All animals in the herd should be treated regardless of the number showing infestation.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
If the stable or pasture is infested with ticks, the animal should be placed in a tick-free inclosure to prevent additional infestation with these parasites and the introduction of fresh infection into the blood.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler
If the treatment used were absolutely effective in destroying each and every tick on the animals treated there would be no renewal of the infestation after the treatment is begun.
"Special Report on Diseases of Cattle"
U.S. Department of Agriculture J.R. Mohler