Cross sections of two intraepidermal acarids from the pinna of a fox. This fox was killed by farm dogs in South Dakota. There was severe encrustation which involved the ears and face. Auricular dermatitis, with marked purulent and hyperkeratotic epidermitis and associated mange parasites, chronic, severe. In the normal host, the mites burrow into the stratum corneum and feed on cells of the stratum granulosum and stratum spinosum.
Epidermal damage induces epithelial hyperplasia and the development of parakeratotic crusts.
The females lay 40 to 50 eggs which develop into larva and then nymphs in the intracorneal burrows. Neither adults nor eggs survive well in the environment. Transmission is predominantly by direct contact, although indirect contact with fomites is another possible mechanism. The initial lesions of sarcoptic mange are localized and nonpruritic. Immunosuppressed animals do not mount adequate hypersensitivity reactions and develop severe lesions with large numbers of mites.