382 DISEASES OF SWINE 



manner a permanent immunity is assured to every animal in the 

 herd. Otherwise, some of the healthy hogs may never take up 

 enough of the virus to produce a reaction and, as a result, are only 

 temporarily protected. 



In very young pigs the double treatment is not overly advisable, 

 as these little fellows do not seem capable of taking up the work of 

 antibody formation. Giving of the double treatment does not in 

 itself do any harm to the httle pigs, but it very often does not give 

 a permanent immunity unless the pigs be at least six weeks of age. 

 The better plan in small pigs, then, is to give the single injection 

 when a few days old if cholera threatens. In case there is no close 

 outbreak of the disease it is as well to wait until about weaning time 

 and then administer the double treatment. In case the single 

 treatment is given to very young pigs, it is advisable to follow this 

 later on with the double injection, giving the treatment again at the 

 age of about six weeks. 



In pigs that are born of an immune sow there is a temporary 

 immunity which seems to last for several weeks. In such pigs it 

 is not necessary to give any treatment until they are about six 

 weeks of age, and then the double injection is the more advisable. 



DOUBLE OR SIMULTANEOUS METHOD OF TREATMENT 



We have seen, in the preceding section, how we may make 

 use of the serum alone as a weapon in our fight against the dis- 

 ease hog-cholera. This serum alone, when injected into the body 

 of a healthy animal, supphes it temporarily with sufficient of the 

 antibodies, or germ fighters, to keep it free from the disease, and 

 enables it to withstand the attack of almost any number of the 

 disease-producing germs. 



This immunity, however, we found was only temporary in 

 nature, and passed off in about thirty days or a httle over. This 

 would make it necessary for us to treat the animals with serum 

 about every six weeks during seasons when cholera is present 

 throughout the entire summer, as is often the case, and, in the end, 

 it would make the treatment too expensive to be of value. 



In the case of animals that are to be fattened and got 

 ready for market this period of six weeks during which they are 

 protected might be enough to complete the fattening process, 



