262 DISEASES OF THE SKIN 



Psoroptic Mange. — Occurrence. — This form of mange or 

 scab is widely prevalent in the United States^ Through the 

 efforts of the Bureau of Animal Industry, with the coopera- 

 tion of the great sheep-grazing States (Colorado, Montana, 

 Wyoming), sheep scab has been greatly reduced in the past 

 few years. 



Symptoms. — Psoroptic mange affects the parts of the 

 skin which are covered with wool. It therefore usually 

 appears in the shoulder region, along the back, croup, sides 

 of the chest and neck. It does not involve the ventral chest 

 or abdominal regions. 



The first symptoms noted are usually those of itchiness. 

 The sheep are uneasy, bite and rub the affected skin. The 

 wool soon becomes loose and tufted. The itchiness is most 

 noticeable in hot weather, after exercise, in warm stables and 

 at night. If the wool is separated and the skin examined red 

 or yellowish papules the size of a hemp seed are noted; 

 eventually vesicles or pustules, as well as thin, yellowish, 

 fatty crusts and scabs, appear. By confluence large irregular 

 areas are formed, covered with thick yellow crusts. The 

 crusts or scales adhere to the wool and by its growth are 

 elevated from the underlying skin. The wool soon becomes 

 tufted and the surface of the fleece uneven; or it falls out, 

 leaving bald areas, especially along the back and sides. In 

 shorn sheep or on the bald areas the scales are dry and brown 

 in color. The disease develops rapidly under the fleece, 

 especially in stables, so that in six to eight weeks the whole 

 body may be denuded of wool. When the whole trunk is 

 involved on account of the loss of albumin, unrest, and inter- 

 ference with feeding, the weaker sheep become anemic, emaci- 

 ated, cachectic, and often die. This is especially true in 

 winter when the sheep are stabled. After shearing and turn- 

 ing out on grass temporary improvement is noted. 



Diagnosis. — The diagnosis depends upon finding the mites 

 by scraping freshly infected areas where the scabs are soft, 

 placing the scraping on a piece of black paper in the sun and 

 with a hand lens noting the minute mites which are seen 

 crawling toward the edge of the paper. Obviously a better 

 view may be obtained through the microscope. In very old 



Digitized by Microsoft® 



