314 ACUTE GENERAL INFECTIOUS DISEASES 



and even violent convulsions occur, the temperature rapidly 

 falls and death follows. 



Course. — ^The course is rapid and fatal. Most patients die 

 in from twelve to forty-eight hours. Isolated cases may 

 linger several days (mild invasion, high resistance), then die, 

 or in rare instances recover. 



Diagnosis. — Blackleg is a disease easily diagnosed, pro- 

 vided the typical swellings are in evidence. As a rule the 

 owner or ranchman recognizes it without professional aid. If 

 the characteristic emphysematous enlargements are absent, 

 however, as is common in the first cases of some outbreaks, 

 a diagnosis intra vitam is very difficult. Blackleg may be 

 confused with malignant edema and anthrax (see these). 



Necropsy. — ^The cadaver is greatly bloated and swollen, 

 especially about the tumors. Hemolysis develops early in 

 the body. Although the blood corpuscles are broken down 

 and the hemoglobin set free, oxygen is still absorbed. This 

 causes the parts exposed to the air to become a scarlet color. 

 Therefore animals which have died of blackleg and have been 

 skinned show a characteristic scarlet coloring of the surface. 

 The affected muscle, however, does not undergo this change 

 but remains almost black in color. When the swellings 

 are cut into, a foamy, dark fluid flows out. The affected 

 muscle is of a dirty brown to blackish color, very friable, and 

 often smells like rancid butter. The blood is dark-colored 

 but coagulates readily. In the serous cavities blood-stained 

 fluid is found. The hTnph glands corresponding to the 

 tumors are swollen and blood-shot. The spleen is usually 

 normal. The characteristic postmortem lesions are : Normal 

 blood, normal spleen, and emphysematous swellings. 



Prognosis. — In young cattle fully 98 per cent. die. In older 

 individuals a few recover. 



Treatment. — A medicinal treatment is uspless. Surgical 

 intervention as recommended in malignant edema is rarely 

 advisable except in very valuable individuals. It is further- 

 more a menace, as the discharge from the incisions spreads 

 the infection. 



Prophylaxis. — When an outbreak ocdu-s all cattle two years 

 old and under should be promptly removed to a preferably 



Digitized by Microsoft® 



