2.86 ACUTE GENERAL INFECTIOUS DISEASES 



mechanical (sand particles) or chemical agencies (lactic acid) 

 or the toxins of other bacteria which may be present (staphy- 

 lococci) . 



Symptoms. — In the neighborhood of the infected wound a 

 rather diffuse edematous swelling appears. The swelling is 

 at first painful, firm, and hot, but later becomes softer, less 

 painful, and on palpation crepitates. It spreads rapidly and 

 in a few hours can involve the whole body and head. In' a 

 horse so afflicted the patient assumes the appearance of a 

 hippopotamus. With the advance of the external swelling 

 dyspnea develops with foamy nasal discharge (lung edema), 

 cyanotic mucous membranes, and rapid, weak, irregular 

 pulse. The temperature is elevated early and does not sink 

 to normal until the patient becomes moribund. 



In cows infected during obstetrical manipulations, in two 

 to four days the lips of the vulva begin to swell, the swelling 

 rapidly involving the perineum, thighs, and udder. There is 

 an offensive brownish discharge from the vagina. The tem- 

 perature is up and bloating and diarrhea noted. 



Diagnosis. — The cardinal symptoms of malignant edema 

 are: rapid development, emphysematous character of the 

 swellings, high fever, and fatal course. It resembles black- 

 leg in cattle, but may be distinguished from this disease by 

 the following: malignant edema usually affects the repro- 

 ductive organs of cows at the time of parturition; it affects 

 connective tissue rather than muscle, is not confined to young 

 cattle, and appears in districts free from black-leg. Black-leg 

 is common in the United States, and occurs enzootically, 

 while malignant edema is rare in cattle and is sporadic. It 

 would hardly be confused with phlegmons resulting from pus 

 infection. Such swellings do not develop so rapidly, do not 

 crepitate, and are not usually fatal. Ordinary emphysemas 

 of the skin which accompany rib-fracture, pulmonary emphy- 

 sema, or wounds (median neurectomy, trocaring, intentional 

 inflation of the scapular region to conceal muscular atrophies) 

 are not attended by fever and comparatively benign in course. 

 The postmortem emphysema noted in parenchymatous organs 

 in delayed necropsies during hot weather would hardly 

 mislead a careful observer. 



Digitized by Microsoft® 



