168 



DISEASES OF CATTLE. 



healthy, pregnant cows by the introduction of exudate and material 

 from aborting animals. Xocard (1888) isolated from the exudate 

 between the mucous membrane of the uterus and fetal membranes 

 a micrococcus and a short bacillus which were found continually 

 in contagious aborticm, but he failed to reproduce the disease by 

 inoculations of pure cultures of these organisms into health}^, preg- 

 nant animals. In 1897 Bang, assisted by Stribolt, published their 

 findings regarding infectious abortion of cattle, in which they in- 

 criminated Bang's bacillus of abortion as the causative agent. With 

 pure cultures of this bacillus they were able to produce the disease 

 artificially and to recover the same organism from the experimental 

 cases. Since that time many noted investigators, both in this country 

 and in Europe, have confirmed these findings. 



Cause. — The Bacteriwn abortus of Bang is now generally recog- 

 nized as the causative agent of the disease of cattle. Formerly it 

 w^as thought that abortion was due to injury, such as blows, horn 

 thrusts, falls, etc., or the eating of spoiled feed and certain plants, 

 and while this may be true in a limited number of cases, careful 

 investigations have demonstrated these claims to be largely un- 

 founded. It is now generally recognized that when abortion occurs 

 in herds from time to time, it is safe to assume that the disorder is 

 of an infectious nature and should be so treated. 



Natural mode of infection. — This phase of the disease is of greatest 

 importance for a clear understanding of the methods of 2>revention. 

 Manj^ investigators have demonstrated that the infection is trans- 

 mitted through the digestive tract, through contaminated feed and 

 water. The germ^ are taken up by the body from the intestines 

 ■with the liquid nourishment, reach the blood, and are carried to the 

 genital organs, where they find conditions best suited to their devel- 

 oiDment. Soma assert that calves are infected in this manner by 

 suckling infected mothers, the germs being present in the milk, or 

 the teats having been contaminated by coming in contact with infec- 

 tive discharges. It is claimed that infection contracted in this man- 

 ner remains dormant in the body of the calf until pregnancy begins, 

 and then the organism, finding conditions suitable for its develop- 

 ment, produces the disease. 



Abortion may occasionally be transmitted from cow to cow by 

 direct contact. The discharges from diseased cows, swarming with 

 the germs, soil the external genitals, tail, and hind quarters, and then 

 a susceptible animal, by contact, gets the infective material upon the 

 vulva, the infection traveling up the genital canal and directly 

 infecting the uterus. 



The belief long entertained that the female acquires the disease 

 at the time of copulation as a result of transference of the infection 

 from affected to healthy females on the genital organs of the bull 



