Tubercle bacilli in the feces of cattle

Abstract

Between June, 1908, and August, 1910, a number of tests upon the feces of cattle were made at the Illinois Agricultural Experiment Station to determine the presence or absence of tubercle bacilli. These tests were of two kinds, (1) by direct microscopic examination and (2) by inoculation of animals.

The microscopic method included the examination of stained slide preparations of (a) mucus on the exterior of the fecal mass, (b) the mixed feces, and (c) watery mucus scraped from the rectum, each stained slide being searched fifteen minutes with the aid of a mechanical stage. If organisms indistinguishable in appearance from bovine tubercle bacilli were found upon any of these slides the examination was recorded as positive. One hundred and nineteen samples from 53 cows which had reacted to tuberculin were examined in this way, with a positive result 53 times in samples from 34 of the cows. Thirty-five other samples from these same cows were negative. Nineteen cows gave negative results at all examinations, 31 in number. Thus, of the 53 cows tested, 34, or 64.2 per cent., gave a positive result at one or more tests, and 19, or 35.8 per cent., gave only negative results. Forty samples from 18 non-reacting cows were tested in the same way, with 23 positive and 17 negative results. Fifteen of the 18 cows, or 83 per cent., gave a positive result at one or more tests, while only 3, or 17 per cent., were negative at all tests. From this it appears that no significance in respect to the presence of tubercle bacilli can be attached to the finding of a few acid-fast bacteria in the feces of cattle.