260 VETERINARY STUDIES 



very serious, because unsuspected, source of spread. Under 

 natural conditions, infection may occur by way of the respira- 

 tory, digestive, or genital tract in breeding. The afterbirth, 

 discharges from the womb and vagina, and manure of abortion 

 calves are all probably infectious. 



Results. — A serious percentage of cows which abort subse- 

 quently become sterile. Most cows do not abort more than 

 twice and thereafter may become either regular breeders, or 

 shy breeders or sterile, or they may become immune ' ' carriers, ' ' 

 i.e. raise calves but remain infectious. Contamination with the 

 virus of abortion may result in abortion, or in a birth at or near 

 full term, with the calf weak and predisposed to diarrhea. 

 Cows which abort are likely to retain placenta and be unthrifty 

 for a long time. Some contract infection of the udder probably 

 from vaginal discharge, terminating in serious case of garget; 

 or there may be a general septicemia or blood poisoning. 



Diagnosis. — ^We have first the history of an unusual number 

 of cows in a herd dropping their calves prematurely. Fre- 

 quently the vaginal discharge wdiich accompanies abortion is 

 dirty in appearance with shreds of tissue and a foul odor. The 

 mucous membrane of the vagina may become congested and the 

 lips of the vulva swollen several days before abortion occurs. 

 A coming abortion in heifers is often indicated by marked pre- 

 mature development of the udder, and the ligaments at the tail 

 head on each side relax and drop. Older cows are apt to abort 

 without any warning. 



There are two serum tests which give useful, but limited in- 

 formation. In a general herd test they furnish information as 

 to the general condition of the herd with reference to the dis- 

 ease. But they do not tell whether a certain cow has aborted 

 or will abort or is a spreader of the disease. 



Prevention. — It is necessary to bear in mind the probable 

 cause of this disease and the common methods of dissemination. 

 A farmer owning a healthy herd should not purchase cattle of 

 breeding age from a herd in which this disease has prevailed 

 within three years. He is safer in any case if he buys unbred 

 heifers or mature cows that are heavy springers with good 

 breeding history. He should not do public service with a herd 

 bull where there is possibility of contamination, nor should he 

 use a neighbor's bull if it is possibly contaminated with this 

 infection. It is also safer policy for the breeder to raise his 



