Bovine tuberculosis

“ Though the important question whether man is susceptible to bovine tuberculosis at all is not yet absolutely decided, and will not admit of absolute decision to-day or to-morrow, one is nevertheless already at liberty to say that, if such a susceptibility really exists the infection of human beings is but a very rare occurrence. I should estimate the extent of infection by the milk and flesh of tuberculous cattle and the butter made of their milk as hardly greater than that of hereditary transmission, and I therefore do not deem it advisable to take any measures against it. ”

“ A striking fact is the comparatively small amount of tubercle in calves. It shows, as Nocard has pointed out, that heredity cannot play an important part in the transmission of bovine tuberculosis. The infrequency of the disease in sheep is attributed to the open-air life they lead, and no doubt that is an important factor. The more animals and persons are herded together and breathe the same air in a confined and covered space, the more prevalent is tuberculosis among them. ”

“ If they were to be reinfected by the presence of any consumptive person we might well despair of success in face of a wide prevalence of tuberculosis in man, but since it is only exceptionally that cattle suffer from man, outbreaks coming from this source can the more easily be taken care of. In this view tuberculosis is approximated somewhat more closely to the other bovine plagues (lung plague, rinderpest) which can be stamped out with the greatest ease and certainty, so that as a purely economic measure the argument for the speedy extinction of tuberculosis in our herds is reinforced. ”

“ The increasing amount of evidence pointing to the identity of human and animal tuberculosis, combined with the extraordinary mortality of human beings from this disease, often amounting to 10 to 14 per cent, has raised the question in all civilized countries as to how far animal, and especially bovine, tuberculosis is to blame for this high mortality. ”

“ In view of the general fact that the bovine bacilli show a greater degree of pathogenic action for the lower mammals than the human bacilli, it was natural to assume that bovine bacilli would be powerfully pathogenic for man also. To test this probability directly by experiment is, of course, not permissible. But the belief that tuberculosis in cattle is a menace to man is expressed in the many regulations by which it is aimed to control and prevent the use as food of products derived from tuberculous animals. ”

“ Economic aspects of bovine tuberculosis. Not only is this disease invested with much importance because of its inter-relation with the human, but from an economic point of view alone, it is undoubtedly the greatest scourge that affects the dairyman. ”

“ Such bovine diseases as the several varieties of anthrax, the foot and mouth disease, and especially tuberculosis, are now believed to be transmissible through ingested meat. It has been proved that the pig fed with tuberculous flesh becomes itself tuberculous, and the inference is fair that man might acquire the disease if subjected to the same ordeal. This last disease is very common amongst animals, and is now recognised as identical with that which is so fatal to the human race. ”

“ In view of the wide-spread distribution of this disease in both the human and the bovine race, the relation of the same to milk supplies is a question of great importance. It is now generally admitted that the different types of tubercular disease found in different kinds of animals and man are attributable to the development of the same organism, Bacillus tuberculosis, although there are varieties of this organism found in different species of animals that are sufficiently distinct to permit of recognition. ”

“ A cat inoculated in the same manner died in 23 days of generalized tuberculosis. A rabbit similarly inoculated died in 59 days of pulmonary tuberculosis. Another rabbit inoculated with a bovine culture for comparison lived 10 days longer than the one inoculated with this sputum germ. Mohler also inoculated subcutaneously a 1-year-old heifer with a culture derived from the tuberculosis mesenteric gland of a boy 4 years of age. This culture was always refractory in its growth under artificial conditions, and the bacilli were short, stubby rods, corresponding in appearance to the bovine type. ”

“ Again, we have half a dozen similar instances in the case of tuberculosis itself. The horse and the sheep, for instance, are both most intimately associated with cattle, pastured in the same fields, fed upon the same food, and yet tuberculosis is almost unknown in sheep and decidedly uncommon in horses, and when it does occur in them is from a human source. The goat is almost equally immune from both human and bovine forms, while the cat and the dog, although developing the infection with a low degree of frequency, almost invariably trace that infection to a human source. ”

“ Rabbits are less vulnerable to the bovine or human form.
Sheep and goats, kept under usual conditions, show a remarkable immunity from tuberculosis, yet if directly inoculated an inherent susceptibility is easily shown. Habitual immunity may be in some degree due to their open air life, to the heavy winter fleece protecting them against chills, to the comparative absence of the heavy and continuous milk yield demanded of cows, to the more restricted development of the lymph plexuses in the lungs and elsewhere, and to the limited opportunity offered by the small tonsils for infection entrance. ”

“ It has been a disputed question for some years whether the organisms producing bovine and human tuberculosis are identical or from the practical standpoint, whether the bovine type of disease is transmitted under natural conditions to man. The bacteriologist can readily detect differences in appearance, in growth of cultures, and in disease-producing properties between the two strains. Of the two, the bovine is much the more virulent when inoculated into experimental animals. In a considerable number of cases, record of accidental infection from cattle to man has been observed. ”

“ On this view the answer to the question, Can the bovine bacillus affect man? is obviously in the affirmative. The same answer must also be given to those who hold the theory that human and bovine tubercle bacilli are different in kind, since the ' bovine kind ' are readily to be found as the causal agents of many fatal cases of human tuberculosis. ”

“ These various manifestations are all produced by the inroads of the specific organism, Bacillus tuberculosis. The bovine, as well as swine, fowls, and other warm-blooded animals, are also affected with similar diseases. In man, the importance of the malady is recognized when it appears that fully one-seventh of the human race die of this scourge. In cattle, the disease is equally widespread, particularly in those countries where live stock has been intensively developed. ”

“ Smith, Dinwiddie and Adami, while showing a very marked limitation in the susceptibility of the sound bovine system to weak bacilli from man, cannot disprove the many well authenticated cases of the transmission of tuberculosis from cow to man and the reverse. The greater potency of the bovine bacillus over that of man, in its 483action on the small rodents and pigs, utterly forbids the unproved assumption that it is on the contrary harmless to man. ”

“ Unless this disease is so far advanced as to affect the general health of the cow, or it has spread to the milk organs, the udder and the teats, it is not so dangerous as has heretofore been supposed. It is now held by the great majority of physicians that 36bovine tuberculosis is hardly ever transmitted to grown persons and seldom to children. ”

“ It follows from what has been said that the only way in which we can acquire tuberculosis is by getting into our bodies tubercle bacilli from tuberculous men or animals. The only animals liable to convey the disease to man are tuberculous cattle, and these through the use of either meat or milk. The danger from the use of uncooked meat or the unboiled milk from tuberculous cattle is real and serious, but it will not be considered here at length, because the great and prevailing danger of infection comes from another source. ”

“ Many (not all) cattle, when injected with tuberculin repeatedly at short intervals, acquire a tolerance of the agent and fail to react as at the first test. We have in such cases examined the animals post mortem and found active tuberculosis. Unscrupulous owners, aware of the fact, have their diseased cattle injected repeatedly every few weeks, and as soon as they fail to respond, sell them under the guarantee of the tuberculin test. The cattle, of course, carry the infection into other herds. ”

“ It has not been definitely decided at the present time whether the drinking of milk from tuberculous cows brings with it the danger of tuberculosis for mankind. It will certainly be best to avoid such milk, especially when the cow's udder is found to be tuberculously diseased or when tubercle-bacilli can be traced in the milk.
The use of meat as food may also become dangerous to man, but this is a rare occurrence. It is particularly dangerous to eat the liver, kidneys and lymphatic glands of tuberculous animals. ”

“ There is to-day no greater danger to the cattle and hog industries than that which confronts them in the form of tuberculosis, a disease already widespread and rapidly extending. Furthermore, in view of the results revealed by numerous tests covering vast numbers of animals, tuberculin must be considered as harmless for healthy animals. It has also been clearly demonstrated that tuberculin interferes in no way with the milking function in healthy cattle; neither in the quantity of milk nor in butter-fat value has any variation been detected. ”

“ As man, cattle, swine and Guinea pigs show a much greater vulnerability than the carnivora in general, so certain families in each of these genera show a more decided susceptibility to tuberculosis under similar conditions than do certain other families. This goes far to explain the appearance of tuberculosis, in certain lines of blood, and its advance to the extinction of the family, while under no better environment, other families can count on a practical immunity. ”

“ This low percentage of failures being the case, cattle owners should welcome the tuberculin test, not only for their own interest but for the welfare of the public as well. Where this method of diagnosing the disease has been adopted tuberculosis is gradually being eradicated. Without its use the disease can not be controlled and the owner is confronted with serious and continuous losses; with its use the disease can be eradicated from the herd, a clean herd established in a few years without very serious loss or hardship, and the danger of its spread to man removed. ”

“ In fact, I have never heard of range cattle being tubercular. Nevertheless, under conditions that exist on the average farm, the tuberculosis germ will thrive and cause havoc. It pays to be careful not to introduce such a disease into the herd. Often the fattest, sleekest cattle are affected and while they do not die from it quickly, yet as it progresses in a herd an animal will now and then die from the disease. Hogs and even chickens running with the cattle become affected and much loss results.
The accuracy of the tuberclin test in the main has been established beyond doubt. ”

“ However, cattle showing any weakness, or the above symptoms should be tested for tuberculosis by the administration of tuberculin.
Treatment.—It is not advisable to treat tuberculosis. Thus far, medicine has failed to relieve the affected animal, or kill the bacillus of tuberculosis in a living animal. The infected animals should be disposed of on account of tubercular cows giving birth to tubercular calves, the milk being unfit for human consumption, unless it is thoroughly pasteurized. Infected cattle should be separated from healthy ones, as the disease spreads very rapidly. ”

“ It is impossible to adopt in man the summary measures that are so successful in the speedy stamping out of the plagues of the lower animals, so that tuberculosis in the human family can only be eradicated by slow degrees, and therefore there will long continue for our herds the danger from the human side, but just so far as the susceptibility of cattle to human tuberculosis is limited, in the same ratio are our hands strengthened in effective work for the extinction of consumption in our herds and for preserving their soundness after they have once been purified. ”

“ It should be strongly emphasized in this connection that the failure of extension and generalization of the sputum germ when transferred to cattle does not distinguish it from the tubercle bacillus as conveyed from ox to ox. Everyone at all experienced with the tuberculin test well knows that in most herds the majority of the tuberculous animals show no generalization, but only a localized tuberculosis. There is reason to believe that even recoveries take place after slight infection, and it is certain that many tuberculous cattle continue for years in what appears to be good general health. ”

“ But the mere possibility of demonstrating that a small percentage of tubercular cows will cause human tuberculosis is sufficient to justify all possible precautions against tubercular animals and against the distribution of tubercular milk. In this connection it is worth while noting that the cows most affected by tuberculosis are those confined in small crowded stables, with no fresh air, with no exercise, and with insufficient or improper food. ”