USE OF SERUM IN HOG-CHOLERA 381 



Indications for Single Treatment. — The question now naturally 

 arises as to the indications for use of the single method of treatment. 

 These are briefly as follows: 



Some men are unalterably opposed to the use of the double 

 treatment. These are usually persons who do not thoroughly 

 understand the principles upon which the double method is founded. 

 They have, perhaps, had a bad experience with this form of serum 

 management through use of a poor quality of serum. In other 

 cases, they have got the idea that use of double treatment will 

 permanently infect their premises. In all these cases, after a 

 reasonable amount of argument has failed to show the owner that 

 the double treatment would be of more advantage in his herd, it is 

 better to allow the use of the single method, if so desired, rather 

 than not use any serum at all on this farm. 



In herds that are about to be placed in exposed feed lots the use 

 of the single treatment at the time they are turned into the feed lot 

 will often be all that is necessary to protect them from the disease. 

 For at least six weeks they will all enjoy a complete protection from 

 cholera if the serum used be of proper quality. At the end of this 

 time the effects of the serum begins to wear off, and unless enough 

 of the germs have been met with to set up a reaction on the part 

 of the tissue-cells themselves the animals may again become sus- 

 ceptible to hog-cholera. The use of the double treatment in these 

 cases is more advisable, as it is equally or even more safe, and, at 

 the same time, is much more positive in its final outcome. By in- 

 jection of the virus we make sure that every hog receives his al- 

 lotted dose. When simply turned into infected pens they may all 

 come in contact with the virus, or, on the other hand, one or two 

 may entirely escape the virus and be left unprotected at the end of 

 six weeks. 



In herds that are in the same pens with or on an adjoining 

 pasture to those that have cholera the single treatment is often 

 advised as preventive of further spread of the disease. In this 

 connection it is usually successful in nearly 100 per cent, of cases. 

 However, in these exposed herds I think the best plan to follow is 

 to take all temperatures, and give the single treatment in all 

 animals with a temperature of 104° F. or higher, and the double 

 treatment in all that show a temperature below 104° F. In this 



