75 



The number of animals dead and visibly sick 

 at the time of serum treatment forms our chief 

 basis of estimate. Assuming that a herd is kept 

 under average farm conditions, and that there is 

 no evidence of complications, as a very general 

 rule we expect to save about as many hogs as are 

 eating greedily and are free from abnormal tem- 

 peratures on the date of serum administration. 

 Some of those that show no fever will die, and a 

 few of those that show fever will recover, one 

 class approximately compensating the other. 



In herds in which it is not possible to secure 

 reliable temperature readings, the prognosis must 

 be more guarded. In general, during the early 

 days of an outbreak, we expect about as many 

 deaths to follow serum treatment as the combined 

 sum of the hogs that have previously died and 

 those visibly sick when serum is administered. 

 If fifty per cent of the animals in a herd are dead 

 or visibly sick we expect the salvage to offset the 

 cost of serum treatment, and leave something to 

 spare, but we cannot promise much in such a herd. 



Evidence of secondary infection, coexisting par- 

 asitisms, improper feeding and housing, a history 

 of recent shipping or other weakening influences 

 all call for a guarded prognosis. If the hogs have 

 not been confined closely, or if they are in several 

 pens some of which remain uninfected, the prog- 

 nosis is relatively more favorable. 



