Part 8 (1/2)

The question of prime importance is, whether the bovine type is transmissible to the human or not Artificial inoculation of cattle with tuberculous human sputum as well as pure cultures of this variety show that the huht headway in cattle This would indicate that the danger of cattle acquiring the infection froht, but these experiments offer no answer as to the possibility of transmission from the bovine to the human Manifestly it is impossible to solve this problem by direct experiment upon man except by artificial inoculation, but coht on the question

Theo Smith[81] and others[82] have s, rabbits and pigeons, inoculated with both bovine and huanism The results obtained in the case of all animals tested show that the virulence of the two types was much different, but that the bovine cultures were much more severe

While of course this does not prove that transmission from bovine to human is possible, still the importance of the fact must not be overlooked

In a number of cases record of accidental infection from cattle to ed inpost-mortem examinations on tuberculous animals, and the tubercular nature of the wound was proven in some cases by excision and inoculation

In addition to data of this sort that is practically experi clinical reasons for considering that infection of huh the medium of milk

Naturally such infection should produce intestinal tuberculosis, and it is noteworthy that this phase of the disease is quite coes of two and five[84] It is difficult to deterh the intestine, for, usually, other organs also become involved

In a considerable number of cases in which tubercular infection by the most common channel, inhalation, see that the disease was contracted through the medium of the milk, but it is always very difficult to exclude the possibility of pulmonary infection

Tuberculosis as a bovine disease has increased rapidly during recent decades throughout many portions of the world This has been ions Its extrenition by physical means, and it was not until the introduction of the tuberculin test[85] in 1892, as a diagnostic aid that accurate knowledge of its distribution was possible The quite general introduction of this test in e of animals as affected In Dennosed as tubercular In some parts of Gerhter-house statistics also show that the disease has increased rapidly since 1890

In this country the disease on the average is ularly distributed In herds where it gained a foothold soo, often the majority of anireat majority, are wholly free from all taint The disease has undoubtedly been h the purchase of apparently healthy but incipiently affected aniions where stock has been i,the western and southern cattle

[Illustration FIG 21: Front view of a tuberculous udder, showing extent of swelling in single quarter]

~Infectiousness ofanimals~ Where the disease appears in the udder the anism

Under such conditions the appearance of the milk is not resses the percentage of fat generally dies where the physical condition of the udder is changed (Fig 21), the e of anie, usually notto Ostertag)

On the other hand, in the earlier phases of the disease, where its presence has been recognized solely by the aid of the tuberculin test, before there are any recognizable physical syenerally unaffected Between these extre which so definite data are not available The results of investigators on this point are conflicting and further infor as the udder itself shows no lesions that no tubercle bacilli would be present,[86] but the findings of a considerable nuators[87] indicate that even when the udder is apparently not diseased the anism as revealed by inoculation experiments upon animals In some cases, however, it has been demonstrated by post-mortem examination that discoverable udder lesions existed that were not recognizable before autopsy waspercentage of reacting aniave positive results; and this nuer of using h apparently no disease could be found in the udder

The infectiousness of milk can also be proven by the frequent contraction of the disease in other anis which may be fed on the ski the swine of Germany and Denmark,[88] and the frequently reported cases of intestinal infection of young stock also attest the presence of the organism in milk

The tubercle bacillus is so markedly parasitic in its habits, that, under ordinary conditions, it is incapable of growing at norer in milk after it is drawn from the animal, unless the sah the erous organis the test, it is quite i it will reeneralized, or if tuberculous lesions should develop in the udder, the milk may pass from a healthy to an infectious state

This fact makes it advisable to exclude from milk supplies intended for human use, all milk of animals that respond to the tuberculin test; or at least to treat it in a manner so as to render it safe Whether it is necessary to do this or not if the milk is made into butter or cheese is a somewhat different question Exclusion or treatment is rendered reater with children hom milk is often a prominent constituent of their diet, and also for the reason that the child is more susceptible to intestinal infection than the adult

The danger of infection is much lessened in butter or cheese, because the processes of inally present in the rowth can ordinarily take place in these products the danger is minimized Moreover, the fact that these foods are consuenerally the case where reater extent by adults, lessens still further the danger of infection

Notwithstanding this, numerous observers[89] especially in Ger the tubercle bacillus inwhen it is ree fraction of their cattle show the presence of the disease as indicated by the tuberculin test, a condition that does not obtain in any large section in this country

The observations on the presence of the tubercle bacillus in butter have been questioned somewhat of late[2] by the deteranis stained in the saanism Differentiation between the two forms is rendered anis in anih a careful examination reveals definite differences Petri[90] has recently deter butter organism may be readily found in market butter

In the various milk products it has been experimentally determined that the true tubercle bacillus is able to retain its vitality in butter for a number of months and in cheese for nearly a year

~Treatment of milk from tuberculosis cows~ While it has been shown that it is practically i animal actually contains tubercle bacilli or not, still the interests of public health demand that no milk from such stock be used for human food until it has been rendered safe by so_ By far the best treativen such milk is to heat it The temperature at which this should be done depends upon the thermal death point of the tubercle bacillus, a question concerning which there has been considerable difference of opinion until very recently According to the work of soators, the tubercle bacillus in its vegetative stage is endoith powers of resistance greater than those possessed by any other pathogenic organism This work has not been substantiated by thethe theranism, as of any other, not only must the temperature be considered, but the period of exposure as well, and where that exposure is made in milk, another factor must be considered, viz, the presence of conditions per of the formation of a ”scalded layer,” for as Sanisreatly increased under these conditions If tuberculous milk is heated in a closed receptacle where this scalded membrane cannot be produced, the tubercle bacillus is killed at 140 F in 15 to 20 minutes These results which were first determined by Smith, under laboratory conditions, and confirs,[92] where tuberculous milk was heated in commercial pasteurizers, have also been verified by Hesse[93] A great practical advantage which accrues fro is practically unaffected Of course, where a higher temperature is employed, the period of exposure may be materially lessened If milk is momentarily heated to 176 F, it is certainly sufficient to destroy the tubercle bacillus This is the plan practiced in Denmark where all skim milk and whey must be heated to this temperature before it can be taken back to the farned to prevent the dissemination of tuberculosis and foot and mouth disease by means of the mixed creamery by-products This course renders it possible to utilize with perfect safety, forto the tuberculin test, and as butter of the best quality can be h teht expense ould otherwise entail a large loss

_2 Dilution_ Another ested for the treate volume of perfectly healthy milk It is a well known fact that to produce infection, it requires the sianisms, and in the case of tuberculosis, especially that produced by ingestion, this nuht to be considerable Gebhardt[95] found that the milk of tuberculous cohich was virulent when injected by itself into animals, was innocuous when diluted with 40 to 100 times its volume of healthy milk This fact is hardly to be relied upon in practice, unless the proportion of reacting to healthy cows is positively known

It has also been claial separation of creaer number of tubercle bacilli were thrown out with the separator slime Moore[97] has shown that the tubercle bacilli in an artificially infected er microscopically deh to prevent the infection of animals inoculated with the milk