Intradermic tuberculin testing in cattle / by T. Dalling, J.H. Mason, and W.S. Gordon.

  • Dalling, Thomas.
Date:
[1928?]
Catalogue details

Licence: In copyright

Credit: Intradermic tuberculin testing in cattle / by T. Dalling, J.H. Mason, and W.S. Gordon. Source: Wellcome Collection.

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    2 Dalling—Mason—Gordon : Tuberculin Testing in Cattle reactions, but experience in reading reactions will cause one to classify different degrees and types of reaction as positive. (b) Strength of Tuberculin.—While most of our tests have been made with tuberculin equal in potency to the Frankfurt standard, lately we have used tuberculin of double and even quadruple strength. In our experience, a cleaner cut reaction is obtained by such a preparation. We have had the feeling that a strong tuberculin, while giving clearer positive reactions, produced some degree of non-specific reaction even in non-reacting cattle, and that the more marked reaction in tuberculous cattle was due to this non-specific reaction. Our numerous tests, however, convince us that, allowing for an increase in non-specific reaction, a strong tuberculin gives a more definite and more easily read positive reaction than one of standard potency. In all our experience there have been only four cattle in which a very marked degree of difference in reaction has occurred when a standard and a fourfold strong tuberculin were used, and it is very probable that, using tuberculin equal to standard, these cows would have been passed as non-reactors. We believe that the benefit derived from the use of this strong tuberculin is that there will be fewer indefinite reactions recorded. Indefinite reactions do occur and some cattle will continue to show such indefinite reactions at all tests, no matter how often applied. With the use of strong tuberculin these indefinite reactions are reduced in number but are still observed. It may be that when purified tuberculin has been thoroughly worked out and is available for general work, the “ indefinite reaction ” will be further reduced or will disappear entirely. (c) Comparison of Subcutaneous and Intradermic Tests.—We have tested many cows and heifers by both methods, usually leaving an interval of about one month between the two tests, and as a rule the results are in very close agreement. We have, however, records of the testing of cattle in which exactly opposite results have been recorded. In one cow only have we observed that positive reactions were obtained by the use of tuberculin subcutaneously, while the intradermic tests were negative. This cow was tested on many occasions and never once did she react to the intradermic tests, while on every occasion a typical temperature chart followed the use of diluted tuberculin subcutaneously. This cow died, and post-mortem examination showed advanced generalized tuberculosis, which was confirmed by guinea-pig inoculation. In five cows only are we able to record the reverse, viz., they reacted to the intradermic test while subcutaneous tuberculin gave no reaction. These cows were tested intradermically and a month later received a dose of tuberculin subcutaneously. They reacted typically to the first test but gave an entirely negative reaction to the secoud test. In six months’ time they were again tested by both methods, one month elapsing between the tests, and the results were as before. These cows are now isolated and will be subjected to further testing in the near future. It should be noted that a double dose of tuberculin was used for the subcutaneous test and temperatures were taken every three hours after injection. Oases of similar results are recorded in the literature, but after a series of over 300 tests by both methods these five cows are the only ones which in our hands have yielded such results. The conclusion one would draw from the large series of tests we have carried out is that the double intradermic method of tuberculin testing is reliable and the amount of error is probably somewhat smaller than when the subcutaneous method is used. John Balk, Sons & Danielsson, Ltd., 83-91, Great Titchfield Street, London, W. 1.