Trembling in Sheep, etc. 507 



much in this direction. Their destruction is rendered even more 

 complete by ploughing and putting the land under a series of 

 cultivated crops. By this means not only is the winter shelter of 

 the tick removed, but the animal host which it requires for its 

 complete development is denied it, and it must perish before the 

 land is again seeded to grass. When the land is unsuited to cul- 

 tivation, the same end may be in some measure secured by fenc- 

 ing off half the pasture, and leaving it unpastured for a season, 

 meanwhile burning the dry grass or temporarily suppressing it 

 by a liberal application of salt. The following year the pasture 

 so treated may be restored to pasturage, and the other half sub- 

 jected to the same course of treatment. In the absence of such 

 thorough treatment, a liberal application of lime to a virgin soil 

 will often bring a growth so fresh and appetizing that the stock 

 keeps it closely cropped and thus removes the shelter for the of- 

 fensive ticks. Finally, the ticks may be prevented from attacking 

 the animals, by repeated use during April, May and June of a 

 dip in which tar oil, cade oil, heavy petroleum or other odorous 

 insecticide forms a component part (see the dip of Meek and 

 Greig-Smith). 



A very obvious precaution is to avoid the movement of sheep 

 during April, May and June, from tick-infested pastures to others 

 which furnish rank grass, brush or other suitable shelter for the 

 preservation of the parasite. 



It has been noticed that sheep indigenous to the tick-infested 

 and louping-ill pastures are less susceptible than those that have 

 been introduced from outside, but, as yet, no attempt appears to 

 have been made to secure immunity by the use of sterilized 

 products of the microbe, nor therapy by the resort to anti-toxin. 

 A liberal and tonic diet is an important element in prevention. 

 Grain and hay should therefore be allowed whenever necessary 

 to bring the sheep to early summer in good condition. 



Treatment can hardly be said to have been attempted, though 

 mild cases are allowed by the shepherds to recover. According 

 to Meek, the deaths often average 10 to 20 per cent, of the flock. 



