In studying the statistics of bovine tuberculosis of this province, I have had the hearty support of the government officials as well as of many county veterinary surgeons. After my colleague, Dr. Römer, had examined several thousand head of cattle we ceased our labors because we were confronted by the depressing fact that larger herds of cattle were rarely ever free from tuberculosis. As a test to discover the presence of tuberculosis we made use of small infections of Koch’s tuberculin. We are aware that there are tuberculous animals which do not react to this test. On the other hand, if the method of making the test be faultless, a positive reaction always indicates that the animal in question is infected with tuberculosis. Our figures for these cases are therefore without doubt too low. Despite this, and despite the fact that young cattle, even though infected with tuberculosis, often do not react to the usual dose of tuberculin, we found frightfully high figures for herds of more than twenty animals. We had to admit that in this respect we were no better off than other countries. I will cite one of the most experienced of the investigators of tuberculosis, Prof. Bang of Copenhagen, who says that in Denmark, in stables of more than fifty head of cattle, an average of 60% of the animals are tuberculous. Bang says further: “If one is dealing with a large herd in which tuberculosis has existed for many years, one may as well omit testing the full-grown animals. Most of them will react, even though they appear perfectly healthy.” To this, as a result of many years’ observation, I should like to add, and though they may apparently remain perfectly healthy for their entire life.
As a rule a herd of cattle on a large farm, though infected with tuberculosis, presents a fine appearance. Nor does their state of nutrition, milk production, or calf-raising leave anything to be desired. Now and then a cow coughs, or, despite plentiful food, loses flesh. This animal is put aside and the herd, as such, resumes its magnificent appearance. If in a herd reacting to tuberculin things are allowed to go on in this way for a number of years, especially if the cattle be barn-fed, then, to be sure, the number of coughing animals increases, the offspring deteriorate, the milk and meat production decrease, until finally the scourge of tuberculosis is plainly marked.
Carefully conducted epizootic researches in our province have led me to the discovery that a single, native, mountain breed of cattle, that of Vogelsberg, was probably free from tuberculosis as late as twelve years ago. Through imported cattle the tubercular infection was then introduced. But even now the percentage of animals responding to the tuberculin test is about one-quarter that of other breeds. What is curious, however, in these cattle is, that whereas, according to common experience in all other breeds, the percentage of reacting animals increases with their age, in these Vogelsberg cattle the percentage from the fifth year on even decreases. This may depend on the smaller number of animals infected five years ago. Some of the exceptions, however, I must account for by the definite healing of lesions and a consequent disappearance of the reaction. The favorable termination of the tuberculosis in these Vogelsberg cattle I ascribe to the smaller accumulation of the tubercular virus in the still relatively little-infected stables, or, what amounts to the same thing, to a smaller dose of the virus infecting the suckling calves. These, of course, take up the infecting agent not only from the mother cow, but also from the other cattle. One can plainly see how the percentage of reacting cattle in this Vogelsberg breed increases from year to year, and I feel certain that ten years hence these cattle will be as badly off in this respect as other breeds, provided measures are not taken to check the advancing infection. Such measures we have had at our command for some time, and their usefulness has been thoroughly proven. I know of a large number of herds which, by means of Bang’s rules, have been made free from tuberculosis and kept so. It is, however, an expensive procedure and requires the constant supervision of an expert, and even then is usually possible only on large estates where any reacting animal may immediately be separated from the unaffected herd. When, therefore, I published a method of protective inoculation against tuberculosis, one which I had proved in my own stables, I was pleased with the spirit of hearty cooperation shown by the owners of large dairies who had already experimented largely with Bang’s procedures.
Through the courtesy of Count Zedlitz I was enabled to make numerous preventative inoculations on cattle in three counties of Hesse-Nassau; from there the experiments were extended to the neighboring grand duchy of Hesse, and to the large dairy of Bolle in Köpenik near Berlin. As a result of this work I was able in the beginning of this year to establish the harmlessness of the procedure. Since then I have had abundant opportunity to inoculate calves under three months on the immense Hungarian possessions of Prince Ludwig of Bavaria; also on those of Archduke Frederick of Austria. Under my direction scientific researches regarding the protection afforded by the inoculations have been undertaken by Prof. Eber in the veterinary school of the University of Leipzig and by Prof. Schlegel in that of the University of Freiburg; further also by Ober-med. Rath Lorenz in Darmstadt and by Prof. Hutyra in Budapest. In Marburg I myself have made studies on highly immunized cattle regarding the production of anti-bodies, have reared calves on cows immune to tuberculosis, and have investigated the subject of immune milk.
All the details have been carefully recorded. Some of these protocols have already been printed, and at the close of this year I hope to commence the publication and working out of the rest of this enormous mass of material in my “Beiträge zur experimentellen Therapie.”
In the mean time, however, the practical application of my immunizing procedure continues steadily to gain in extent. Austrian as well as Swedish investigators, sent by their governments to study the inoculation technique at Marburg, are to make extensive inoculations in their native countries. The government of the grand duchy of Hesse has ordered that the counties use part of their police fund to defray the expense of inoculating all calves free of charge, provided that the owners bind themselves to allow the county veterinarian to supervise the inoculated animals. From all sides I receive requests for this preventative virus.
Until recently I prepared this virus myself and distributed it free of charge with the help of private funds. I was able to do the entire scientific, technical, and administrative work with only a few assistants. But this is no longer possible, for the expenses have outgrown not only my financial means, but also, even with great zeal for the work, my bodily strength. I should gladly have postponed any change in the manufacture and distribution of the virus until the Prussian government was ready to take charge of the entire matter. But the daily increasing labor has made it necessary for me to rid myself of this burden now, and I have therefore provisionally arranged that the firm of Drs. Seibert & Ziegenbein of Marburg undertake the manufacture.
That this free distribution of the protective virus for tuberculosis of cattle has been completely justified is seen by the report of Koch’s Institute, entitled, “Ueber Immunisierung gegen Tuberculose.” To be sure, this report contains nothing positive that, as a result of a large number of experiments, I had not already maintained for some years. And it lacks, what is especially important in the practical immunization of cattle, namely, proof in the form of protocols. Possibly these were omitted because they would fail to substantiate Neufeld’s assertion that Koch, previous to my publication regarding protective inoculations of cattle with living tubercle bacilli, had already made use of the same procedure. I cannot refrain from observing that Neufeld treats this question of priority in rather unusual fashion, for he now claims for Koch an immunizing procedure which I had published as long ago as 1901. It would surely have been more reasonable to have made these claims sooner, before the success of the method became so generally recognized in agricultural circles. Finally I must criticise the author for making similar uncalled-for claims for the English investigator Macfadyan. As the one most concerned, such claims might have been made by Macfadyan himself, yet, so far as I know, that investigator has not even suggested such a thing. In the case of my diphtheria-serum discovery I can entirely overlook similar baseless and unjust claims for Roux and for Ehrlich. Such claims have often been made by medical authors, but neither Roux nor Ehrlich has ever authorized such a perversion of facts.
However, apart from these inaccuracies, the report of Neufeld regarding Koch’s tubercular immunizing experiments shows an agreement with my results which extends into the smallest details. This, then, must demonstrate to the world the absolute reliability of my immunizing principle. The entire suppression of bovine tuberculosis is now only a question of conscientious and properly conducted protective inoculations, and, of course, also a matter of time.
Just now I am studying the important practical point which for a long time occupied the attention of students of vaccination. We now know that protection against variola is only then secured when the vaccination is followed by a typical inflammatory reaction. Are the requirements the same for bovine tuberculosis? This I cannot yet definitely answer; and even under the most favorable conditions I shall be able to answer it only after a lapse of two years. By that time the calves that were injected only once and that did not, so far as we could ascertain, react to the inoculation, will have grown to maturity.