► Definition: benign, raised, crusty, white skin growths on the interior surface of the ear ► Causes: a papillomavirus infection, most likely spread by the bites of black flies; the bites may also cause irritation and inflammation that stimulates
the growth of the lesions. ► Signs: unpigmented thickening of the keratinous (structural) layer of the skin; the lesions are raised, with a hard, scaly appearance. Rounded, knoblike protuberances may also develop within the scaly area. Usually the plaques are painless, but in some horses they cause itchiness and sensitivity. In
these cases, the pain may cause a horse to resist having his ears handled. ► Diagnosis: observation of signs. Aural plaques have a distinctive appearance, but it’s wise to have a veterinarian look at them to rule out other skin tumors, such as sarcoids, that can also appear on the ears. This is especially true if the growths develop rapidly, are
tall or cause the horse pain. ► Treatment: If aural plaques are causing no pain or discomfort, no treatment is necessary. In cases where the plaques cause severe itchiness or discomfort, a veterinarian may prescribe topical cream containing imiquimod, a drug that can help reduce the size and severity of the plaques by modifying the immune response.