PARASITES AND PARASITIC DISEASES OF HORSES 



41 



The mites penetrate the upper layer of the skin, each female making 

 a separate burrow or gallery, which usually extends to the sensitive 

 tissues or "quick." The presence and activities of the mites on the 

 sensitive tissues cause great irritation and itching, and the skin be- 

 comes inflamed and swollen, so that small nodules are formed over and 

 around the burrows. As the disease develops vesicles are formed 

 which break and discharge serum. As the serum dries, small scabs 

 are formed, and the hair over the affected parts stands erect and some 

 of it drops out. In some cases the affected areas of skin become dry 

 and scurfy, and may have a leatherlike appearance. (Fig. 28.) 



The mechanical injury to the skin resulting from rubbing and biting- 

 causes large scabs to form, which adhere firmly to the underlying- 

 tissues. The large scabs often are broken by the movements of the 

 animal, and blood or serum may stain the scabs a reddish yellow. 



Figure 29. — A well-developed case of sarcoptic mange 



As the disease advances the skin becomes more or less bare in irregu- 

 lar-shaped, bald patches, and is greatly thickened and thrown into 

 wrinkles or folds. (Fig. 29.) In severe cases the horse loses flesh 

 rapidly, becomes greatly weakened, and unless properly treated may 

 die. 



Contagiousness. — Sarcoptic mange is transmissible from one species 

 of animal to another, and also from animals to man. Ordinarily when 

 one species of animal contracts the contagion from another species the 

 mites live only a limited time on the new host, Sarcoptic mites of the 

 sheep, hog, camel, dog, cat, and rabbit may live on horses, and those of 

 the horse, dog, and hog are known to be readily transmissible to man. 



Sarcoptic mange of horses is contagious to all classes of horses and 

 is usually transmitted by direct contact with infested animals. It may, 

 however, be transmitted by other objects, such as currycombs, blankets, 

 or harness, or in stables or other premises. It is important that mangy 



