312 ACUTE GENERAL INFECTIOUS DISEASES 



In France, Leclainche and Vallee have practiced preventive 

 inoculations with attenuated spores from edematous fluid 

 and cultures. Good results are claimed. Of scientific 

 interest is the fact that such inoculations do not immunize 

 against blackleg. 



BLACKLEG. 



Definition. — Blackleg is an acute infectious disease of 

 young cattle, due to a specific bacillus and characterized by 

 fever and the formation of emphysematous swellings involv- 

 ing muscular groups in various parts of the body. It is not 

 directly contagious. 



Occurrence. — While, generally speaking, blackleg has a 

 world-wide distribution, outbreaks occiu* usually only in 

 certain so-called blackleg districts. In this respect it 

 resembles anthrax, with which it was long confused. In the 

 United States the western states suffer most, although 

 sporadic outbreaks have been observed in the central and 

 eastern states. The southern Atlantic and eastern Gulf 

 states are said to be free. In some of the western states 

 (Kansas, Dakotas, Nebraska) the animal losses from black- 

 leg exceed those from all other diseases combined. The 

 worst infected area on this continent seems to be that 

 boimded north and east by the Missoxiri and Mississippi 

 Rivers and west by the Rocky Mountains, the great cattle 

 country. 



Etiology. — The Bacillus gangraenre emphysematosa;, an 

 anaerobe which occurs in soil, water, and in infected districts 

 in the droppings of cattle. Morphologically and culturally 

 the blackleg bacillus so closely resembles the malignant 

 edema bacillus that differentiation is very difficult. 



Natural Infection. — (a) Through wounds in the skin and 

 mucous membranes. Stubble, thorns, spines, barbed wire, 

 etc., causing small punctured woimds, which on account of 

 their character are most apt to become infected with soil, 

 etc., containing the rods or spores. 



(6) Through the digestive tract from the ingestion of con- 

 taminated food and water. The presence of the blackleg 

 tumor in the throat, bowels, and other internal organs, and 



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