BREEDING TROUBLES 155 



or entirely prevented by feeding, but the question of deeding can- 

 not be ignored in this connection. 



241. How the diseases are spread.— It seems clear that 

 infection may gain entrance both through the feed and through 

 the genital organs and perhaps by other means. It is not known 

 what is the most common way. Experience indicates that an 

 entire herd may become infected by a bull having infected organs; 

 on the other hand, many infections have occurred where the bull 

 quite evidently had nothing to do with them. B. abortus, the 

 specific organism, has been found in the milk and in the dis- 

 charge from the vagina of cows that have aborted; thus, these are 

 sources of infection. 



242. Preventive measures.— Since we know that abortion 

 and related troubles are due to an infection but are not sure as to 

 its source or method of spreading, the preventive measures must 

 be primarily those of general sanitation. Cows which abort or 

 calve prematurely and even those which calve normally may have 

 a discharge from the vagina which is dangerous to other animals. 

 Such a cow should be placed in a separate pen until the discharge 

 has ceased. A cow should be so isolated as soon as there is any 

 evidence that an abortion or premature birth is likely to occur. 

 If abortion takes place the foetus and afterbirth should be burned. 

 When a cow is removed from the separate pen after the discharge 

 has ceased, the bedding should be burned and the pen scrub- 

 bed and sprayed with a coal-tar disinfectant. This isolation 

 cannot be expected to stop all abortions, for others will occur 

 from cows already infected and cows may become infected 

 from some other source. Isolation simply shuts off one channel 

 of infection. 



There is no point in keeping a cow that has aborted isolated 

 after the discharge has stopped. It is true that she may retain the 

 infection in her system, but there is little danger of the spread of 

 the disease merely from a cow being stabled next to one that has 

 aborted. Further, cows which are due to abort may be giving off 

 the infection in their milk and thus be a menace, but they cannot 

 be isolated because they are not recognized. 



