S40 GENERAL THERAPEUTIC MEASURES 



in a limited number of cases^ careful investigations have demonstrated 

 these claims to be largely unfounded. 



It is now generally recognized that in herds where abortion occurs 

 from time to time, it may be safely assumed that the disorder is of an 

 infectious nature and should be treated as such. 



Natural Mode of Infection. 



The manner in which pathogenic organisms gain admittance to the 

 tissues of the host in any disease is of greatest importance for a clear 

 understanding of the methods of its prevention. Many investigators 

 claim to have demonstrated that in abortion disease, the infection is 

 transmitted through the digestive tract, by the ingestion of contaminated 

 food and water. The germs are taken up from the intestines into the 

 lymph vessels, thence reach the blood stream and are carried by it to the 

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

 ment. Some claim that calves are infected in this manner by suckling 

 infected mothers, the organisms being present in the milk; or, on the 

 teats, having been contaminated by coming in contact with infective dis- 

 charges. It is claimed that infection contracted in this manner remains 

 dormant in the body of the calf until pregnancy begins, and then the or- 

 ganism finding conditions suitable for its development produces the 

 disease. 



Still other investigators believe that the natural habitat of the B. 

 abortus (Bang) is the udder of cows and that it will exist but a short 

 time in the nonpregnant uterus or other tissues of cattle. From the udder 

 it reaches the uterus by way of the blood stream; if pregnancy exists, it 

 develops in the uterus causing abortion, retained afterbirth, pyometra 

 and other sequela of the disease. The udders of healthy cows are in- 

 fected from contamination with the discharge from the uteri of aborting 

 cows or from milk from infected udders; the organisms entering by way 

 of the teat openings. 



Diagnosis. 



The diagnosis of abortion disease is made upon the history and symp- 

 toms of the disease and from the changes occurring in the fetal mem- 

 branes and in the expelled fetus. This, however, is substantiated with 

 certainty only by the isolation of the B. abortus Bang. The fact, how- 

 ever, that repeated abortions are observed in a herd is sufficient evidence 

 of the presence of this disease. The fact that animals may be affected 

 with the disease and disseminate the germs, even though they carry the 

 fetus to full time, renders the control of the disease very difficult. 

 Prevention and Treatment. 



The enforcement of the strictest sanitary measures alone are fre- 

 quently of no avail in the attempt to check contagious abortion in in- 

 fected herds. Medicinal treatment has likewise proved ineffective. On 

 the other hand, in view of the fact that self-immunization of infected 

 animals is now almost uniformly recognized, it appears self-evident that 

 this might be hastened by timely injection of proper biological products; 

 and furthermore, that susceptible animals might be rendered immune or 

 highly resistant against the infection. 



Unfortunately up to the present no absolute specific vaccine or bac- 

 terin has been develop^^gfff^^^^Tji^^yQffi^ abortion disease. While 



