Popular Science Monthly/Volume 42/December 1892/Protective Inoculation for Cholera
|PROTECTIVE INOCULATION FOR CHOLERA.|
IT would be difficult to say where the idea first originated of the possibility of artificially producing occult changes in the organism of a healthy individual, so that, if exposed to a contagious or an infectious disease, there would be an acquired resistance that would prevent the development of such a disease. Tradition states that, in the case of small-pox, the custom existed in South Wales of rubbing matter from the pustules of a small-pox patient on the skin of a healthy person's arm, in order to protect the latter individual from acquiring that malady; and, for a similar purpose, it was the custom in the Scottish Highlands to wind about the wrists of children worsted threads that had been moistened with such matter. Inoculation of healthy persons with variolous matter had long been practiced in Oriental countries when Lady Mary Wortley Montagu introduced it into England. And as recently as our civil war this procedure has been employed, because the usually mild attack of small-pox following the inoculation is less dangerous than the ordinarily acquired form of that disease.
The discovery of the protection afforded by vaccination suggested new working theories; for it was as remarkable that the contagious principle of small-pox should undergo some modification in the human system as it was that it was decidedly modified in the cow. It has been demonstrated by many experimenters that, in a calf that has not had cow-pox, inoculation of small-pox virus will cause that disease; and, furthermore, that matter from the eruption on the calf's udder will, if inoculated in an unvaccinnated person, produce the well-known phenomena of vaccinia. Science, accordingly, learned two facts from this: that the virus of a disease may be diminished, or attenuated, in its development in an animal organism other than that in which it found its most poisonous growth; and that this attenuated virus, introduced into the organism of an individual susceptible to the influence of the original disease, protected that individual by conferring an artificial immunity.
To these known facts regarding small-pox was added that knowledge gained during years of observation by both medical and lay men, that one attack of a contagious or infectious disease protected the individual, as a rule, from a subsequent attack if exposed thereto in later years. Little or no perceptible alteration existed in the human organism, and yet it had acquired some singular quality that enabled it to resist the infection of that disease if ever again exposed thereto.
It is to-day believed by excellent authorities that the processes by which this immunity is obtained vary as widely as do the processes of disease themselves. Each of these infectious diseases produces in the blood certain poisonous substances; and as man can be, so to speak, familiarized with a poisonous drug by the administration of doses that gradually increase from one that is harmless to one that ordinarily would be at once fatal, so there is probably a similar Mithridatic transformation in the character of the fluids of the body that have once met and conquered the toxic principle of an infectious or contagious disease.
Working on this hypothesis scientists have been experimenting with the introduction into the animal organism of the poisonous substances called toxines, toxalbumins, leucomaïnes, or ptomaïnes, that are produced by the micro-organisms of the various diseases, in order to determine the possibility of preventing the susceptibility for acquiring these diseases.
The discovery of a method that would protect an individual from cholera would be of great usefulness. For in India, the home of that disease, the average annual mortality therefrom in the cities is 3·32, and in the country 1·52 per 1,000 living. The army statistics show that 2·49 per cent of the European soldiers are admitted to the hospital for cholera, while only 0·95 per cent of the native soldiers are admitted for the disease; but the mortality, 33·69 per cent for the former, 35·5 per cent for the latter, is almost equal. In the various epidemic manifestations of cholera in various parts of the world the mortality has often exceeded 50 per cent of those attacked. In 1884 and 1885 cholera was epidemic in southern Europe, and in Spain in the latter year the official report states that there were almost one hundred and twenty thousand deaths. There were fifty-one persons affected in each thousand living, and the mortality was 36 per cent. These statistics stimulated investigators to attempt to solve the problem of affording immunity to cholera.
In March of 1885 Dr. J. Ferran, living in a small town in Catalonia, sent a communication to the French Academy of Sciences in which he described some experiments he had made with the specific organism of cholera, the comma bacillus, Koch's comma bacillus, the cholera spirillum, or the cholera vibrio, as it has been variously termed.
By experiment it had been learned that the cholera spirillum, like many other micro-organisms, would develop plentifully in certain nutritive substances, such as a very rich beef broth or jelly if kept at a certain temperature. Such an artificial propagation of a micro-organism is called "a culture" of that organism. Ferran found that the maximum virulence of the cholera spirillum was obtained in a culture of rich, slightly alkaline bouillon, and that from thirty to sixty drops of this culture would kill a guinea-pig, if inoculated under the animal's skin; but, if a smaller dose was inoculated, a local inflammation followed that might slough though the ulceration would heal spontaneously without forming pus; and this animal would not be subsequently affected by the injection of a quantity of the culture of the cholera spirillum that would rapidly prove fatal in an unprotected animal.
Ferran reasoned that if such a result could be obtained in the organism of a lower animal, why could it not be secured in the highest animal? Accordingly, he injected hypodermically in man, fifteen drops of his virulent culture: a hot, painful tumor, with local fever, and malaise followed, but without choleraic discharges from the bowels; and these symptoms disappeared in twenty-four hours. If a similar quantity was reinjected in the man a week later no general and few local symptoms followed. He therefore considered that by these injections of graduated doses he could arouse in each person's system that resistance to the disease that has been heretofore referred to. He did not believe that the cholera spirillum multiplied in the cellular tissue that is beneath the skin, but that it produced in the tumor formed at the point of inoculation a rapidly diffusible toxine that exercised some influence upon the nervous centers. The dangers of an attack of, and death from, cholera begin to disappear five days after the first inoculation, and each successive inoculation increases the guarantee of immunity; three inoculations, each of thirty drops of the bouillon culture, at intervals of five days, produced a profound immunity.
He continued his experiments, and in 1886 sent another memoir to the French Academy of Sciences, wherein he stated that cultures of the comma spirillum in which the living organism had been destroyed by a high temperature, would, when inoculated confer a tolerance that successfully resisted the effects of the living spirillum. He furthermore stated that an active principle was generated by the spirillum, that could be isolated by certain familiar chemical methods, and that conferred the power of resisting the living micro-organism.
During the epidemic in Spain, Ferran's inoculations were practiced in more than thirty thousand persons. In the province of Valencia there were 62·33 cases per thousand of population, and 31·11 per thousand died of cholera. Where inoculation was generally practiced the cholera affected 76·95 per thousand, with a mortality of 33·58, of the total uninoculated; while among the inoculated 12·69 per thousand were attacked, and only 3·41 per thousand died. In other words, in the latter class 6·06 times fewer people were attacked, with a mortality 9·84 times less than that of the uninoculated.
Ferran's methods were investigated by commissions from several of the European scientific societies; and by several, notably that from France, he was condemned for having made claims that could not be demonstrated.
In 1888 Dr. Gamaleia published the results of experiments he had made with the cholera spirillum. He found that the cultures of this organism, as obtained from the human body, lose their virulence in the laboratory. In order to restore this virulence, and possibly to enhance it, Dr. Gamaleia first inoculated a guinea-pig with the cholera spirillum, and when the disease was apparent in that animal made an inoculation from it into a carrier-pigeon. This was on the principle employed by Pasteur to increase or attenuate the virus of chicken-cholera, rouget, anthrax, and rabies by inoculating different animals with the respective virus of those diseases. So toxic does the cholera spirillum become in the pigeon, that a few drops of its blood rapidly kill an animal susceptible to cholera. He also found that in a sterilized culture of the spirillum there was a principle that, administered in non-toxic doses to an animal, would afford subsequent protection from cholera. The phenomena produced by these inoculations were similar to those observed by Ferran in his own experiments, though no inoculations were made in man by Gamaleia. G. Klemperer has reported this year experiments that verify those made by Ferran and Gamaleia. He discovered that a guinea-pig could be protected against cholera by inoculating it with the serum of the blood of a rabbit that had been protected by inoculation of mild cultures of the spirillum; and in one rabbit that had been rendered immune to pneumonia as well as to cholera, its serum afforded protection from cholera to guinea-pigs, and from pneumonia to mice. He considered that these results corresponded with the immunity observed in human beings after an attack of Asiatic cholera.
During this year Haffkine has reported to the Paris Biological Society experiments that he has made with the spirillum. One of the objections that has been made regarding the acceptance of this organism as the sole cause of cholera has been the difficulty of reproducing in animals, by injections of the spirillum, a disease that generally resembled human cholera. Haffkine adopted the ingenious plan of using diluted serum obtained from rabbits as the medium for the development of the spirillum, and transferring a few drops from this to a less diluted serum, and so on until the micro-organism lived in the undiluted serum. If the spirillum thus acclimatized, so to speak, be injected into the blood-vessels of a healthy rabbit, the animal will die with all the symptoms of cholera; this serum might be called a virulent culture. By passing an ordinary bouillon culture of the spirillum through a series of guinea-pigs he could also obtain a virulent culture that rapidly killed if injected into the abdominal cavity, but that, when injected under the skin, produces phenomena similar to those described by Ferran, and results, as the latter stated, in rendering the animal immune against inoculation with cholera in any strength whatever. Rabbits and pigeons were rendered immune in the same way. These results induced Haffkine to try the inoculations on himself and seven other persons; the phenomena observed in each of these individuals were similar to those reported by Ferran, and a second inoculation made after an interval of seven or eight days produced far less general and local disturbance than the first. While differing slightly in the methods employed, all these later experimenters, it may be seen, have confirmed Ferran's original report, although none of them mentions his name or the priority of his discovery.
What is the value of these inoculations? This may in part be answered by the question, What is the harm? All observers concur in stating that in animals, as well as in man, the inoculations, made in moderate doses, are harmless beyond producing a slight local irritation and temporary malaise. And any one who has been subjected to the inoculations can easily determine at any future period whether he is then protected, by receiving another inoculation; just as a later determines the protection of the individual by an earlier vaccination.
It is necessarily conceded that the factors that enter into the question of natural are not those of artificial infection. But it is necessary to recall the facts stated in the first portion of this paper; and it is seen that there are good grounds for believing that immunity against natural infection is correlated with immunity against artificial infection. There may be no exact and absolute demonstration of this fact, for no vaccinated person willingly associates with a small-pox patient, or has himself inoculated with matter from a small-pox sore, in order to determine his immunity toward that disease. The vital statistics of this century answer the question regarding the utility of vaccination. Whether those of the coming century will answer that regarding the utility of inoculation as a preventive not only of cholera, but of other infectious or contagious diseases, remains to be decided.