If you have scaly leg in some fowls it is inevitable eventually to infect a large proportion if not most of your fowls irrispective of breed.
The most common source of infection is a hen with it and she passes the mite onto the chicks she rears, but it will pass one to another in time.
Many suggestions as to how to eradicate it have been suggested including sump oil and even WD40 but as it is a live mite that burrows under the skin must be killed.
The use of sump oil is an old remedy but it is messy and relies on smothering the mite .
I use Malawash for fleas and ticks, at tick strength.
Anything with Malathion in it will mix with water OR oil for use and is an effective insecticide.Use anything that has Malathion as the base ingredient, ie Malawash, Malaban etc etc.
The trick is to get it to penetrate into the spongy mass, that is where the mites have burrowed and reside.
For this purpose I mix it with "Goanna Oil" as it is a very thin penetrating oil that carries the Malathion to the source and kills the mite.But you can use any oil, ie Veg, Olive, sewing machine oil or any other fine oil as a carrier for the insecticide.
If they have been infect for any length of time you may find scale damage to the legs and will have scarring that prevents you from showing but with time and patience it can be erradicated from your flock and all birds introduced after should be treated with this mixture as a preventative precaution.