480 PARASITIC SKIN DISEASES 



Daily application may be made over small areas but in 

 generalized' cases only a part of the body should be treated 

 at a time. The mixture is irritating, hence when the animal 

 shows signs of exhaustion its use should be discontinued for 

 a few days. Other preparations used are balsam of Peru in 

 alcohol (5 to 10 per cent.), creolin ointment, styrax ointment 

 (5 per cent.). 



Demodex Mite.— Etiology.— Demodectic scabies is pro- 

 duced by the parasite, Demodex folliculorum. This parasite 

 lives in the hair follicles and sebaceous glands, locations 

 favoring much irritation and making treatment most difficult. 

 The demodex mite is decidedly different in appearance from 

 the sarcoptes. Its body is elongated, and provided with 

 eight short legs emanating from its anterior third. The 

 posterior part tapers to a blunt point. The head is short 

 and thick. The total length is about six times the body 

 width. Some one of the many varieties may be found on all 

 kinds of small animals. The dog, however, is the principal 

 sufferer. Cats are rarely attacked. 



Pathology.— The skin in mild cases shows only slight inflam- 

 matory symptoms. In severe cases the skin is greatly 

 thickened, and shows intact or ruptured pustules. In micro- 

 scopic cross-sections the parasite is found within the glands 

 and follicles. 



Symptoms.— The early indications of demodex mange are 

 the presence of isolated inflammatory areas from one-half to 

 two inches in diameter. The hair covering them appears as 

 though clipped off closely. The condition gradually spreads 

 and may cover the entire body. Occasionally demodex 

 mange occurs in the well named squamous form. In this 

 there is only slight irritation and no marked inflammatory 

 symptoms. The hair becomes thin, and gray- white scales 

 cover the skin. This condition may continue without change 

 for months especially when the dog is brushed and bathed 

 frequently as may be done with house pets. The disease 

 makes progress by a gradual peripheral spread over the skin, 

 or less often by the occurrence of new isolated areas over the 

 body. The skin thickens, pustules develop and erupt form- 

 ing crusts; the hair falls out. Emaciation follows and the 



