COMBATING T.B.

Hawke's Bay Herald-Tribune, Issue 169, 4 August 1937, Page 13

COMBATING T.B.

What Tuberculin Testing Has Done i RESULTS IN U.S.A. Tlie Bureau of Animal Husbandry of che sUnited States Department of Agriculture issues a. monthly oiiicial bulletin. That for. April, 1937, giv.es the i'oilowing iigures for tuberculosis eradleation work dui-jng March, 1937 : — Herds under supervision . . 6,734,4.11 Oattle test.ed by the tuberculin test (luring month 1,182,152 Cattle fouud infected with tuberculosis 8,115 (i.e. well under 1 per cent of those tested were infected.) A common estimate of the number of dairy cows in Great Britain affeeted with tuberculosis is in the neighbourhood of 40 per cent., and in that country tuberculosis eradication work is npt organised to the extent that is the case \n America. The constrast is striking, and it is to the use of the tuberculin test that the relatively advantageous position of America with regaTd tp the present ineidence of this disease in cattle must be very largely attributed. It is to be hoped that the farmers of New Zealand will continue to take advantage of this test as a means of diag-

nosing the disease at an eariy stage ana enabling the removal of a possible souree of infeetion from a herd. A coming, generation will thus be able to bonefit by the closing-down of a serious avenue of human infeetion and of a source of heavy loss to the farm-ng industry. But what is the tuberculin test? It |s diSicult to explain it briefly, but a bare outline of essentials is that, if an auixual body becomes infected by a disease, the proeess of resisting that disease causes a minute change to oecur in the blood serum (the liquid part of the blood). These changes differ in the case of each disease, and they can be recognised by suitable laboratory methods. ' In the case of tuberculosis, wh-en the tuberculosis germs havo eatablished themselves in the cow, the injection of the substance tuberculin causes a reaction in the shape of a swelling or a rise in body temperature, according to the form of test used. The preparation of tuberculin may be very briefly described. The germs of this disease are grown artificially on what is known as a culture. The culture is sterilised by being held at $12 degrees (the • temperature of boiling water), for two hours. It may not be out of place here to state that a tem perature of 160 degrees for five minutes will completely destroy the bacillus of tuberculosis. The cujture is now filtered through a very fine porcelain filter, the holes beiug under pne 40,000th of an inph in eize. This strains out the dead baeteria, A small quantity of carbolic aeid is then added, and this is the substance known as tuberculin, It will readily be seen from the foregpiug that the injection of tuberculin in carrying out the test cannot do any possible harm whatsoever to the animal, but must be a great benefit to the milk consumer in' safeguardiug his health and to the farmer in preventing the is^read of the disease.