IMPROVED METHODS OF IMMUNIZATION AGAINST 
SYMPTOMATIC ANTHRAX (BLACKLEG) 
By R. A. KnrsER 
Veterinary Inspector , Pathological Division , Bureau of Animal Industry , United States 
Department of Agriculture 
INTRODUCTION 
During the past several years exceptional interest has been manifested 
by various investigators in the United States in prophylaxis against 
symptomatic anthrax. Up to that time the method of immunization 
practically exclusively employed in this country for the prevention of 
the disease was that of Kitt’s, or a modification of his method. 
Since 1897 the Bureau of Animal Industry of the United States Depart¬ 
ment of Agriculture has prepared and distributed to stock owners through¬ 
out the country millions of doses of blackleg vaccine, employing in its 
preparation the method outlined by Kitt with some modifications. The 
drinciple of the method 1 lies in the attenuation of affected muscle 
tissue from animals that had died of blackleg, and is accomplished by 
subjecting the same to a temperature of 95 to 96° C. for a period of six 
hours. The finished product consists of finely powdered muscle tissue 
containing the attenuated organisms. The results obtained from the 
use of this vaccine have been very satisfactory, and its use has been a 
leading factor in the control of the disease in the United States and 
elsewhere. 
At the present time, however, there are, of the more recently intro¬ 
duced products, two which bid fair to surpass in efficacy the various 
other agents for immunization against blackleg. One of these repre¬ 
sents a so-called “germ-free vaccine” or “natural aggressin,” and is a 
sterile filtrate prepared from affected animal tissues. The other is a 
toxic culture filtrate and is prepared from cultures of the bacillus of 
symptomatic anthrax produced with special culture media for toxin pro¬ 
duction and subsequently rendered free from organisms by filtration 
through bacteria-retaining filters. 
Both of these biological products have been found to possess valuable 
immunizing properties against blackleg, and their methods of prepara¬ 
tion are such that the finished products are superior to the powdered 
vaccine. 
1 For details of this method see Norgaard, V. A. btacexeg: its nature, cause, and prevention. 
U. S. Dept. Agr. Bur. Animal Indus. Circ. 31, 23 p. 1900. 
Journal of Agricultural Research, 
Washington, D. C. 
oq 
Vol. XIV, No. 6 
Aug. 5, 1918 
Key No. A-40 
(253) 
