Part 18

The pathological change in all the above cases consisted chiefly of intense congestion of intestines, both large and small.

Cultures from the original case of ratin, on agar, bouillon, and in fermentation tubes, negative except staphylococcus in one tube.

Cultures taken from heart’s blood and other organs of the 4 dead rats all negative, except in one case a growth of a staphylococcus resembling _S. pyogenes citreus_.

April 20: Two rats fed on half agar slant culture of the staphylococcus obtained from heart’s blood of rat No. 1. Result of feeding negative after several weeks.

NOTE. The absence of a colon-like organism in this virus and the rapid death of the animals with convulsions suggested a chemical poison, which it is believed this can contained.—M. J. R.

EXPERIMENTS WITH MICRO-ORGANISMS FOR DESTROYING RATS, CONDUCTED BY THE UNITED STATES BIOLOGICAL SURVEY.[AV]

Footnote AV:

This report was furnished by Dr. A. Hart Merriam, Director of the Biological Survey.

RATIN.

The Biological Survey, Department of Agriculture, in cooperation with the Bureau of Animal Industry, has experimented with “ratin.” The material (ratin No. 2—labeled “Transatlantic ratin”) was furnished by the American agents in New York. Although the agent claimed that this was a bacterial preparation and that “it would kill for six generations,” it proved to be a glucoside poison (probably squills) and contained no bacteria of any kind. A number of experiments were made with it, and it proved to be an effective rat poison. In some instances the animals died within two hours after eating it, and in two experiments all the animals fed died within twelve hours. In other experiments, however, a considerable percentage of the affected rats recovered, and subsequent attempts to kill them with ratin No. 2 failed. Some were immune to its effects and others too wise to eat it a second time. More than a hundred rats were used in the experiments; but the main object—to test the communicability of the disease caused by ratin bacteria in healthy rats—failed, of course, since, as above stated, the preparation experimented with contained no bacteria, but was merely a vegetable poison. Before its character was fully determined, 15 rats killed in the experiments were eaten by 5 healthy rats; the latter were unaffected.

It should be noted that the labels on the tins containing transatlantic ratin were misleading. The user was warned to open the packages in dim light and to allow no moisture to come in contact with the contents, as the bacteria were very sensitive to light and moisture. The contents of the can were to be used at once. As a matter of fact the contents of one can were exposed to severe drying in heat and sunlight for four days and then soaked in water for two days. Afterwards the preparation was fed to different rats for a further period of four days, and its virulence was retained to the last.

The transatlantic ratin is in a solid medium, apparently bread and molasses. Its keeping qualities are excellent, and it is an effective poison for rats, but far too expensive for extensive use. A can costing $1.50 is enough for only 15 baits.

Its harmfulness to domestic animals was not fully tested. Dogs and cats refused to eat it and vomited it when it was forced upon them. Several animals, including a dog, were killed by injections of the poison in concentrated form.

A shipment of ratin No. 1 (the solid bacterial ratin, said to retain its virulence for two months) was received June 4, 1909. This preparation was dated May 8 and should have been still virulent. The contents of a can mixed with milk was fed to 8 adult rats on June 7. All of the baits were eaten, but no result followed. Cultures of the bacteria showed strong growths of new colonies.

On July 6 the contents of another can were fed to 1 adult and 16 young rats. One of the young was found dead on the morning of July 14. Cultures were made from the dead rat, but the bacillus was not recovered. Up to July 28 none of the other rats have been affected.

AZOA.

Several trials of azoa for the destruction of rats have come under the observation of members of the Biological Survey. Experiments made in the building occupied by the Interstate Commerce Commission were at first promising, but from a second invoice of the virus no results were obtained. In the buildings of the National Zoological Park 72 bottles of azoa were used, but the results were for the most part negative. In a store in south Washington where this preparation had been used the stench of dead rats was very strong, showing a measure of success.

DANYSZ BACILLUS.

Some three years ago the Biological Survey, assisted by the Bureau of Animal Industry, tested the efficiency of Danysz virus. In the laboratory from 10 to 50 per cent of rats fed on the virus died. In the field, however, results obtained were unsatisfactory. Only 1 dead rat was found from which the bacillus was recovered. Experiments with field mice gave better results. All the mice fed in confinement died, and field experiments resulted in many dead mice from which the bacillus was recovered.

EXPERIMENTS DURING THE SAN FRANCISCO PLAGUE OUTBREAK.[AW]

Footnote AW:

These experiments were made by Passed Asst. Surg. G. W. McCoy, United States Public Health and Marine-Hospital Service, in 1907–8 during the plague campaign in San Francisco and here published for the first time.

Several proprietary biological products sold as rat exterminators were made the subject of seven experiments on wild San Francisco rats, for the purpose of ascertaining whether they were efficient for the purpose for which they were sold. Seventy-six rats were used in these experiments. About 10 per cent died within a month and there was considerable doubt as to whether all of the deaths that occurred were due to the agent used.

The following is a brief statement of the work done with these agents. In each case the rats used were wild _Mus norvegicus_, caught in San Francisco.

RATIN NO. 1.

Made by the Bakteriologik Laboratorium, Copenhagen, marked: “Effective two months from April 28, 1908.” The preparation comes ready for use in the form of a moist, mealy mass. On May 28, about 6 ounces of the material was fed to 12 rats. They all remained well until thirty days after feeding them when the experiment was regarded as terminated.

DANYSZ VIRUS.

The Danysz Virus Company (Limited), of London, furnished a preparation in the form of a culture on a slant of solid medium, said to be gelatine. The tube was marked: “To be used before June 1, 1908.” The contents of the tube, mixed with bread, according to directions, was fed to 6 rats. On the twenty-first day but 4 rats remained, 2 having died and been devoured by their companions. The 4 that remained were chloroformed, as the cage was needed for other purposes. Post-mortem examination showed them to be entirely normal.

RATITE.

Furnished by the Pasteur Vaccine Company, Chicago. This preparation is in the form of a culture in a liquid medium, presumably broth. The bottle was dated April 10, 1908, and the label stated that it should be used within twenty days from date of preparation. On April 29, 1908, 9 rats were fed with about 6 ounces of the preparation, mixed according to directions. The rats all remained alive and well, and when chloroformed on June 1, 1908, presented no abnormality on post-mortem examination. In another experiment the contents of a bottle of ratite was fed to 6 medium-sized _Mus norvegicus_. None of the animals died from the effects of the agent, and when they were killed on the fifty-fifth day after the feeding were found to present no lesions.

The remaining work was done with rat virus, sometimes called “Mouratus.” It is made by the same concern that makes the ratite. The rat virus comes in the form of a culture on a solid medium. The contents of three tubes was fed to 6 rats on May 26, 1908. Three of these rats died within thirty days. Only one was secured for examination before it had been mutilated beyond the possibility of making a satisfactory examination. This rat had a large yellow liver and a very large, dark, firm spleen. These appearances were probably due to the agent used and it is not unlikely that these 3 rats died from its effect. It will be observed that a very large dose was given. On another occasion four tubes of Mouratus were used for feeding 6 _Mus norvegicus_. One of the rats died on the fifteenth day, showing at autopsy an enlarged granular spleen and a granular liver. The other rats were alive and well at the end of thirty-four days when the experiment was discontinued.

Subcultures on broth were made from this preparation on three occasions, always well within the time limit on the label. The cultures were incubated in the dark, at room temperature, for forty hours on each occasion. Liberal amounts of the subculture were fed to a total of 31 rats. At the end of thirty days, it was found that only 2 of these rats had died. The others were alive and apparently well.

One objection to these agents which I have not seen stated is the following: The lesions caused by at least some of these members of the paracolon group may readily be mistaken for the lesions of plague, or it will perhaps be more accurate to say they give rise to lesions that create in one’s mind a suspicion of plague infection, and I have had to put many a rat to the guinea-pig test in order to make certain that a Danysz infection was not associated with the infection of plague, or that a Danysz rat was not a plague rat. Of course, this is of no consequence except in a community where antiplague measures are being taken, and an observer of limited experience who did not put a rat to a pretty rigid test would probably call some plague infected when in reality such is not the case.

In addition to the data set forth in this report, I have on several occasions fed the tissue of rats dead of Danysz infection to other rats, but have never succeeded in reproducing the disease. In other words, I have had no success whatever in raising the virulence by passage through animals.

OPINIONS OF OTHERS.

Kitasato,[AX] 1906, states that the typhoid bacillus of the rat, which has been effectively used for killing field mice, has been found useless for house rats (_Mus rattus_) and therefore they no longer employ it.

Footnote AX:

Kitasato, S.: Combating plague in Japan. Philippine Journ. Sci., vol. 1, 1906, p. 465.

Melvin,[AY] 1908, reports that recently several new rat viruses were investigated in the Bureau of Animal Industry, with the result that the experiments clearly demonstrated the ineffectiveness and unreliability of the preparations tested.

Footnote AY:

Melvin, A. D.: Report of the Chief of the Bureau of Animal Industry for 1908. Washington, 1908.

Räbiger and Schwinning,[AZ] 1906, tested the culture discovered by G. Neumann and prepared by the joint stock company “Ratin” at Copenhagen by applying it to rat destruction. Of house rats 90 per cent died; black rats 42.9 per cent; while horses, dogs, goats, sheep, fowls, and pigeons suffered no harm. Of seven experiments practically carried out, six showed very good results; in one favorable results were absent, which agrees with the experiments made in Denmark. There it was likewise found that in individual locally limited places the rats were able absolutely to withstand the infection of ratin.

Footnote AZ:

Räbiger and Schwinning: Versuche mit Ratin, einem neuen Ratten tötenden Bacillus. Mitth. d. deutsch. Landw.-Gesellsch., 1906, No. 18. Rev. by Ehrenberg in Centblt. f. Bakt., 2. Abt., vol. 18, 1907, p. 375.

Räbiger,[BA] 1905, states that experiments with Loeffler’s mouse typhus bacillus and the bacillus of Danysz virus have been carried to the conclusion that these bacterial preparations must be characterized as practically worthless.

Footnote BA:

Räbiger, H.: Ueber Versuche zur Vertilgung der Ratten durch Bakterien. Landw. Woch. f. d. Prov. Sach., 1905, p. 142. Rev. by Stift in Centblt. f. Eakt., 2 Abt., vol. 15, 1905, p. 86.

In 1903 Neumann discovered in Denmark a rat-killing bacillus, which has been placed on the market by a society under scientific control under the name of “ratin.” Feeding experiments with this bacillus were tried under conditions as nearly natural as possible upon white mice, gray house mice, long-tailed field mice, and gray rats. The experiment animals were fed with cubes of white bread impregnated with virulent cultures. White mice show the least power of resistance, since they die within six days; house mice died in six to nine days; the greater part of the rats died from the sixth to the sixteenth day after feeding; a small percentage lived. The long-tailed field mice, which are shown to be insusceptible to Loeffler’s bacillus, also remained perfectly healthy after repeated feedings with bread infected with ratin.

Brooks,[BB] 1908, reports the results of tests made with azoa on rats and mice, both in captivity and at large, but without any apparent discomfort to the animals. One of the tests is described as follows:

Footnote BB:

Brooks, Fred E.: Notes on the habits of mice, moles, and shrews. A preliminary report. Bull. 113, W. Va. Univ. Agric. Exper. Sta., Morgantown, W. Va., Jan., 1908.

A supply of the azoa was obtained direct from the laboratories of the manufacturers. On July 27, 1907, while the material was yet fresh, three young Norway rats were caught and kept confined in a large wire rat trap. Beginning with the date given, and for a period of forty days thereafter, azoa was fed to the rats at intervals of a few days until ten 75-cent bottles had been consumed. The rats ate the cracked grain with which the virus was mixed very readily, and other food was denied them each time the azoa was given until every particle was eaten. At the end of the forty days the rats were still apparently in a healthy condition, and were removed from the trap and killed with a club.

Thompson,[BC] 1906, states that three laboratory attempts have been made to destroy rats with imported strains of Danysz rat virus without success. Danysz having arrived at Sydney to study a similar method of destroying rabbits, the opportunity was taken of making a further attempt under his supervision with virus which had been imported and subsequently increased to the requisite degree of virulence, and had been placed at Thompson’s disposition. The grounds of the Gladesville Asylum, a large institute for the insane, were chosen for the tests, which were conducted by Dr. R. J. Millard.

Footnote BC:

Thompson, J. Ashburton: Report of the Board of Health on plague in New South Wales, 1906. On a sixth outbreak of plague at Sydney, 1906. Legislative assembly, N. S. W., 1907.

Millard summarized his result by stating that they can not be considered a satisfactory demonstration of the efficacy claimed for the Danysz virus. The results indicate a rapid loss of virulence, which must be obviated if this virus is to be of utility for rat destruction.

Again, in 1907, during the seventh outbreak of plague in Sydney, Thompson[BD] had Millard test the preparations known as azoa and ratin. The laboratory results with these preparations were similar to those made by other investigators. Experiments made upon the ship _Hartfield_ with azoa produced no considerable epizootic. The fatality among such rats as were infected was small. The practical tests with azoa upon several areas along the harbor front also resulted in disappointment.

Footnote BD:

Thompson, J. Ashburton: Report of the board of health on plague in New South Wales, 1907. On a seventh outbreak of plague at Sydney, 1907. Legislative Assembly, N. S. W., 1908.

The tests made with ratin upon the bark _Quilpe_ produced no epizootic among the rats, and of the rats caught none of them showed infection; and the field experiment at Gladesville also resulted negatively so far as dead or sick rats were concerned. Nevertheless, there was apparently considerable diminution in the rat population of this area.

Foster,[BE] 1908, reports unfavorably upon the results of tests made of some of these rat viruses. Laboratories were opened for the use of different parties who wished to make tests. The tests were conducted under their own supervision. The rats which were not fed on anything but grain died as freely as those that had been fed on azoa. So far as this preparation is concerned Foster states that it is absolutely useless to depend upon it.

Footnote BE:

Foster, N. K.: The danger of a general plague infection in the United States. Proc. Confer. State and Prov. Boards of Health of N. America, 1908, p. 15.

Several reports are found in print in which the rat virus was laid out in certain localities and shortly afterwards the rats disappeared—at least no more were noticed. Such observations are apt to be misleading, for rats are migratory. They come and go, especially when disturbed. Further, it is doubtful, as far as plague is concerned, whether it is desirable to drive the rats away, for they may thus scatter the infection.

S. S. Mereshkowsky and E. Sarin[BF] have recently studied ratin II, put out by a Copenhagen firm—“Bakteriologisches Laboratorium Ratin.” The label upon the can of ratin II states that it is a bacterial culture, which produces in rats an infectious and fatal disease, killing them in two to eight days. The samples used by the authors were obtained as needed from the St. Petersburg representative of the firm. Feeding experiments carried out with gray rats (_Mus decumanus_) showed that the rapidity and severity of the symptoms was proportional to the amount ingested. No positive results were obtained from the bacteriological examination of the bodies.

Footnote BF:

Ueber das Ratin II. Centralb. für Bakt. Parstk. u. Infectsk. Originale. Bd. 51. Heft 1. July 17, 1909, p. 6.

The ratin itself was sometimes found to be sterile, sometimes found to contain several varieties of bacteria and fungi, but no one variety was constantly present.

The potency of the ratin was not altered by exposure to 100° C. for one hour or 120° C. for five minutes. It was destroyed, however, by burning to an ash.

Identical poisonous results were obtained upon rats by feeding them with “Scilla maritina cum bulbo rubro.”

Microscopical examination disclosed a small portion of a lamella, identified as belonging to the Liliaciæ, to which family squill belongs.

The authors conclude that ratin II is not a bacterial culture, but a poison rendered more dangerous to persons and domestic animals by the misleading statements of its makers.

PATHOGENICITY FOR MAN.

Loeffler[BG] rather took it for granted at first that his _Bacillus typhi murium_ was harmless for man. In order to remove the fears of the peasants in his campaign against the field mice in Thessaly he fed pieces of bread impregnated with the cultures to chickens, pigeons, dogs, hogs, horses, asses, sheep, and goats. No ill effects resulted. Further, some of the men who were distributing the prepared virus ate pieces of the infected bread in the presence of all and, it appears, suffered no ill effects.

Footnote BG:

Loeffler, F.: Die Feldmausplage in Thessalien und ihre erfolgreiche Bekämpfung mittels des Bacillus typhi murium. Centblt. f. Bakt., vol. 12, 1892, p. 1.

Up to this time Loeffler had made no human experiments, but thought it improbable that his bacillus was harmful to man. He considered this view confirmed by the fact that he and his companions and still more so the peasants, handled large quantities of the virus without thorough disinfection of their hands and suffered no untoward effects.

Since that time, however, several mishaps have occurred. Instances of serious sickness and even death have been attributed to infection with the bacterial virus used for the destruction of rats.

Further, there is practically no difference between the _Bacillus typhi murium_ and the para-typhoid bacillus which is the well-known cause of meat poisoning, and the _Bacillus enteridion_ of Jarbues, which is associated with intestinal disorders.

It is true that persons have purposely partaken of the rat virus to prove that it is harmless to man; but it must be remembered that persons have partaken of cultures of cholera, typhoid, and other bacteria without apparent injury to themselves. The flora and condition of the gastro-intestinal tract, the amount and virulence of the infection, and other conditions (“Y” and “Z” of Pettenkofer) play an important rôle in the production of these diseases.

The following references from the literature give the instances in which the _B. typhi murium_, or similar rat viruses, have been held responsible for the disease in man:

Trommsdorff[BH] carefully studied 13 suspected cases near Munich in early May, 1903. Nine of these came into direct contact with the virus, three ate and associated with these, and the remaining one only smelled of the virus. One died from vomiting and severe diarrhea. The illness, which set in usually two days after contact with the virus, was for the most part simple diarrhea of two to seven days’ duration (two to eight stools daily); in only three or four cases was there vomiting. The one fatal case seemed due to a confusing chain of circumstances, gross dietetic and alcoholic excesses in a weak, emaciated, presumably phthisical man whose three brothers had died of phthisis. One man, case No. 2 in the table, known to have eaten three pieces of infected bread, suffered only with a mild diarrhea.

Footnote BH:

Trommsdorff, R.: Ueber Pathogenität des Löfflerschen Mäustyphusbazillus beim Menschen. Münch. med. Woch., vol. 50, 1903, p. 2092.

In all cases errors of diet could be proven, and diarrhea was not uncommon at that season. The same physician attended during this period ten other cases of similar diarrhea in the vicinity having nothing to do with rat virus. The stools, however, did not have the same pathogenicity for mice, guinea pigs, or rabbits.

Trommsdorff specially points out the fact that the bacillus of mouse typhoid can multiply vigorously in the human intestine. It demands greater caution in the application of the cultures and more careful supervision over their use.

Finally, attention is invited to the fact that, contrary to the usual custom, the cultures of rat virus here used had been grown on milk, which might account for the increased virulence.

The following table gives a brief summary of ten cases with the results of the agglutination tests: