PIROPLASMOSES 487 



1. If the pasture be cultivated for one year, and all tieky 

 cattle kept out of it, it will become rid of ticks. 



2. Burning ticky pastures each spring and fall will keep 

 them free so long as no ticky cattle are permitted on them 

 in the interim. 



3. Early in September the cattle are moved from the 

 infested .pasture and cleaned of ticks. They are then 

 placed on a non-infested pasture and all contact with ticky 

 animals prevented. The original pasture is kept free from 

 animals until the following April when it will be free from 

 ticks. In the eight months during which the field has not 

 been used for pasture, the seed ticks which hatch in the fall 

 have died of starvation having had no access to cattle. 



4. Feed-lot Method. — A field of corn or other forage crop 

 is fenced off into three different enclosures. Around each 

 enclosure a furrow is plowed and a board placed so as to 

 prevent the escape of ticks. The cattle are placed in this 

 field for a period of sixty days, spending twenty days in the 

 first enclosure, twenty in the second and twenty in the third. 

 At the end of this period they are free from ticks, as they were 

 not allowed to remain in any one of the enclosures long enough 

 for reinfestation. In moving the cattle from one enclosure 

 to another they should be driven over plowed ground and 

 after they are taken out the furrow should be sprayed with 

 crude petroleum. Obviously the cattle should not be fed 

 hay nor given water from tick-infested pastures. 



Protective Inoculation. — Susceptible cattle shipped to tick- 

 infested regions, especially animals from six to eighteen 

 months old, may be immunized against Texas fever by one of 

 the following methods : 



1. The animals are confined in a tick-free enclosure and 

 a small number of (25 to 50) virulent seed ticks placed upon 

 them. A month later a greater number of seed ticks (200 to 

 400) is used. This will often produce a non-fatal type of 

 Texas fever which renders the animal immune to natural 

 infection. 



2. The susceptible young cattle are injected subcuta- 

 neously with the defibrinated blood of a native calf or a 

 recovered adult animal. Usually eight to ten days after the 



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