than a suspicion that it is concerned in relapsing fever, in kala-azar, and it has been accused of carrying the bacteria of tuberculosis, leprosy, and many other diseases.

KALA-AZAR

Kala-azar is a tropical infection characterized by anemia and enlargement of the spleen. It is caused by a parasite which occurs in great numbers in the spleen and which, upon culture media, develops into a flagellated organism resembling the trypanosomes. The trypanosomes were discovered by Leishman and Donovan in the spleen and liver and the epithelium of the blood vessels. Manson and Low found similar bodies in the ulcerous mucous membranes of the intestines, and Marchand and Ledingham found the same peculiar bodies in the cells of the bone marrow and lymphatic glands. Rogers cultivated the parasites from the spleen of patients suffering with kala-azar upon agar streaked with fresh human blood. Flagellate forms developed. This was confirmed by Christophers, who used Novy's method of growing trypanosomes upon the water of condensation of blood agar tubes. The kala-azar parasites grown in artificial culture media have a cilium but no membrane.

References. The literature upon insects and insect-borne diseases is very widely distributed. Many of the entomological facts contained in this chapter have been taken from "The Insect Book" by L. 0. Howard and the many excellent publications of Howard and his colleagues of the Bureau of Entomology, Department of Agriculture. The Government publications may be had upon application to the Superintendent of Documents, Washington, D. C. Many of the facts concerning the prevention and destruction of mosquitoes have been taken from articles in the Public Health Reports of the Public Health and Marine Hospital Service. In the chapter upon insecticides free reference has been made to my own book upon "Disinfection and Disinfectants," as well as my other writings and unpublished work in different phases of this subject.

CHAPTER V

MISCELLANEOUS DISEASES

INFANTILE PARALYSIS

(Acute Anterior Poliomyelitis)

An entirely new literature upon the subject of infantile paralysis is now being constructed. The chief contributors to this recent advance in our knowledge have been Wickman of Sweden, who, in 1905-06, gave us a new symptomatology, and defined clinical types not before recognized. Wickman made the first systematic study of the disease from an epidemiological point of view, and found evidence that it was contagious, though usually slightly so. He directed especial attention to several factors in its spread, viz.: routes of travel, public gatherings of children, abortive or ambulant cases, and healthy intermediate carriers. In the spring of 1909 Landsteiner, and Popper succeeded in transmitting the disease to two monkeys by inoculating them with the spinal cord of a child who had died of infantile paralysis. Later in the year Flexner and Lewis obtained the same results, and further transmitted the infection from monkey to monkey through an indefinite number of passages. To Harwitz and Scheele of Norway we are indebted for formulating the pathologic anatomy of the affection.

Infantile paralysis is now properly regarded as a communicable disease. The virus is filterable, that is, "ultramicroscopic," yet coccæ forms have been described by Noguchi and Flexner in artificial cultures. (J. A. M. A., Feb. 1, 1913, LX, 5, 362.)

It appears that infantile paralysis is becoming more and more common and more widespread of late years. This increase cannot be accounted for by the fact that the disease is now better known and more readily recognized. Bergenholtz, in 1881, described the first outbreak with sufficient accuracy to accept infantile paralysis as a new disease. Since that time the number of outbreaks and the number of cases have progressively increased, as shown in the following table:

Recent outbreaks have occurred in Norway and Sweden, Austria, Germany, Holland, England, Spain, France, the United States, and Cuba. Of the 8,054 cases reported in 5 years (1905-09), the United States contributed 5,514 cases or about five-sevenths of the total number.

Epidemics of poliomyelitis have prevailed in all quarters of the world. The disease has been most prevalent in the northern parts of Europe and of the United States. Epidemics have been more severe, and the case rates have been higher, in small towns and rural districts than in the more densely populated cities. Even in the cities the disease does not especially strike the crowded districts. Cold countries having marked seasonal variations in temperature have been most affected, but the disease is always most prevalent in the warm, dry months, from May to November in the northern hemisphere and November to May in the southern hemisphere. Sporadic cases may occur at any time throughout the year. The great majority of cases occur in children under five years of age. From the standpoint of prevention it is important to note that social and hygienic conditions apparently have no influence whatever in determining the infection. All classes are affected in about equal proportion.

The virus of the disease is present in greatest virulence or concentration in the spinal cord of infected persons and animals. One onehundredth of a cubic centimeter of an emulsion of cord, or less, is sufficient to infect a monkey. The virus is also quite constantly present in the brain and other organs and tissues, as, for instance, the mucous membrane of the nose and pharynx, the mesenteric glands, the axillary and inguinal lymph nodes, also in the blood, and in the cerebrospinal fluid. The virus has been demonstrated in the feces. The suspicion. that the alvine discharges may, therefore, be virulent is sufficient indication that they should be disinfected in all cases until further knowledge of the subject is at hand.

The experimental disease in monkeys may be produced with certainty by injecting the virus directly into the central nervous system, preferably the brain. Monkeys may also be infected by introducing the virus subcutaneously or into the peritoneal cavity, and even by intravenous inoculation. They have been infected by placing virulent

material upon the healthy mucous membrane of the nose and also by inhalation of the infectious material forced into the trachea, and finally by introducing the virus into the stomach, along with an opiate, to restrain peristalsis. Leiner and Weisner have infected monkeys through the uninjured nasal mucous membrane. This, however, is an uncertain method of inoculation. Monkeys have so far never been known to contract the disease spontaneously, even though they are kept in intimate association with infected monkeys. There are many similar paralytic diseases of the lower animals, but, so far as known, infantile paralysis as a natural infection is peculiar to man. Recently Rosenau and Brues, and also Anderson and Frost, have transmitted the disease from monkey to monkey through the bite of the stable fly.

Resistance of the Virus.-The virus of anterior poliomyelitis is killed by a temperature of 45° to 50° C. in half an hour; also by comparatively weak disinfectants, such as a 1-500 solution of permanganate of potash, 1 per cent. menthol in oil, a powder containing menthol, 0.5 per cent., salol, 5 per cent., boric acid, 20 per cent. (Landsteiner and Levaditi), and a dilution of perhydrol (Merck) equivalent to 1 per cent. of peroxid of hydrogen. The virus is not destroyed by very low temperatures nor by drying over caustic potash, or in vacuo for a considerable period. A virulent cord has been kept for almost 5 months in pure glycerin without losing its virulence, resembling in this respect rabies, vaccine, and other filterable viruses, and differing for the most part from non-spore-bearing pathogenic bacteria which are usually killed by pure glycerin in a short while.

Immunity. One attack of infantile paralysis apparently confers a high degree of immunity. Recurrent cases and second attacks have been reported. Monkeys which have recovered from the infection show a high degree of resistance, in that they are not susceptible to infection by again inoculating them, and their blood serum contains antibodies capable of rendering the virus harmless. That is, if the blood serum of an immune monkey is mixed with an emulsion of virulent spinal cord and the mixture allowed to stand for several hours, the virus is no longer capable of producing the infection in susceptible animals. This property has been used by Anderson and Frost to corroborate the clinical diagnosis in abortive cases. The blood of a person who has not had the disease does not neutralize the virus; therefore, if the injection of the virus previously treated with human serum fails to produce the infection in susceptible monkeys, it may be taken as evidence that the serum contained specific antibodies and came from an individual who has had the disease.

Modes of Transmission.-CONTACT THEORY (BASED UPON THE ASSUMPTION THAT THE VIRUS IS DISCHARGED FROM THE MOUTH AND NOSE AND ENTERS THROUGH THE SAME CHANNEL).-There is evidence to sup

port the theory that the disease is directly transmissible from person to person and there is a suspicion that healthy carriers play an important rôle in spreading the infection. This view was enunciated by Wickman and received support through the experiments of Kling, Pettersson and Wernstedt, and also Flexner. It is known that the mucous membrane of the nose and throat contains the virus, and in one case the salivary glands were shown to be infective. Osgood and Lucas demonstrated that the nasal mucous membrane of two monkeys experimentally inoculated with poliomyelitis remained infective for 6 weeks in one case and 52 months in another. This very important observation strengthens the suspicion of the existence of chronic human carriers. If healthy carriers continue to spread the infection months after the attack, it increases the difficulty of suppressing the disease, and further renders doubtful the efficiency of strict isolation and prophylactic measures directed only to persons in the acute stage of the disease. The fact that the mucous membrane contains the virus is not, however, sufficient proof that the virus is liberated and discharged in sufficient amount in the secretions from the mouth and nose to be a menace. In a series of 18 cases Rosenau, Sheppard and Amoss were unable to demonstrate the virus in the nasal and buccal secretions obtained from persons in various stages of convalescence. Strauss 2 had similar negative results in a series of 10 cases. On the other hand, Kling, Pettersson and Wernstedt 3 report successful results; by experiments upon monkeys they demonstrated the infectiousness of buccal and intestinal secretions of living subjects. Flexner has recently also reported one successful attempt in demonstrating the virus in the buccal secretions.

THE INSECT-BORNE THEORY.—Infantile paralysis shows no tendency to prevail in congested centers or to spread in hospitals, schools, institutions, and other crowded places; its seasonal prevalence corresponds to the seasonal prevalence of most insects, and does not correspond to the seasonal prevalence of diseases spread through secretions of the mouth and nose, such as diphtheria, scarlet fever, smallpox, etc. Many other factors, brought to light by the studies of the State Board of Health of Massachusetts upon the epidemiology of the disease, under the able direction of Dr. Mark Richardson, indicate that the disease is not a contagious one. These studies gradually focused attention upon some 1 Rosenau, M. J., Sheppard, P. A. E., Amoss, H. L., Boston Med. and Surg. Jour., May 25, 1911, CLXIV, 21, pp. 743-748.

3

Strauss, I., J. A. M. A., April 22, 1911, LVI, 16, 1192.

Kling, C., Pettersson, A., and Wernstedt, W., Report from the State Medical Institute of Sweden to the XV International Congress on Hygiene and Demography, Washington, D. C., 1912. Also, Zeitschr. f. Immunitätsforch. u. exper. Therapie, Bd. XII, Jena, 1912.

Richardson, M. W., Monthly Bull., State Board of Health of Mass., Sept., 1912, 7, 9, pp. 308-315.

Lovett, R. W., Report to the Mass. State Board of Health, 1907.

Report to the Mass. State Board of Health, 1908, 1909, 1910, 1911.