INFECTIOUS ABORTION 431 



portance not only because it leads to the loss of a number 

 of calves or foals but also in cows- to the cases of sterility, 

 retentions of afterbirth, chronic uterine catarrhs, 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. 



Etiology. — (a) In cows the disease is caused by the Bacillus 

 abortus. This is a small, non-motile, non-spore-bearing 

 ■ 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 months after they have aborted. The 

 disease is spread primarily by -the uterine discharge, fetal 

 membranes, and fetuses of infected cows. 



(6) The abortion of mares is not due to the abortus 

 bacillus but to a streptococcus which is Gram-negative. It 

 is found in the uterus, fetal membranes, and fetuses of 

 infected mares. 



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

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

 causal germ contaminating the food and water; (b) 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 

 which have collected on the penis during copulation with an 

 infected female. 



Whether the bull is merely a mechanical carrier or the 

 abortus bacillus may proliferate in the genitalia causing him 

 to become also infected and therefore a permanent distributor 

 remains undecided. Experimentally, abortion has been 

 induced in pregnant animals by introducing pure cultures 

 of the abortus" bacillus into the vagina, stomach, and veins. 



The disease is practically always brought into a herd 

 through an infected female which has either recently aborted 



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