Aural plaques

Veterinary advice should be sought before applying any treatment or vaccine.

Aural Plaques

Aural Hyperkeratosis, Pinnal Acanthosis, Hyperplastic Aural Dermatitis

Aural plaques are a skin disease in horses that is associated with Equus caballus papillomavirus (EcPV). The virus is spread to horses through black flies (Simulium species). Aural plaques are characterized by the development of small areas of round to oval, white raised, papillomatous, depigmented skin lesions that appear on the inside surface of the horse's ear. The skin lesions consist of hypertrophied epidermis, and do not cause the horse any irritation or discomfort. Aural plaques are caused by a papillomavirus infection that is spread by black flies (Simulium species). Although infectious, the skin lesions are not of any concern as they are benign.
Aural Plaque location on horses

Horses with aural plaques tend to be very sensitive about people touching their ears, which may cause them to act up when trying to put on or take off a halter or bridle. The horse generally raises its head or quickly pulls its head away if someone even gently touches their ear.

The geographical reach of aural plaques is generally limited to horses in North America, however it has been recently introduced to New Zealand from horses imported from the United States and Canada.


Raised, white-colored plaques in the inner ear
Ear and head hypersensitivity
Difficulty getting halter on and off
Thickened hyperkeratotic skin


  • History
  • Clinical signs
  • Physical exam
  • Biopsy
  • PCR


Imiquimod treatment
Topical cream
Management - applying fly repellent, stabling the horse during fly feeding times, turning out with a break-away halter to minimize ear contact


  • Insect control
  • Fly sheets

Scientific Research References

Good Overviews

  • plaques ear icon
  • plaques icon

Risk Factors

  • High insect populations