406 .CHRONIC INFECTIOUS DISEASES 



after years, unless something is done to check its advance, 

 a large percentage or the whole herd, irrespective of age, is 

 infected. 



Prognosis. — Generally speaking, the prognosis in animal 

 tuberculosis is unfavorable. While undoubtedly in some cases 

 the process never develops beyond a few local lesions, and in , 

 others it may become arrested (encapsulement of foci of infec- 

 tion), in the majority of cases the disease progresses con- 

 tinuously and finally leads to clinical symptoms, decline, 

 and death. That the sanitary conditions surrounding the 

 tuberculous animal are of influence in the earlier stages of the - 

 disease, there is little doubt. It is frequently noted, however, 

 that infected cattle kept under ideal conditions as to light, 

 cleanliness, and ventilation not only do not improve in 

 health, but actually become worse, the disease making 

 recognizable progress in the individual and in the herd. 

 This is especially true if open cases are not eradicated but 

 kept to infect and reinfect their companions. 



Treatment. — A medicinal treatment is useless. In man, 

 light, cleanliness, and ventilation, coupled with rest (especi- 

 ally if the patient has fever), have checked or even healed 

 the disease, provided it was not too far advanced. Whether 

 similarly good results are obtainable among tuberculous cattle 

 has not been adequately demonstrated. Too few scientific- 

 ally conducted experiments in this regard have been made. 

 Furthermore, the trouble, expense, and danger of treating 

 individual animals would be prohibitive, and when com- 

 pared with the preventive measures now employed to control 

 and eradicate the disease (see Prophylaxis) become in- 

 significant. Repeated injections of small doses of tuberculin 

 has given good therapeutic results in man. In cattle the 

 expense and trouble of administration make its use 

 prohibitive. 



Prophylaxis. — (a) Tuberculosis may be kept out of a healthy 

 cattle herd by preventing infected individuals from coming 

 in contact with it. The disease is practically always intro- 

 duced by a tuberculous animal. One open case of tuberculosis 

 may in time infect a whole herd. Therefore all cattle brought 

 into the herd should be proven free from tuberculosis by the 



Digitized by Microsoft® 



