I don't know if you can get any of the tick borne illnesses where you are, but, I just spent 5 weeks very sick from lyme disease. Ticks carry 8 different diseases, and many locations still cannot diagnose them. Where the Off.
You can dust your chickens with diatomaceous earth powder. You can also just put a bunch of it in their pen and they will dust bathe in it. I've never used it for that purpose, but the farming communities here in MS use it on their pets and livestock and its is reported to give immediate relief. Research it and try it out.