936 Scabies. 



anal region. There is probably no doubt that the sarcoptes 

 mites, while boring passages under the epidermis layer, as well 

 as dermatocoptes mites that bite and hold on to the skin, cause 

 an inflammation by their mechanical irritation, which manifests 

 itself by hyperemia of the cutis, exudation, and further sequelae. 

 Scab mites also produce an especially injurious effect by an 

 acrid juice which they secrete and inoculate into the epidermis 

 and deeper parts, through which sarcoptes and dermatocoptes 

 mites cause an existing inflammation to become more intense. 

 Rubbing in of powdered dead mites as well as extracts obtained 

 from their bodies actually causes itching and soon also the de- 

 velopment of papules and vesicles (Bourguignon, Gerlach). 

 Rul)bing, scratching and the like caused by the itching visibly 

 increase the aggravation of the inflammatory process. 



Symptoms. The duration of incubation, the degree and 

 extent of the mange, depend, apart from the variety of mites, 

 very largely on the number of mites present on the skin. Symp- 

 toms of disease Avill be noticed only in the presence of numerous 

 mites; if only isolated mites get on the healthy skin, 4 to 6 

 weeks may elapse before they have increased sufficiently to 

 cause perceptible changes in the skin, while after an intense 

 infection the first symptoms may become evident after two 

 weeks. 



Scab is essentially an eczematous dermatitis. From the 

 ])ite or puncture of mites transient red spots arise, or at other 

 places nodules, vesicles and pustules and at these points the 

 clinical picture of eczema squamosum develops or more fre- 

 quently of eczema crustosum with subsequent thickening of the 

 skin. In more severe cases the skin is changed into thick folds, 

 the hair falls out and the surface of the skin is covered with 

 crusts of varying thickness under which the cutis, robbed for 

 the most part of its epidermis, appears bright red, sensitive, 

 moist and bleeding. The pathological changes are the more 

 severe the longer the disease continues; besides the variety of 

 mite has an influence in so far as the sarcoptic mites generally 

 cause a more severe disease of the skin than the dermatocoptes 

 and dermatophagus, which are parasitic only on its surface. 



Itching is a constant symptom and it is characteristic to a 

 certain degree that it increases with w^armth; in summer it is 

 more intense than in winter; at night or under cover affected 

 animals are more restless than in the daj^ime and out of doors, 

 and the itching will be more intense when the animals become 

 warmed up by work. This severe itching partly changes the 

 external appearance of the affection, while rubbing, biting and 

 scratching aggravate the inflammatory process, and the con- 

 tinuous unrest leads to loss of condition. Mange declines in 

 cool weather, and in the course of the winter it may appear to 

 be healed, but on the return of warm summer weather it makes 

 its appearance again and assumes larger extension. With 



