If thinking of using Frontline (Fipronil) for this problem, or any other infestation, please be aware that it is illegal to use it on poultry, which are classed as food-producing animals even when kept mainly as pets. It's one of those substances which has an indefinite withdrawal period for eggs and meat, and strictly speaking, you should never subsequently eat eggs from a hen treated with it.
Interesting article here about using this, and other medicines which are not Approved, or Allowed under the veterinary Cascade.
http://www.chippingnortonvets.co.uk/modules/downloadspl2/files/Backyard%20Poultry%20review%20JSAP.pdf