HEMORRHAGIC SEPTICEMIA GROUP 297 



Immunity. No true toxin has been demonstrated for the 

 B. avisepticus. Endotoxins are produced. One attack of the 

 disease with recovery confers immunity. Agglutination in dilu- 

 tions of 1 : 6000 has been shown with blood of animals artificially 

 immunized. The nature of this immunity is not certainly known, 

 although opsonins have been demonstrated. 



Pasteur, in 1880, worked out a method of prophylaxis by the 

 use of vaccines prepared from attenuated cultures. He attenu- 

 ated the organism by long-continued cultivation upon artificial 

 media. Broth cultures were allowed to stand from three to ten 

 months. Under these conditions the virulence is gradually lost, 

 and inoculation into the fowl is followed by a mild local reaction 

 only. This immunizes against subsequent injections of the 

 virulent form. Pasteur believed that the attenuating factor was 

 the abundant presence of oxygen, for cultures which he sealed 

 from the free entrance of air he found to retain their virulence 

 even after ten months. He also found that various strains showed 

 great differences in their rate of attenuation. The Pasteur method 

 of vaccination has never come into general use. Tests have shown 

 that the use of the vaccine sent out by the Pasteur Institute was 

 apt to produce typical cholera in some fowls. It has been shown 

 that some degree of immunity is conferred by the injection of 

 killed cultures of the organism. 



It has also been found that immunization against one of the 

 members of the hemorrhagic septicemia group immunizes like- 

 wise against others. Injections of the Bacillus bovisepticus, for 

 instance, will protect against subsequent injection with Bacillus 

 avisepticus. Ligniere has prepared a polyvalent vaccine by grow- 

 ing at 42 to 43 organisms isolated from sheep, cattle, horses, 

 dogs, hogs, and fowls in bouillon. When allowed to grow for five 

 days, it constitutes the Vaccine I.; for two days only, Vaccine II. 

 One-eighth c.c. of I. is injected, and twelve to fifteen days later 

 the same amount* of Vaccine II. By this means he claims to be 

 able to immunize against all types of hemorrhagic septicemia in 

 animals other than fowls. This method has not been utilized in 

 practice, although a few recorded tests have been favorable. In 

 summary, therefore, it may be stated that no practicable method 

 of vaccination against fowl cholera has been evolved. 



