[All Rights Reserved.] VETERINARY PAPERS FOR FARMERS.

Otago Witness, Issue 2456, 10 April 1901, Page 5

[All Rights Reserved.] VETERINARY PAPERS FOR FARMERS.

VIII.— TUBERCULOSIS. (Bt Professor Wortlet Axe.)

EOW TUBERCULOSIS IS SPREAD.

The propagation of the di=ease from anf» mal to animal requires the transference of the infectiiig organism, directly or indirectly, from the sick to the healthy. In this cc nnection pp.tholo gists of all countries have shown by experiments, repeated again and again, that the virus of tuberculosis may 2?rove effective by entering the body in ono cf three ways. (1) It may gain access through tha . digestive organs, m food and v-ater; (2) i£ may reach the lungs in the respired air; (3) it may enter the body through a wounded Furface. By whichever of these stveral chamiels it gains admission, it J3 cupable of exercising the same destructive ci ergy. Of these three modes of access, that by inhaling contaminated air is by far the most common. Here the infecting crganism may exist as dust derived from the desiccated discharges of the sick, or be transferred directly from diseased to healthy stock in the expired air, or the humid exhalations of other excretions. Next in importance is the digestive tract, into which the virus is conveyed by specifically infected food and water. Having entered the victim. by one or another of these ways, the parasitic life of the organism is commenced. Established in the tissues of the body, it grows and multiplies more or less rapidly, depending upon the suitability of its environment and the natural resistance of its host. While it lives and thrives on the juices of the bociy, it elaborates within itself a poison with which it impregnates the tissues, causing their death and disintegration. In this way organ after organ is assailed and destroyed, until life is sapped and finally rendered impossible. Long, however, ere this, the body of the victim commences to give out its crop of deadly germs in foul discharges from the lungs, the bowels, the womb, or the udder, in accordance as the one or the other is the seat of disease, and the liability to spread of infection from such sources will be greater or less in proportion as they are guarded and destroyed.

DIAGNOSIS OF THE DISEASE

Although W'> speak of "symptoms of ths disease," it must be cleaily under=tood than their entire absence, nay, even the outward manifestations of robust health, are quite consistent with the existence of advanced tuberculosis Hundreds of affected cattle, laden with flesh and fat, find their -nay to the shambles, where, for the first time, the presence of disease is made known. Notwithstanding our long acquaintance with this malady, and the cntical observation to whicn it Las been subjected in all its vanous forms-, we me still unable to i ely on clinical phenomena, alone as a means of diagnosis. It is true that in its .more advanced stages symptoms may afford grounds for tho strongest suspicion, but they cannot be said to be afc -aJiy time conclusive of its presence. Sines tlio diseo\ery and identincd.l ion ct t'-.e Tubercular para c ite, it ha-> become possible in mrny instances to affiim with certainty Ilia existence of the disease during- life, by Ftibmitting the di s charq;es from affected oigans to miscro c copieal inspection, or morulating them into healthy animal*. In the one case the organism is brought directly urder observation, in the other its effects are, sooner or later, seen in the de\elopment of thi di?ease.

ACTI'OX OF TVBFFCUI IX,

Tho merits of tins preparation, as a d ie; no=tic agent lia\o lecer, ed universal iccc^nition by meinl.ois ot the \etermary profusion, m both lh'- and other countries. All Mho ha\e submitted it to the test of ex-r-eiiment agioe Ihit ie pn^c^ej the power to mark out the tubeivu'iGU 8 from the healthy, and «o fui one of 'j\o obstacles to legislation ioi coiitiol or the cli&ca=e has been removed. That, li^e otl.ot" physiological methodo, it shou'd have sometimes failed to yield sati-sfactmy i exults is not surprising, but it is by no means clearthat the reputed failures of tuberculin wcie not in great part due to want of cxpeiicr.ee m the lequnements of its u-e. For the exercise of its specification tubeiculm requues that the tubercular miciobe shall be ■present in the body into wJvch it is inoculated, and that the former «hall be introduced into the system either directly byway of the blood-ves->els, or by being injected beneath the skin. Wheit tubfrculiu

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is given by the^ mouth, even though the ditease be present, no obvious effects follow its use. If injected into the veins or under the skin of a healthy animal, there is no visible disturbance, but where tuberculosis exists the effect is most marked. Here % distinct febrile reaction is induced, the tnost conspicuous feature of whicli is a rise pf the body temperature, varying in different cases from 2deg to 6deg. This takes place tat- different periods between the tenth and (fifteenth hour after inoculation, and eonftlnues for eight or ten or more hours later. «W-hor© proper precautions are observed in' ••arrying out the test — and this is of the first importance — such a result may be accepted )b.3 evidence of the presence of the malady. The duration and severity of the fever reWaiting from tuberculin bearß no fixed relation to the extent of the existing disease. Qndeed, it may- be said that the reaction induced is generally least pronounced where *be disease is most advanced, while cases ."which afford no outward indications of its existence react with the greatest energy. CAN Tr/iEECTJLOSIS BE ST4MPED OUT? Cn this, as on many another question relating .to the spreading diseases that threaten the lives of men and animals, opinions vary, not only among veterinarians, but also among sanitarians and pathologists. The extermination of contagious diseases of animals has been shown to. be passible. Cattle plague, fpot-and-moutlU disease, and pleuropneumonia have each in turn yielded to measures of sanitary legislation, and there are -hose who appear to think that the exteranination of tuberculosis must necessarily follow the same course of action. This, however, is an assumption for which there is aio real foundation. The prospect of eradicating a contagious disease must depend_ on considerations of (1) the zoological distribution of the disease; (2) the vitality of the *.rganism out of which it springs, and the various conditions under which such organism is capable of existing; (3) the manner •_n' which it spreads from one animal to another ; and (4) the duration and course of the cdeeaeo. As to the zoological distribution of the disease, we have seen that, besides "being the greatest of human plagues, it is common -to all our domesticated creatures. This in itself is a eerious drawback to the adoption of those heroic measures on which success would depend. When to this is lidded the great tenacity of life displayed by the tubercular organism, the various ways an which it may enter its victims, and the etealtby nature and long endurance of the tlisease, extermination must be regarded as a uopeless, endless ta^k. The stamping-out «ystem, however energetically applied to ■cattle alone, could not reasonably be expected to succeed, unless other animals affected with the disease were also dealt with, and even then the task would be rendered -raitless by that host of infected people — estimated to number no less than 150,000 to 200,000 in England and Wales alone — from •whom the disease would continue to be impprted to our animal population.

■Votwithstanding these obstacles to complete success, everyone will agree that the time has arrived when some attempt should Tje made to diminish the waste of human life now going on, and lighten the burden that pi esses so heavily on the stockowner from this terrible scourge. To stamp out the diEea3e in our cattle, whose tainted milk and meat contribute so much to the sickness crate and death rate of our noble selves, is a consummation most devoutly to be wished ; but, apart from obstacles already referred to, there is still another, w!JKch cannot be lightly eet aside. Few of those who call for heroic measures of eradication have calculated the possible cost of the enterprise, and it may ibe interesting to examine the question from the standpoint of those who would require m find the mean 3. Our total cattle population is returned at 11.519,417. These comprise 4,014,055 cows and heifeis in milk or in calf, and 7,505,362 head of other description of stock. It is necessary for the purpose of this estimate to keep these two groups separate, for although it is impossible to state precisely the ft'nount of disease existing in either, it is certain that the malady prevails to a much greater extent in the one group than in the other. We have but few stptittics on which to base a calculation of t^e extent of pie- \ alence"~of tubesculosiß in the herda of tlii3

I country, but such as 'are available have the merit of being reliable as far as they go, and may suffice for an approximate estimate i of the cost which a general crusade against lit would incur. When the Pleuro-pneu-j monia Act of 1890 came into operation, it j was considered by the veterinary experts of the Board of Agriculture a favourable opportunity of collecting information as to the prevalence of tuberculosis, with the result that, of the total cattle slaughtered by order of the board in the 16 months between September, 1890, and the end of December, 1891, 12.22 per cent., or about 1 in 8 of all cattle dealt with, were found to be affected with the disease. When the returns were analysed in regard to particular classes of cattle, it Tfas found that cows suffered to the extent of 16.09 per cent., bulls in the proportion of 1.53 per cent., while other cattle over one j year old were affected to the extent of 2.77 , per cent., and those under one year old to 1.2 per cent. The percentage of tuberculous cows varied in different herds, being in some cases as high as 75 per cent. As tli3 result of the inspection in 1892, it was found that, of the cows slaughtered by order of the board, 22.3 per cent, were tuberculous, ■wjiile of the other cattle, nearly 15 per cent, were affected. These figures, considerable though they be, cannot be taken to represent tV actual proportion of disease existing in our cow stock, since the post-mortems were not of that searching character which later experience of the malady has shown to be necessary, but they mark the extent of prevalence of the disorder only in that palpable form which reveals itself to ordinary obser- | vet ion. t Since the advent of the tuberculin test, it has been made clear that the large numbers of animals suffering from tuberculosis in whom th' 3 lesions can only be brought to light by a most critical and exhaustive examination of the various organs of the body, and the experience gained by the use of this agent for diagnostic purposes, added to that here and elsewhere referred to, warrant the con- , elusion that of our four millions of cows, j 1 in 5, or 20 per cent, at the least, are the victims of tuberculosis. On this estimate, the number of infected animals in the cow group will amount to 800,000, which, valued at £14 prjj, head as healthy stock, shows a money value of £11,200.000. If. as it would appear, the remaining 7,505,352 animals suffer to the extent of 3 per cent., we get an additional 211,500 affected animals, which, estimated at £10 per head as healthy stock, would, in round numbers. amount to ' £2,115,000 sterling. This, added to the sum j of £11,200,000. the value of affected cows, ! "shows a grand total of £13,315.000 worth of catt'e hopelessly diseased and dangerous be1 sides, both to man and animals. 1 Assuming the average duration of the disorder to be two year 3, and the whole of the infected animals were permitted to die out, our annual loss directly from cattle alone would amount to £6,657.500. As, however, large numbers are slaughtered in different stages of the disease, and sold for human consumption, a substantial set-off must on this account be allowed. We have no data on which to base a calculation here, but we ' cannot appraise the losses by death and depreciation at less than half the amount last given. This would reduce the annual loss to £3,328,750. It must, however, be observed that no account is taken of wasted j food, fruitless labour, veterinary fees, and abortion, of which tuberculosis is a muck 1 underrated cause. If there is no hope of effectually stamping out tuberculosis, there is certainly no reason to doubt the power of preventive medicine to very largely diminish its prevalence. For 50 years pleuro-pneumonia ravaged our herds, and in* 50 weeks it was well ni^h exterminated. Few, very few, realised until then the efficacy of veterinary sanitary science and police, and from the present at- ' titude of the stockowner and the general public in regard to tuberculosis, the lesson then taught would not appear to have created in them a long-abiding faith, for as yet neither the one nor the other has sought protection against the common enemy.

WHAT TO DO. What to do, and how to do it, is the question that awaits solution. So far as cattle are concerned, it has been pointed out repeatedly that milch cows, animals habitu i ally kept in confinement thioughout a laige port-on oi tlxe year, are especially the vic-

tims of the disease, and in connection with this fact, it is important to remember that the transmission of the malady from animol to animal is mainly effected by the breathing of specifically contaminated air. To prevent contamination, therefore, by this means, and to insist on those piovisions which admit of it 3 removal when existing, are clearly the two conditions requiring v be fulfilled.

Prompt isolation of the obviously sick, it would be thought, would be generally adopted by stock owners as a matter of common prudence and self-interest, but, with some notable exceptions, this is not the case. Animals far advanced in disease — obviously tuberculosis— are allowed to continue to cohabit with healthy stocla for months, in some of our largest milking herds, to the common danger of both man and beast. To allow this state of things to continue, in view of the untold sacrifices it entails, is not only a discouragement of those who labour in the cause of veterinary sanitary science, but a disgrace to the nrtion.

If it be inexpedient, on the ground of expense, to adopt the stamping-out system, it is surely desnable to minimite the evils of infection by isolation and extermination of the obviously s:ck. For cairying out this puiposc, it is imperative that, all danies, both in town and country, whence milk is sold for human consumption, shall be periodically inspected, and reasonable compensation allowed for animals slaughtered. It should also be provided that no animal having a diseased condition oi the udder, should be allowed to supply nvlk for public use. Where dairymen and ttockown 1 - s desire to have their animals tested, tuberculin for this purpose ehall be provided by the Government. Still more important to the success of prevention is the question of capacity, ventilation, and cleanliness of byres, for so long 8 5 animals actually, but not obviously, diseased, are permitted to cohabit in largo numbers with healthy stock, spread of the malady will be greater or less, in proportion as these conditions are increased or diminished.

It docs not appear to be realised that the chief factor in the spread of infection is the pernicious and unrestrained practice of overcrowding, and the studied exclusion of air and light from the sheds in which dairy stock aie housed.

If we cannot strike at the root of this Upas tree, we may, by improving the sanitary conditions of cow life, materially check its destructive growth. To insist on ample Epace, and still more on the free and uninterrupted ingress and egress of air in our byres, ifi the first and most urgent requirement in the cause of prevention. That to lower the temperature of cowsheds would, in some degree, increase the cost of milk production goes without saying, but the loss from this cause would be far outweighed by the gain in animal health, to say northing of the mitigation of human suffering and sacrifice. Cowsheds, then, as well as cows whose- milk is sold for public UEe, should be periodically inspected, and all reasonable sanitary requirements insisted on. Such a scheme might require the registration of all dairy establishments, but this is not an insuperable difficulty, and cannot be allowed to stand in the way of reform in animal sanitation in which such serious issues are involved.