70 THE COMMON SHEEP- SCAB. 



This estimate of their rapid multiplication, which is by 

 no means exaggerated, but is a very moderate one, plain- 

 ly proves that the farmers keeping sheep can not be too care- 

 ful to prevent the scab from infecting their flocks. Mites, 

 and their eggs as well, if removed from their abodes and 

 placed upon a moist piece of blotting paper, or if kept in a 

 moist atmosphere, can exist from fourteen days to four weeks, 

 but in dry surroundings they will soon perish. This shows the 

 necessity of preventing healthy sheep from sleeping upon 

 moist soil upon which diseased animals have been resting. 

 All such scab-mites seem to become more active in warm 

 stables, and thus cause more violent itching. In the case of 

 the human itch-mite it has been observed that the mites leave 

 their tunnels at night, if the patient is in a Avarm bed, and 

 commence to make new tunnels, hence the increased itching 

 at that time. 



The skin disease caused b^" the common scab-mite has a 

 diflerent appearance upon different breeds of sheep. Upon 

 some breeds, characterized by w^ool nearly free from fat, the 

 disease can spread over the whole bod \% Startingfrom small 

 and isolated spots the scab extends slowly but steadily. In 

 Merino sheep the disease is not so readily communicated, 

 and affects mainly spots free from long wool. The first indi- 

 cation of the disease is violent itching, which the infested 

 animals show by rubbing against all sorts of objects and 

 bj^ biting the infested spots. This itching sensation becomes 

 more evident w^hen the animals become heated by exercise. 

 The sensation produced by rubbing against posts, etc., 

 is evidently of a pleasant character to the sheep, as is 

 shown bj^ a trembling motion of their lips, as well 

 as by the rapid opening and closing of their jaws. 

 The spots of skin infested usually upon the back 

 — show small yellowish knots, which soon change 

 to little pus balls filled with lymph. Later this 

 fluid is discharged and dries, forming small yellowish- 

 brown scabs. The wool upon the invaded spots becomes 

 paler and dry, is slightly lifted, but usually remains in posi- 

 tion, being glued to the skin by the drying lymph. Very 

 often these first indications are very slight, and escape de- 



