BLACKLEG 263 



the carcass has been brought to the place of final disposal. 

 Such simple precautions may be cheap insurance against 

 future trouble. 



Blackleg. A disease frequently mistaken for anthrax is 

 that commonly called blackleg or symptomatic anthrax. 

 Before the causal organisms of the two diseases were discov- 

 er^ 1. it was thought that blackleg was a special form of 

 anthrax. The disease is also known under the names quar- 

 ter-ill or quarter-evil. The causal organism is called Bncil- 

 ius Chtnird. It is a large rod which grows only under 

 anaerobic conditions. It produces spores in the tissues of 

 the unope:K'd animal, a property that differentiates it 

 sharply from the anthrax bacillus. 



Blackleg is found in all parts of the world, from the 

 tropical regions to the northernmost limits at which cattle 

 are kept. In the United States it is most common in the 

 great grazing States of the Southwest. There are infected 

 localities in many of the States east of the Mississippi River. 

 The disease has often been mistaken for poisoning in local- 

 it ies in which it was not known to occur. It has been 

 probably the most important disease in the great beef-pro- 

 ducing districts of this country. Recently, means of pre- 

 vention have been so effectively used that the disease has 

 greatly decreased in importance. 



Cattle between the ages of six and eighteen months are 

 virtually the only ones that are susceptible to the disease. 

 It represents one of the few cases of age immunity to a 

 disease noted in the lower animals. 



A great increase in blackleg followed the introduction 

 of the improved breeds of beef cattle on to the ranges of 

 the Southwest. It is believed that the thinner the skin, 

 the more likely is the animal to acquire infection. 



Again, animals that are gaining in flesh rapidly and that 

 are taking little exercise seem to be the most susceptible. 



