DISEASES OF SWINE 467 



causes a reaction and slight fever in the animal, and for several days 

 the temperature may vary several degrees, sometimes going to 106 

 degrees and even higher. From 6 to 10 days after vaccination the 

 temperature should be back to normal again, about 103 degrees. 

 (Kan. B. 163.) 



The statements concerning the protective power of serum from 

 hyperimmunized immunes are based upon tests on several thousand 

 hogs. These tests were carried out not only in small experiment 

 pens, but in great part upon farms under practical conditions. Dur- 

 ing the fall of 1907 approximately 2,000 hogs were treated on 50 dif- 

 ferent farms, a considerable proportion of untreated hogs being left 

 in all cases as a control on the action of the serum. Both methods 

 of treatment were used, and the herd conditions varied widely. The 

 herds can be roughly classified as (1) those in an infected district, 

 but themselves free from disease; (2) those known to have been ex- 

 posed by contact with sick hogs, but which had not developed disease 

 at the time of treatment; and (3) herds in which hog cholera was 

 present and hogs were sick and dying at the time of treatment. 



In no case were any of the ordinary methods of combating hog 

 cholera by disinfection and separation of the sick from the appar- 

 ently healthy practiced. Where disease was present at the time of 

 treatment, the treated animals were allowed to run with the sick 

 along with a number of untreated animals which served as controls, 

 and the success following treatment can therefore be attributed to the 

 action of the serum. In the herds where hog cholera appeared sub- 

 sequent to treatment, practically all of the treated hogs remained 

 well while more than 65 per cent of the checks died. In the herds 

 which had been exposed but were apparently well at the time of treat- 

 ment, 4 per cent of the treated animals died while approximately 90 

 per cent of the checks succumbed. In the herds where disease existed 

 at the time of treatment, and where very great success was not ex- 

 pected, 13 per cent of the treated animals were lost, whereas 75 per 

 cent of the checks died. 



These successful field trials, confirming as they do numerous 

 tests carried out under experimental conditions, have convinced us of 

 the efficiency of this method of dealing with hog cholera; and al- 

 though improvements will undoubtedly be made in many of the de- 

 tails of producing the serum, the method is believed to be now in 

 such condition as to make the practical use of it entirely feasible. 

 (B. A. 1, 25th A. R.) 



Duration of Immunity. Experimental evidences warrant the 

 statement that a hog once immunized to the disease of hog cholera 

 will retain the protection for a period of several months. Thus the 

 successfully vaccinated or immunized hog may be kept with no risk 

 of infection for a period long enough to fatten and prepare the ani- 

 mal for market. (Kan. B. 157.) 



Transmission of Disease by Hogs Treated by Serum-Simulta- 

 neous Methods. To test the possibility of disease being conveyed to 

 normal hogs by hogs that had been vaccinated, 58 shoats were placed 

 in the pens with the vaccinated hogs. Of these pen checks none be- 



