414 CHRONIC INFECTIOUS DISEASES 



ance of either connective-tissue enlargements, bone growths, 

 or abscesses which usually occur about the head of the animal 

 affected. The disease is not contagious. 



Occurrence. — While most common among cattle, actino- 

 mycosis occurs occasionally in swine and rarely in horses. 

 Cattle which have access to straw stacks, especially of 

 barley or bearded wheat,, are most often attacked. It may 

 happen that a whole herd of steers or heifers running about 

 a straw stack, which serves them for shelter and in part 

 food, will become victims. Stable-fed cattle are often 

 infected by forage fed in a dry state, but which was grown 

 on lowlands subject to overflow. While clinically the disease 

 is more important to the surgeon than to the internist, 

 it not infrequently affects internal organs (lungs, liver, 

 stomach), and leads to the condemnation of the carcass in 

 the abattoir. 



Etiology. — The cause of the infection is a thread-like 

 fungus known as the Streptothrix actinomyces or the Actino- 

 myces bovis. A common name for it is the ray fungus. 

 This fungus grows on various kinds of grasses, but particu- 

 larly on the awns and glumes of barley and related grasses, 

 especially when these have grown on bottom lands subject 

 to overflow. 



Natural Infection. — Infection takes place through the 

 mucous membrane, usually of the mouth, or through wounds 

 in the skin. Forage infested with the fungus, provided it 

 contains sharp awns or glumes or the sharp cut ends of 

 coarse' straw (stubble), easily cuts the mucous membrane, 

 introducing the fungus into the wound at the same time. 

 Cattle from the Southwest suffer from eating cactus, the 

 sharp spines of which wound the mouth. Obviously when the 

 mucous membrane of the mouth is edematous and tender as 

 occurs when the deciduous teeth are being shed the op- 

 portunity for infection is greatest. Sometimes the infection 

 enters the alveolus of a tooth, leading to the development of 

 disease of the bone of the jaw (periostitis, osteitis, osteomye- 

 litis) . If the mucosa of the cheek is infected either abscesses 

 (young animals) or connective-tissue growths appear about 

 the head. If the tongue is invaded either a diffuse connect! ve- 



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