BIOLOGICAL THERAPEUTICS 



53.3 



for the numerous failures resulting therefrom. Special mention might be 

 made of the unstable keeping qualities of the Pasteur vaccine, and further, 

 that it requires two handlings of the animal before immunity is estab- 

 lished, that its standardization is not carried out accurately and that in 

 herds where the disease has already appeared it is apt to induce losses 

 through the temporary reduction of the resistance of the animal during 

 the development of immunity. 



These conditions are, no doubt, responsible for tlie extensive experi- 

 mental work undertaken by the U. S. Bureau of Animal Industry during 

 the past three years on immunization against anthrax. The results of the 

 work have been published in the Bureau of Animal Industry Bulletin, 

 No. 34'0, by the writer, in which the advantages of the simultaneous treat- 

 ment with anti-anthrax serum and attenuated spore vaccine are pointed 

 out and endorsed. 



Anti-anthrax serum is prepared from horses which have been im- 

 munized against anthrax. Then they are injected with minute doses of 

 virulent cultures which are gradually increased until the animals tolerate 

 intravenous injections of suspensions of mass cultures of virulent anthrax 

 bacilli. The serum is then subjected to potency tests on guinea pigs and 

 rabbits and if found satisfactory the animals are bled and re-injected at 

 regular intervals. 



The spore vaccines are produced from specially selected anthrax cul- 

 tures which have been proven 

 good spore producers. They are 

 subjected to attenuation by cul- 

 tivating them at a temperature 

 of 421/2° C. (108.5° F.). The 

 No. 1 vaccine or the vaccine of 

 greater attenuation, is attenuated 

 from 18 to 21 days, and must be 

 pathogenic only to mice. The 

 second or stronger vaccine is at- 

 tenuated from 11 to 13 days and 

 should be pathogenic to guinea 

 pigs and mice but not rabbits. 

 The attenuated vaccines retain 

 their weakened pathogenic prop- 

 erties for an indefinite period. 

 They are then cultivated for the 

 vaccine production on agar me- 

 dia for four to six days until the 

 maximum spore formation has 

 been attained. After washing off 

 the growth it is heated to 60° C. 

 (140° F.) for one hour in order 

 to destroy the vegetative forms. The suspension is then standard- 

 ized by plating to establish the number of spores contained per mil. The 

 suspension of spores is then diluted to a desirable strength and properly 

 preserved. 



The simultaneous method consists of the injection of a potent anti- 



intravenous Injection of Virulent Anthrax 

 B.T,cilli in the Production of Anti- 

 Anthrax Serum 



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