This worldwide problem caused by the stable fly, Stomoxys calcitrans (see Flies: Stable Flies), typically affects dogs and horses. The fly bite causes small papules and wheals with central hemorrhagic crusts that itch. Lesions are found on the apexes of the pinnae of dogs with erect ears or on the folded surfaces of the pinnae of dogs with flopped ears. In horses, this fly can cause a hypersensitivity reaction or severe dermatitis resulting in lesions on the dorsal and/or ventral trunk and face in addition to the pinna. Treatment includes fly repellents, controlling the fly population with environmental clean up (manure, compost, etc), and insecticides.
Last full review/revision July 2011 by Sheila Torres, DVM, PhD, DACVD; Scott A. Dee, DVM, MS, PhD, DACVM