490 BACTERINS, SERUMS — VACCINES — ANTITOXINS 



anthrax vaccine for long periods of time, as it does not seem to regain 

 its virulence. The second injection consists of a culture similarly 

 made and likewise incubated at the high temperature of 42° — 43° C. 

 for a period of 12 to 18 days or until its virulence has been reduced 

 to a point where it will kill gTiinea pigs but not rabbits. When such 

 attenuated cultures are injected into animals, a very mild and usually 

 clinically unnoticeable attack of anthrax is produced which confers 

 an active immunity. 



Recently Eichhom, working in the Bureau of Animal Industry, 

 has developed what is termed a " spore vaccine." It is prepared by 

 first attenuating cultures by growing them at 42.5° 0. for varying 

 periods. The cultures which had been grown at the high temperature 

 for 20 days proved satisfactory. The test inoculation showed that 

 their virulence was such that they would kill mice and guinea pigs but 

 not rabbits. 



These cultures should be inoculated onto a peptone-free agar 

 medium and grown at a temperature of 37.5° C. for 4 to Y days, by 

 which time an abundance of spores will have formed. The growth is 

 then washed from the slants and collected in a sterile flask and 

 heated at a temperature of 60° C. for one-half hour, to destroy the 

 vegetative forms of the organism. A measured quantity of this sus- 

 pension can then be plated out in the usual manner and the spore 

 content of 1 mil of the suspension established. A dilution can then 

 be made to the desired amount for inoculation purposes. Thus, if 

 it is desired to use for vaccination 1,000,000 spores, it is best to dilute 

 the vaccine to a quantity of which 1 mil would contain this number; 

 Of such vaccine 1 mil would constitiite the dose for cattle and horses, 

 with correspondingly smaller doses for calves and sheep. 



In all forms of vaccination against anthrax in_ sheep the greatest 

 care must be exercised, since these animals are very susceptible to the 

 disease, and at times vaccines which have no ill effects on cattle will 

 prove fatal to sheep ; therefore the dose of the spore vaccine for sheep 

 should not be more than one-fourth the amount given cattle. 



In the preparation of spore vaccines it is essential to submit every 

 lot to a test for pathogenicity by inoculating approximately 250,000 

 spores — that is, 0.25 mil of the standard suspension — into guinea 

 pigs and rabbits before employing the same for vaccination purposes. 

 The guinea pigs should die in from 2 to 5 days, whereas the rabbits 

 should remain alive. 



In consideration of the keeping qualities of the spore vaccine, 

 large lots can be prepared without fear of deterioration. In the bot- 

 tling and storing of the same, however, proper care should be taken to 

 prevent contamination. 



This spore vaccine is often used in connection with an anthrax 

 serum. That is, the so-called simultaneous treatment is employed. 

 This consists in injecting an animal with a dose of the spore vaccine 



