Such animals are as susceptible to Texas fever as nonimmune northern cattle, and inasmuch as there is in many States only one out of every four farms infested with ticks, the cattle on the remaining farms will in many cases contract Texas fever when exposed to the fever tick.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
Another instance in which it is difficult to figure the injury done by the ticks is in the case of death of nonimmune cattle in the tick-free pastures of the South.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler