Insects and parasites commonly cause dermatitis of the pinnae either through direct damage from the bite of the parasite or as a result of hypersensitivity. Ticks can cause irritation at the site of attachment and may be found on the pinna or in the ear canal. The spinous ear tick (Otobius megnini), found in the southwestern USA, south and central Americas, southern Africa, and India, is a soft-shelled tick, the larval and nymphal forms of which parasitize the external ear canal of horses, cattle, sheep, goats, deer, rabbits, cats, and dogs. Clinical signs include head shaking, head rubbing, or drooped pinnae. Both the animal and the environment should be treated. Pyrethrin/pyrethroid products are effective.
Last full review/revision July 2011 by Sheila Torres, DVM, PhD, DACVD; Scott A. Dee, DVM, MS, PhD, DACVM