MILK-BORNE INFECTIONS 477 



always infected. There seems to be no difference in the sus- 

 ceptibility among various breeds. 



The Bacillus abortus is widely disseminated among cows. In 

 one instance Cooledge found that 27 per cent, of the cattle ex- 

 amined had udders infected with the organism. It is not un- 

 common in market milk, as shown by a number of investigators, 

 among whom may be mentioned Schroeder and Cotton, Fabyan, 

 Melvin, Evans, Cooledge, and others. Miss Evans found Bacillus 

 abortus in 23.4 per cent, of the samples examined. The highest 

 number counted was 50,000 per cubic centimeter. The author 

 distinguished three types of the organism, and named the type 

 occurring most frequently Bacillus abortus lipolyticus, because it 

 decomposed butter-fat. The bacillus was found in certified milk 

 by Fleischner and Meyer. Milk containing the germs of abor- 

 tion should be pasteurized before it is fed to calves. 



Cows suffering from contagious abortion develop an immunity, 

 as has been shown by complement-fixation and agglutination tests. 

 Artificial immunity can be produced by vaccination with hving 

 cultures, while killed cultures do not appear to have a similar 

 effect. Hadley states that 93.5 per cent, of cattle vaccinated with 

 living cultures acquired immunity which lasted for a variable 

 length of time. When immunized for one gestation period few 

 animals aborted, and when immunized for two periods the im- 

 munity seemed to be permanent. But it should be emphasized 

 that the artificial inununity does not necessarily eliminate the 

 germs, and vaccinated animals may remain a menace to those 

 free from disease. Only unbred heifers and open cows at least 

 two months before being bred should be vaccinated. 



When a cow shows S3miptoms of contagious abortion she 

 should be isolated. The symptoms are not difficult to discover. 

 The udder and vulva swell, there is a whitish discharge, the 

 ligaments above the seat of the tail sink, and the milk becomes 

 thick. After abortion the fetus and all discharges should be 

 burned. The external parts, including tail, rump, and thighs, 

 should be bathed in a 3 per cent, solution of hquor cresohs com- 

 positus, and the vagina should be douched with a 1 per cent, 

 solution of sodium chlorid. 



Hadley recommends the following measures for prevention of 

 contagious abortion: "1. Daily douching with the salt solution of 

 all cows that have a vaginal discharge; 2, provision for a food- 

 supply that is adequate as to nutritive and mineral content and 

 free from contamination; 3, complete removal of retained after- 

 births, with subsequent cleansing of the womb ... to pre- 

 vent an accumulation of pus which is likely to result in sterihty; 

 4j disposal of aborted fetuses and contaminated bedding by burn- 



