Fowl ticks in the chicken coop

I am very new to the business of raising chickens (inherited them with the house we bought). We just found something that looked like a tick on one of our hens and we think that there is a problem with ticks in the chicken coop.  The hen is very lethargic and not eating.  We want to disinfect the coop just in case and we were wondering if anybody has had any experience with it?  What works and is safe for the chickens?

We live in the US in Virginia so I am not sure if the products here would be the same as in the UK.  What would be safe to use ON the chickens since they will need to be treated too?

I would really appreciate quick response since the hen is really not doing well and we want to help her and protect the other chickens as well.