ELEVENTH ANNUAL YEAR BOOK— PART X ".tilt 



METHODS OF IMMUNIZING AM) PREVENTING OUTBREAKS OF HOG OHOLERA. 



First. Serum Alone. Method. This consists of using the preventive 

 serum alone and should be employed in outbreaks or upon exposure of the 

 herd before they show symptoms of the disease. If the exposure is not 

 present or subsequent to the use of the serum alone method, the immunity 

 is only temporary or passive nature, lasting possibly two months. This 

 method, therefore, should be employed in outbreaks upon hogs which 

 show no symptoms. It is often used by men who ship hogs to state fairs 

 or exhibitions to tide them over the period of travel and avoid any in- 

 fection to which they might be submitted in cars or stock yards. In 

 chronic cases of hog cholera, the serum does not give reliable results, 

 showing again the serum is a preventive, not a curative. 



Second. Serum Simultaneous Method. This method requires the same 

 dose of serum, but in conjunction with it a small amount of virulent blood 

 is used, being injected into the opposite side. This method is employed 

 when the disease or exposure is not present and produces a permanent 

 active artificial immunity. This method has been questioned by some in 

 the past, but it seems to be coming into prominence on account of the 

 longer period of immunity produced by this method. Some stations em- 

 ploy this method almost exclusively. 



CHOLERA BLOOD FOR HTPERTMMUNIZING. 



After years of work and experimentation, Drs. Dorset and Niles of the 

 United States Bureau of Animal Industry put forth an anti-hog cholera 

 serum, which proved its efficiency in preventing and controlling outbreaks 

 of hog cholera. The state experimental station, and live stock sanitary 

 boards have taken up this work in the different states, and are now pro- 

 ducing hog cholera serum by the Dorset-Niles method. 



The cultures of the specific organisms of hog cholera cannot be pro- 

 duced in the laboratory, but instead the fresh blood from cholera hog 

 is used. This' is drawn under sterile conditions a few hours before death. 

 Shoats weighing from sixty to one hundred pounds are used for this pur- 

 pose. They receive five cubic centimeters of the virus subcutaneously in- 

 to the muscles of the inside of the thigh. In from eight to fourteen days, 

 providing the hog is susceptible, and the blood virulent, the hog will 

 develop acute hog cholera. Just before death, the blood is caught in 

 sterile jars under antiseptic precautions, by bleeding from the carotid 

 artery. The blood so drawn is defibrinated, and used immediately for 

 hyperimmunizing purposes after examination of the dead carcass to ascer- 

 tain the lesions of cholera present. 



In our work at the Iowa State Laboratory, we have carried on at times 

 experiments w r ith sodium citrate in the virulent blood as a defibrinator 

 to eliminate the process of stirring and pressing out the clot. As yet, we 

 point favorably to its use. Our work with sodium citrate was carried out 

 in this way. To one-half of the blood drawn from a cholera shoat, we 

 would add sodium citrate, and to the other half we would remove the clot 

 by stirring and pressing, using a small fruit press. With this blood all 

 from the same shoat, but one part having sodium citrate, we made eight 



