LECTURE XLVII. 



SHEEP SCAB. 



Sheep scab is a result of irritation caused by little animal 

 parasites as they burrow tunnels into the skin or puncture it from 

 the surface. There are three types of these mites and three types 

 of the disease which they cause. One variety of these mites pro- 

 duces body scab, another produces head scab, and a third produces 

 foot scab. 



BODY SCAB. 



General history. — This is the most common and serious type 

 of sheep scab, because it spreads most rapidly ovc" the individual 

 body, and also spreads most rapidly through the flock. 



This disease appears insidiously, and is liable to become quite 

 serious before being noticed by the owner. The parasites which 

 cause this type of the disease do not tunnel into the skin, but they 

 cause intense irritation by reason of their presence and mode of life 

 beneath the scabs. The owner will usually remember, after he has 

 become aware that body scab exists in his flock, that his sheep 

 have seemed uneasy and some of them have been rubbing and 

 biting themselves occasionally for some time. 



The parasites live beneath the crusts after the disease is well 

 under way, and constantly migrate outward, while the skin slowly 

 heals in the center. The fleece of scabby sheep is usually rough, 

 the wool is matted in places and easily rubbed off. The parasites 

 which cause this form of the disease confine their work almost 

 exclusively to parts of the body where the wool is long and thick. 



How spread. — This form of the disease spreads rapidly 

 through the flock ; partly because of the location of parasites upon 

 the body of the sheep, and partly because of the freely moving 

 habits of the parasites. As a rule, the disease spreads more rapid- 

 ly in autumn and winter, because the wool is then long and thick. 



