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TEXAS FEVER 



Fig. 6o. Photograph of animal sn'k with Texas fever. (Photo- 

 graphed by Connaway). 



1. Adult ticks drop to the ground in from i to 3 daj's 

 after the infested cattle are placed in the field. 



2. Adult ticks laj' their eggs in about 7 days after drop- 

 ping to the ground. 



3. Eggs are hatched in about 20 days after they are laid. 



4. Young ticks crawl upon cattle from i to several days 

 after they are hatched. 



5. In about 10 daj-s from the time the young ticks crawl 

 upon the susceptible cattle the rise of temperature appears. 



The length of time that must elapse { period of incubation ) 

 from the exposure of susceptible cattle to the development of 

 the disease depends on whether or not the whole life cycle of 

 the tick must be passed or part of it has already gone by. 

 If susceptible animals are placed in a pasture where the young 

 ticks are just ready to crawl upon them the infection of the 

 cattle is accomplished at once and the high fever appears in 

 about ten days, practically the minimum time. It has been 

 experimentally demonstrated that the young ticks are able to 



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