SHEEP SCAB 



131 



How spread. — This form of the disease spreads rapidly 

 through the Hock ; because of the location of parasites upon the 

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

 the parasites. As a rule, the disease spreads most rapidly in 

 autumn and winter, because the wool is then long and thick, 

 furnishing favorable conditions for the parasites, and because 

 the sheep are kept in closer contact at these seasons. The dis- 

 ease makes more rapid progress then and is much more fatal 





Fig. 44. — A Plain Case of Sheep Scab. 



with the weaker sheep. These parasites may be transferred from 

 one sheep to another in a great variety of ways ; for instance, 

 tags of wool may be rubbed off and dropped almost anywhere. 

 Diseased sheep infect posts and fences by rubbing against them, 

 also the parasites escape from one sheep to another Avhile the 

 sheep are in close contact in yards and sheds. A loaned buck 

 is liable to bring back scab. 



Open pastures and yards usually become safe again after 

 two months. Indoor pens, sheds, etc., once infected, may not 

 be safe in less than a year without radical cleaning and dis- 

 infection. 



Foot Scab 



The disease caused by foot scab mites (Chorioptes) appears 

 on the feet and limbs. The diseased area extends very slowly, 



