INFECTIOUS DISEASES 209 



Bacillus necrophorus produces necrosis, or abscess forma- 

 tion, in cattle, sheep, swine, and horses. 



Source of infection. The Bacillus necrophorus 

 inhabits the digestive tube of swine and, less frequently, 

 the digestive tube of other animals; therefore the micro- 

 organism is found in the feces of practically all animals. 

 Soil, yards, pens, floors in fact, practically all of the 

 surroundings easily become contaminated with fecal 

 matter, and the disease may be obtained from anything 

 that has been contaminated with feces. Infection is 

 usually indirect, although the Bacillus necrophorus may 

 be transmitted from an affected to a healthy animal by 

 contact. 



Channel of entrance. This infective agent may be 

 successfully introduced into the susceptible swine in food 

 or drink by way of the mouth, upon inhaled dust particles 

 by way of the respiratory organs, or it may be introduced 

 through abrasions of the skin, and, more rarely, into the 

 genital organs daring copulation. 



Lesions. The Bacillus necrophorus is capable of 

 invading practically any tissue of the body, and the 

 lesions produced so closely resemble each other that one 

 general description will suffice. The lesion consists of 

 a coagulation necrosis, the necrotic material later becom- 

 ing caseated. The local lesion has a tendency to become 

 larger, due to the infiltration of the surrounding tissue 

 with the products of the Bacillus necrophorus. The 

 infection, and therefore the lesions, may occur elsewhere 

 in the body, due to metastasis. There may be general 

 emaciation due to absorption of the products of the 

 Bacillus necrophorus, and tissue destruction. 



The local specific lesion is a sharply circumscribed 

 yellowish or brownish area containing a homogeneous, 

 dry, mealy, or cheese-like substance from which a pungent 

 and disagreeable odor emanates. Microscopic examina- 

 tion of a section of one of these areas reveals a central 

 mass of tissue debris composed of disintegrating and de- 

 stroyed cells which do not stain. Surrounding the 

 necrotic area is a zone made up of leukocytes, damaged 



