4. THE FREQUENCY OF TUBERCLE BACILLI IN THE

MARKET MILK OF THE CITY OF

WASHINGTON, D. C.

24907-Bull. 41-08- -11

THE FREQUENCY OF TUBERCLE BACILLI IN THE MARKET

MILK OF THE CITY OF WASHINGTON, D. C.

By JOHN F. ANDERSON,

Passed Assistant Surgeon and Assistant Director Hygienic Laboratory, Public
Health and Marine-Hospital Service, Washington, D. C.

Numerous investigators in recent years have shown the infectiousness of milk containing tubercle bacilli for animals. Whether the milk from animals with tuberculosis but with healthy udders contains tubercle bacilli is not definitely settled. Many prominent scientists seem to have shown that at times the milk from such animals does contain tubercle bacilli virulent for laboratory animals, but in the view of recent work there may be some doubt as to whether the bacilli really passed through the udder but gained access to the milk from contamination with feces containing tubercle bacilli.

Schroeder and Cotton have recently shown that cows so slightly affected with tuberculosis as only to be discoverable by the tuberculin reaction pass virulent bacilli in their feces. Many believe that milk from a tuberculous cow with unaffected udder is free from infection and becomes infected from the feces of the animal or its environment. This observation is of the very greatest importance, and if confirmed shows, more than ever, that the greatest care is necessary in guarding milk from contamination from the time it is drawn until it is consumed.

The milk supply of many of the cities of Europe and England has been examined for tubercle bacilli. Most observers have used the animal test; they have injected various amounts, either centrifugalized or not, into guinea pigs or rabbits. The percentage of samples showing tubercle bacilli has varied between very wide limits, no doubt dependent upon the difference in the number of tuberculous cows in the herds supplying milk to the different cities and on difSchroeder, C. C. and Cotton, W. E.: Bull. of the Bureau of Animal Industry,

1907.

ferences in technic. Some observers have found that when a number of animals are inoculated with the same samples of milk only one. perhaps, will develop tuberculosis. Some centrifugalized the milk and gave sediment alone, while others gave sediment and cream.

I will not enter into the question whether the tubercle bacilli found in milk are virulent for man, but give my results solely as to whether the market milk of the city of Washington contains tubercle bacilli virulent for guinea pigs. For myself I object most strenuously to using milk containing tubercle bacilli virulent for laboratory animals and prefer to leave the question as to their pathogenicity for man to be discussed by others.

Before presenting the results obtained by me with the market milk of the city of Washington it will be interesting to refer briefly to results obtained elsewhere by others.

Bang, B.

REVIEW OF LITERATURE.

Deut. Zeit. f. Thiermed. XI, 1884, p. 45.

Injected apparently normal milk from the sound quarter of an udder another part of which was diseased, into the belly wall of two rabbits, which developed inoculation tuberculosis and died after 24 and 3 months, respectively. This was repeated later with two more specimens of milk, with the same result. He also demonstrated that the milk of tuberculosis cows without demonstrable udder lesions, could contain tubercle bacilli.

Stein, G. Experimentelle Beitrage zur Infektion der Milch perlsuchtiger Kuhe. Inaug. Dissert., Berlin, 1884.

Intraperitoneal inoculation of guinea pigs with raw milk of tuberculous cows. Ten negative and four positive results. In two of the latter tubercle bacilli were demonstrated, and two negative. Some of the cows had tuberculosis of the udder.

Hirschberger, K. Experimentelle Beiträge zur Infectiosität der Milch tuberculöser Kühe. Deut. Arch. f. klin. Med., XLIV, 1889, p. 400.

Twenty specimens of milk from tuberculous cows injected into the peritoneum of guinea pigs. None of the animals inoculated died of septic peritonitis. Eleven of the specimens proved to contain tubercle bacilli. (Other acid-fast organisms, of course, were not differentiated.) By microscopic examination only one of the specimens of milk was shown to contain tubercle bacilli. Tubercle bacilli occurred not only in milk from tuberculosis udders, but also where the udders were sound, and where the cow was but slightly affected

with tuberculosis.

Gebhardt, F. Experimentelle Untersuchungen ueber den Einfluss der Verdün nung auf die Wirksamkeit des tuberkulösen Giftes. Virch. Arch., CIX, 1890, p. 127.