INFECTIOUS ABORTION 471 



animals leads to an affection of the fetal membranes and 

 often to the prematm-e birth of the fetus. 



Occurrence. — Infectious abortion occurs frequently among 

 cows. It is widely distributed, forming one of the commonest 

 diseases with which we-have to deal. In many of the eastern 

 states, where cattle breeding is carried on extensively, fully 

 70 per cent, of the herds are infected. The disease is chronic 

 and does not seem to affect the general health of the preg- 

 nant cow. Infectious abortion attains economic importance 

 not only in that it leads to the loss of large numbers of calves, 

 but because of the sterility, retention of afterbirth, chronic 

 uterine catarrh, and diseases of the udder which follow in its 

 wake. It not only destroys the young but may greatly 

 lessen the value of or even extirpate the dam as a breeder. 



Etiology. — ^In cows the disease is caused by the Bacillus 

 abortus.^ This is a small, non-motile, non-sporebearing 

 bacillus which stains irregularly with anilin dyes but is Gram- 

 negative. In cultures the bacillus is originally anaerobic but 

 gradually assumes aerobic characteristics. It is found in the 

 uterine exudate, fetal membranes, and in the fetus; also in 

 the udder (milk) of infected cows. The germ is highly 

 resistant and may remain virulent in the uterus of infected 

 cows for several weeks (usually three) after they have aborted. 

 The disease is spread primarily by the uterine discharge, fetal 

 membranes, and fetuses of infected cows. Spread through 

 infected milk can also occur. 



Natural Infection. — ^The infection is taken up by the 

 susceptible mother: (a) Through the digestive tract, the 

 causal germ contaminating the food and water; (6) through 

 the genital organs which may become infected by the stable 

 litter, manure, etc., or by contact with such utensils as 

 buckets, milking stools, ropes, halters, sponges, douching 

 hose, obstetrical instruments, etc. The bull may also be a 

 carrier of infection as he can transmit by coitus the bacilli 



1 The experiences of Theobald Smith, M'Fadyean and Stockman indicate 

 that occasionally bovine abortion may be due to causes other than the Bang 

 bacillus. The former found in a limited number of outbreaks a Spirillum, 

 and the latter a Vibrio. However, in the light of our present knowledge, 

 most bovine abortion is caused by the Bang bacillus. 



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