170 HOG CHOLEKA 



sentative farm herd. A permanent immunity is 

 desired for all of these, and we follow the general 

 plan of giving simultaneous treatment to all ani- 

 mals in condition to receive it, and protecting the 

 others with serum alone pending the time when 

 they may safely receive serum and virus. 



Assuming that breeding stock of this character 

 is on the farm with the infected shoats, but that 

 after numerous temperatures have been taken 

 there is no evidence of disease, it may be handled 

 as follows : the boar may be given serum and virus 

 at once, or if he is of exceptional value, follow-up 

 treatment; sows in early pregnancy may be han- 

 dled in the same manner, but always after the 

 breeder has been informed that simultaneous 

 treatment will sometimes produce abortion, and 

 that the slight danger must be accepted as a lesser 

 evil ; sows due to farrow in less than three weeks 

 and those that have pigs a few hours or days old 

 cannot safely receive virus. It is true that the 

 infection on the farm will in most cases ultimately 

 reach them, but our aim should be to delay this as 

 long as possible, and to protect the sows with 

 serum alone in the meantime. Continued isola- 

 tion of the sows is desirable. Two or even three 

 doses of serum alone at three or four-week inter- 

 vals may be required before the time is ripe for 

 the final simultaneous treatment, but the extra ex- 

 pense is greatly to be preferred to the alternative 



