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

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.