The advice hub Scaly Leg Mite
Scaly leg mites and depluming mites are two closely related mites which both belong to the genus Knemidocoptes. The scaly leg mite (Knemidocoptes mutans) commonly infests older hens by burrowing underneath the scales of the leg. This causes damage and inflammation, often with white crusting and exudate, sometimes this may become infected causing swelling and bleeding. Scaly leg mite causes severe irritation.
In the early stages, the affected bird will be no more than mildly irritated by the scaly leg mites but as the scales become thickened and the mites cause more extensive damage, this may become very painful if left untreated. It is important to note that it takes several months for the scales of the legs to become raised and consequently to heal again after treatment.
Prevention and treatment of scaly leg mite is the same. Gently cleanse the legs, with the aid of a soft toothbrush or cloth. Thoroughly dry the legs with a paper towel. Apply a solution of Dergall (1ml in 100ml of water) in a hand sprayer or by dipping the foot and leg in the Dergall solution. Dergall will suffocate the scaly leg mite and also help the legs to heal. Repeat this once a week for a few weeks.
Ivermectin 1% spot on drops are advised too, but it is important to note that because Ivermectin drops are not licensed for chickens. The prescribing vet will advise to discard of any eggs produced by the treated birds for one week after application. Repeat in 3 weeks.
Smoothing Vaseline on the legs will help to soften the scales once they start to heal. Scales can take twelve months to heal completely.