172 HOG CHOLERA 



We have been called on repeatedly to handle 

 herds of sows infected with hog cholera just at 

 farrowing time. Whenever it is possible we dip 

 the animals, segregate them as best we can and 

 administer serum alone, carrying both sows and 

 pigs along with doses of serum alone at four- 

 week intervals until the latter are weaned and at 

 least nine weeks old, at which time sows and pigs 

 receive simultaneous treatment. In herds in 

 which isolation is impossible, we follow the same 

 course in regard to administering serum, giving 

 the first dose, about 4 mils, when the pigs are a 

 day or two old. It is possible to bring pigs safely 



These observations do not carry the weight that may be attached 

 to carefully controlled experiments, but they suggest caution in 

 regard to the sweeping conclusion that all young pigs acquire 

 permanent immunity as a result of simultaneous treatment. 



Closely bound up with this question is the one of the immunity 

 of sucking pigs to hog cholera. Pickens found that 100 per cent 

 of pigs nursed by immune mothers were themselves immune, but 

 any person with extensive experience in handling hog cholera 

 knows that we cannot always, or usually, depend on this immunity. 

 We have repeatedly seen pigs born of immune mothers and 

 nursed by them dead with hog cholera before they were four 

 weeks old, but there are others, as Pickens' experiments show, 

 that are immune. 



Collectively, all experimental work and clinical observations so 

 far recorded point to the conclusion that some pigs of cholera 

 immune mothers are themselves immune, and others are not; some 

 will acquire active immunity as a result of simultaneous treat- 

 ment, others will not. We have no way of knowing whether any 

 particular young pig or litter will acquire permanent immunity 

 if simultaneous treatment is given, so we prefer to maintain the 

 immunity of all young pigs with serum alone, and to finish with 

 simultaneous treatment when the animals are about twelve weeks 

 old. A cheaper plan than this will be available in well-kept herds 

 f the findings of Niles are confirmed; a more effective one is not 

 likely to be found as long as we use serum and virus as they are 

 now prepared.. 



