PARASITES AND PARASITIC DISEASES OF HORSES 43 
Symptoms.—Psoroptic mange may start on any part of the body: 
covered thickly with hair, but the first lesions usually appear on the 
head under the foretop, on the top of the neck around the mane, or 
on the rump. From the starting point the disease spreads slowly 
over the body. 
The mites prick the skin and probably introduce a poisonous se- 
cretion into the wound. A slight inflammation is caused, accom- 
panied by an intense itching. In the early stages of the disease the 
lesions are not sufficiently prominent to attract attention, but the 
animals rub and bite 
themselves to relleve 
the intense itching, 
and these symptoms 
should always be in- 
vestigated to learn the 
cause. 
As the mites multi- 
ply, large numbers of 
small wounds are 
made in the skin, fol- 
lowed by the forma- 
tion of papules, in- 
creased inflammation 
and itching, and the 
exudation of serum. 
The serum which 
oozes to the surface 
becomes mixed with 
foreign matter and 
microorganisms, and 
this mass soon hard- 
ens into yellowish or 
eray-colored scabs. 
The scabs are fre- 
quently stained with 
blood. In the early 
stages the _ hairs 
around the lesion 
aay. be glued ie Figure 30.—Psoroptic mange mite. Female. (Magnified 
gether in a_ small 100 times) 
clump and the nodule 
or scab may be about the size of a pea. As the mites constantly seek 
the healthy skin around the edges of the wound, the scab or lesion 
gradually increases in size. 
Some of the mites migrate to other locations and start new lesions, 
which extend until they cover large areas. As the disease advances 
the skin becomes thickened, tumefied, and thrown into wrinkles or 
folds. Large areas become denuded of hair and covered with thick, 
adherent scabs. When the disease reaches this stage it is difficult to 
differentiate it from sarcoptic mange. 
Itching is intense and irritation continues throughout the course 
of the disease. The skin becomes bruised and raw from the reck- 
less rubbing against any available surface. The uniform thickening 
