434 CHRONIC INFECTIOUS DISEASES 



tubercle bacillus, has failed to give uniformly satisfactory 

 results. The reaction is a thermic one with which are some- 

 times associated constitutional symptoms. 



Course. — Infectious abortion usually persists in a herd 

 for years. After tJue first abortions, often overlooked or 

 attributed to other causes by the owner, new cases occur 

 with a few weeks' interval between. Finally the abortions 

 become more and more frequent until a full-term calf is a 

 rarity in the, herd. In time, however, the abortions occur 

 at less frequent intervals. Cows which have aborted one or 

 more times carry to full term (become tolerant — so-called 

 "immunes")- Clean cows introduced into the herd may be 

 the only ones to abort. Ultimately, in two or three years, 

 the abortions cease entirely, provided the herd has been 

 kept intact. However, there are exceptions to this rule 

 and not infrequently individual cows fail to produce full- 

 term calves. 



Treatment. — Once the disease has gained a foothold in a 

 cow herd treatment is rarely successful. The reason for "this 

 is that the germs of the disease are within the uterus and 

 obviously in the pregnant animal cannot be reached with 

 disinfectants. Very fashionable is the administration of 

 phenol. It may be administered subcutaneously in doses 

 of 10 c.c. of a 2 per cent, solution during the fifth to seventh 

 months of pregnancy or it may be given with the food. A 

 simple method of dosage is to make up a 3 per cent, solution 

 of phenol, giving to each cow daily four ounces of the solution 

 in the food.. In ten days the dose can be increased to sixteen 

 or even twenty-four ounces daily, provided this quantity is 

 given in two or three feeds. 1 The fundamental principles 

 underlying the control of infectious abortion are the same 

 as for the eradication of any infectious disease, viz.: (a) 

 The separation of the sick from the healthy. (6) The dis- 

 infection of the premises, including the safe disposal of the 

 dead, (c) The care of the sick. - 



1 If gradually brought up to it cattle will stand enormous doses of phenol. 

 A thousand-pound bull was given without injury in one day nearly 2 pounds 

 of phenol divided into four doses. 



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