^6 DISEASES OF THE DOMESTIC ANIMALS 



propagate in the lower layers of the skin; (2) dermatodectes, or 

 sucking mites, which live on the outer surface of the skin, prick it 

 and suck up serum and lymph; (3) symbiotes, or scale-eating mites, 

 which live on the surface of the skin of the extremities and feed on 

 epidermis. The sarcoptes can only be seen with a hand lens; the 

 others possibly with the naked eye, but to better advantage with a 

 magnifying glass. The different species attack different parts of 

 the body. Thus the sarcoptes attack the head and parts least cov- 

 ered by hair: the dermatodectes inhabit protected regions, as the 

 inside of the thigh, root of the mane and tail, sheath, and under the 

 jaw ; while the symbiotes affect extremities of the body, as the 

 feet (horses and sheep), the root of the tail (cattle), external 

 auditory canal (dog). Sarcoptic mange is transmissible to man 

 from animals, and from one species of animal to another, also from 

 man to animals. The other varieties of mange are not. The symp- 

 toms of mange are intense itching with rubbing, biting, scratching, 

 stamping (on feet), especially at night and after overheating of 

 the body, with the appearance on the skin of redness, papules, 

 vesicles, pustules, weeping, bloody or suppurating surface, thicken- 

 ing of the integument, roughened, matted, and falling hair, with 

 alopecia. The disease may simulate eczema or other skin lesions, 

 but the intense itching, the tendency for the disease to attack other 

 animals, the locality affected characteristic of the variety of mange, 

 and finally, the positive discovery of the parasite by microscopic 

 examination, are diagnostic evidences. 



Preventive measures consist in isolation of infected animals; 

 in disinfection of the premises and everything coming in contact 

 with the patients, as coverings, brushes and other cleaning utensils ; 

 in destruction of bedding ; in changing the customary pastures and 

 routes; and in burning the hair clipped from patients. Disinfection 

 is done as for any contagious disease (see p. 282). 



Mange in the Horse. — This is comparatively rare. Sar- 

 coptes scabei attacking the head, neck, shoulders and spreading to 



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