Introduction/Clinical Signs: Aural plaques (hyperplastic dermatitis of the ear) is a problem that occurs on the inside surface of the ear. These lesions are usually grey to white crusts that form over the surface of the skin. The crusts can be removed and a pink skin surface is found below. Aural plaques can be found in horses of both sexes and of all ages.
Causative Agents/Diagnosis: Unfortunately, the cause of aural plaques is unknown. Some researchers think the condition may be caused by an equine papilloma virus. All cases of aural plaques can be diagnosed based on appearance and noting the signs mentioned previously.
Treatment: Because the cause for aural plaques is not known, it is often difficult to impossible to treat the condition consistently or effectively. Through the years, numerous treatments for plaques have been tried with varying degrees of success. In some cases, the plaques may diminish in size or seem to disappear with treatment, only to return months later. In a large number of cases, the treatment has little or no effect. Some treatments that may have a more long-term effect would include laser surgery (using a carbon-dioxide laser) and chemotherapy (e.g. a topical anti-tumor cream used to treat sarcoids).
Some veterinarians report that certain plaques seem to be associated with insect bites (especially Culicoides midges and black flies). The theory behind this is that the insect bites may actually initiate the plaques by spreading the papilloma virus. Even if the insect bites do not spread any virus, they definitely can cause significant irritation to any existing plaques. As a result, if flies or other insects are attracted to the plaque area, fly repellents should be routinely applied to the ears and surrounding areas. This can help prevent additional irritation and potential increase in size and spread of the plaques.
Because insects can irritate existing plaques, anti-inflammatory ointments and creams containing cortisone can sometimes decrease the size of some plaques. In most situations, this is a temporary solution and will not resolve the plaques completely. One treatment that sometimes helps involves the use of a simple triple antibiotic with steroid in it. This is applied to the ear 2-3 times a day. Many times the horse becomes so sensitive to the irritation and constant application of medication that it becomes very "ear shy." In many instances, it is often best to simply ignore the problem.
Prevention: Because the cause for aural plaques is not known, there is really no way to prevent this problem. The best suggestion is to keep fly and insect irritations to a minimum.