Mites

• While horses suffer from few ear problems, otitis externa is an infection of the ear canal caused by mites. This infection sometimes migrates to the middle ear, where it can be very painful. Usually characterized by a waxy buildup, it requires flushing of the ear and treatment with antibiotics.
  
  

Black Flies

• In parts of the country where black flies are a problem, horses often exhibit aural plaques--flat, gray lesions--on the inside of the ear. While these cause no real problems and veterinarians usually recommend leaving them alone, they can become large and unsightly. Black flies carry the virus believed to cause these growths.
  
  

Guttural Pouch Infections

• Infections in the guttural pouch--sacs that open into the Eustachian tube--will often migrate into the inner ear. These infections usually start in the upper respiratory tract and are caused by bacteria. When these infections travel to the inner ear, they are painful and often cause hearing loss. They are usually treated with systemic antibiotics.