SHEEP SCAB. 9 



the mites are usually present in large numbers and are easily found. 

 On the other hand, if the lesion is dull and dry in appearance it in- 

 dicates that the mites are inactive at that point and that they will 

 be difficult to find. Usually the latter condition is found in the 

 center of a patch of scab of comparatively long standing or where 

 the mites haAe been destroyed or rendered dormant. The white, 

 glossy appearance is seen in cases of recent infestation or on the outer 

 edges of old lesions. It is often difficult to find mites during cold, 

 stormy weather, as they apparently leave the infested area, wiiere 

 the wool is light, and seek shelter A^liere it is heavier. 



Any condition which causes the sheep to bite and scratch should 

 be investigated at once and the cause definitely learned. Scab on 

 certain parts of the sheep's body may be overlooked. It is usually 

 found on the back or sides, but may start on any part of the body. 

 Lambs are sometimes infected around the head between the horns and 

 ears, and as these parts are frequently covered with dirt the lesions 

 may not be noticed unless close examination is made. Scab mites are 

 sometimes found in the ear and in the groove beneath the eye, which 

 may explain some cases of fresh outbreaks after treatment, the mites 

 in these places surviving imperfect dipping. On wrinkled breeds, 

 and especially on the buclcs of these breeds, scab may be so well con- 

 cealed in the wrinkles as to render its detection difficult. The breasts 

 and bellies of suspected bucks of all breeds should be closely ex- 

 amined, as these parts are frequently affected. In some cases a con- 

 siderable area of scab may be present, especially on the back of the 

 sheep, without causing a break in the fleece. In these cases, most 

 often found in tight- wool sheep, the wool will be "raised" from the 

 skin but is held so firmly by the surrounding wool that it may escape 

 detection. Bucks are not so sensitive to the effects of scab as other 

 sheep ; consequently they may have scab a long time without showing 

 any breaks in the fleece. In some cases they do not bite or rub the 

 affected parts enough to cause dislodgment of the wool. (See fig. 7.) 



Well-advanced cases of hard scab are usually easy to diagnose, but 

 the disease should never be allowed to reach this stage, as it entails 

 lieaA-y loss to the owner and the entire premises may become infec- 

 tious. The experienced sheep grower realizes that a case of common 

 scab, if neglected and allowed to spread, wnll materially reduce the 

 profits and often place the balance on the wrong side of the ledger. 



CONDITIONS WHICH MAY BE MISTAKEN FOR SCAB. 



Any parasite or condition w^hich causes itching and thus leads the 

 sheep to scratch themselves may temporarily be mistaken for scab, 

 but if it is remembered that scab is caused only by scab mites, and 

 25745°— Bull. 713—16 2 



