Scab 321 



are the mites. If they are examined with a lens, their 

 outlines can be seen. 



Scab of Sheep 



(Psor.optes comtnunis, var. ovis) 



At first, itching of the skin is shown by the 

 animal's scratching with its hind feet, or biting 

 and pulling wool. In bad cases, the wool may be 

 shed over very large surfaces; but in ordinary cases the 

 fleece has a ragged appearance and is wet and matted 

 where the animal has bitten at it and pulled out tags 

 of wool. The itching is more intense when the animals 

 are warm with exercise. If the wool is parted over an 

 itching spot and the skin examined closely, yellow pim- 

 ples will be found -which, on being pinched, exude a 

 watery fluid. This fluid dries on the skin into yellow- 

 ish, greasy scabs, which increase in area and thickness. 

 These scabs are often torn off by the sheep, thus in- 

 creasing the irritation. 



An animal affected with scab falls away in flesh, 

 becomes weak and debilitated, and presents an unthrifty, 

 ragged appearance. The disease is most severe during 

 the fall and winter months, when sheep are closely con- 

 fined and are fed on dry food. In the large sheep- 

 growing regions of the Southwest, scab is a common 

 and very serious disease, causing heavy losses, not so 

 much from the death of animals as from the general 

 debility which it produces in large herds, and the con- 

 sequent loss of flesh. The scab mites are transmitted 

 by direct contact and by means of the tag? and scabs 

 scattered on the ground in yards and pens. Infested 



U 



