EDITORIAL ARTICLES.

E D ITO R I A L ART I C L E S. --0--

VACCINATION AGAINST ANTHRAX.

IN an article which appeared in this J oumal for March last, we said that it appeared to us that when veterinary surgeons were consulted as to what should be done in an outbreak of anthrax, unless they had sufficient reasons for doubting the accuracy of the published statistics, they ought to advise the owner to have his animals submitted to the Pasteurian vaccination.

At that time there were scarcely any available statistics except those relating to vaccinations practised abroad, and these certainly appeared to prove that anthrax vaccination was attended with very little risk in itself, and was very valuable as a means of checking the disease. The experiments and observations recorded at an earlier page of this number (p. 325), were made with the object of obtaining information on this subject that would probably come home with more force to British veterinary surgeons, and it was confidently expected that they would give an impetus to the system of Pasteurian vaccina­tion in this country. It is almost certain that they will have precisely the opposite effect. In future when a British farmer asks for infor­mation bearing on the safety of anthrax vaccination he may still be told that the French statistics indicate that the operation itself is attended with very little risk, but he must also be told that the proportion of accidents or deaths directly ascribable to the vaccination has been by no means inconsiderable in the few cases in which the method has been tried in Great Britain. In the meantime no prudent man can advise a stock-owner to have his animals-or at least his sheep-vaccinated; one might be justified in laying all the available information before the stock-owner, and then allowing the latter to decide whether he will have the vaccinations carried out or not, but we rather think that if advice is sought it must be given against the operation.

Probably many at first sight will think that the most serious point in connection with the vaccinations described in the article referred to is the danger of the operation as indicated by the deaths among the vacr:inated sheep on Farm 11., but to our thinking the thing most destructive to faith in this method of dealing with the disease is the fact that the vaccinated animals failed to withstand the test of inoculation or feeding with virulent material. The fact that in a few hundred animals vaccinated in this country the mortality from the operation has b~en 3 or 4 p er cent., does not discredit the foreign statistics, for these admit that while the loss in, say, 10,000 vaccinations, is quite trifling, it is every now and again as high as 10 per cent. in individual flocks. Perhaps if 10,000 animals were vaccinated here the

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average loss would be no greater than it has been in France. Indeed, we are bound to admit that that is not only possible but probable, unless British breeds of sheep and cattle are by nature unusually susceptible to anthrax, and therefore unable to bear a vaccin safe enough for French animals. If we could dismiss this latter supposition, and assume that a vaccin suitable for French sheep is not more dangerous for those of British breeds, one would be justified in telling a farmer that, according' to the theory of probabilities, no serious mortality from the operation will occur in the next 10,000 vaccinations in Great Britain.

But the other aspect of the question is much more serious. It is well known that the immunity conferred by any form of vaccination is never absolute. It is only a relative immunity that is claimed for animals that have been vaccinated with the Pasteurian vaccins, but the immunity ought to be very decided after the use of a vaccin whose strength is up to the limit of safety. The second vaccin used on Farm II. was obviously strong beyond the limits of safety, and yet the animals vaccinated with it, with the exception of the pony, could not stand the test of inoculation with virulent anthrax baciili. The test inoculation failed to show that the sheep had deri\'ed any protection whatever from the vaccinations. It is true that the pony when tested displayed a marked resistance to infection, while the heifer survived for seven days after the virulent inoculation, and one therefore cannot assert that no protection was conferred by the vaccination in the case of these animals. But, on the other hand, the result does not warrant the conclusion that the resistance which the heifer and the pony offered to infection was the result of the vaccination, for in many instances the natural immunity of both horses and cattle is quite strong enough to enable them to withstand inoculation with virulent anthrax bacilli in blood or artificial culture.

It must also in fairness be admitted that the test inoculation did not prove that the natural resistance of the sheep had not been strengthened in some degree by the vaccinations, for there are all degrees of immunity, and perhaps if a less virulent material or a smaller dose had been used the test inoculations might have proved that the vaccinated sheep had a greater power of resistance than the control animals from the same flock. Furthermore, it is open to anyone to contend that although the vaccination, as proved by the experiment, had not conferred a degree of immunity sufficient to protect against subcutaneous inoculation or feeding with a considerable dose of the strong virus, it may nevertheless have given all the protection necessary to prevent the sheep from falling victims to what may be called natural infection, and that the true test of the value of vaccination is a comparison of the death-rate from natural anthrax before and after vaccination, or among vaccinated and unvaccinated animals pastured together. We frankly admit that this is the true

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criterion of the value of anthrax vaccination, but only when large numbers are available for comparison, and in this country, unless we can give farmers confidence in the method by a demonstration similar to that which M. Pasteur thought it necessary to give at Pouilly-le­Fort, we shall never have available for purposes of comparison a sufficient number of cases to enable us to estimate the value of the vaccinations in this way.

To show how fallacious this test may be when applied to small numbers of animals, we need only cite the case of the farm on which the unfortunate accidents occurred. On this farm eleven animals had died fro~ anthrax during the twelve months before the vaccinations were carried out. Since that date none of the vaccinated animals have died, and one might have been tempted to conclude that the vaccinations had arrested the disease. But for some months after the vaccinations the vaccinated ewes were pastured along with their own unvaccinated lambs, and no cases of anthrax occurred among the latter.

It may be urged by the advocates of vaccination that the experiments of Pouilly-le-Fort, and many others equally successful, ought to be just as convincing to British agriculturists as they were to the farmers in France, and that there is not the least reason to doubt that the vaccinations, if carried out on the same scale, would be just as successful here in reducing the annual mortality from anthrax as they have been in France. But to the first part of this it may be replied that while the experiment of Pouilly-Ie-Fort was absolutely demonstrative of the fact that a vaccin may be both safe and efficacious, every other experiment of the same kind in France was not equally successful. It cannot be denied that the vaccin prepared by M. Pasteur was sometimes sufficient to confer a higher degree of immunity without killing any considerable proportion of the animals vaccinated, but it is just as certain that this was not invariably the case. And with regard to the other point-the success of the vaccinations in reducing the mortality from anthrax in France­doubts may remain in the mind even of one who is anxious to be convinced. It is quite common to find the lessened mortality from anthrax in France set down exclusively to the practice of the Pasteurian vaccination, but very brief consideration will show that this is quite unwarrantable. Vv'e may accept it as accurate that on many French farms fourteen years ago-before M. Pasteur had made his great discovery regarding the attenuation of the anthrax bacillus­the annual loss from anthrax was as high as 10 per cent., and we may also unreservedly accept the statement that on many of these same farms, since the introduction of the system of vaccinating against the disease, the annual loss has fallen to less than I per cent., but this in no way binds us to admit that the lessened death-rate ought to be entirely placed to the credit of the vaccinations. It must be remembered that prior to the time when the researches of Koch and

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Pasteur made plain to the world how anthrax is propagated, there was everywhere the most utter neglect of every precaution calculated to prevent the spread of the disease. Sheep and other animals dead of anthrax were skinned where they died, and no one thought of attempting to disinfect the ground where the dung or urine of anthrax animals had been voided or where anthrax blood had been spilled. But we cannot doubt that uuring the last ten or twelve years all this has been changed in France, just as it has been with us. Farmers now know the danger attaching to the spilling of anthrax blood, and the careless burial-or the neglect of burial-of anthrax carcases, and surely some share of credit for the lessened mortality ought to be awarded to the precautions which this knowledge has dictated. In this connection it is interesting to recall the fact that M. Pasteur himself, before he had discovered the method of vaccinating with attenuated cultures, declared in very precise language his belief in the easy extinction of anthrax (" J e crois fermement a la facile extinction de ce fleau" 1) by the exercise of proper care in disposing of animals dead of anthrax. In support of this belief he cited a most instructive case, in which the annual loss from anthrax on one farm had in ten years been reduced from 100 animals to 3, by the simple precaution of burying every anthrax carcase in a special piece of ground, fenced off so as to prevent the access of animals to it.

We share the belief so confidently expressed by M. Pasteur. In this country, even easier than in France, anthrax can be held in check, and perhaps even exterminated, without the aid of vaccination. Where a farm is seriously contaminated the disease cannot be got rid of in a day. It will probably take years, but a decline in the death­rate is bound to follow if proper care is taken in dealing with the carcases of animals dead of the disease.

INSPECTION OF DAIRY COWS.

THE Board of Health of Philadelphia has recently brought into force an important regulation with regard to the inspection of cows supplying milk for sale in the city. Recognising that physical examination alone is an uncertain, and therefore unreliable means of detecting the existence of tuberculosis, and that the use of tuberculin is the only trustworthy means of ascertaining whether an animal is tuberculous or not, the Board has instructed their Chief Inspector of Milk to endorse as "untrustworthy" all certificates of the freedom of herds of milch cows from tuberculosis that are not based upon the use of the tuberculin test. The Chief Inspector of Milk is to keep a register of all herds of milch cows that supply the city of Philadelphia with milk, such register to distinguish between the herds that have been certified as free from tuberculosis by the tuberculin test, and

1 Acadamie des Sciences, 2nd Nov. 1880.