10 



FAEMERS BULLETIN 713. 



that unless they are present there can be no scab, the diagnosis is 

 rendered more simple. 



Common sheep scab may be differentiated from conditions caused 

 by other parasites, such as sheep ticks, common ticks, and lice, by 

 finding the parasite and by the nature of the lesion. If the itching 

 is caused by ticks an examination will reA'eal the ticks. (See fig. 8.) 

 They are much larger than the scab mites and are of a dark-brown 

 color. If lice cause the sheep to scratch they can be found on ex- 

 amination, and as they are much larger than a scab mite thev are 



Fiu. 0. — A caso of scab more advanced than that in figure 5, showing area deniulod of wool. 



easily identified. Ticks and lice do not, as a rule, produce pronounced 

 local lesions. They move more or less from place to place on the 

 skin, so that scratching and biting is not repeated persistently in one 

 place as in the case of scab. It should be remembered, however, that 

 ticks or lice may be present on scabby sheep and that their presence 

 in itself is not enough to warrant the exclusion of scab as a possibility 

 in the diagnosis. 



Bearded seeds of grass and weeds, thorns and spines from cacti 

 and various other plants, often become lodged in the fleece and prick 



