INFECTIOUS ABORTION '433 



comes dead. After the abortion the placenta is often retained 

 and a vaginal discharge persists. For tw6 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 semisolid and of light brownish- 

 yellow color. The fetus appears normal. In other cases 

 symptoms 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 diag- 

 nosis from the physical signs alone is not difficult. All 

 cases of multiple abortions in a cow herd or horse stud 

 should be looked upon with suspicion, and until disproven 

 considered cases, of infectious abortion. As contributory 

 to diagnosis a bacteriological examination 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 extensively 

 employed. While this test is not so accurate as the comple- 

 ment-fixation test for glanders it nevertheless forms a 

 valuable contribution to the diagnosis. In cases of doubtful 

 reaction (incomplete hemolysis) a retest should be made in 

 four to six weeks. A negative reaction does not necessarily 

 exclude the abortion bacillus, as the infection may have 

 occurred so recently that the immime bodies have not yet 

 formed in sufficient amount to bring about the reaction. 

 The agglutination test is also used. It is found that the 

 blood serum of cattle suffering from infectious abortion 

 possesses an average agglutinating value of 1000 and may 

 cause agglutination in dilutions as high as 16,000. In 

 healthy cows the agglutinating value of the serum is rarely 

 above 50. So-called "abortin," which is prepared from the 

 abortus bacillus much as tuberculin is prepared from the 

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