Bang’s disease in a naturally infected herd

Abstract does not appear. First page follows.

The studies to be reported herein were begun in 1922 in a herd of dairy cattle in which 19.0 per cent of the animals were infected with Brucella abortus, as indicated by the agglutination test of the blood serum. The particular objects were to determine what correlation exists between agglutinins in the blood and those in the milk, and what relation these agglutinins bear to the presence of the organisms in the milk and in the products of normally or prematurely terminated pregnancies.

Unfortunately the herd upon which these observations were made was not maintained solely for the purpose of these investigations, and the procedures carried out were necessarily limited in scope and in many cases were terminated by death or disposal of the animals or by their use for other purposes before conclusions could be drawn. However, certain of the animals have contributed significant data.

Previous to 1922 this herd was known to be infected with Bang’s disease. Occasional abortions had occurred and agglutination tests on the blood had proved positive, but since there were no alarming symptoms of the disease, no particular effort was made to blood-test the animals systematically and regularly. The aborters were isolated until uterine discharges ceased and were then returned to the herd. From 1922, when 19.0 per cent were discovered to be reactors to the test, to 1926, more hygienic procedures were practiced with the aborters and the positive-reacting cows that calved normally, in an effort to control the spread of the disease. The disease remained stationary during 1923 and 1924 and increased in virulence in 1925 and 1926, and in these latter years reached one of the typical peaks that is characteristic of infected herds.