356 



TEXAS FEVER 



from ticks they would not when kept together in small 

 enclosures transfer the disease to susceptible animals, but that 

 when susceptible cattle become infested with the ticks either 

 by grazing in infested pastures or by having placed upon them 

 young ticks hatched in the laboratorj- the disease appeared. 

 The infection of northern cattle with Texas fever bv 



■ .-r 



Fig. 95. Photograph of animal sick with Texas fever. {Photo- 

 graphed by Connaway). 



southern animals consists therefore in first infesting them with 

 the cattle tick.-'- The number of ticks necessary to carry the 

 disease is small so that frequently they will not be observed 

 unless the sick animals are carefullv examined. The life 



*It is interesting to add the results of an experiment conducted by 

 Dr. Cooper Curtice in the Bureau of Animal Industry which shows the 

 necessity of the tick in inoculating cattle. In a tick infested district in 

 the south, a field was cleared of ticks by fencing and keeping cattle off 

 for a year. Susceptible northern cattle were transported to and placed 

 in this field where they thrived for a season. The second year they 

 were placed in a second cleared pasture where they kept well for an- 

 other year. The third year they were placed in a tick infested pasture 

 where they died promptly of Texas fever. 



