What is Inner Ear Plaque?
Aural plaques in horses are also called papillary acanthoma or ear papillomas and result from papillomavirus. The plaques present as whitish or gray flaky sores on the inside of your horse’s ear. Present in one or both of the horse’s ears, they are somewhat raised and appear scaly. It is thought that the plaques are a scar tissue that is the result of the ongoing inflammatory response of your horse’s body to a papilloma viral infection, likely occurring as a result of biting black flies. In some horses the aural plaques are only a cosmetic problem; typically, they don’t itch much and are not painful. In other horses, they lead to the horse’s ear or ears being extremely sensitive.
Also known as papillary acanthoma or ear papillomas, aural plaques in horses are a result of papillomavirus, presenting as white or gray sores on the inside of one or both of the horse’s ear.
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Symptoms of Inner Ear Plaque in Horses
Should your horse develop aural plaques, they will appear as white or gray flaky sores on the inside of his ear. The plaques are usually smooth and in most cases don’t bleed. Should the plaque peel, the skin is usually smooth and underneath healthy, pink skin is present. In most cases the plaques will not bother the horse as they are usually not painful or very itchy. The plaques may occur in one or both of your horse’s ears.
Four papillomaviruses have been found among aural plaques. While most horses will not be bothered by the plaques, some will be bothered by them and can resent having their ears touched, making it challenging to bridle them.
Causes of Inner Ear Plaque in Horses
It is thought that your horse’s body is having a chronic inflammatory response to an infection with the papilloma virus, leading to the plaques, which are thought to be a scar tissue that result from the ongoing inflammatory response of your horse’s body. Black flies (Simulium spp) are thought to transmit the virus. They are active at dawn and dusk, and the flies may bite the head, ears, and abdomen of the horse.
Diagnosis of Inner Ear Plaque in Horses
Should you notice any plaque on the ears of your horse, or that your horse’s ear or ears seem to be bothering him, it is a good idea to visit your veterinarian. Your veterinarian will examine the ears of your horse as well as ask you when you first noticed the lesions. Usually, you or your veterinarian will not notice any symptoms aside from the lesions, though in some cases the bite from the fly can cause dermatitis and discomfort for your horse.
As it may be hard for your veterinarian to tell whether the lesions are from a young equine sarcoid or a squamous cell carcinoma, he may choose to examine scrapings from a lesion under a microscope. Plaques from the papilloma virus will demonstrate mild papillated epidermal hyperplasia and marked hyperkeratosis. The epidermis may also show keratohyalin granules of increased size, koilocytosis and hypomelanosis.
Treatment of Inner Ear Plaque in Horses
Many treatments have been tried in order to resolve aural plaques, though unfortunately, they appear to have little effect on eliminating them. As the plaques usually have little impact on the comfort of your horse, they are likely of more concern to you than they are to him. Handling the ears of your horse to provide certain treatment has been known to inflame their ears, therefore veterinarians will often not recommend any treatment for aural plaques.
There has been some success with ointments, in particular those with steroids or that are anti-inflammatory. Imiquimod cream has been shown to be effective, however it can cause significant inflammation, which makes its use challenging (and most horses need to be sedated). Should you choose to use an ointment, it is important that you don’t scrub or scrape the ears of your horse when applying it.
Recovery of Inner Ear Plaque in Horses
Your veterinarian may recommend that you provide a fly mask with ears for your horse, as this will protect him from new fly bites or irritation from them. Applying fly repellant often and keeping your horse in his stable during the feeding times of flies will help to minimize your horse’s discomfort and prevent further aural plaques.
The aural plaques may make the ears of your horse more sensitive to grooming and other handling; it is important to keep this in mind as you work with your horse should he have developed aural plaques.