BLACKLEG 315 



higher and drier pasture. In stable-fed victims a change to 

 known uninfected food is imperative. The dead should be 

 disposed of as recommended under anthrax. Exposed ani- 

 mals should be vaccinated, which successfully protects against 

 serious infection. There are several anti-blackleg vaccines, 

 aggressins, filtrates and sera on the market. The Bureau of 

 Animal Industry and many of the agricultural experiment 

 stations produce them. 



(a) Originally the vaccine was made from blackleg muscle, 

 dried, attenuated at 93.5° C, tested on guinea pigs and 

 classified according to its ability to kill. It is used in the 

 form of powder, pills or strings. The dose is 3 to 5 mg. 

 While the use of this vaccine has greatly reduced the losses 

 from blackleg, its action has always been variable, the losses 

 reaching as high as 20 per cent, of the vaccinated animals on 

 some farms. 



(b) The aggressin is a vaccine produced by taking the 

 blackleg lesion and all of the edematous tissues around it, 

 pressing it in a hydraulic press, in order to extract all juices, 

 after which it is preserved with phenol, clarified and filtered 

 free of all organisms. The dose is 5 c.c. Goss, in Kansas, in 

 three years distributed over 112,000 doses of blackleg aggres- 

 sin with a total loss of less than 50 animals. While the use 

 of attenuated vaccine necessitated that the animals be treated 

 two or more times a year, with aggressins only one treat- 

 ment in the life of an animal is necessary. 



(c) The filtrate is made by growing the organisms on 

 culture media for seven to ten days after which phenol is 

 added. It is then clarified and filtered free of all organisms. 

 The dose is 5 c.c. Properly made filtrate has given excellent 

 results. As with the aggressins immunity is produced in 

 four to ten days. 



(d) Anti-blackleg serum is produced by injecting horses 

 with blackleg cultures in doses of 50 to 150 c.c. weekly for a 

 period of five to seven weeks. Administered in the early 

 stages of blackleg in doses of 250 to 500 c.c. many animals 

 suffering from the disease are cured. It is recommended to 

 administer before the temperature drops. The serum should 

 be followed in ten or twelve days with a dose of aggressin or 

 filtrate. 



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