482 IOWA DEPARTMENT OF AGRICULTURE 



is what we ordinarily call the serum. It contains a substance which will 

 protect other hogs against cholera when it is injected in small doses, that 

 is, about two-thirds of an ounce for a hog weighing a hundred pounds. 

 When you use this serum on a hog that has never had hog cholera, that 

 hog does not take part in producing those substances because you in- 

 ject them into its body after they have been produced by another hog. 

 Consequently it is not lasting and when all this substance has been elim- 

 inated the hog will take hog cholera again. But when it is exposed to 

 hog cholera it must overcome that infection and take some active part in 

 overcoming the disease and in that case you have lasting immunity. So 

 we have the two methods which consist of serum and serum and dis- 

 ease producing blood. 



"In regard to the indications for the two methods. Of course circum- 

 stances will vary on different farms and in different outbreaks but I 

 think the most successful method is being carried out in Ohio. There 

 they go into the herd and take the temperature of every hog. The hogs 

 that show a rise of temperature, indicating that they are infected, get a 

 dose of serum alone. All those with a normal temperature, indicating 

 that if they are infected the disease has not made much headway, get a 

 dose of virulent blood and serum and in that way they confer lasting im- 

 munity on all animals that are treated. 



"Results vary a great deal. Just why this is I do not know. There are 

 so many factors to take into consideration in the manufacture of the 

 serum, the keeping of it, and the intelligent use of it that it is hard to 

 say just where the fault is but it is quite easy to make a little mistake 

 or get a faulty test on the serum. It must be tested after it is drawn 

 from the animal because some hogs do not produce a good serum. In 

 order to test it you take varying quantities and inject it into several dif- 

 ferent pigs, each receiving a different sized dose, and then inject disease 

 producing blood, and in that way you get a check on the serum. Some- 

 times you get very strong serum and sometimes rather weak. 



"Then there is another thing that has come to our attention a number 

 of times and that is that where you have an old outbreak of hog cholera 

 where say fifty per cent of the animals have died, you usually do not get 

 very good results. In that case most of the animals are suffering from the 

 disease and you hardly ever get satisfactory results. 



"The disease can be checked a great many times in a locality by the 

 use of the serum. That is, if one farmer has cholera in his herd and the 

 neighbors all vaccinate you can check the disease in that way. In ad- 

 dition to vaccinating I always advise dividing the herd into small lots 

 and taking the different lots to different parts of the farm. Then use the 

 serum and simultaneous method if you know you have good serum. The 

 danger comes in that if you nave not good serum you will inoculate your 

 hogs with hog cholera and you may lose many of them. Be sure that the 

 serum is absolutely good." 



DISCUSSION. 



''Will hogs that have not been vaccinated contract the disease 

 from those that have been vaccinated?" 



