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publications of 
 The American Academy of Political and Social Science 
 
 No. 620 
 
 Tropical Diseases and Health in the 
 United States 
 
 BY 
 JOHN M. SWAN, M.D. 
 
 Medical Director of The Glen Springs; Secretary of the American Society of Tropical Medicine, 
 
 Watkins, N. Y. 
 
 Reprinted from THE ANNALS of the American Academy of Political 
 and Social Science, March, 1911 
 
 PHILADELPHIA 
 
 The American Academy of Political and Social Science 
 
 Prke. 25 cents 
 
The American Academy op Political and 
 Social Science. 
 
 The American Academy of Political and Social Science was 
 formed In Philadelphia, December 14, 1889, for the purpose of pro- 
 moting the study of political and social problems of the present day. 
 
 Besides the general fields of sociology, political science and eco- 
 nomics, a special el^ort is made to collect and publish material deal- 
 ing with the more important practical questions of the time, such 
 as taxation, banking and finance, colonial policy, municipal govern- 
 ment, public administration, education, charities and correction, na- 
 tional and International commerce, corporations, and the various 
 phases of the labor problem. 
 
 In all of these departments of Investigation it Is the aim of the 
 Academy not to espouse the view of a single school, but rather to 
 offer the materials upon the basis of which an intelligent opinion 
 may be formed. 
 
 Applicants for membership in the Academy should file their 
 names with the Secretary, Dr. Carl Kelsey, Logan Hall, University of 
 Pennsylvania, Philadelphia, Pa. The only financial obligation In- 
 volved is the payment of the annual membership fee of five dollars, 
 or life membership fee of one hundred dollars. Members are 
 entitled to receive the regular publications of the Academy, submit 
 papers and communications, and to attend and take part in all scien- 
 tific meetings. Life members are exempt from all annual fees. 
 
 Papers and communications which the writers wish to submit 
 to the Academy with a view of their being read in a Scientific Ses- 
 sion or published in "The Annals," as well as applications for mem- 
 bership, should be sent to the following address: 
 
 American Academy of Political and Social 
 Science, 
 
 West Phila. Station, Philadelphia, Pa. 
 
 N. B. — Fees and subscriptions may be remitted by postal order 
 on Philadelphia, or by draft on New York, drawn to the order of the 
 Treasurer, Mr. Stuart Wood, Box 4050, West Philadelphia Station, 
 Philadelphia, or may be sent to B, S. Harvey, Esq., care of Messrs. 
 Glyn, Mills, Currie & Co., 67 Lombard Street, London, E. C. 
 
5'w 2- 
 
 TROPICAL DISEASES AND HEALTH IN THE UNITED 
 
 STATES 
 
 By John M. Swan, M.D., 
 
 ^ledical Director of The Glen Springs ; Secretar}' of the American Society 
 of Tropical Medicine, Watkins, N. Y. 
 
 Introduction. — Many of the problems that demand solution at 
 the hands of the sociologist concern the parasites that infest the 
 body politic, impairing its efficiency. The physician, on the 
 other hand, particularly he who is engaged in the solution of the 
 problems of sanitation, is concerned to a very large extent with 
 the study of the parasites that infest the physical body, producing 
 sickness and death. 
 
 Since the development of modern bacteriology, which saw its 
 beginning in about 1870, the knowledge of the causes of the acute 
 infectious diseases of man has had an interesting and rapid evolu- 
 tion. Following naturally the discovery of the exciting causes of 
 various diseases, the methods of preventing the development of those 
 maladies were rapidly worked out. But it was soon found that 
 some afifections that acted like other acute infectious diseases of 
 known etiology could not be associated with a discoverable bac- 
 terium in the relation of cause and efifect. The discovery by 
 Laveran, in 1880, of the Plasmodium malarise and the demonstra- 
 tion of its animal characteristics led to fresh investigations. These 
 studies, in turn, showed that some of the acute infections were 
 due to animal parasites. The understanding of the life history of 
 these organisms, however, has proved to be a much more com- 
 plicated matter than the description of the biological characters 
 of the vegetable parasites. 
 
 It has been found that many of the animal parasites of which 
 man is the host cannot be transmitted from one individual directly 
 to another. The parasitic organism requires a developmental period 
 in an intermediate host before it can be inoculated into another 
 individual there to develop and produce disease. The parasitic 
 form which infects the intermediate host is usually different in 
 
 (.304) 
 
Tropical Diseases and Health in United States 151 
 
 morphology from that which produces the disease in man. The 
 intermediate hosts are usually insects or some other animal low in 
 the zoological scale. These low animal forms require warmth, 
 moisture, and oxygen for their development. These three requisites 
 are also necessary for the development of the parasites themselves, 
 as well as for the growth of the vegetable parasites, bacteria, that 
 produce disease. 
 
 All of the lower forms of life, whether animal or vegetable, 
 flourish best in warm, moist climates, so that we find some regions 
 of the earth more unhealthy than other regions, on account of the 
 greater amount of moisture and heat with the resulting profuse 
 growth of the lowest forms of life. In addition to heat and moisture, 
 the lower forms of life require a certain amount of food in the 
 nature of decomposing animal and vegetable material. This is 
 found in abundance in hot, moist climates, particularly when no 
 effort is made to prevent the accumulation of such decomposing 
 masses. Furthermore, a hot, moist climate is debilitating to the 
 human organism, so that initiative and energy are lacking and a 
 disposition is developed to let things go as nature apparently means 
 that they shall go : the spirit to improve conditions is lacking. Con- 
 sequently, we observe the establishment of a vicious circle; the 
 native is lacking in energy; he permits masses of decomposing 
 animal and vegetable matter to accumulate in the vicinity of his 
 dwelling; this breeds the lower forms of life which are able to 
 develop the parasites that produce disease ; these parasites infect 
 the dweller in their neighborhood. Those inhabitants that escape 
 death are still further reduced in vitality and their efficiency is still 
 further impaired. Furthermore, they are carriers of disease-pro- 
 ducing parasites which increase in number, until finally, the neigh- 
 borhood acquires an unenviable reputation as a pest hole. 
 
 Climate. — The climates of the world are divided by Dr. C. Hart 
 Merriam (National Geographic Magazine, 1894, Vol. VI) into the 
 Tropical Zone, the Lower Austral Zone, the Upper Austral Zone, the 
 Transitional Zone, and the Boreal Zone, according to the total 
 amount of heat present during the year. In the Tropical Zone 
 there is 26,000° F. of heat during a year, the hottest period showing 
 a maximum temperature of 78.8° or over. In the Lower Austral 
 Zone the total heat amounts to 18,000° F. with the hottest period 
 above 78.8°. In the Upper Austral Zone the total heat is 11,500° F., 
 
 (305) 
 
152 The Annals of the American Academy 
 
 w ilh the hottest pcn'cKl below 78.8° F. In the Transitional Zone the 
 total lieat is 10,000° F., with the hottest period 1)elow 71.6° F. In 
 the lloreal Zone the total heat for the year is below 10,000° F. and 
 the hottest period is below 64.4° F. 
 
 The Tropical Zone extends from the Tropic of Cancer, 23° 30' 
 north of the equator, to the Tropic of Capricon, 23° 30' south of 
 the equator. But north of the Tropic of Cancer and south of the 
 Tropic of Capricorn there is a belt, the Lower Austral Zone, in 
 which for a considerable part of the year the climatic conditions 
 are similar to those in the Tropical Zone. In the United States, 
 this zone includes all of the Southern and Western states below the 
 thirty-fifth parallel of north latitude : South Carolina, Georgia, 
 Florida, Alabama, Mississippi, Louisiana, and Texas, and parts 
 of North Carolina, Arkansas, Indian Territory, Oklahoma, New 
 Mexico, Arizona, and California. It is even probable that this line 
 could be pushed as far north as the fortieth parallel. In 1909, for 
 example, Philadelphia had a total amount of heat of 20,153° F., 
 this is over 18,000° F. During the hottest period the thermometer 
 registered above 78.8° F. Even subtracting the 558 degrees excess 
 temperature over the normal temperature for Philadelphia in 1909 
 the total heat would be 19,593 degrees, enough to include Philadel- 
 phia, which is 39° 57' north latitude, in the Lower Austral Zone. 
 In 19 10 the total amount of heat was 19,861° F., with the hottest 
 period above 78.8° F. Similar studies would show that many places 
 in the L^nited States possess the necessary amount of temperature 
 for their inclusion in this zone. 
 
 Requisites for the Development of a Disease from the Tropics. 
 In order, however, that any disease shall develop in a given 
 region of the world, three essentials, in addition to a proper cli- 
 matic condition, must be present : the cause of the disease, the 
 proper transmitting agent, and susceptible individuals. Climatic 
 features may be suitable, the cause of the disease may be present, 
 susceptible individuals may reside in the district ; but if the trans- 
 mitting agent is absent the disease will not develop. If now the 
 transmitting agent is suddenly introduced into that locality an 
 epidemic of the disease will result. 
 
 On the other hand, the transmitting agent may be present and 
 susceptible individuals may reside in a locality ; but if individuals 
 harboring the parasites be not present, the disease will not be 
 
 ^396) 
 
Tropical Diseases and Health in United States 153 
 
 found. If now human hosts of the parasite come to the region in 
 question bringing the parasites with them an epidemic will follow. 
 
 Relations of the United States nHth the Tropics. — The Anglo- 
 Saxon race has had intimate relations with the tropics for over 
 three hundred ye^ars. In 1579 Thomas Stevens sailed from Lisbon 
 to Goa in India. So far as is known he was the first Englishman 
 to visit that great empire. In 1583 three London merchants started 
 overland for India. This enterprise was followed by the endeavor 
 of three ships to make the journey around the Cape of Good Hope 
 in 1 591. The fabulous wealth reported to be in existence led to 
 the formation of the British East India Company, which was char- 
 tered in 1600, and sent out its first expedition in 1601. Ever since 
 then England has had intimate relations with the tropics and has 
 known at first hand of the ravages of its diseases. That part of 
 the Anglo-Saxon race which resides in the Western Hemisphere 
 has had a merely casual acquaintance with the tropics until the 
 occurrence of the Spanish- American War, in 1898. The acquisi- 
 tion of the Philippine Islands, Puerto Rico, and Guam, followed 
 by our intimate relations with Cuba and the undertaking of the 
 Panama Car.al has brought the problems of tropical pathology and 
 tropical hygiene strongly to our attention. We suddenly realize 
 that many of our home ports are within the limits of the Lower 
 Austral Zone: Galveston, 28° 18' N. ; New Orleans, 29° 57' N. ; 
 Mobile, 30° 45' N. ; Jacksonville, 30° 45' N. ; Savannah, 32° 4' N., 
 and that the United States-Mexican border extends for a varying 
 distance north and south of the thirtieth parallel of north lati- 
 tude. We then find that other of our ports have a total degree of 
 heat that would be suitable, for a portion of the year at least, for 
 the development of diseases supposed to be peculiar to the tropics, 
 provided all the essentials were present. 
 
 We find 424,313 immigrants landing on our shores from tropical 
 and subtropical countries in 1907, and 224,930 immigrants from the 
 same regions in 1908. Our soldiers, our sailors, our missionaries 
 and our business men are visiting the tropics in greater numbers 
 with the advancing years. We further find that at home we have 
 had for many years a disease comrnon in the tropics, uncinariasis, 
 or hookworm disease, probably imported from Africa with slaves. 
 Tropical medicine, consequently, is a matter of intimate concern 
 to the health authorities of our country, and not a mere academic 
 
 (397) 
 
154 ^^'^ Aufials of the American Academy 
 
 question. The immigrant and the homecoming citizen are important 
 enough to require consideration in this respect, if we had never 
 had an epidemic of yellow fever, of plague, or of cholera in our 
 home territory. The prevention of an epidemic of imported disease, 
 however, is a comparatively easy matter when the cause is known, 
 and, at the hands of the United States Public Health and Marine- 
 Hospital Service the introduction of epidemics has been and will 
 be prevented so far as foreknowledge, foresight, and purisdiction 
 can accomplish the result. 
 
 The Essential Feature of the Prevention of Tropical Disease. 
 — The one essential feature of prevention of tropical diseases is the 
 cleanliness of our seaports, the cleanliness of our inhabitants, the 
 cleanliness of our houses. By cleanliness is meant the drainage of 
 mosquito breeding marshes and streams, the prevention of the devel- 
 opment of flies, and the destruction of rats and mice, as well as 
 the washing of bodies, the fumigation of houses and vessels, the 
 sweeping of streets, the proper disposition of sewage and garbage, 
 and the inspection of food products. 
 
 The Tropical Diseases. — The following list of disorders may 
 be looked upon as including the diseases indigenous to tropical and 
 subtropical countries which can be transmitted to temperate climates, 
 upper austral and transitional, provided the requisite conditions 
 of heat, moisture, intermediate hosts, parasites, and susceptible 
 population are present in the given locality. 
 
 A. Disease due to protozoan (one-celled) parasites: 
 
 I, malaria; 2, hemoglobinuric fever; 3, amebiasis; 4, try- 
 panosomiasis; 5, kala azar; 6, spirochetosis: (a), re- 
 lapsing fever; (b). Rocky Mountain fever; (c), 
 tabardillo. 
 
 B. Diseases due to metazoan (many-celled) parasites: 
 
 I, trematode infection; 2, cestode infection; 3 nematode 
 infection. 
 
 C. Diseases due to bacteria: 
 
 I, plague; 2, cholera; 3, dysentery; 4, Malta fever; 5, 
 leprosy. 
 
 D. Diseases of unknown etiology: 
 
 I, yellow fever; 2, dengue; 3. beriberi; 4, pellagra. 
 ^398) 
 
Tropical Diseases and Health in United States 155 
 
 Malaria is a disease indigenous to the tropics and to subtropical 
 countries. It is caused by a genus of protozoan parasites, known 
 as Plasmodium, of which there are at least three, and, according to 
 some writers, more species. The parasite is known to undergo a 
 cycle of development within its human host, which perpetuates 
 the disease in the individual. While the various steps in this cycle 
 are taking place regularly, a second form of development of the 
 parasite takes place, which results in the production of forms that 
 produce no symptoms in the human host ; but which are capable 
 of infecting the intermediate host. The intermediate host of the 
 Plasmodium is the female mosquito of the subfamily Anophelinse. 
 Not all species of anopheles mosquitoes can become infected from 
 the human host, but at least seven have been shown by actual experi- 
 ment to be the efficient agents for the transmission of the disease. 
 Manson, however, gives a list of thirty-two species from various 
 parts of the world which are known or suspected to be efficient 
 hosts of the Plasmodium. After the parasite has passed through 
 its developmental stage in the body of the mosquito, forms result 
 that can be inoculated into a susceptible human subject by the bite 
 of the insect, and so the disease is spread. No other method of 
 transmission from man to man is known. 
 
 Mosquitoes always breed in water. Some species prefer clean, 
 slowly running water ; others prefer stagnant water ; still others 
 breed in collections of water in artificial containers. The members 
 of the subfamily Anophelinse prefer, as a rule, the clean, slowly 
 running water found at the edges of streams and in marshes in 
 which there is some current. 
 
 The amount of sickness due to malaria in a malarial country 
 is incalculable. Woldert (Texas Medical Nezvs, April, 1908) esti- 
 mates that malaria causes the loss of an equivalent of over five 
 million dollars a year in the State of Texas alone. The most effi- 
 cient way to prevent the sickness and death due to this disease is 
 the destruction of the breeding places of the intermediate host of 
 the parasite. Marshes should be drained or filled in. Streams 
 should be cleaned of the growth of grasses, flags, and sedges which 
 are found near the banks, delaying the currents, and providing by 
 their interlacing roots safe retreats for the mosquito larvse from 
 their natural enemies. Artificial collections of water should be 
 destroyed or efficiently screened so that the adult female cannot 
 
 (399) 
 
156 The Annals of the Aincrican Academy 
 
 gain access to them for the purpose of depositing her eggs. All 
 money spent by the state in this work is well invested. The return 
 is seen in the increased efficiency of the individual, in the lowered 
 death rate and sick rate, and, in the case of drained marshes, in the 
 increase in the area of arable land. 
 
 A district in which there is no malaria may owe its freedom 
 to the absence of the proper malaria carrying mosquito, to the 
 absence of individuals harboring that form of the malarial para- 
 site in their blood which can infect the mosquito, or to both. If 
 the proper mosquitoes exist in a given neighborhood, but no infected 
 individuals are present, no malaria will be found ; but if human 
 hosts, apparently in perfect health, with the suitable form of the 
 malarial parasite in the blood are brought to the region, an epidemic 
 of malaria will result. For example, if a rural district contains 
 swamps or choked streams in which anopheles mosquitoes are breed- 
 ing, and a gang of Italian or West Indian laborers, many of whom 
 harbor malarial parasites, are imported for the purpose of some 
 public work such as road building or canal excavating, an epidemic 
 of malaria will follow. 
 
 On the other hand, a malarial district may be rendered almost 
 nonmalarial by destroying the breeding places of the mosquitoes. 
 The active work of the Department of Sanitation of the Isthmian 
 Canal Commission in searching for and destroying the breeding 
 places of mosquitoes in the Canal Zone, and screening the quarters 
 of the employees, has resulted in the reduction of the morbidity 
 from malaria from 821 per 1,000, in 1906, to 282 per 1,000 in 1908, 
 and 215 per 1,000 in 1909. The mortality was reduced from 8.77 
 per 1,000 in 1906, to 1.34 per 1,000 in 1908, and i.io per 1,000 in 
 1909. This result can be paralleled in any American community 
 by similar methods with a relatively small outlay of money. 
 
 The Italian method of furnishing quinine to the inhabitants for 
 prophylactic purposes is- not nearly so efficient ; nor is a method 
 which relies on screening the dwellings of the inhabitants without 
 a campaign for the destruction of the mosquitoes and their breeding 
 places. 
 
 liemoglobinuric fever, or blackwater fever, is believed by 
 many writers to be dependent upon previous malaria. If this be 
 so, the control of the latter will be attended by the disappearance 
 of the former disease. There arc students of tropical problems, 
 
 (400) 
 
Tropical Diseases and Health in United States 157 
 
 however, who believe that hemoglobinuric fever is an independent 
 disease. If this be true it should be placed among the diseases of 
 unknown etiology. Hemoglobinuric fever is present in the Philip- 
 pine Islands, in the West Indies, in Central and South America, in 
 the Canal Zone, in Texas, and in Arkansas, and probably in other 
 parts of the lower austral zone of the United States. So far as 
 we know at present its deleterious influence upon the public health 
 is not great and no alarm need be felt for an extensive propagation 
 of cases. 
 
 Amebiasis is a disease due to a protozoan parasite, Entameba 
 histolytica, which attacks the large intestine of man and of the 
 lower animals. The infection manifests itself by attacks of dysen- 
 tery, and in many of the cases, as high as 33 per cent in some 
 instances, it is followed by abscess of the liver. The parasite is 
 apparently transmitted from man to man by potable water. It is 
 possible that it may be transmitted by green vegetables, in localities 
 where human feces is used as a fertilizer, as is the custom in China 
 and other Eastern countries. Its spread may be stopped by boiling 
 the drinking water, by the prohibition of the use of human excre- 
 ment as a fertilizer, and by the prohibition of indiscriminate defeca- 
 tion into streams or other sources of water supply for towns, vil- 
 lages, or isolated farm houses. 
 
 Amebiasis is prevalent in the Canal Zone, certain of the West 
 India Islands, some of the Southern states, for example, Louis- 
 iana, Puerto Rico, and the Philippine Islands. Individuals with 
 intestinal trouble returnirrg from these countries should be carefully 
 studied for the detection of these parasites. 
 
 Trypanosomiasis is a disease due to a protozoan parasite, 
 Trypanosoma gambiense. It is at first a febrile complaint which 
 bears some resemblance in its clinical manifestations to malaria ; 
 but in its last stages it is accompanied by a marked degree of 
 lethargy and is commonly known as sleeping sickness. The parasite 
 is transmitted from man to man by a dipterous insect ; the Tsetse 
 fly, Glossina palpalis. The disease is confined to the valley of the 
 Congo River, the shores of Victoria Nyanza, and other parts of 
 tropical Africa. • So far as is known Glossina palpalis does not 
 breed on the American Continent, consequently no harm is to be 
 apprehended from this disease in the United States, even if an 
 infected individual should land upon our shores. If Glossina pal- 
 
 (401) 
 
158 The Annals of the American Academy 
 
 palis can be 1)rcd in our own lower austral region, the United States 
 Public Health and Marine-Hospital Service will have to institute 
 active fumigation measures on all ships coming from African ports 
 to our Gulf and South Atlantic ports to prevent the domestication 
 of the fly. 
 
 Kala Azar is a disease due to a protozoan parasite, Leishmania 
 Donovani. It is found in Assam, Madras and Bengal. The method 
 of transmission of the parasite is not known, and no danger is to 
 be apprehended from this disease. Dr. S. T. Darling, however, 
 has observed a few cases in the Canal Zone similar to Kala Azar, 
 and has found a parasite of similar appearance in the organs of the 
 patients at necropsy. This parasite has been called Histoplasma 
 capsulatum. The possibility of serious danger to the public health 
 from such a source is remote. 
 
 The best known example of spirochetosis is the European 
 relapsing fever, due to an organism known as Spirocheta recurrens. 
 A few imported cases have been seen in this country and small 
 epidemics have been recorded in New York and in Philadelphia in 
 past years. The parasite is supposed to be transmitted by the bed- 
 bug or the body louse. No extensive epidemic of this disease has 
 been observed in this country and its further prevention will be 
 accomplished by isolating imported cases and by the disinfection 
 of the belongings of the patients for the destruction of any vermin 
 that they may harbor. 
 
 In the Bitter Root Valley of Wyoming, and in some other parts 
 of our Rocky Mountain region there is an epidemic disease, known 
 as Rocky Mountain fever, which is known to be transmitted by 
 the bites of certain ticks, Dermacentor occidentalis. It is probable 
 that this is a spirochetosis. 
 
 The disease endemic in Mexico known as tabardillo, which 
 caused the death of the investigator who proved the transmission 
 of Rocky Mountain fever by the bites of infected ticks, Dr. H. T. 
 Ricketts, is in all probability of the same nature. The public health 
 authorities of the states forming the United States-Mexican border. 
 Texas, Arizona, New Mexico and California, will have to meet 
 the problem of the prevention of the importation of this infection 
 into our domain with the increased communication across the 
 border. 
 
 The disease caused by metazoan parasites are, as a rule, intes- 
 
 (402) 
 
Tropical Diseases and Health in United States 159 
 
 tinal disturbances due to the presence of the parasites in the alimen- 
 tary tract. There are one or two exceptions to this rule, notably 
 the disease known as schistosomiasis, in which the parasites and 
 their eggs are found in the blood vessels of the gastro-intestinal 
 canal or of the genito-urinary organs, and the disease known as 
 filariasis, in which the parasites are found in the lymphodes or the 
 connective tissue in the various parts of the body. In filariasis the 
 embryos are found in the circulating blood. 
 
 Many of these parasites gain entrance to the human body with 
 food or drink, others require development up to a certain stage in 
 intermediary hosts, still others gain entrance to the human body 
 through the skin. Much work remains to be done on the life his- 
 tories of many of these animals before definite knowledge of the 
 manner of infection is to be had. 
 
 The trematodes are low forms of the natural order Vermes. 
 With one exception they are hermaphroditic organisms which infect 
 ihe various parts of the gastro-intestinal tract. One variety, which 
 is indigenous to the Philippine Islands and other far Eastern 
 countries, is found in the lungs. The parasites are not known 
 to be indigenous to any part of the United States although it is not 
 beyond the range of possibility that they may be represented in 
 our home territory. However, climatic conditions are such in our 
 lower austral zone that, provided suitable intermediary hosts are 
 present, they may become established in this country. So far as 
 we know, cleanliness in personal habits, care in the preparation 
 of food, and abstention from eating uncooked fruit and vegetables 
 are all that is necessary to prevent the spread of such infections. 
 
 Schistosomiasis is the disease produced by a trematode para- 
 site, in which the male and female generative orgai.!s are contained 
 in separate bodies. The disease is also known as bilharziasis. It 
 is common in Egypt and in some other parts of Africa, and in Asia. 
 A form of the disease has been met with in the West Indies and 
 in some parts of Central and South America. Th.=i symptoms 
 depend upon the location of the parasites and their Ova. Some- 
 times an inflammation of the bladder results ; in othei* cases the 
 symptoms resemble those of dysentery. A variety of this i.^fection is 
 met with in China and Japan, one case of which has beei'i imported 
 into this country. 
 
 The cestodes are the tapeworms. Infection with the?^ parasites 
 
 (403) 
 
i6o TJic .iitiials of the American Academy 
 
 is by no means confined to tlie tropics or to subtropical countries; 
 l)ul in both these regions cestode infection is more common than 
 in temperate climates. Nearly all of these parasites depend for 
 their development in man upon the eating- of insufficiently cooked 
 meat. The inspection of our abattoirs by the officials of the United 
 States Department of Agriculture prevents the marketing of infected 
 meat, and is a public health measure of tlie first order. The proper 
 cooking of meat is further responsible for the rarity of the occur- 
 rence of these worms in Americans. 
 
 The nematodes are the round worms. Infection with one of 
 these is fairly common even among the children of the better class. 
 Infection with the hookworm, Necator americanus, has been shown 
 within the past ten years to be very common in the Southern states. 
 Trichiniasis, infection with Trichina spiralis, is seen in rare cases. 
 Filarial infections have been reported in our home territory. Pre- 
 vention of these infections varies with the individual parasite. 
 
 Ascaris lumbricoides infection is to be prevented by teaching 
 children to be careful of the things which they put into their mouths. 
 \\'e do not know the life history of this parasite, but infection 
 appears to be the result of taking the embryos or the ova into the 
 digestive tract. 
 
 Hookworm disease, uncinariasis, is a serious problem in our 
 Southern states. The embryos develop in moist, sandy soil, and 
 gain entrance to the body through the skin. The wet sand adheres 
 to the skin of the legs and feet, and the embryos burrow into the 
 underlying tissues and finally reach the intestine by a circuitous 
 route. The disease has long been known in Egypt and other parts 
 of the tropics of the Eastern Hemisphere as anchylostomiasis. It 
 was a serious public health problem during the construction of the 
 St. Gothard Tunnel, in 1880. Our army medical men found it 
 in Puerto Rico, and subsequently the parasites were discovered 
 in the South. Its presence results in a severe anemia which may 
 be fatal. The prevention of the extension of the disease can be 
 accomplished by the prohibition of soil pollution and by educating 
 the people to wear shoes. In many localities the inhabitants arc 
 too poor to buy shoes. In such circumstances prevention of indis- 
 criminate soil pollution is first in order. The amelioration of pov- 
 erty, on the other hand, so that each individual can obtain enough 
 
 (404) 
 
Tropical Diseases and Health in United States i6i 
 
 compensation for his work to be able to buy shoes for his family 
 is a question for the political economist and the tariff commission. 
 
 It has been found in Puerto Rico that in cases of certain ladies 
 of the better class who harbored Necator americanus, the infection 
 had occurred through the skin of the hands from working in flower 
 gardens, the soil of which had been fertilized by human feces. It 
 has also been suggested that uncinariasis was one of the causes of 
 the high morbidity and mortality among the Union prisoners in 
 Confederate prisons from 1861 to 1865, particularly in Andersonville. 
 
 The Rockefeller commission will undoubtedly succeed in ban- 
 ishing this infection from our Southern States. It must, however, 
 prosecute a long campaign of education before it can improve the 
 sanitary conditions in the rural districts and inculcate new habits 
 of personal hygiene in the inhabitants. 
 
 In filariasis the adult parasite inhabits the lymphnodes and the 
 connective tissues. The embryos circulate in the peripheral blood. 
 The presence of these parasites excites a train of diseases, the best 
 known of which is elephantiasis. The disease is present in certain 
 of the West India Islands. The embryos are taken into the stomach 
 of a female mosquito and undergo a metamorphosis in the thoracic 
 muscle of the insect. After the change in the embryos is completed, 
 they migrate to the proboscis of the mosquito and are inoculated 
 into the new individual by the bite of the insect. 
 
 Whatever of danger there may be in the importation of filariasis 
 into the United States is to be obviated by a mosquito campaign. 
 In this infection the intermediate host is not only the mosquito 
 of the subfamily Anophelinse but also certain species of the sub- 
 family Culicinse. The culex mosquito will breed in any kind of 
 water, some species developing in almost pure filth. Consequently, 
 it is not only necessary to drain marshes and to clean out streams, 
 but also to dispose of all collections of still or stagnant water ; the 
 water in flowerpots in cemeteries, in discarded tin cans, in broken 
 bottles, drains, cisterns, etc., has been found swarming with culex 
 larvse. The collections of water in the hollow branches and the 
 trunks of trees, and in the corollas of many plants, such as the 
 pitcher plant, have been found to be breeding places for these 
 insects. There is no danger of the direct transmission of filarial 
 infection from man to man. 
 
 Of the diseases due to bacteria, plague is the one of most 
 
 (405) 
 
i62 The .liinals uf the American Academy 
 
 interest to the American health officer. The disease is due to an 
 organism known as Bacillus pestis. Through the work of the Eng- 
 lish Plague Commission, done in Bombay and its environs, it has 
 been definitely established that the disease is originally one of rats 
 and mice and that it is carried from rat to rat by the bites of infected 
 fleas. After the rat population of a city has been reduced by 
 the epizootic, the fleas, no longer finding sufficient animal food, 
 turn their endeavors to and become temporary ectoparasites of 
 man. The epidemic then spreads from man to man by the bites 
 of infected fleas. In a few cases, about one per cent in a large epi- 
 demic, the disease exists in man as a pneumonia excited by the 
 Bacillus pestis, and this form of the infection is transmissible from 
 man to man directly by infected sputum, which is disseminated by 
 coughing, and by soiled bed linen and personal linen. 
 
 In the prevention of an epidemic of plague, the destruction 
 of rats and mice, is the important sanitary problem. The isolated 
 patient is not dangerous provided he is not suffering from the 
 pneumonic form of the disease. Plague has been present in San 
 Francisco twice within the past ten years. In 1900 the business 
 men and health officials of San Francisco and California made a 
 serious blunder in denying the existence of the disease, and, by 
 their attitude, causing the resignation of an officer of the United 
 States Public Health and Marine-Hospital Service who was emi- 
 nently equipped for coping with the situation. As a result, the 
 disease ran for a period of two or three years with occasional cases 
 reported, and the rat population of San Francisco became gener- 
 ally infected so that in 1907 plague again appeared in that city. 
 This time, however, profiting by the former error, the health author- 
 ities of California and of San Francisco summoned the federal 
 authorities to their aid and. by placing the matter entirely in the 
 hands of the latter, had the satisfaction of seeing the epidemic 
 stopped in eight months Avith a total of 160 cases and 78 deaths. 
 Fifteen cases occurred in Oakland and Seattle with 10 deaths. 
 During this period the Public Health and Marine-Hospital men 
 were killing 10,000 rats a week, about three per cent of which were 
 found infected with Bacillus pestis. The officers in charge of the 
 work further developed the fact that the wood squirrels about Oak- 
 land were infected with plague, and measures have been taken to 
 destroy these rodents. 
 
 (406) 
 
Tropical Diseases and Health in United States 163 
 
 The destruction of rats in our seaports is a problem that should 
 at once receive attention from the proper sanitary authorities. A. 
 ship coming from a plague port with infected rats in its hold 
 should be so moored that these animals cannot get ashore. For 
 this purpose rat guards have been devised for the purpose of pre- 
 venting the rodents from leaving the vessel at night by way of the 
 hawsers, and starting an epizootic among the rats on land. Once 
 started in New York or Philadelphia these cities would pass through 
 an experience similar to that of San Francisco. The rat population 
 is ready to hand, the rat flea is ready with his host, and the climatic 
 conditions from May to October are suitable. 
 
 No advantage except a temporary one, is ever gained by deny- 
 ing the exisence of an epidemic in any city. The hiding of the 
 facts gives a chance for the disease to gain headway and to result 
 finally in a greater loss to business and a more appalling loss of 
 life than though the disease were admitted to exist from the begin- 
 ning and proper prophylactic measures immediately instituted. 
 
 Cholera is due to the Bacillus cholerse. It is a water-borne dis- 
 ease, the infected individual polluting the water supply by improper 
 disposition of his feces. Flies are sometimes responsible for epi- 
 demics by first alighting on objects contaminated with the bacilli 
 and then alighting upon exposed food stufifs. It is hardly to be 
 conceived that an epidemic of this disease should start in any of 
 our American cities. The quarantine officers are constantly on 
 the lookout for cases of intestinal disturbance in immigrants from 
 parts in which cholera exists, as well as in the members of the 
 crews of the vessels. 
 
 In Mohammedan countries many pilgrims returning from 
 ]\Iecca bring holy water with them from the Holy City. In order 
 to give all the faithful an opportunity to benefit from the water, 
 the contents of the bottle are emptied into the well or other source 
 of water supply of the village to which the pilgrim belongs. Since 
 the holy water frequently contains cholera bacilli, an epidemic 
 results. With the increasing Mohammedan population of the 
 Pacific coast this is a problem that may confront our health offi- 
 cers in the future. Infection of the individual is to be prevented 
 by boiling the drinking water, by abstaining from the use of 
 uncooked foods, and by care in the production of the milk supply. 
 The house fly should not be neglected. The patient is not dan- 
 
 (407) 
 
164 J he Aiiiials of ilic xlmcricun .Uddciiiy 
 
 gerous provided his intestinal and other discharg^cs are properly 
 sterilized before being consigned to the cesspool or sewer, burn- 
 ing is the most efficacious method of disposing of infected human 
 feces. 
 
 Dysentery, except the amebic form, already referred to under 
 the head of amebiasis, is due to Bacillus dysenteriae. The epidemics 
 are of minor import, so far as they have occurred in our own land. 
 Tn the tropics and in subtropical countries, where the climate 
 is depressing and where the poorer classes are more constantly 
 underfed and overworked than wnth us, the disease often assumes 
 serious proportions. It is water-borne and requires the same ])re- 
 ventive measures that apply to cholera. The fly problem is impor- 
 tant in its relation to this infection. 
 
 Malta fever is caused by the Micrococcus meltensis. Cases of 
 the disease are found in the Mediterranean littoral in greatest 
 numbers. Cases have been found in Cuba and Puerto Rico, Cen- 
 tral and South America, and it is not beyond the range of possi- 
 bility that cases occur along the United States shores of the Gulf 
 of Mexico. In Malta, the disease is supposed to be transmitted 
 by drinking the milk of infected goats ; these animals supplying 
 the milk for the inhabitants of the island. The disease is not very 
 severe and the death rate is small, about three per cent. It is respon- 
 sible, however, for a large amount of invalidism. The problems 
 to be solved in case it should ever be found in our country are 
 entirely hypothetical. 
 
 The attitude of the public toward leprosy is a blot upon our 
 civilization. The disease is caused by the Bacillus leprae. It is not, 
 strictly speaking, a tropical disease, Norway and Iceland being 
 countries in which it is indigenous. It is transmitted only by very 
 intimate personal contact. The patient is not a danger to the 
 community in which he dwells, unless it be proved that the sus- 
 picion, now entertained, that the organism is transmitted by the 
 bites of infected bedbugs is warranted. Even then cleanliness is 
 the answer to the public health question involved. The segrega- 
 tion of lepers in colonies is advisable on account of the repulsive 
 nature of the deformities seen in the advanced cases : but not 
 because there is any fear of an epidemic. 
 
 Leprosy is endemic in many Central and South American 
 States. There is a leper colonv in Louisiana. It is common in 
 
 (408) 
 
Tropical Diseases and Health in United States 165 
 
 the Hawaiian Islands, in China, in Japan, and in the Philippine 
 Islands. The treatment of the unfortunate victim of this disease 
 who was discovered in a village in Maryland about two years ago 
 is shameful, productive of no good to the general public, and an 
 insult to twentieth century knowledge. 
 
 Of the diseases of unknown etiology, yellow fever has been 
 our most serious tropical problem. The disease is endemic in Cuba 
 and in Brazil and has frequently been seen in epidemic outbreaks 
 in our Southern states and in Central and South America. Some 
 cases have been seen on the west coast of Africa, and epidemics 
 have occurred in the past in Philadelphia, New York, and Baltimore. 
 
 The work of the Yellow Fever Commission of the United 
 States Army in Havana, in 1900, has proved that the disease is 
 transmitted by the bite of infected Stegomyia calopus mosquitoes. 
 The problem of prevention of epidemics, therefore, resolves itself 
 into the destruction of Stegomyia calopus. This was successfully 
 demonstated in New Orleans in 1908. Stegomyia calopus appar- 
 ently always breeds in artificial collections of fairly clean water. 
 Consequently the screening of cisterns, wells and reservoirs is abso- 
 lutely necessary. The patient must be treated in a ward or an 
 apartment screened from the access of mosquitoes, and the apart- 
 ment from which he was removed at the onset of the disease must 
 be fumigated for the purpose of killing what adult mosquitoes 
 may be contained in it ; but for no other reason. The patient is 
 harmless, except he is bitten during the first three or four days 
 of his illness. 
 
 The American people owe a debt of gratitude to Dr. James 
 Carroll, Dr. Walter Reed, Dr. Jesse Lazear, and Dr. Aristides 
 Agramonte which pensions and monuments can but partially repay. 
 It is a parsimonious congress indeed that will neglect the widows 
 of Dr. Carroll and Dr. Reed while it corrects the military records 
 of patriotic deserters. 
 
 Dengue is frequently met with in epidemic form in the Southern 
 United States and in the West Indies. It is a considerable factor 
 in morbidity statistics in the Philippine Islands. It is met with in 
 many tropical and subtropical countries. It is not dangerous to life, 
 the death rate being less than one per cent, and the fatal cases 
 being seen in individuals who were already sufifering from some 
 chronic complaint when attacked by dengue. Our knowledge of 
 
 (409) 
 
i66 The Aiuials of the American Academy 
 
 the transmission of dengue is due to the work of the United States 
 Army Board for the study of tropical diseases as they occur in 
 the PhiHppine Islands, Dr. P. M. Ashburn and Dr. Charles F. 
 Craig. These investigators, following the methods pursued by 
 the Yellow Fever Commission in Cuba, have demonstrated the 
 transmission of the disease by the mosquito Culex fatigans. The 
 prevention of epidemics of dengue is a question of mosquito exter- 
 mination. 
 
 Beriberi is a disease indigenous to China, Japan, the Philippine 
 Islands, the Malay Peninsula, and India. It is characterized by 
 an acute febrile period, followed by dropsy, and later, by paralysis. 
 The cause of the disease is unknown. The majority of students 
 of tropical pathology are of the opinion that it is the result of the 
 consumption of spoiled rice. Some few observers believe it to 
 be dependent upon an unknown parasite. 
 
 The presence of a case of beriberi upon a vessel from an 
 Indian, a Chinese, or a Japanese port is no excuse for scareheads 
 in the newspapers. It is perfectly safe to treat such a patient in 
 the general wards of a New York hospital. 
 
 Conclusion. — It is no part of the intention of the writer of 
 this paper to increase the causes of uneasiness of certain suscep- 
 tible individuals among his countrymen. The knowledge that cer- 
 tain diseases exist, that they have well known causes, that they 
 are disseminated by well understood agents, and that their spread 
 can be prevented by well tried methods, should make for peace 
 of mind rather than for worry. A man who is on his way home 
 at night will not fall into the ditch, provided he knows where the 
 ditch is. The knowledge of the existence of an epidemic disease 
 is the most important element of the campaign to eradicate the 
 disorder. 
 
 The application of the various sanitary methods referred to 
 in the course of this paper is of the first importance wherever men 
 are gathered together. We are fairly well informed as to the value 
 of a noncontaminated water supply, of a clean milk supply, of 
 clean streets, of proper garbage and sewage disposition. All these 
 things cost money, but we now know that the money is well spent. 
 Campaigns of mosquito extermination, of fly destruction, of rat 
 and mouse extirpation will be found to be investments that will pay. 
 
 (410) 
 
Tropical Diseases and Health in United States 167 
 
 In the Xobel Lecture at Harvard on December 14. 1910, ex- 
 President Roosevelt said: 
 
 JNlany men have rendered high and honorable service to the United 
 States in connection with the work of the Panama Canal, but by far the 
 greatest and most important work has been rendered by Colonel Goethals. 
 It is to him more than to any other one man that we owe the successful 
 accomplishment of one of the great business and engineering feats of all 
 the ages. 
 
 When it is completed, Colonel William C. Gorgas will have 
 made possible "more than any other one man" the construction 
 of the Panama Canal. The Canal would have been a French 
 achievement, had it not been for yellow fever and malaria. What- 
 ever of dishonestv in affairs may have existed in the French com- 
 pany was of small import beside these two tropical diseases. 
 Shoulder straps have never prevented the bite of a malaria carrier, 
 nor of a yellow fever carrier. 
 
 [Note. — The author would acknowledge his indebtedness to Mr. George 
 S. Bliss, of the Philadelphia office of the United States Weather Bureau, 
 for valuable help concerning the climatological data herein contained.] 
 
 (411) 
 
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