12 VETERINARY PARASITOLOGY 
Predisposing Causes, etc.—Mange arises from con- 
tagion, which may be either mediate or immediate. 
The condition of the animal and its environment have 
a great influence upon the chances of contagion, and 
upon the severity and duration of the disease. 
Army horses, under ordinary conditions, become 
affected with mange, with usually mere reddening of 
the skin. The symptoms rarely last more than a few 
days under these circumstances. 
Mange in Horses. 
Three forms of mange affect horses—viz., sarcoptic, 
psoroptic, and symbiotic. Of these, psoroptic is the 
most common, and symbiotic the least. Sarcoptic 
mange offers the greatest difficulty in treatment, as the 
mites burrow and are little affected by parasiticides 
smeared on the surface. : 
Sarcoptic Mange in Horses.—In horses the parasite 
is known as the Sarcoptes equi, and is extremely 
small. This form of mange principally attacks the 
trunk, more particularly the shoulders, neck, withers, 
and that portion of the body covered by the saddle. 
It then extends on to the quarters, and the patches 
may increase in size until the whole of the trunk is 
covered. It avoids the limbs and those parts covered 
with long hair, such as the mane and tail. It begins as 
small patches, which gradually increase in diameter. 
The areas are denuded of hair, become irregular in size 
and shape, and exhibit a greyish or pinkish surface, 
almost completely covered by a scab, usually thin and 
composed of dried blood and exudate. Occasionally 
the parts may bleed from rubbing. The skin becomes 
thickened and may crack, and, as a result of infection, 
pus may appear in the fissures. It is most commonly 
seen in horses in low condition and during emaciation 
resulting from various causes, but it may attack 
