Prevention, Immunization 73 



this source of danger. Accordingly, healthy animals should be 

 separated from the affected ones, and they should be kept from 

 contaminated pastures and stables. Carcasses should be deeply 

 buried, or still better cremated. Infected stables and premises 

 should be properly disinfected, and the excrement of the 

 affected animals collected and destroyed. Infected pastures 

 should not be used as ranges for swine for a long time. 



If the disease has already appeared in a herd it is advisable 

 to place the apparently healthy animals in an unsuspected 

 pasture, or in the absence of such, pasturing should not be per- 

 mitted until the complete disappearance of the disease ; in this 

 way it is frequently possible to eradicate the outbreak. Inas- 

 much as the infective agent is present in all parts of the emer- 

 gency slaughtered hogs the disease may be disseminated by 

 the marketing of such carcasses, and therefore the sale of meat 

 of such carcasses should not be permitted until it has been 

 sterilized. Such a procedure appears the more advisable, as 

 according to Petri's and Stadie's investigations ordinary con- 

 servation of the meat and the products prepared therefrom 

 (salting, pickling, smoking) destroys the erysipelas bacilli only 

 after a long time. (See page 62.) _ _ 



When the possibility or even probability of an infection ex- 

 ists, the occurrence of the disease may be successfully pre- 

 vented by means of protective inoculation. 



Immunization. One attack of erysipelas conveys immunity 

 to hogs against later natural infection. This experience would 

 also indicate that the artificially produced mild affection affords 

 a similar immunity. This idea was practically demonstrated 

 by Pasteur in 1882 by inoculations of artificially attenuated cul- 

 tures, while later Lorenz as well as Leclainche established the 

 value of protective inoculation with immune serum and cultures 

 in practice. 



I. Protective inoculation with attenuated cultures (Pas- 

 teur's method). Pasteur showed in his experiments that the 

 passage of erysipelas virus through the body of rabbits in- 

 creases its virulence for these animals. On the other hand, it 

 reduces it for hogs, so that the inoculation with such virus in 

 the latter animals causes only a slight febrile disease. Virus 

 attenuated up to a certain degree retains this degree of viru- 

 lence even if transferred from the rabbit blood to a suitable 

 artificial medium, for instance, bouillon and if further cultivated 

 at body temperature. The bouillon culture attenuated by the 

 above method produces the vaccine which is injected subcu- 

 taneously into young pigs in form of a weaker and a stronger 

 modification. 



The effectiveness of Pasteur's protective inoculation has 

 been positively established. Besides Pasteur, Schiitz, Schotte- 

 lius and others found that vaccinated hogs cannot be infected 



