196 



COMMON DISEASES. 



portion of the head. Occasionally it invades the neck and other 

 portions of the body where the wool is short. 



Local treatment. — The same as for foot scab. 



GENERAL PREVENTION. 



Prevention is more important than treatment in any case 

 where it can be secured ; because it is surer ; it is cheaper ; and is 

 usually much easier to administer than medical treatment. 



FIG. 72. A PLAIN CASE OF SHEEP SCAB. 



The spread. — Whether the disease spreads rapidly over the 

 body or not depends to some extent upon the thriftiness or un- 

 thriftiness of the individual animal. When sheep are fat and the 

 wool is well supplied with yolk this disease spreads slowly, and is 

 much less serious. It should be borne in mind that sheep cannot 

 have scab unless the mites first reach the surface of the body. 

 The infection is frequently made when one sheep rubs against 

 posts or fences where scabby sheep have previously rubbed. In 

 the latter case the mites are first transferred from the diseased 

 sheep to the post, and then from the post to the healthy sheep. 

 In other cases the mites are transferred when a diseased sheep 

 rubs against a healthy one. 



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