz) 15
Classification of rats 15
Distribution of the genus _Mus_ in America 17
History of the brown rat 19
General description of the species in America and key to the species 20
Habits of rats 22
Breeding habits 22
Abundance 23
Migrations and invasions 24
Food 26
Feeding habits 26
Ferocity 27
_Plague Infection in Rats_ (George W. McCoy) 29
Mode of examination 30
Gross lesions of natural rat plague, acute 32
Subcutaneous injection 32
The bubo 33
The granular liver 34
The spleen 35
Pleural effusion 35
Gross lesions of natural rat plague, chronic 36
Rat plague without gross lesions 37
Microscopical examinations 37
Bacteriological diagnosis of rat plague 38
Pest-like bacteria found in rats 41
Artificial infection of rats with plague 41
Modes of infection 42
Local reaction 43
The bubo 44
The liver and spleen 44
Chronic plague due to artificial inoculation 44
The histology of rat plague 45
Natural rat plague 46
Immunity of rats to plague 46
References 48
_Rat Leprosy_ (Walter R. Brinckerhoff) 49
Introduction 49
Review of literature 49
Description of disease 50
Etiology 52
Summary 52
Bibliography 53
_Bacterial Diseases of the Rat other than Plague_ (Donald H. Currie) 55
Danysz bacillus or bacillus typhi Murium of Loeffler 55
Pneumonia 55
Staphylococcus abscesses 56
Bacillus pseudo-tuberculosis rodentium (Pfeiffer) 57
Toyama’s bacillus 57
Infections of mice 57
_Organic Diseases of the Rat, Including Tumors_ (George W. McCoy) 59
Usefulness of wild rats for laboratory purposes 59
Circulatory apparatus 60
Pulmonary apparatus 60
Digestive tract 61
Cirrhosis of the liver 61
Fatty degeneration of the liver 61
Hernia 61
Genito-urinary tract 62
Nephritis 62
Abscess of the kidney 62
Atrophy of the kidney 63
Vesical calculi 63
Tumors 64
Metastases 67
Histological structure 67
Lipomata 67
Fibromata 67
Sarcomata 67
Adenomata and Carcinomata 67
_Ectoparasites of the Rat_ (Nathan Banks) 69
Fleas—Siphonaptera 69
Lice—Anoplura 77
Mites—Acarina 80
_Internal Parasites of Rats and Mice in Their Relation to Diseases of Man_ (Ch. Wardell Stiles and Charles G. Crane) 87
Summary 87
Introduction 87
Protozoa 88
Cestoda 95
Nematoda 101
Acanthocephala 108
_Compendium of Animal Parasites Reported for Rats and Mice—(Genus Mus)_ (Ch. Wardell Stiles and Albert Hassall) 111
_The Flea and Its Relation to Plague_ (Carroll Fox) 123
Theories as to the transmission of plague 123
Insects that have been suspected in the transmission of plague 124
Experiments proving that fleas can transmit plague 125
The bacillus in the flea 126
How the flea clears itself of bacilli 127
Regional distribution of fleas on rats 127
Anatomy of the mouth parts of the Ceratophyllus Fasciatus 128
Outside the head 128
Inside the head 129
The act of biting 131
How the flea infects its host 132
Enumeration of fleas that have been found on rats 133
Results of identification of fleas in California 135
Synopsis of fleas commonly found on rats 136
Ceratophyllus Fasciatus, Bosc 136
Lœmopsylla Cheopis, Rothschild 138
Ctenopsyllus Musculi, Dugés 140
Pulex Irritans, Linnæus 142
Ctenocephalus Canis, Curtis 143
References 144
_Rodents in Relation to the Transmission of Bubonic Plague_ (Rupert Blue) 145
Epidemiological observations in San Francisco 147
Theories as to the cause of seasonal prevalence 149
The occurrence of plague in the marmot of Asia and ground squirrel of California 150
Plague infection in ground squirrels 150
The natural habitat of plague 151
References 152
_Rodent Extermination_ (Wm. Colby Rucker) 153
Trapping 154
Poisoning 156
Natural enemies 159
Cutting off of the rat’s food supply 160
Building the rat out of existence 161
_Natural Enemies of the Rat_ (David E. Lantz) 163
Animals that destroy rats 163
Hawks 163
Owls 164
Wild mammals 166
Skunks 166
Weasels 166
Minks 167
Domestic animals 167
Dogs 167
Cats 167
Ferrets 168
Other animals 168
Mongoose 168
Alligators 168
Snakes 169
Bounties on predatory animals 169
_Rat-Proofing as an Antiplague Measure_ (Richard H. Creel) 171
Rat-proofing of primary importance 173
Rat-proofing is expensive 174
Methods of rat-proofing 175
Rat-proofing ordinances should be specific 177
Choice of architecture and building materials 178
_Inefficiency of Bacterial Viruses in the Extermination of Rats_ (Milton J. Rosenau) 179
Introduction 179
Experiments upon rat virus in the Hygienic Laboratory 183
Experiments with microorganisms for destroying rats by the U. S. Biological Survey 186
Experiments during the San Francisco plague outbreak 188
Opinions of others 190
Pathogenicity for man 193
References to the literature 201
Résumé 204
_Plague Eradication in Cities by Sectional Extermination of Rats and General Rat-Proofing_ (Victor G. Heiser) 205
_The Rat in Relation to Shipping_ (Wm. C. Hobdy) 207
Adaptability of the rat to his surroundings 208
Damage to cargo 209
Fumigation 211
Summary 213
_The Rat as an Economic Factor_ (David E. Lantz) 215
Introduction 215
Utility of the rat 215
Destructiveness of the rat 216
Grains 216
Merchandise in stores and warehouses 218
Merchandise in transit 219
Poultry and eggs 219
Game and wild birds 220
Fruit and vegetables 221
Flowers and bulbs 221
Fires 222
Buildings and furniture 222
Miscellaneous 223
Amount of losses caused by rats 224
Indirect losses 225
_The Rat in Relation to International Sanitation_ (John W. Kerr) 227
International sanitary regulations 228
Inquiry into the crusade against rats throughout the world 230
Rat extermination in United States ports 231
Rat extermination in Chinese cities 232
Rat extermination in Madras, Bombay, and Calcutta, India 234
Rat extermination in Yokohama and Nagasaki, Japan 235
Rat extermination in East Africa 237
Rat extermination in Cape Town, South Africa 238
Rat extermination in Alexandria and Cairo, Egypt 238
Extermination of rats at the port of Constantinople 238
Rat extermination in Russian ports 239
Destruction of rats in Trieste, Austria 240
Destruction of rats in Genoa, Italy 240
Destruction of rats in Barcelona, Spain 241
Rat destruction in French ports 241
Ministerial decree relating thereto 242
Destruction of rats in German ports 243
Measures against rats in Rotterdam, Holland 245
Destruction of rats at Antwerp, Belgium 245
Destruction of rats in Denmark 245
Danish law of March 22, 1907 245
Collection and destruction 247
Destruction of rats in Swedish ports 248
Destruction of rats in English ports 249
Measures against rats in Australian ports 250
Measures against rats in South American ports 252
Measures against rats in West Indian ports 252
Destruction of rats in Panama 253
Measures against rats in Vancouver, B. C. 253
Necessity of concerted action of nations 254
LIST OF ILLUSTRATIONS.
Page.
Fig. 1a. Upper molars of the brown rat (_Mus_): tubercles in 16 three rows
Fig. 1b. Upper molars of the rice rat (_Oryzomys_): tubercles in 16 two rows
Fig. 2a. Right hind foot of brown rat, showing long sixth foot 17 pad
Fig. 2b. Right hind foot of house mouse, showing round sixth 17 foot pad
Fig. 3a. Ears of brown rat and black rat, showing relative size 21 fig. 3b.
Fig. 4. Necropsy appearance of normal rat 48
Fig. 5. Necropsy appearance of plague-infected rat 48
Fig. 6. Flea, showing the various parts 70
Fig. 7. Louse—_Polyplax spinulosus_ 78
Fig. 8. Mite—_Lælaps echidninus_ 81
Figs. 9 Internal parasites of rats and mice 90–109 to 58.
Fig. 59. Isolated plague-infected center, Manila, P. I. 206
Fig. 60. Scheme for testing rat-plague infection, Manila, P. I. 206
Plate I. Mouth parts of _Ceratophyllus fasciatus_ 130
II. _Ceratophyllus fasciatus_ 136
III. _Lœmopsylla cheopis_, Rothschild 138
IV. _Ctenopsyllus musculi_, Duges 140
V. _Pulex irritans_, Linnæus 142
VI. _Ctenocephalus canis_, Curtis 144
THE RAT AND ITS RELATION TO THE PUBLIC HEALTH.
By WALTER WYMAN,
_Surgeon-General of the Public Health and Marine-Hospital Service_.
INTRODUCTION.
The science of bacteriology has elucidated many facts with respect to the causation of disease, and with this advance in knowledge, old theories regarding the miasmatic and humoral origin of human ills have been abandoned.
Epidemiological studies have likewise determined the methods of transmission of many of the infectious and contagious diseases, thus eliminating erroneous conceptions that they are attributable to some mysterious condition of the atmosphere or soil, or to a visitation of the wrath of the Almighty.
Both these sciences have contributed to our knowledge of the relationship of living things, particularly with respect to their influence upon each other in relation to health and disease. It is now known, for instance, that mosquitoes are the pests of man, not only because of their bites, but because they at times transmit malaria, dengue, filariasis, and yellow fever. So, too, it is known that rodents are the enemies of man, not only because of the toll exacted from him, but because they are the principal agents in the propagation and spread of bubonic plague.
Ancient writings abound in allusions to pestilences and their connection with epizootics among rats and mice.
In the Book of Samuel there is reference to a pestilence having relation to mice, and that it might be stayed the Philistines made offerings of golden images of the mice that marred the land.
During the centuries that have intervened rats have migrated to practically every quarter of the earth, causing untold losses on account of their depredations. They have also, in all probability, been the primary agents of transmission in the pandemics of plague which have visited the earth. The fact that plague is due to a specific microorganism, and that its presence in man is also associated with epizootics in rats, has led to a more careful study of this animal, particularly in relation to his habits, the diseases from which he suffers, and the methods necessary to his control. Prior to the beginning of the present pandemic of plague which had its origin in China, interest in the rat was almost wholly an economic and financial one. Since that time evidence has been rapidly accumulating which proves that this animal and his parasites are responsible for the transmission of plague and that plague itself is essentially a disease of the rat.
A knowledge of this animal on the part of the sanitarian therefore becomes essential. During the enforcement of antiplague measures in California, Hawaii, the Philippine Islands and elsewhere, observations of great value have been made and their practical application has resulted in better directed efforts for the elimination of the disease.
In studies of plague and leprosy with the view to their diagnosis and control, it is not enough now to isolate the microorganisms responsible for these diseases, but the sanitarian must be able to recognize the pathological conditions present in animals affected, and to do so he must have practical knowledge of this subject in order that he may differentiate between the various diseases from which these animals suffer.
Opportunity for observation and study of the diseases of rats and the methods necessary to their eradication has been afforded to the officers of the Public Health and Marine-Hospital Service who are constantly stationed on the outposts in the warfare against exotic diseases. The results of these observations have been utilized by officers of the service, and some of them have been published for the benefit of others.
The rat has received much attention of late in other parts of the world. In Denmark, for instance, a legalized warfare against rodents has been begun, principally on account of their influence in the transmission of trichinosis. In England there exists The Incorporated Society for the Destruction of Vermin, and in other places rat destruction is being agitated both from economic and public health standpoints.
In view of the great importance of the rat in relation to the public health, it has been thought advisable to collect and publish all pertinent information on the subject, in order that public health officials who should be on the lookout for the appearance of plague among rodents might have available a reliable treatise on the subject.
Studies of rodents from a biologic and economic standpoint come within the province of other departments of the public service, and the cooperation of the Biological Survey and Bureau of Entomology of the Department of Agriculture was therefore requested and received.
The subjects dealt with in this publication have been prepared by those having wide experience.
In the chapter on natural history by Mr. David E. Lantz there is given a classification of rats as well as the distribution of the genus _Mus_ in America. An interesting and important fact is mentioned that the Biological Survey has no records of the presence of the brown rat in Nevada, Utah, Wyoming, Idaho, and the greater part of Montana. Mr. Lantz also describes the different species in America, and refers to their habits as to breeding, feeding, migrations, invasions, and ferocity. The facts presented by him emphasize the great difficulty of ridding cities of these pests.
Passed Assistant Surgeon McCoy discusses plague infections in rats and describes the methods of examination. He also describes the gross lesions found in plague rats, gives the bacteriologic diagnosis of rat plague and the cultural characteristics of the plague bacillus on various media. He gives the methods of artificial infection of rats with plague, and reviews the recent work of Ledingham in relation to the histology of rat plague. Finally, he presents results of his own investigations to show that the wild rat is not especially susceptible to plague infection, and that a certain percentage of such animals enjoy a natural immunity to plague.
Doctor Brinckerhoff discusses rat leprosy; states that it is very similar to human leprosy, and that it is caused by a bacillus which closely resembles the bacillus of Hansen. He describes the pathological changes found, and expresses the hope that the disease will receive further earnest study, in order that additional information may throw light on the problems presented by leprosy in man.
Passed Assistant Surgeon Currie briefly outlines the bacterial diseases of the rat, other than plague and leprosy. He mentions the great utility that would follow the discovery of a rat destroying bacterium, but states that it appears now more than probable that few such natural diseases of rats exist.
In a chapter on organic diseases of the rat, Doctor McCoy summarizes the results of his observations made during examinations of these animals in the Federal laboratory of the service at San Francisco. These observations are of interest, and will assist those engaged in such work to further classify the pathological changes noted as well as differentiate them from plague.
The ectoparasites of the rat are classified and described by Mr. Nathan Banks, and he has presented in condensed form information of much practical value upon the subject.
Dr. Ch. Wardell Stiles discusses the internal parasites of rats and mice in relation to the diseases of man. He regards the rat as a permanent reservoir for trichinosis, and states that this disease will probably never be eradicated from man until rats and mice are practically eradicated, and a national campaign directed against trichinosis must take the rat into consideration.
A compendium of animal parasites reported for rats and mice is presented in a chapter by Ch. Wardell Stiles and Albert Hassall. While, as the authors state, no list of this kind can ever lay claim to being complete, it represents the present knowledge of the subject.
In a discussion of the flea and its relation to plague, Passed Assistant Surgeon Fox summarizes the theories as to the transmission of this disease. He also mentions the insects that have been suspected of transmitting plague and presents accumulated evidence that fleas actually convey the infection. He then gives the anatomy of the mouth parts of the _Ceratophyllus Fasciatus_, the common rat flea of North America. He also enumerates the fleas that have been found on rats, and gives the results of identifications of 19,768 fleas in San Francisco and Oakland, Cal. The plates accompanying this article, and their description should be of great value to those engaged in antiplague measures.
Surgeon Blue briefly discusses the subject of rodents in relation to the transmission of bubonic plague. He discusses the theories as to the cause of seasonal prevalence of this disease and presents a table showing the number of rats examined during the different months of the year, the number found infected, the average temperature and rainfall for those months and the character of the days, as to the number clear, partly cloudy, or cloudy. He refers to plague infection in ground squirrels in California and warns against the possibility that this animal may become responsible for the establishment of a permanent focus of plague on the Pacific coast of the United States, as the marmots are so concerned with regard to India.
The all-important subject of rodent extermination is considered in detail, various phases of the subject being dealt with by different authors.
Passed Assistant Surgeon Rucker discusses the destruction of these animals by trapping, poisoning, cutting off of food supply, and destroying of existing nests and at the same time preventing the making of new ones. He describes the methods of use of the various mineral poisons, but finally states that rodents must be builded out of existence; in other words, habitations must be rendered rat proof.
Mr. Lantz, in discussing the natural enemies of the rat, mentions the animals that destroy these pests. He concludes that on account of this function bounties for the destruction of small animals that prey on rodents can not be justified and that they should in the future be protected in every way possible.
Passed Assistant Surgeon Creel discusses rat proofing as an antiplague measure, and gives in detail the principles of construction necessary. He concludes that rat proofing is the most valuable antiplague measure, and that it should precede auxiliary measures such as trapping and placing of poisons.
Surgeon Rosenau discusses the bacterial viruses in relation to rat destruction. As a result of his investigations in the hygienic laboratory and the reports of investigations and practical use elsewhere, he concludes that the bacterial viruses have signally failed to accomplish the mission for which they were intended, and that they are not entirely harmless to man, as has been stated.
Passed Assistant Surgeon Heiser briefly outlines the measures recommended for the eradication of plague in cities by means of sectional extermination of rats and general rat proofing. He gives results following this method of procedure in Manila, and presents charts showing how to deal with infected city districts.
Passed Assistant Surgeon Hobdy, in a chapter on the rat in relation to shipping, refers to the voyage-making tendencies of the rodent, its destructiveness aboard ship, and its power of adapting itself to unusual conditions and surroundings. In one small lumber vessel fumigated by Doctor Hobdy at the Angel Island quarantine station there were collected 525 dead rats. Mention is also made of another vessel on which were collected 1,700 rats after fumigation. He discusses the methods by which it gains access to vessels, and outlines the practices that should be observed to keep it off. He also describes in some detail the measures to be adopted for its destruction after it has gotten aboard ship, and mentions the different methods of fumigation.
Mr. Lantz, in a third paper, discusses the rat as an economic factor, and states in his paper that they do not serve any useful purpose. On the other hand, they cause enormous loss through damage to grain, merchandise, poultry and eggs, game and wild birds, fruit and vegetables, and flowers and bulbs. They also cause damage by setting fire to buildings and destroying furniture. He refers to various estimates made of the losses in the United States from rats, and they vary from $35,000,000 to $50,000,000 a year; but at the same time he states that, with present information, any attempt to state the amount of loss from rats would be largely guesswork.
Assistant Surgeon-General Kerr refers to the rat as a factor in international sanitation, and briefly outlines the provisions contained in international sanitary agreements for their eradication. He reviews the efforts being made at the more important seaports to exterminate rats, as well as the methods being employed to that end. The information presented is, in part, compiled from consular reports received through the Department of State. There are given, so far as obtainable, copies of laws and ordinances enacted for the destruction of rats and the different methods practiced in ports where plague has prevailed, and the facts presented indicate that a more or less widespread crusade against rats is being carried on. He expresses the belief that it is too much to expect that the rat population can ever be exterminated from any city, but that it is not too much to expect that ocean carriers can be freed from rodents and kept so, which action would confine plague within continental boundaries.
Epidemiological studies made of plague since the adoption of the International Sanitary Convention of Paris and the International Sanitary Convention of Washington have proven that the rat and its parasite, the flea, are the agents of transmission of the disease. In other words, where rats go plague will go. I believe, therefore, that in order to stop the further progress of plague, radical measures should be adopted, and in a communication of February 26, 1909, addressed to the Secretary of State, I suggested the advisability of submitting the question of a systematic destruction of rodents aboard ship to an international sanitary conference, with the view to the adoption of an international sanitary regulation on the subject. The adoption of such a regulation would undoubtedly lessen quarantine restrictions, prevent the destruction of cargo by rodents, and obviate the danger of the further spread of plague.
Until ships are freed from rats, each country must take all necessary precautions, consistent with international agreements, to destroy rats; and the sanitary authorities of infected localities must, at great expense, determine the extent of infection among rodents, with the view to its elimination. This problem when it presents itself in a community is of great magnitude, and those responsible for its solution should be familiar with all its phases.
It is with the view to supplying the necessary information in one treatise that this publication is issued. In its preparation the bureau has had the cooperation of the Department of Agriculture and acknowledgements are due, and here made to, the officers of that department for their hearty cooperation in contributing some of the chapters which follow.
NATURAL HISTORY OF THE RAT.
By DAVID E. LANTZ.
_Assistant, U. S. Biological Survey, Department of Agriculture_.
INTRODUCTION.
The extermination of rats has become one of the serious problems of modern times. That such noxious animals should have flourished so long is not creditable to our civilization. While no kind of rat can be regarded as harmless, the various species differ greatly in harmfulness. In comparison with the cosmopolitan species that have reached our shores from the Old World, our native rats do little damage. It is important, therefore, to be able to recognize the introduced forms, to understand their habits, and to concentrate efforts for their extirpation.
CLASSIFICATION OF RATS.
Rats and mice belong to the _Rodentia_, an order which comprises more than a third of all living species of mammals. Also, it exceeds any other mammalian order in the number of its individuals.