INFECTIOUS ABORTION 473 



may carry to full term and be delivered of a viable, fully 

 developed calf. Such a cow is spoken of as an "immune" in 

 the sense that she will not abort again although she is still 

 diseased and can infect other cows. Abortion seems most 

 common in the fifth to seventh months of pregnancy, usually 

 occurring on or about the 190th day, but varying from the 

 149th to the 254th day. Quite often before the actual abor- 

 tion occurs the cow shows prodromal, symptoms, such as 

 filling of the udder, edema of the vulva, colostral milk, 

 sinking on each side of the tail root, congestion of the vaginal 

 mucosa and the discharge of a reddish or yellow, odorless, 

 viscid fluid. The expulsion of the uterine contents usually 

 occurs, however, without marked labor pains and the fetus 

 comes dead. After the abortion the placenta is often retained 

 and a vaginal discharge persists. For two or three weeks or 

 longer the discharge is of a dirty, reddish-brown color, odor- 

 less or odorous, the flow either continuous or interrupted. 

 In time the discharge usually diminishes. When bred during 

 this period the cow may not conceive. It occurs occasionally 

 that cows, especially heifers, may show all of the premonitory 

 symptoms of abortion, fail to abort and carry to full term. 



Necropsy. — On postmortem the uterus appears externally 

 normal. Between the mucosa and the chorion is found an 

 exudate which is fluid to semi-solid and of light brownish- 

 yellow color. The fetus appears normal. In other cases 

 sjTnptoms of hydropsy and mummification of the fetus are 

 present, conditions which can begin in the third month of 

 pregnancy. 



Diagnosis. — On account of its great prevalency the diagnosis 

 from the physical signs alone is not difficult. All cases of mul- 

 tiple abortions in a cow herd should be looked upon with sus- 

 picion, and until disproved considered cases of infectious abor- 

 tion. As contributory to diagnosis a bacteriological examina- 

 tion of the vaginal discharge, the uterine exudate, the placenta 

 or the fetus may be made. However, this is rarely feasible in 

 practice. Of late the complement-fixation test has been ex- 

 tensively employed. While this test is not so accurate as the 

 complement-fixation test for glanders, it nevertheless forms a 

 valuable contribution to the diagnosis. In cases of doubtful 



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