8 



CIRCULAR 338, U. S. DEPT. OF AGRICULTURE 



examined, the procedure being as given for the diagnosis of sarcoptic 

 mange. 



Symptoms. — Demodectic mange may occur in dogs of all ages and 

 breeds but appears to be more common in young animals and short- 

 haired breeds. The first evidence of demodectic mange, as a rule, 

 consists in the appearance of hairless spots, often somewhat red- 

 dened, these spots commonly occurring about the eyes or at the 

 elbows and hocks, though they may appear first in other places. 

 There is very little itching at this time, and though itching may be 

 more evident later there is usually less of it than in cases of sarcoptic 

 mange, and when present it is usually intermittent. As the disease 

 progresses the hairless areas become more extensive and redder, 



Figure .5. — Dos with demodectic mange, depilatory form 



though later the skin may be lead gray in color. This is the so- 

 called depilatory stage of the disease (fig. 5). At this stage the 

 mites are increasing in the hair follicles, and the visible skin changes 

 are evidences of inflammatory conditions about the follicles and their 

 sebaceous glands. As many as 200 mites may occur in a single hair 

 follicle. 



Usually the depilatory form of demodectic mange, due to the 

 uncomplicated cases of mite infestation as described above, becomes 

 complicated in time through the invasion of the weakened and dis- 

 eased skin by pus-forming bacteria, and sometimes these complica- 

 tions appear to be present from the onset of the disease. This con- 

 dition is the pustular stage of the disease (fig. 6) and in this stage 

 the previously hairless and reddened areas now show numerous pus- 

 tules. In and under the skin there are numerous cbscesses or pus 



