It looks like scaly leg mites. It can be treated by soaking the legs in warm soapy water, and using a toothbrush to gently loosen the scales. When dry, apply a thick oil such as coconut oil, castor oil, mineral, vegetable, or vaseline rubbing the oil under the scales to smother the mites. Repeat often or weekly until new scales grow back. Ivermectin pour-on may be helpful as well. Dosage is 0.1 ml per every 2 pounds of weight, applied to the base of the neck on the spine, and repeat in 14 days.